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  • 1.
    Aghbolagh, Mahdi Shahmohammadi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Meynaq, Mohammad Yaser Khani
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shimizu, Kenichi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lindholm-Sethson, Britta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Aspects on mediated glucose oxidation at a supported cubic phase2017Ingår i: Bioelectrochemistry, ISSN 1567-5394, E-ISSN 1878-562X, Vol. 118, s. 8-13Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A supported liquid crystalline cubic phase housing glucose oxidase on an electrode surface has been suggested as bio-anode in a biofuel. The purpose of this investigation is to clarify some aspect on the mediated enzymatic oxidation of glucose in such a bio-anode where the mediator ferrocene-carboxylic acid and glucose were dissolved in the solution. The enzyme glucose oxidase was housed in the water channels of the mono-olein cubic phase. The system was investigated with cyclic voltammetry at different scan rates and the temperature was varied between 15 degrees C and 30 degrees C. The diffusion coefficient of the mediator and also the film resistance was estimated showing a large decrease in the mass-transport properties as the temperature was decreased. The current from mediated oxidation of glucose at the electrode surface increased with decreasing film thickness. The transport of the mediator in the cubic phase was the rate-limiting step in the overall reaction, where the oxidation of glucose took place at the outer surface of the cubic phase.

  • 2.
    Aisenbrey, Christopher
    et al.
    Institut de Chimie Universit0 Louis Pasteur Strasbourg—CNRS, UMR 7177 4, Rue Blaise Pascal, 67000 Strasbourg (France); Max-Planck-Institut f>r Biochemie Am Klopferspitz 18A, 82152 Martinsried (Germany).
    Cusan, Monica
    Lambotte, Stephan
    Jasperse, Pieter
    Georgescu, Julia
    Harzer, Ulrike
    Bechinger, Burkhard
    Specific Isotope Labeling of Colicin E1 and B Channel Domains For Membrane Topological Analysis by Oriented Solid-State NMR Spectroscopy2008Ingår i: ChemBioChem, ISSN 1439-4227, E-ISSN 1439-7633, Vol. 9, nr 6, s. 944-951Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An approach is presented to selectively label the methionines of the colicin E1 and B channel domains, each about 200 residues in size, and use them for oriented solid-state NMR investigations. By combining site-directed mutagenesis, bacterial overexpression in a methionine auxotroph E. coli strain and biochemical purification, quantitative amounts of the proteins for NMR structural investigations were obtained. The proteins were selectively labeled with 15N at only one, or at a few, selected sites. Multidimensional heteronuclear correlation high-resolution NMR spectroscopy and mass spectrometry were used to monitor the quality of isotopic labeling. Thereafter the proteins were reconstituted into oriented phospholipid bilayers and investigated by proton-decoupled 15N solid-state NMR spectroscopy. The colicin E1 thermolytic fragment that carries a single 15N methionine within its hydrophobic helix 9 region exhibited 15N resonances that are characteristic of helices that are oriented predominantly parallel to the membrane surface at low temperature, and a variety of alignments and conformations at room temperature. This suggests that the protein can adopt both umbrella and pen-knife conformations.

  • 3.
    Ajaikumar, Samikannu
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ahlkvist, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Larsson, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kordas, K
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Piispankatu 8, FIN-20500, Turku/Åbo, Finland.
    Oxidation of α-pinene over gold containing bimetallic nanoparticles supported on reducible TiO2 by DPU method2011Ingår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 392, nr 1-2, s. 11-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of bimetallic catalysts Au–M (where M = Cu, Co and Ru) were supported on a reducible TiO2 oxide via deposition-precipitation (DP) method with a slow decomposition of urea as the precipitating agent. The characteristic structural features of the prepared materials were characterized by various physico-chemical techniques such as X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XPS results indicated the formation of alloyed bimetallic particles on the TiO2 support. TEM results confirmed the fine dispersion of metal nanoparticles on the support with an average particle size in the range of 3–5 nm. An industrially important process, oxy-functionalization of α-pinene was carried out over the prepared bimetallic heterogeneous catalysts under liquid phase conditions. Reaction parameters such as the reaction time, temperature, and the effect of solvent were studied for optimal conversion of α-pinene into verbenone. The major products obtained were verbenone, verbenol, α-pinene oxide and alkyl-pinene peroxide. The activity of the catalysts followed the order; AuCu/TiO2 > AuCo/TiO2 > Cu/TiO2 > Au/TiO2 > AuRu/TiO2. Upon comparison of the various catalysts, AuCu/TiO2 was found to be an active and selective catalyst towards the formation of verbenone. The temperature, nature of the catalysts and the choice of solvents greatly influenced the reaction rate.

  • 4. Alonso-Mori, R.
    et al.
    Asa, K.
    Bergmann, U.
    Brewster, A. S.
    Chatterjee, R.
    Cooper, J. K.
    Frei, H. M.
    Fuller, F. D.
    Goggins, E.
    Gul, S.
    Fukuzawa, H.
    Iablonskyi, D.
    Ibrahim, M.
    Katayama, T.
    Kroll, T.
    Kumagai, Y.
    McClure, B. A.
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Motomura, K.
    Nagaya, K.
    Nishiyama, T.
    Saracini, C.
    Sato, Y.
    Sauter, N. K.
    Sokaras, D.
    Takanashi, T.
    Togashi, T.
    Ueda, K.
    Weare, W. W.
    Weng, T-C
    Yabashi, M.
    Yachandra, V. K.
    Young, I. D.
    Zouni, A.
    Kern, J. F.
    Yano, J.
    Towards characterization of photo-excited electron transfer and catalysis in natural and artificial systems using XFELs2016Ingår i: Faraday discussions, ISSN 1359-6640, E-ISSN 1364-5498, Vol. 194, s. 621-638Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ultra-bright femtosecond X-ray pulses provided by X-ray Free Electron Lasers (XFELs) open capabilities for studying the structure and dynamics of a wide variety of biological and inorganic systems beyond what is possible at synchrotron sources. Although the structure and chemistry at the catalytic sites have been studied intensively in both biological and inorganic systems, a full understanding of the atomic-scale chemistry requires new approaches beyond the steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure at ambient conditions, while overcoming X-ray damage to the redox active catalytic center, is key for deriving reaction mechanisms. Such studies become possible by using the intense and ultra-short femtosecond X-ray pulses from an XFEL, where sample is probed before it is damaged. We have developed methodology for simultaneously collecting X-ray diffraction data and X-ray emission spectra, using an energy dispersive spectrometer, at ambient conditions, and used this approach to study the room temperature structure and intermediate states of the photosynthetic water oxidizing metallo-protein, photosystem II. Moreover, we have also used this setup to simultaneously collect the X-ray emission spectra from multiple metals to follow the ultrafast dynamics of light-induced charge transfer between multiple metal sites. A Mn-Ti containing system was studied at an XFEL to demonstrate the efficacy and potential of this method.

  • 5.
    Andersson, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Brant Carvalho, Paulo H. B.
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden.
    Häussermann, Ulrich
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden.
    Hsu, Ying-Jui
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Evidence suggesting kinetic unfreezing of water mobility in two distinct processes in pressure-amorphized clathrate hydrates2022Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, nr 34, s. 20064-20072Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Type II clathrate hydrates (CHs) with tetrahydrofuran (THF), cyclobutanone (CB) or 1,3-dioxolane (DXL) guest molecules collapse to an amorphous state near 1 GPa on pressurization below 140 K. On subsequent heating in the 0.2-0.7 GPa range, thermal conductivity and heat capacity results of the homogeneous amorphous solid show two glass transitions, first a thermally weak glass transition, GT1, near 130 K; thereafter a thermally strong glass transition, GT2, which implies a transformation to an ultraviscous liquid on heating. Here we compare the GTs of normal and deuterated samples and samples with different guest molecules. The results show that GT1 and GT2 are unaffected by deuteration of the THF guest and exchange of THF with CB or DXL, whereas the glass transition temperatures (Tgs) shift to higher temperatures on deuteration of water; Tg of GT2 increases by 2.5 K. These results imply that both GTs are associated with the water network. This is corroborated by the fact that GT2 is detected only in the state which is the amorphized CH's counterpart of expanded high density amorphous ice. The results suggest a rare transition sequence of an orientational glass transition followed by a glass to liquid transition, i.e., kinetic unfreezing of H2O reorientational and translational mobility in two distinct processes.

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  • 6.
    Andersson, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johari, Gyan P.
    Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada.
    Thermal conductivity of Glycerol’s liquid, glass, and crystal states, glass-liquid-glass transition, and crystallization at high pressures2016Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 144, artikel-id 064504Artikel i tidskrift (Refereegranskat)
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  • 7.
    Andersson, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Yasuhiro, Nakazawa
    Research Center for Structural Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
    Thermal Properties and Transition Behavior of Host –Guest Compounds under High Pressure2014Ingår i: Current inorganic chemistry, ISSN 1877-9441, Vol. 4, nr 1, s. 2-18Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The thermal properties and transition behavior of the host-guest inclusion compounds: urea, thiourea, Dianin’s compound, clathrate hydrates and hydroquinone have been reviewed. In particular, we summarize their thermal conductivities, heat capacities and transitions at high pressures. Two of the systems: urea inclusion compounds and clathrate hydrates, show unusual glass-like thermal conductivity k, i.e. their k is low and only weakly dependent on temperature  despite their crystalline structure. Moreover, results for k of Dianin’s compound with guests such as ethanol and CCl4 indicate a change from glass-like k  at atmospheric pressure to crystalline-like k at elevated pressure, whereas k of hydroquinone and thiourea inclusion compounds appears not to have been studied. Despite the technological and fundamental importance of the unusual glass-like k, e.g. the use of inclusion compounds as structural model systems for finding improved thermoelectrical materials, the origin of the glass-like k is not established. More specifically, the commonly employed rattling model, in which rattling guest motions cause resonance scattering of the acoustic host phonons, has recently been challenged, and we discuss alternative models. Heat capacity studies of these compounds reveal numerous transitions, which are associated with guest and host disorder-order transitions upon cooling and pressurization. A transition in hydroquinone may be of second order, or have only a small first-order component, which can explain discrepancies in the observed transition behavior. On pressurization at low temperatures, clathrate hydrates collapse to an amorphous state, which appears to be a glassy state of a water solution with perfectly spaced solute molecules.

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  • 8. Andrew, Rhiann E.
    et al.
    Ferdani, Dominic W.
    Ohlin, C. Andre
    Chaplin, Adrian B.
    Coordination Induced Atropisomerism in an NHC-Based Rhodium Macrocycle2015Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 34, nr 5, s. 913-917Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reversible interaction with carbon monoxide results in the onset of dynamic atropisomerism at 298 K in an otherwise static NHC-based rhodium pincer complex, [Rh(C boolean AND N boolean AND C-(CH2)(12))(CO)][BArF4] (1, ArF = 3,5-C6H3(CF3)(2)). The mechanism of this process has been comprehensively interrogated by a combination of variable-temperature NMR spectroscopy, IR spectroscopy, and computational modeling. In addition, a structural analogue of a high-energy symmetrical intermediate species-invoked in the process but not directly observed spectroscopically-has been prepared and characterized in solution and the solid-state.

  • 9.
    Annamalai, Alagappan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Robin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boulanger, Nicolas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Muehlbacher, Inge
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Double donor Sb5+doped hematite (Fe3+) photoanodes for surface-enhanced PEC water splitting2018Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 256Artikel i tidskrift (Övrigt vetenskapligt)
  • 10. Arafa, Wael A. A.
    et al.
    Kärkäs, Markus D.
    Lee, Bao-Lin
    Åkermark, Torbjörn
    Liao, Rong-Zhen
    Berends, Hans-Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Siegbahn, Per E. M.
    Åkermark, Björn
    Dinuclear manganese complexes for water oxidation: evaluation of electronic effects and catalytic activity2014Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, nr 24, s. 11950-11964Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During recent years significant progress has been made towards the realization of a sustainable and carbon-neutral energy economy. One promising approach is photochemical splitting of H2O into O-2 and solar fuels, such as H-2. However, the bottleneck in such artificial photosynthetic schemes is the H2O oxidation half reaction where more efficient catalysts are required that lower the kinetic barrier for this process. In particular catalysts based on earth-abundant metals are highly attractive compared to catalysts comprised of noble metals. We have now synthesized a library of dinuclear Mn-2 (II,III) catalysts for H2O oxidation and studied how the incorporation of different substituents affected the electronics and catalytic efficiency. It was found that the incorporation of a distal carboxyl group into the ligand scaffold resulted in a catalyst with increased catalytic activity, most likely because of the fact that the distal group is able to promote proton-coupled electron transfer (PCET) from the high-valent Mn species, thus facilitating O-O bond formation.

  • 11. Azinas, S.
    et al.
    Bano, F.
    Torca, I.
    Bamford, D. H.
    Schwartz, G. A.
    Esnaola, J.
    Oksanen, H. M.
    Richter, R. P.
    Abrescia, N. G.
    Membrane-containing virus particles exhibit the mechanics of a composite material for genome protection2018Ingår i: Nanoscale, Vol. 10, nr 16, s. 7769-7779Artikel i tidskrift (Refereegranskat)
  • 12. Bandyopadhyay, Sulalit
    et al.
    Singh, Gurvinder
    Sandvig, Ioanna
    Sandvig, Axel
    MI Lab and Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
    Mathieu, Roland
    Kumar, P. Anil
    Glomm, Wilhelm Robert
    Synthesis and in vitro cellular interactions of superparamagnetic iron nanoparticles with a crystalline gold shell2014Ingår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 316, s. 171-178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fe@Au core-shell nanoparticles (NPs) exhibit multiple functionalities enabling their effective use in applications such as medical imaging and drug delivery. In this work, a novel synthetic method was developed and optimized for the synthesis of highly stable, monodisperse Fe@Au NPs of average diameter similar to 24 nm exhibiting magneto-plasmonic characteristics. Fe@Au NPs were characterized by a wide range of experimental techniques, including scanning (transmission) electron microscopy (S(T)EM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS) and UV-vis spectroscopy. The formed particles comprise an amorphous iron core with a crystalline Au shell of tunable thickness, and retain the superparamagnetic properties at room temperature after formation of a crystalline Au shell. After surface modification, PEGylated Fe@Au NPs were used for in vitro studies on olfactory ensheathing cells (OECs) and human neural stem cells (hNSCs). No adverse effects of the Fe@Au particles were observed post-labeling, both cell types retaining normal morphology, viability, proliferation, and motility. It can be concluded that no appreciable toxic effects on both cell types, coupled with multifunctionality and chemical stability make them ideal candidates for therapeutic as well as diagnostic applications.

  • 13. Bar, Laure
    et al.
    Dejeu, Jérôme
    Lartia, Rémy
    Bano, Fouzia
    Richter, Ralf P.
    Coche-Guérente, Liliane
    Boturyn, Didier
    Impact of antigen density on recognition by monoclonal antibodies2020Ingår i: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 92, nr 7, s. 5396-5403Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Understanding antigen–antibody interactions is important to many emerging medical and bioanalytical applications. In particular, the levels of antigen expression at the cell surface may determine antibody-mediated cell death. This parameter has a clear effect on outcome in patients undergoing immunotherapy. In this context, CD20 which is expressed in the membrane of B cells has received significant attention as target for immunotherapy of leukemia and lymphoma using the monoclonal antibody rituximab. To systematically study the impact of CD20 density on antibody recognition, we designed self-assembled monolayers that display tunable CD20 epitope densities. For this purpose, we developed in situ click chemistry to functionalize SPR sensor chips. We find that the rituximab binding affinity depends sensitively and nonmonotonously on CD20 surface density. Strongest binding, with an equilibrium dissociation constant (KD = 32 nM) close to values previously reported from in vitro analysis with B cells (apparent KD between 5 and 19 nM), was obtained for an average inter-antigen spacing of 2 nm. This distance is required for improving rituximab recognition, and in agreement with the known requirement of CD20 to form clusters to elicit a biological response. More generally, this study offers an interesting outlook in the understanding of the necessity of epitope clusters for effective mAb recognition.

  • 14. Barišić, Antun
    et al.
    Lützenkirchen, Johannes
    Bebić, Nikol
    Li, Qinzhi
    Hanna, Khalil
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Begović, Tajana
    Experimental Data Contributing to the Elusive Surface Charge of Inert Materials in Contact with Aqueous Media2021Ingår i: Colloids and interfaces, E-ISSN 2504-5377, Vol. 5, nr 1, artikel-id 6Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    We studied the charging of inert surfaces (polytetrafluoroethylene, i.e., PTFE; graphite; graphene; and hydrophobic silica) using classical colloid chemistry approaches. Potentiometric titrations showed that these surfaces acquired less charge from proton-related reactions than oxide minerals. The data from batch-type titrations for PTFE powder did not show an effect of ionic strength, which was also in contrast with results for classical colloids. In agreement with classical colloids, the electrokinetic results for inert surfaces showed the typical salt level dependence. In some cases, the point of zero net proton charge as determined from mass and tentatively from acid–base titration differed from isoelectric points, which has also been previously observed, for example by Chibowski and co-workers for ice electrolyte interfaces. Finally, we found no evidence for surface contaminations of our PTFE particles before and after immersion in aqueous solutions. Only in the presence of NaCl-containing solutions did cryo-XPS detect oxygen from water. We believe that our low isoelectric points for PTFE were not due to impurities. Moreover, the measured buffering at pH 3 could not be explained by sub-micromolar concentrations of contaminants. The most comprehensive explanation for the various sets of data is that hydroxide ion accumulation occurred at the interfaces between inert surfaces and aqueous solutions.

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  • 15.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Jia, Xueen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Palladium nanocrystals supported on photo-transformed C-60 nanorods: effect of crystal morphology and electron mobility on the electrocatalytic activity towards ethanol oxidation2014Ingår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 73, s. 34-40Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the synthesis and decoration of high-aspect-ratio crystalline C-60 nanorods (NRs) by functionalized palladium nanoparticles with an average size of 4.78 +/- 0.66 nm. In their pristine form, C-60 NRs suffer from partial damage in the solution-based decoration process resulting in poor crystallinity. However, by modifying the NR surface via in situ photochemical transformation in the liquid state, we are able to prepare highly stable NRs that retain their crystalline structure during the decoration process. Our method thus opens up for the synthesis of highly crystalline nanocomposite hybrids comprising Pd nanoparticles and C-60 NRs. Bys measuring the electron mobility of different C-60 NRs, we relate both the effect of electron mobility and crystallinity to the final electrocatalytic performance of the synthesized hybrid structures. We show that the photo-transformed C-60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity. These findings give important information in the search for efficient catalyst support.

  • 16.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Solution-Based Phototransformation of C-60 Nanorods: Towards Improved Electronic Devices2013Ingår i: Particle & particle systems characterization, ISSN 0934-0866, E-ISSN 1521-4117, Vol. 30, nr 8, s. 715-720Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A modified liquid-liquid interface precipitation synthesis of C-60 nanorods, effects and opportunities following an in situ photochemical transformation in the liquid state, and an electronic characterization using a field-effect transistor (FET) geometry are reported. The nanorods feature a high aspect ratio of approximate to 10(3) and a notably small average diameter of 172 nm. Interestingly, it is found that a decreased nanorod diameter appears to correlate with distinctly improved electronic properties, and an average electron mobility of 0.30 cm(2) V-1 s(-1), as measured in a FET geometry, is reported for as-grown nanorods, with the peak value being an impressive 1.0 cm(2) V-1 s(-1). A photoexposure using green laser light ( = 532 nm) is demonstrated to result in the formation of a polymer-C-60 shell encapsulating a monomer-C-60 bulk; such photo-transformed nanorods exhibit an electron mobility of 4.7 x 10(-3) cm(2) V-1 s(-1). It is notable that the utilized FET geometry only probes the polymer-C-60 nanorod surface shell, and that the monomer-C-60 bulk is anticipated to exhibit a higher mobility. Importantly, photoexposed nanorods can be conveniently processed as a stabile dispersion in common hydrophobic solvents, and this finding is attributed to the insoluble character of the polymer-C-60 shell.

  • 17.
    Bengtsson, Åsa
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Persson, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sjöberg, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Phase Transformations, Ion-Exchange, Adsorption, and Dissolution Processes in Aquatic Fluorapatite Systems2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 4, s. 2355-2362Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A synthetic fluorapatite was prepared that undergoes a phase transformation generated during a dialysis step. A surface layer with the composition Ca9(HPO4)2(PO4)4F2 is formed, which is suggested to form as one calcium atom is replaced by two protons. A surface complexation model, based upon XPS measurements, potentiometric titration data, batch experiments, and zeta-potential measurements was presented. The CaOH and OPO3H2 sites were assumed to have similar protolytic properties as in a corresponding nonstoichiometric HAP (Ca8.4(HPO4)1.6(PO4)4.4(OH)0.4) system. Besides a determination of the solubility product of Ca9(HPO4)2(PO4)4F2, two additional surface complexation reactions were introduced; one that accounts for a F/OH ion exchange reaction, resulting in the release of quite high fluoride concentrations (∼1 mM) that turned out to be dependent on the surface area of the particles. Furthermore, to explain the lowering of pHiep from around 8 in nonstoichiometric HAP suspensions to about 5.7 in FAP suspensions, a reaction that lowers the surface charge due to the readsorption of fluoride ions to the positively charged Ca sites was introduced: ≡CaOH2+ + F− ⇋ ≡CaF + H2O. The resulting model also agrees with predictions based upon XPS and ATR-FTIR observations claiming the formation of CaF2(s) in the most acidic pH range.

  • 18.
    Bhowmick, Asmit
    et al.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Hussein, Rana
    Department of Biology, Humboldt Universität zu Berlin, Berlin, Germany.
    Bogacz, Isabel
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Simon, Philipp S.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Ibrahim, Mohamed
    Department of Biology, Humboldt Universität zu Berlin, Berlin, Germany; Institute of Molecular Medicine, University of Lübeck, Lübeck, Germany.
    Chatterjee, Ruchira
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Doyle, Margaret D.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Cheah, Mun Hon
    Molecular Biomimetics, Department of Chemistry — Ångström, Uppsala University, Uppsala, Sweden.
    Fransson, Thomas
    Department of Theoretical Chemistry and Biology, KTH Royal Institute of Technology, Stockholm, Sweden.
    Chernev, Petko
    Molecular Biomimetics, Department of Chemistry — Ångström, Uppsala University, Uppsala, Sweden.
    Kim, In-Sik
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Makita, Hiroki
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Dasgupta, Medhanjali
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Kaminsky, Corey J.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Zhang, Miao
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Gätcke, Julia
    Department of Biology, Humboldt Universität zu Berlin, Berlin, Germany.
    Haupt, Stephanie
    Department of Biology, Humboldt Universität zu Berlin, Berlin, Germany.
    Nangca, Isabela I.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Keable, Stephen M.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Aydin, A. Orkun
    Molecular Biomimetics, Department of Chemistry — Ångström, Uppsala University, Uppsala, Sweden.
    Tono, Kensuke
    Japan Synchrotron Radiation Research Institute, Hyogo, Japan; RIKEN SPring-8 Center, Hyogo, Japan.
    Owada, Shigeki
    Japan Synchrotron Radiation Research Institute, Hyogo, Japan; RIKEN SPring-8 Center, Hyogo, Japan.
    Gee, Leland B.
    Linac Coherent Light Source, SLAC National Accelerator Laboratory, CA, Menlo Park, United States.
    Fuller, Franklin D.
    Linac Coherent Light Source, SLAC National Accelerator Laboratory, CA, Menlo Park, United States.
    Batyuk, Alexander
    Linac Coherent Light Source, SLAC National Accelerator Laboratory, CA, Menlo Park, United States.
    Alonso-Mori, Roberto
    Linac Coherent Light Source, SLAC National Accelerator Laboratory, CA, Menlo Park, United States.
    Holton, James M.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States; Department of Biochemistry and Biophysics, University of California, CA, San Francisco, United States; SSRL, SLAC National Accelerator Laboratory, CA, Menlo Park, United States.
    Paley, Daniel W.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Moriarty, Nigel W.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Mamedov, Fikret
    Molecular Biomimetics, Department of Chemistry — Ångström, Uppsala University, Uppsala, Sweden.
    Adams, Paul D.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States; Department of Bioengineering, University of California, CA, Berkeley, United States.
    Brewster, Aaron S.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Dobbek, Holger
    Department of Biology, Humboldt Universität zu Berlin, Berlin, Germany.
    Sauter, Nicholas K.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Bergmann, Uwe
    Department of Physics, University of Wisconsin–Madison, WI, Madison, United States.
    Zouni, Athina
    Department of Biology, Humboldt Universität zu Berlin, Berlin, Germany.
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Molecular Biomimetics, Department of Chemistry — Ångström, Uppsala University, Uppsala, Sweden.
    Kern, Jan
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Yano, Junko
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Yachandra, Vittal K.
    Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, CA, Berkeley, United States.
    Structural evidence for intermediates during O2 formation in photosystem II2023Ingår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 617, nr 7961, s. 629-636Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In natural photosynthesis, the light-driven splitting of water into electrons, protons and molecular oxygen forms the first step of the solar-to-chemical energy conversion process. The reaction takes place in photosystem II, where the Mn4CaO5 cluster first stores four oxidizing equivalents, the S0 to S4 intermediate states in the Kok cycle, sequentially generated by photochemical charge separations in the reaction center and then catalyzes the O–O bond formation chemistry. Here, we report room temperature snapshots by serial femtosecond X-ray crystallography to provide structural insights into the final reaction step of Kok’s photosynthetic water oxidation cycle, the S3→[S4]→S0 transition where O2 is formed and Kok’s water oxidation clock is reset. Our data reveal a complex sequence of events, which occur over micro- to milliseconds, comprising changes at the Mn4CaO5 cluster, its ligands and water pathways as well as controlled proton release through the hydrogen-bonding network of the Cl1 channel. Importantly, the extra O atom Ox, which was introduced as a bridging ligand between Ca and Mn1 during the S2→S3 transition, disappears or relocates in parallel with Yz reduction starting at approximately 700 μs after the third flash. The onset of O2 evolution, as indicated by the shortening of the Mn1–Mn4 distance, occurs at around 1,200 μs, signifying the presence of a reduced intermediate, possibly a bound peroxide.

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  • 19.
    Bi, Zenghui
    et al.
    School of Electronic Communication Technology, Shenzhen Institute of Information Technology, Shenzhen, China; Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Materials and Energy, Yunnan University, Kunming, China.
    Wang, Yuwen
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Materials and Energy, Yunnan University, Kunming, China.
    Chen, Jianbing
    Research Academy of Non-metallic Mining Industry Development, Materials and Environmental Engineering College, Chizhou University, Chizhou, China.
    Zhang, Xianxi
    School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng, China.
    Zhou, Shuxing
    Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Hubei University of Arts and Science, Xiangyang, China.
    Wang, Xinzhong
    School of Electronic Communication Technology, Shenzhen Institute of Information Technology, Shenzhen, China.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Materials and Energy, Yunnan University, Kunming, China.
    Three dimensional star-like mesoporous nitrogen-doped carbon anchored with highly dispersed Fe and Ce dual-sites for efficient oxygen reduction reaction in Zn-air battery2022Ingår i: Colloid and Interface Science Communications, ISSN 2215-0382, Vol. 49, artikel-id 100634Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Metal‑nitrogen‑carbon materials (M-N-C) have attracted much attention due to their low cost, high abundance, and efficient catalytic performance. Nevertheless, Fe-N-C materials are considered the most promising oxygen reduction reaction (ORR) catalysts for replacing noble metals. Ce is chemically active and has many metal valence states, and empty orbitals that can participate in coordination. On this basis, Fe, Ce-codoped catalyst was constructed in this study. The synergistic effect of the dual metal centers was verified, and a Fe, Ce-codoped nitrogen-doped carbon (FeCeNC) with six equal branch angles was proposed. The half-wave potential for the ORR catalyzed by FeCeNC is 0.855 V. As a rechargeable Zn-air battery cathode catalyst, FeCeNC exhibits excellent electrochemical performances, with an open-circuit voltage of 1.427 V, a maximum power density of 169.2 mW cm−2 and a stable cycling time of 80 h, demonstrating an excellent cycle performance.

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  • 20.
    Biasi, Pierdomenico
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry and Reaction Engineering, Process Chemistry Center (PCC), Department of Chemical Engineering, Åbo Akademi University,Turku/Åbo, Finland.
    Sterchele, Stefano
    Bizzotto, Francesco
    Manzoli, Maela
    Lindholm, Sten
    Ek, Paul
    Bobacka, Johan
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry and Reaction Engineering, Process Chemistry Center (PCC), Department of Chemical Engineering, Åbo Akademi University,Turku/Åbo, Finland.
    Salmi, Tapio
    Application of the Catalyst Wet Pretreatment Method (CWPM) for catalytic direct synthesis of H2O22015Ingår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 246, nr Special Issue, s. 207-215Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work concerns a new technique to post-modify the catalytic material intended for use in H2O2 direct synthesis. The catalyst chosen was a commercially available 1 wt.% Pd/C. The catalyst was modified with the so-called Catalyst Wet Pretreatment Method (CWPM) that is used to post-modify prepared catalysts with aqueous solutions of NaBr, in different concentrations. The performance of pristine and the pretreated materials were then compared in the H2O2 direct synthesis and characterized before and after the catalytic tests in order to understand the role of the different concentrations of bromide in the CWPM procedure. The surface features of the different catalysts were analyzed with CO chemisorption (metal dispersion and mean particle size), Transmission Electron Microscopy (TEM, for Pd morphology and Pd particle size distributions), Inductive Coupled Plasma (ICP, for Pd content) and Ion Chromatography (IC, for bromide content). Various features of the materials prepared with the CWPM were correlated with the catalytic performance. It was found that the bromide has an active role in the reconstruction of metal phase and it does not only act as a poison for the most active catalytic sites as often reported in literature. By using this new protocol, the production H2O2 was almost doubled compared to the non-modified material when no direct promoters were added to the reaction environment.

  • 21.
    Boily, Jean-Francois
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Fu, Li
    Tuladhar, Aashish
    Lu, Zhou
    Legg, Benjamin A.
    Wang, Zheming M.
    Wang, Hongfei
    Hydrogen bonding and molecular orientations across thin water films on sapphire2019Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 555, s. 810-817Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hypothesis: Water vapor binding to metal oxide surfaces produces thin water films with properties controlled by interactions with surface hydroxo sites. Hydrogen bonding populations vary across films and induce different molecular orientations than at the surface of liquid water. Identifying these differences can open possibilities for tailoring film-mediated catalytic reactions by choice of the supporting metal oxide substrate.

    Experiments: The (0001) face of a single sapphire (α-Al2O3) sample exposed to water vapor and the surface of liquid water were probed by polarization dependent Sum Frequency Generation-Vibration Spectroscopy (SFG-VS). Molecular dynamics (MD) provided insight into the hydrogen bond populations and molecular orientations across films and liquid water.

    Findings: SFG-VS revealed a submonolayer film on sapphire exposed to 43% relative humidity (R.H.), and a multilayer film at 78% R.H. Polarization dependent SFG-VS spectra showed that median tilt angles of free OH bonds on the top of films are at ∼43° from the normal of the (0001) face but at 38° on neat liquid water. These values align with MD simulations, which also show that up to 36% of all OH bonds on films are free. This offers new means for understanding how interfacial reactions on sapphire-supported water films could contrast with those involving liquid water.

  • 22.
    Bokvist, Marcus
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Membrane mediated aggregation of amyloid-β protein: a potential key event in Alzheimer's disease2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The pathogenesis of Alzheimer’s disease (AD), the most common senile dementia, is a complex process. A crucial event in AD is the aggregation of amyloid-β protein (Aβ), a cleavage product from the Amyloid Precursor Protein (APP). Aβ40, a common component in amyloid plaques found in patients, aggregates in vitro at concentrations, much higher than the one found in vivo. But in the presence of charged lipid membranes, aggregations occurs at much lower concentration in vitro compared to the membrane-free case. This can be understood due to the ability of Aβ to get electrostatically attracted to target membranes with a pronounced surface potential. This electrostatically driven process accumulates peptide at the membrane surface at concentrations high enough for aggregation while the bulk concentration still remains below threshold. Here, we elucidated the molecular nature of this Aβ-membrane process and its consequences for Aβ misfolding by Circular Dichroism Spectroscopy, Differential Scanning Calorimetry and Nuclear Magnetic Resonance Spectroscopy. First, we revealed by NMR that Aβ40 peptide does indeed interact electrostatically with membranes of negative and positive surface potential. Surprisingly, it even binds to nominal neutral membranes if these contain lipids of opposite charge. Combined NMR and CD studies also revealed that the peptide might be shielded from aggregation when incorporated into the membrane. Moreover, CD studies of Aβ40 added to charged membranes showed that both positively and negatively membranes induce aggregation albeit at different kinetics and finally that macromolecular crowding can both speed up and slow down aggregation of Aβ.

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  • 23. Boniolo, Manuel
    et al.
    Shylin, Sergii, I
    Chernev, Petko
    Cheah, Mun Hon
    Heizmann, Philipp A.
    Huang, Ping
    Salhi, Nessima
    Hossain, Kamal
    Thapper, Anders
    Lundberg, Marcus
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemistry – Ångström Laboratory, Uppsala University, Sweden.
    Spin transition in a ferrous chloride complex supported by a pentapyridine ligand2020Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 56, nr 18, s. 2703-2706Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ferrous chloride complexes [FeIILxCl] commonly attain a high-spin state independently of the supporting ligand(s) and temperature. Herein, we present the first report of a complete spin crossover with T1/2 = 80 K in [FeII(Py5OH)Cl]+ (Py5OH = pyridine-2,6-diylbis[di(pyridin-2-yl)methanol]). Both spin forms of the complex are analyzed by X-ray spectroscopy and DFT calculations.

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  • 24.
    Bui, Thai Q.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Khokarale, Santosh G.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shukla, Shashi Kant
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry & Reaction Engineering, Department of Chemical Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, FI-20500 Åbo-Turku, Finland.
    Switchable Aqueous Pentaethylenehexamine System for CO2 Capture: an Alternative Technology with Industrial Potential2018Ingår i: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 6, nr 8, s. 10395-10407Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Herein we report the application of polyamine pentaethylenehexamine (PEHA, 3,6,9,12-tetraazatetradecane-1,14-diamine) in CO2 absorption with both neat PEHA and aqueous solutions thereof. The absorption of molecular CO2 in pure PEHA and in PEHA-water systems resulted in the formation of two chemical species, namely, PEHA carbamate and bicarbonate. It was observed that, upon formation of these species, both the CO2 absorption capacity and CO2 absorption rate were controlled by the amount of water in the system. During the CO2 absorption, the neat PEHA and 92 wt % PEHA were capable of forming carbamate species only while other aqueous analogues with higher dilution allowed for the formation of both carbamate and bicarbonate species upon exceeding 8 wt % water in the mixture. The CO2 uptake steadily increased with an increase in the water concentration in the solvent mixture and reached the maximum value of 0.25 g of CO2/(g of solvent) in the case of 56 wt % PEHA in water. However, in the case of more dilute systems (i.e., <56 wt % PEHA in water), the trend reversed and the CO2 loading decreased linearly to 0.05 g of CO2/(g of solvent) for 11 wt % PEHA in water. Meanwhile, it usually took shorter time to achieve the full CO2 absorption capacity (equilibrium) with increasing water content in all cases. The C-13 NMR analysis was used to quantify the relative amount of PEHA carbamate and bicarbonate, respectively, in reaction mixtures. The Kamle-Taft parameters (alpha, beta, and pi*) of aqueous solutions for different concentrations of PEHA were also studied taking advantage of various solvatochromic dyes and correlated with the CO2 absorption capacity. The thermally induced switchable nature of CO2-saturated neat and aqueous PEHA solutions for transformation of ionic PEHA carbamate and bicarbonate moieties to molecular PEHA is also represented. A comparison between aqueous PEHA and aqueous monoethanolamine (industrial solvent) for CO2 capture is reported. Hence, most importantly, a switchable PEHA system is demonstrated for reversible CO2 absorption processes.

  • 25. Cano, A.
    et al.
    Lartundo-Rojas, L.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Reguera, E.
    Contribution to the coordination chemistry of transition metal nitroprussides: a cryo-XPS study2019Ingår i: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 43, nr 12, s. 4835-4848Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The series of coordination polymers under investigation was formed by the assembly of a pentacyanonitrosylferrate(ii) anionic block, [Fe(CN)(5)NO](2-), through monovalent and divalent transition metal ions, e.g. Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Ag+. For divalent ions, the resulting materials have a 3D porous framework with attractive features for applications in gas storage and separation, as electroactive solids, light-driven molecular magnets, and so on; in this study, we report the results obtained for a series of coordination polymers using the cryogenic X-ray photoelectron spectroscopy (cryo-XPS) data; comprehensive details regarding their coordination chemistries were obtained from the acquired spectra in addition to their comparison with the structural and spectroscopic information obtained from other techniques. The results discussed herein are original and contribute towards the understanding of the electronic structures and related properties for this family of coordination polymers. This series of solids was found to be highly susceptible to strong damage induced by X-ray beams throughout the conventional XPS experiment; therefore, the analysis was conducted under cryogenic conditions.

  • 26. Chatterjee, Ruchira
    et al.
    Lassalle, Louise
    Gul, Sheraz
    Fuller, Franklin D.
    Young, Iris D.
    Ibrahim, Mohamed
    de Lichtenberg, Casper
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemistry – Ångström, Molecular Biomimetics, Uppsala University, Uppsala 75237, Sweden.
    Cheah, Mun Hon
    Zouni, Athina
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemistry – Ångström, Molecular Biomimetics, Uppsala University, Uppsala 75237, Sweden.
    Yachandra, Vittal K.
    Kern, Jan
    Yano, Junko
    Structural isomers of the S-2 state in photosystem II: do they exist at room temperature and are they important for function?2019Ingår i: Physiologia Plantarum, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 166, nr 1, s. 60-72Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In nature, an oxo‐bridged Mn4CaO5 cluster embedded in photosystem II (PSII), a membrane‐bound multi‐subunit pigment protein complex, catalyzes the water oxidation reaction that is driven by light‐induced charge separations in the reaction center of PSII. The Mn4CaO5 cluster accumulates four oxidizing equivalents to enable the four‐electron four‐proton catalysis of two water molecules to one dioxygen molecule and cycles through five intermediate S‐states, S0 – S4 in the Kok cycle. One important question related to the catalytic mechanism of the oxygen‐evolving complex (OEC) that remains is, whether structural isomers are present in some of the intermediate S‐states and if such equilibria are essential for the mechanism of the O‐O bond formation. Here we compare results from electron paramagnetic resonance (EPR) and X‐ray absorption spectroscopy (XAS) obtained at cryogenic temperatures for the S2state of PSII with structural data collected of the S1, S2 and S3 states by serial crystallography at neutral pH (∼6.5) using an X‐ray free electron laser at room temperature. While the cryogenic data show the presence of at least two structural forms of the S2 state, the room temperature crystallography data can be well‐described by just one S2 structure. We discuss the deviating results and outline experimental strategies for clarifying this mechanistically important question.

  • 27. Cheah, Mun Hon
    et al.
    Zhang, Miao
    Shevela, Dmitriy
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mamedov, Fikret
    Zouni, Athina
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Molecular Biomimetics, Department of Chemistry–Ångström Laboratory, Uppsala University, 75120 Uppsala, Sweden.
    Assessment of the manganese cluster’s oxidation state via photoactivation of photosystem II microcrystals2020Ingår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 117, nr 1, s. 141-145Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knowledge of the manganese oxidation states of the oxygen-evolving Mn4CaO5 cluster in photosystem II (PSII) is crucial toward understanding the mechanism of biological water oxidation. There is a 4 decade long debate on this topic that historically originates from the observation of a multiline electron paramagnetic resonance (EPR) signal with effective total spin of S = 1/2 in the singly oxidized S2 state of this cluster. This signal implies an overall oxidation state of either Mn(III)3Mn(IV) or Mn(III)Mn(IV)3 for the S2 state. These 2 competing assignments are commonly known as “low oxidation (LO)” and “high oxidation (HO)” models of the Mn4CaO5 cluster. Recent advanced EPR and Mn K-edge X-ray spectroscopy studies converge upon the HO model. However, doubts about these assignments have been voiced, fueled especially by studies counting the number of flash-driven electron removals required for the assembly of an active Mn4CaO5 cluster starting from Mn(II) and Mn-free PSII. This process, known as photoactivation, appeared to support the LO model since the first oxygen is reported to evolve already after 7 flashes. In this study, we improved the quantum yield and sensitivity of the photoactivation experiment by employing PSII microcrystals that retained all protein subunits after complete manganese removal and by oxygen detection via a custom built thin-layer cell connected to a membrane inlet mass spectrometer. We demonstrate that 9 flashes by a nanosecond laser are required for the production of the first oxygen, which proves that the HO model provides the correct description of the Mn4CaO5 cluster’s oxidation states.

  • 28. Chen, Xi
    et al.
    Venkatachalapathy, Muthukumaran
    Dehmelt, Leif
    Wu, Yao-Wen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Multidirectional Activity Control of Cellular Processes by a Versatile Chemo-optogenetic Approach2018Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 57, nr 37, s. 11993-11997Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spatiotemporal dynamics of proteins or organelles plays a vital role in controlling diverse cellular processes. However, acute control of activity at distinct locations within a cell is challenging. A versatile multidirectional activity control (MAC) approach is presented, which employs a photoactivatable system that may be dimerized upon chemical inducement. The system comprises second-generation SLF*-TMP (S*T) and photocaged NvocTMP-Cl dimerizers; where, SLF*-TMP features a synthetic ligand of the FKBP(F36V) binding protein, Nvoc is a caging group, and TMP is the antibiotic trimethoprim. Two MAC strategies are demonstrated to spatiotemporally control cellular signaling and intracellular cargo transport. The novel platform enables tunable, reversible, and rapid control of activity at multiple compartments in living cells.

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  • 29. Chumakova, Natalia A.
    et al.
    Rebrikova, Anastasya T.
    Talyzin, Aleksandr V.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Paramonov, Nikita A.
    Vorobiev, Andrey Kh
    Korobov, Mikhail, V
    Properties of Graphite Oxide Powders and Membranes as Revealed by Electron Paramagnetic Resonance Spectroscopy2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 39, s. 22750-22759Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spin probe technique was used to study graphite oxide (GO) powders swelled in polar liquids (CH3CN, CH3OH, and H2O) and liquid-free GO membranes (GOM). The nitroxide radicals TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl) and TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) readily penetrated into the interplane space of GO from the solution. Electron paramagnetic resonance (EPR) spectra of these radical probes were sensitive to molecular mobility and orientation ordering within the internal space of GO. The radicals embedded in swelled GO were in two states with different rotational mobilities. The small fraction of radicals located in the interplane space of GO and detected in the broad range of temperatures was in the state of fast rotation, similar to the same radicals dissolved in bulk liquids, thus providing experimental evidence of formation of a liquid-like media within the interplane space of GO. Such mobile media may be responsible for the unusual permeation properties of GOM, which is reported in the literature. Second, less-mobile fraction of radicals was found to be immobilized at the internal surface of GO and was sensitive to phase transformations in the swelled GO structures. The transformations were detected as anomalies at temperature dependences of rotational mobility of radicals. The detected dependence of EPR spectra of probe radicals on orientation of GOM, relative to the direction of magnetic field in the EPR spectrometer, was used for quantitative characterization of orientation alignment of GO planes within the membranes. Such an approach may serve as an elegant method to estimate the relative quality of membranes and other GO-layered structures.

  • 30. Cui, Wen
    et al.
    Yao, Mingguang
    Yao, Zhen
    Ma, Fengxian
    Li, Quanjun
    Liu, Ran
    Liu, Bo
    Zou, Bo
    Cui, Tian
    Liu, Bingbing
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Reversible pressure-induced polymerization of Fe(C5H5)(2) doped C-702013Ingår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 62, s. 447-454Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High pressure Raman, IR and X-ray diffraction (XRD) studies have been carried out on C-70(Fe(C5H5)(2))(2) (hereafter, "C-70(Fc)(2)") sheets. Theoretical calculation is further used to analyze the Electron Localization Function (ELF) and charge transfer in the crystal and thus to understand the transformation of C-70(Fc)(2) under pressure. Our results show that even at room temperature dimeric phase and one dimensional (1D) polymer phase of C-70 molecules can be formed at about 3 and 8 GPa, respectively. The polymerization is found to be reversible Upon decompression and the reversibility is related to the pressure-tuned charge transfer, as well as the overridden steric repulsion of counter ions. According to the layered structure of the intercalated ferrocene molecules formed in the crystal, we suggest that ferrocene acts as not only a spacer to restrict the polymerization of C-70 molecules within a layer, but also as charge reservoir to tune the polymerization process. This supplies a possible way for us to design the polymerization of fullerenes at suitable conditions.

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  • 31. da Hora, G. C. A.
    et al.
    Archilha, N. L.
    Lopes, J. L. S.
    Mueller, D. M.
    Coutinho, K.
    Itri, R.
    Soares, T. A.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Departamento de Quı´mica Fundamental, Universidade Federal de Pernambuco, 50740-560 Cidade Universita´ria, Recife, Brazil.
    Membrane negative curvature induced by a hybrid peptide from pediocin PA-1 and plantaricin 149 as revealed by atomistic molecular dynamics simulations2016Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 12, nr 43, s. 8884-8898Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Antimicrobial peptides (AMPs) are cationic peptides that kill bacteria with a broad spectrum of action, low toxicity to mammalian cells and exceptionally low rates of bacterial resistance. These features have led to considerable efforts in developing AMPs as an alternative antibacterial therapy. In vitro studies have shown that AMPs interfere with membrane bilayer integrity via several possible mechanisms, which are not entirely understood. We have performed the synthesis, membrane lysis measurements, and biophysical characterization of a novel hybrid peptide. These measurements show that PA-Pln149 does not form nanopores, but instead promotes membrane rupture. It causes fast rupture of the bacterial model membrane (POPG-rich) at concentrations 100-fold lower than that required for the disruption of mammalian model membranes (POPC-rich). Atomistic molecular dynamics (MD) simulations were performed for single and multiple copies of PA-Pln149 in the presence of mixed and pure POPC/POPG bilayers to investigate the concentration-dependent membrane disruption by the hybrid peptide. These simulations reproduced the experimental trend and provided a potential mechanism of action for PA-Pln149. It shows that the PA-Pln149 does not form nanopores, but instead promotes membrane destabilization through peptide aggregation and induction of membrane negative curvature with the collapse of the lamellar arrangement. The sequence of events depicted for PA-Pln149 may offer insights into the mechanism of action of AMPs previously shown to induce negative deformation of membrane curvature and often associated with peptide translocation via non-bilayer intermediate structures.

  • 32.
    D'Amario, Luca
    et al.
    Department of Chemistry, Ångström Laboratory, Uppsala University, Uppsala, Sweden; Department of Physics, Freie Universität Berlin, Berlin, Germany.
    Stella, Maria Bruna
    Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy.
    Edvinsson, Tomas
    Department of Materials Science and Engineering, Uppsala University, Uppsala, Sweden.
    Persico, Maurizio
    Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy.
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemistry, Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Dau, Holger
    Department of Physics, Freie Universität Berlin, Berlin, Germany.
    Towards time resolved characterization of electrochemical reactions: electrochemically-induced Raman spectroscopy2022Ingår i: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 13, nr 36, s. 10734-10742Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Structural characterization of transient electrochemical species in the sub-millisecond time scale is the all-time wish of any electrochemist. Presently, common time resolution of structural spectro-electrochemical methods is about 0.1 seconds. Herein, a transient spectro-electrochemical Raman setup of easy implementation is described which allows sub-ms time resolution. The technique studies electrochemical processes by initiating the reaction with an electric potential (or current) pulse and analyses the product with a synchronized laser pulse of the modified Raman spectrometer. The approach was validated by studying a known redox driven isomerization of a Ru-based molecular switch grafted, as monolayer, on a SERS active Au microelectrode. Density-functional-theory calculations confirmed the spectral assignments to sub-ms transient species. This study paves the way to a new generation of time-resolved spectro-electrochemical techniques which will be of fundamental help in the development of next generation electrolizers, fuel cells and batteries.

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  • 33. Davidovich, P. B.
    et al.
    Fischer, A. I.
    Korchagin, D. V.
    Panchuk, V. V.
    Shchukarev, Andrey V.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Garabadzhiu, A. V.
    Belyaev, A. N.
    Synthesis, structure, biochemical, and docking studies of a new dinitrosyl iron complex [Fe-2(mu-SC4H3SCH2)(2)(NO)(4)]2015Ingår i: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1092, s. 137-142Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new dinitrosyl iron complex of binuclear structure [Fe-2(mu-S-2-methylthiophene)(2)(NO)(4)] was first synthesized and structurally characterized by XRD and theoretical methods. Using caspase-3 as an example it was shown that [Fe-2(mu-S-2-methylthiophene)(2)(NO)(4)] and its analog [Fe-2(mu-S-2-methylfurane)(2)(NO)(4)] can inhibit the action of active site cysteine proteins; the difference in inhibitory activity was explained by molecular docking studies. Biochemical and in silico studies give grounds that the biological activity of dinitrosyl iron complexes is a mu-SR bridging ligand structure function. Thus the rational design strategy of [Fe-2(mu-SR)(2)(NO)(4)] complexes can be applied to make NO prodrugs with high affinity to therapeutically significant targets involved in cancer and inflammation.

  • 34.
    de Lichtenberg, Casper
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Time-resolved Structural and Mechanistic Studies of Water Oxidation in Photosystem II: water here, water there, water everywhere2020Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Oxygenic photosynthesis is undisputedly one of the most important chemical processes for human life on earth as it not only fills the atmosphere with the oxygen that we need to breathe, but also sustains the accumulation of biomass, which is not only used as nourishment but is also present in almost every aspect of our lives as building material, textiles in clothes and furniture, or even as living decorations to name a few.

    The photosynthetic water-splitting mechanism is catalyzed by a water:plastoquinone oxido-reductase by the name of photosystem II (PSII), which is embedded in the thylakoid membranes of plants, algae and cyanobacteria. As it is excited by light, charge separation occurs in the reaction center of the protein and an electron is extracted by oxidation of Mn4Ca-cluster, that constitutes the active site for the water splitting reaction in PSII. When the Mn4Ca-cluster has been oxidized 4 times, it forms an oxygen-oxygen bond between two water derived ligands bound to the Mn4Ca-cluster and returns to the lowest oxidation state of the catalytic cycle. Understanding what ligands of the cluster that are used in the water splitting reaction is the key to unlocking the underlying chemical mechanism.

    In this thesis I describe investigations, with room temperature X-ray diffraction (XRD) and X-ray emission spectroscopy (XES) on PSII microcrystals, of how the active site looks in all the stable intermediate oxidation states. Furthermore I describe how we uncovered the sequence of events that lead to insertion of an additional water ligand in the S2-S3 state transition of the catalytic cycle.

    Furthermore, through time-resolved membrane-inlet mass spectrometry (TR-MIMS) measurements of the isotopic equilibration of the substrate waters with the bulk in conditions that induce different electron magnetic resonance (EPR) spectroscopic signatures, I present evidence that the exchange of the slowly exchanging substrate water Ws is controlled by a dynamic equilibrium between conformations in the S2-state that give rise to either the low-spin multiline (LS-ML) signal or the high-spin (HS) signal. Based on the crystal structures and litterature suggestions for the conformation of the HS state different scenarios were presented for the assignment of Ws and how it exchanges. This analysis is discussed in the context of all semi-stable intermediate oxidation states in the Kok cycle.

    To further the understanding of this equilibrium, I also studied a selection of mutants positioned at strategic places in the vicinity of the different proposed substrates and at points that were suggested to be critical for substrate entry. With the combination of TR-MIMS and EPR, I reached the conclusion that by mutating valine 185 to asparagine, the water bound A-type conformation was stabilized, meanwhile in the mutant where aspartate 61 was mutated to alanine I observed that the barrier of the equilibrium between the exchanging conformations was so high that the interchange between them was arrested at room temperature. Additionally the retardation of the substrate exchange rates in the S3-states fit best with D61 being in the vicinity of the fast exchanging water. With this information we found the data best explained in a scenario where the water insertion of the S2-S3 transition was determining the if O-O bond formation occurred between the waters that were W2 and W3 or W2 and O5 in the S2 state. In addition, by mutation of glutamate 189 to glutamine that this residue is not important for the exchange of substrate waters in the S2 or the S3 states.

    Finally I use a combination of substrate labelling with TR-MIMS and time resolved labelling of the waters that ligate the Mn4Ca-cluster to show that the briding oxygen O5  is exchanging with a near identical rate to Ws, further supporting the assignment that Ws=O5.

    In conclusion, O-O bond formation most likely occurs between W2 (Wf) and O5 (Ws) via an oxo-oxyl radical coupling mechanism. The newly inserted water thus represents the slow exchanging water of the following S-state cycle.

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  • 35.
    de Lichtenberg, Casper
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Molecular Biomimetics, Department of Chemistry – Ångström, Uppsala University, Uppsala, Sweden.
    Substrate water exchange in the S2 state of photosystem II is dependent on the conformation of the Mn4Ca cluster2020Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, nr 23, s. 12894-12908Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In photosynthesis, dioxygen formation from water is catalyzed by the oxygen evolving complex (OEC) in Photosystem II (PSII) that harbours the Mn4Ca cluster. During catalysis, the OEC cycles through five redox states, S0 to S4. In the Sstate, the Mn4Ca cluster can exist in two conformations, which are signified by the low-spin (LS) g = 2 EPR multiline signal and the high-spin (HS) g = 4.1 EPR signal. Here, we employed time-resolved membrane inlet mass spectrometry to measure the kinetics of H218O/H216O exchange between bulk water and the two substrate waters bound at the Mn4Ca cluster in the SLS2, SHS2, and the S3 states in both Ca-PSII and Sr-PSII core complexes from T. elongatus. We found that the slowly exchanging substrate water exchanges 10 times faster in the SHS2 than in the SLS2 state, and that the SLS2 → SHS2 conversion has at physiological temperature an activation barrier of 17 ± 1 kcal mol−1. Of the presently suggested SHS2 models, our findings are best in agreement with a water exchange pathway involving a SHS2state that has an open cubane structure with a hydroxide bound between Ca and Mn1. We also show that water exchange in the S3 state is governed by a different equilibrium than in S2, and that the exchange of the fast substrate water in the Sstate is unaffected by Ca/Sr substitution. These findings support that (i) O5 is the slowly exchanging substrate water, with W2 being the only other option, and (ii) either W2 or W3 is the fast exchanging substrate. The three remaining possibilities for O–O bond formation in PSII are discussed.

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  • 36.
    Deiana, Marco
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Chand, Karam
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Chorell, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sabouri, Nasim
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Parallel G-quadruplex DNA structures from nuclear and mitochondrial genomes trigger emission enhancement in a nonfluorescent nano-aggregated fluorine-boron-based dye2023Ingår i: The Journal of Physical Chemistry Letters, E-ISSN 1948-7185, Vol. 14, nr 7, s. 1862-1869Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molecular self-assembly is a powerful tool for the development of functional nanostructures with adaptive optical properties. However, in aqueous solution, the hydrophobic effects in the monomeric units often afford supramolecular architectures with typical side-by-side π-stacking arrangement with compromised emissive properties. Here, we report on the role of parallel DNA guanine quadruplexes (G4s) as supramolecular disaggregating-capture systems capable of coordinating a zwitterionic fluorine-boron-based dye and promoting activation of its fluorescence signal. The dye's high binding affinity for parallel G4s compared to nonparallel topologies leads to a selective disassembly of the dye's supramolecular state upon contact with parallel G4s. This results in a strong and selective disaggregation-induced emission that signals the presence of parallel G4s observable by the naked eye and inside cells. The molecular recognition strategy reported here will be useful for a multitude of affinity-based applications with potential in sensing and imaging systems.

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  • 37.
    Deiana, Marco
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Chand, Karam
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Jamroskovic, Jan
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Das, Rabindra Nath
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Obi, Ikenna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Chorell, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sabouri, Nasim
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    A Site-Specific Self-Assembled Light-up Rotor Probe for Selective Recognition and Stabilization of c-MYC G-Quadruplex DNA2020Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 12, nr 24, s. 12950-12957Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Direct and unambiguous evidence of the formation of G-quadruplexes (G4s) in human cells have shown their implication in several key biological events and has emphasized their role as important targets for small-molecule cancer therapeutics. Here, we report on the first example of a self-assembled multitasking molecular-rotor G4-binder able to discriminate between an extensive panel of G4 and non-G4 structures and to selectively light-up (up to 105-fold), bind (nanomolar range), and stabilize the c-MYC promoter G4 DNA. In particular, association with the c-MYC G4 triggers the disassembly of its supramolecular state (disaggregation-induced emission, DIE) and induces geometrical restrictions (motion-induced change in emission, MICE) leading to a significant enhancement of its emission yield. Moreover, this optical reporter is able to selectively stabilize the c-MYC G4 and inhibit DNA synthesis. Finally, by using confocal laser-scanning microscopy (CLSM) we show the ability of this compound to localize primarily in the subnuclear G4-rich compartments of cancer cells. This work provides a benchmark for the future design and development of a new generation of smart sequence-selective supramolecular G4-binders that combine outstanding sensing and stability properties, to be utilized in anti-cancer therapy.

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  • 38.
    Demir, Ayhan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    NMR-the basic principles and its use in studies of water/ethanol/mixture2012Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
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  • 39. Domashevskaya, EP
    et al.
    Ryabtsev, SV
    Turishchev, S Yu
    Kashkarov, VM
    Yurakov, Yu A
    Chuvenkova, OA
    Shchukarev, Andrey V
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    XPS and XANES studies of SnOx nanolayers2008Ingår i: Journal of Structural Chemistry, ISSN 0022-4766, E-ISSN 1573-8779, Vol. 49, nr Suppl 1, s. 80-91Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the results of our XPS (X-ray photoelectron spectroscopy) and XANES (X-ray absorption near edge structure) Studies of tin oxide nanolayers obtained by magnetron spraying of the metal and its further oxidation in air at different temperatures. It was shown that at 240 degrees C (annealing temperature), tin monoxide was dominant in the surface layer of the samples. When the temperature was increased to 450 degrees C, the phase composition corresponded to tin dioxide. Increased sorption ability was found for the samples oxidized at 450 degrees C. The band structure model of SnOx nanolayers obtained by superposition of the XANES and XPS data revealed cross transitions with energy similar to 3.7 eV in the presence of the SnO and SnO, phases. Surface doping of nanolayers with palladium gave the Pd, PdO, and PdO2 components, among which PdO was most intense. Alternate treatments with O-2 and H-2 gases led to the disappearance of palladium dioxide and the reduction of PdO to the Pd metal. After the volume doping of nanoplayers with palladium, the surface layer contained PdO and PdO2; the latter was represented by two types of particles with different sizes.

  • 40. Drager, Luciano F.
    et al.
    Yao, Qiaoling
    Hernandez, Karen L.
    Shin, Mi-Kyung
    Bevans-Fonti, Shannon
    Gay, Jason
    Sussan, Thomas E.
    Jun, Jonathan C.
    Myers, Allen C.
    Olivecrona, Gunilla
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap, Fysiologisk kemi.
    Schwartz, Alan R.
    Halberg, Nils
    Scherer, Philipp E.
    Semenza, Gregg L.
    Powell, David R.
    Polotsky, Vsevolod Y.
    Chronic Intermittent Hypoxia Induces Atherosclerosis via Activation of Adipose Angiopoietin-like 42013Ingår i: American Journal of Respiratory and Critical Care Medicine, ISSN 1073-449X, E-ISSN 1535-4970, Vol. 188, nr 2, s. 240-248Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rationale: Obstructive sleep apnea is a risk factor for dyslipidemia and atherosclerosis, which have been attributed to chronic intermittent hypoxia (CIH). Intermittent hypoxia inhibits a key enzyme of lipoprotein clearance, lipoprotein lipase, and up-regulates a lipoprotein lipase inhibitor, angiopoietin-like 4 (Angptl4), in adipose tissue. The effects and mechanisms of Angptl4 up-regulation in sleep apnea are unknown. Objectives: To examine whether CIH induces dyslipidemia and atherosclerosis by increasing adipose Angptl4 via hypoxia-inducible factor-1 (HIF-1). Methods: ApoE(-/-) mice were exposed to intermittent hypoxia or air for 4 weeks while being treated with Angptl4-neutralizing antibody or vehicle. Measurements and Main Results: In vehicle-treated mice, hypoxia increased adipose Angptl4 levels, inhibited adipose lipoprotein lipase, increased fasting levels of plasma triglycerides and very low density lipoprotein cholesterol, and increased the size of atherosclerotic plaques. The effects of CIH were abolished by the antibody. Hypoxia-induced increases in plasma fasting triglycerides and adipose Angptl4 were not observed in mice with germline heterozygosity for a HIF-1 alpha knockout allele. Transgenic overexpression of HIF-1 alpha in adipose tissue led to dyslipidemia and increased levels of adipose Angptl4. In cultured adipocytes, constitutive expression of HIF-1 alpha increased Angptl4 levels, which was abolished by siRNA. Finally, in obese patients undergoing bariatric surgery, the severity of nocturnal hypoxemia predicted Angptl4 levels in subcutaneous adipose tissue. Conclusions: HIF-1-mediated increase in adipose Angptl4 and the ensuing lipoprotein lipase in activation may contribute to atherosclerosis in patients with sleep apnea.

  • 41.
    Driver, Gordon W.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Huang, Yang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Laaksonen, Aatto
    Sparrman, Tobias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wang, Yonglei
    Westlund, Per-Olof
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Correlated/non-correlated ion dynamics of charge-neutral ion couples: the origin of ionicity in ionic liquids2017Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, nr 7, s. 4975-4988Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Proton/Fluoride spin-lattice ($T_1$) nuclear magnetic relaxation dispersion (NMRD) measurements of 1-butyl-3-methyl-$1H$-imidazolium hexa-fluorophosphate, [$C_4mim][PF_6]$, have been carried out using high field spectrometers and fast-field-cycling instrument at proton Larmor frequencies ranging from 10kHz to 40 MHz, at different temperatures. The NMRD profiles are interpreted by means of a simple relaxation model based on the inter- and intra-ionic dipole-dipole relaxation mechanism. Using an atomic molecular-ion dynamic simulation at 323 K the relevant spin dipole-dipole(DD) correlation functions are calculated. The results indicate the NMRD profiles can be rationalized using intra- and inter-ionic spin DD interactions, however, both are mainly modulated by ionic reorientation because of temporary correlations with cations, where modulation by translational diffusion plays a minor role. Reorientational dynamics of charge-neutral ion couples (i.e. $[C_4mim]^{...}[PF_6]$) and $[C_4mim]^{+}$ ions are in the nano-second (ns) time range whereas the reorientation of $[PF_6]{^-}$ is characterized by a reorientational correlation time in the pico-second (ps) regime. Based on the NMRD profiles we conclude the main relaxation mechanism for $[PF_6]{^-}$ is, due to fast internal reorientational motion, a partially averaged F-F intra and a F-H inter-ionic DD coupling as the anion resides in close proximity to its temporary oppositely charged cation partner. The F-$T_1$- NMRD data display a ns dispersions which is interpreted as being due to correlated reorientational modulations resultant from H-containing charge-neutral ion couple $[C_4mim]^{...}[PF_6]$. The analysis of ionicity is based on the free anion fraction, $f$ and it increase with temperature with $f$ $\rightarrow$ 1 at the highest temperatures investigated. The fraction is obtained from the H-F NMRD profiles as correlated-non-correlated dynamics of the ions. The analysis of $T_1$ relaxation rates of C, H, F and P at high fields cannot generally give the fraction of ion but are consistent with the interpretation based on the NMRD profiles with relaxation contributions due to DD-intra and -inter, CSA-intra (and -inter for C), including spin rotation for P. The investigation has led to a description of the mechanics governing ion transport in the title ionic liquid via identification of transient correlated/non-correlated ion dynamics.

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  • 42. Du, Mingrun
    et al.
    Dong, Jiajun
    Zhang, Ying
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Andersson, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Liu, Bingbing
    Wang, Mingchao
    Li, Zepeng
    Wei, Tong
    Zhou, Qingjun
    Yang, Xiong
    High pressure and high temperature induced polymerization of C60 solvates: The effect of intercalated aromatic solvents2021Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 125, nr 31, s. 17155-17163Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The polymerization of three typical aromatic solvent-doped fullerene materials with similar hexagonal closest packed (hcp) structures (mesitylene/C60, m-dichlorobenzene/C60 and m-xylene/C60 solvates) is studied under high pressure and high temperature (HPHT, 1.5 GPa, 573 K and 2 GPa, 700 K, respectively). Raman and photoluminescence spectroscopies reveal that the intercalated aromatic solvents play a crucial role in tailoring the extent of polymerization of C60 molecules. In the solvates, the solvents confine formation of covalent bonds between C60 molecules to the 001 direction and the (001) plane of the hcp lattices, leading to the formation of mixed polymeric phases of monomers, dimers, one-dimensional (1D) chainlike oligomers, and two-dimensional (2D) tetragonal phase polymers under suitable HPHT conditions. The type and number of substituent groups of the aromatic solvents are found to have significant influence, determining the amounts and types of polymeric phases formed. Our studies enrich the understanding of the formation mechanisms for controllably fabricating polymeric fullerenes and facilitate targeted design and synthesis of unique fullerene-based carbon materials.

  • 43. Du, Mingrun
    et al.
    Zhou, Miao
    Yao, Mingguang
    Ge, Peng
    Chen, Shuanglong
    Yang, Xigui
    Liu, Ran
    Liu, Bo
    Cui, Tian
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. State Key Laboratory of Superhard Materials, Jilin University, Changchun, PR China.
    Liu, Bingbing
    High pressure infrared spectroscopy study on C60*CS2 solvates2017Ingår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 669, s. 49-53Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High pressure IR study has been carried out on C-60*CS2 solvates up to 34.8 GPa. It is found that the intercalated CS2 molecules significantly affect the transformations of C-60 molecules under pressure. As a probe, the intercalated CS2 molecules can well detect the orientational ordering transition and deformation of C-60 molecules under pressure. The chemical stability of CS2 molecules under pressure is also dramatically enhanced due to the spacial shielding effet from C-60 molecules around in the solvated crystal. These results provide new insight into the effect of interactions between intercalants and fullerenes on the transformations in fullerene solvates under pressure.

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  • 44. Du, Xinyu
    et al.
    Zhou, Yihui
    Li, Jun
    Wu, Yan
    Zheng, Ziye
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Yin, Ge
    Qiu, Yanling
    Zhao, Jianfu
    Yuan, Guoli
    Evaluating oral and inhalation bioaccessibility of indoor dust-borne short- and median-chain chlorinated paraffins using in vitro Tenax-assisted physiologically based method2021Ingår i: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 402, artikel-id 123449Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Though ingestion and inhalation of dust have been suggested as important exposure routes contributing chlorinated paraffins (CPs) build-up in humans, the bioaccessibility of dust-borne CPs in the organ environment has not been well-studied, which may hinder an accurate estimation of exposure risks. In this study, the ingestion and inhalation bioaccessibility of dust-borne shortand median-chain CPs (SCCPs and MCCPs) was assessed using (colon-extended) physiologically based extraction test with the addition of Tenax. The ingestion bioaccessibility of SCCPs 51.5 %Cl, SCCPs 63 %Cl, MCCPs 42 %Cl, and MCCPs 57 %Cl was in ranges of 21.1-44.0 %, 11.7-45.8 %, 21.9-36.6 %, and 7.9-32.9 %, respectively. Multiple linear regression analysis demonstrated statistically significant associations of ingestion bioaccessibility with carbon chain length and chlorine substitution. The ingestion bioaccessibility of CPs also increased with co-existence of carbohydrate/protein. The inhalation bioaccessibility of SCCPs (16.7-38.7 % in artificial lysosomal fluid and 15.5-34.1 % in modified Gamble solution) was significantly higher than MCCPs (< 5 %), and varied with dust particle size/total organic carbon content. Our study indicates that modest bioaccessible fractions of CPs in dust should be taken into account to refine the estimation of human exposure, and their bioaccessibility may be affected by CP molecular size, nutritional content and dust property.

  • 45. Dyson, P J
    et al.
    Laurenczy, G
    Ohlin, C A
    Vallance, J
    Welton, T
    Determination of hydrogen concentration in ionic liquids and the effect (or lack of) on rates of hydrogenation2003Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, nr 19, s. 2418-2419Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The solubility of hydrogen and the corresponding Henry coefficients for 11 ionic liquids have been determined in situ at 100 atm H(2) pressure and are much lower than expected; attempts to correlate the solubility of hydrogen in the ionic liquids with the rate of reaction for the hydrogenation of benzene to cyclohexane in these solvents have been made.

  • 46.
    Dzwilewski, Andrzej
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Facile fabrication of efficient organic CMOS circuits2010Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, nr 1, s. 135-140Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Organic electronic circuits based on a combination of n- and p-type transistors (so-called CMOS circuits) are attractive, since they promise the realization of a manifold of versatile and low-cost electronic devices. Here, we report a novel photoinduced transformation method, which allows for a particularly straightforward fabrication of highly functional organic CMOS circuits. A solution-deposited single-layer film, comprising a mixture of the n-type semiconductor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and the p-type semiconductor poly-3-hexylthiophene (P3HT) in a 3:1 mass ratio, was utilized as the common active material in an array of transistors. Selected film areas were exposed to laser light, with the result that the irradiated PCBM monomers were photochemically transformed into a low-solubility and high-mobility dimeric state. Thereafter, the entire film was developed via immersion into a developer solution, which selectively removed the nonexposed, and monomeric, PCBM component. The end result was that the transistors in the exposed film areas are n-type, as dimeric PCBM is the majority component in the active material, while the transistors in the nonexposed film areas are p-type, as P3HT is the sole remaining material. We demonstrate the merit of the method by utilizing the resulting combination of n-type and p-type transistors for the realization of CMOS inverters with a high gain of ∼35.

  • 47.
    Ekspong, Joakim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hydrogen Evolution Reaction Activity of Heterogeneous Materials: A Theoretical Model2020Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, nr 38, s. 20911-20921Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, we present a new comprehensive methodology to quantify the catalytic activity of heterogeneous materials for the hydrogen evolution reaction (HER) using ab initio simulations. The model is composed of two parts. First, the equilibrium hydrogen coverage is obtained by an iterative evaluation of the hydrogen adsorption free energies (ΔGH) using density functional theory calculations. Afterward, the ΔGH are used in a microkinetic model to provide detailed characterizations of the entire HER considering all three elementary steps, i.e., the discharge, atom + ion, and combination reactions, without any prior assumptions of rate-determining steps. The microkinetic model takes the equilibrium and potential-dependent characteristics into account, and thus both exchange current densities and Tafel slopes are evaluated. The model is tested on several systems, from polycrystalline metals to heterogeneous molybdenum disulfide (MoS2), and by comparing to experimental data, we verify that our model accurately predicts their experimental exchange current densities and Tafel slopes. Finally, we present an extended volcano plot that correlates the electrical current densities of each elementary reaction step to the coverage-dependent ΔGH.

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  • 48. Emilsson, Gustav
    et al.
    Röder, Evelyn
    Malekian, Bita
    Xiong, Kunli
    Manzi, John
    Tsai, Feng-Ching
    Cho, Nam-Joon
    Bally, Marta
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi. Umeå universitet, Medicinska fakulteten, Wallenberg centrum för molekylär medicin vid Umeå universitet (WCMM).
    Dahlin, Andreas
    Nanoplasmonic Sensor Detects Preferential Binding of IRSp53 to Negative Membrane Curvature2019Ingår i: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 7, artikel-id 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biosensors based on plasmonic nanostructures are widely used in various applications and benefit from numerous operational advantages. One type of application where nanostructured sensors provide unique value in comparison with, for instance, conventional surface plasmon resonance, is investigations of the influence of nanoscale geometry on biomolecular binding events. In this study, we show that plasmonic "nanowells" conformally coated with a continuous lipid bilayer can be used to detect the preferential binding of the insulin receptor tyrosine kinase substrate protein (IRSp53) I-BAR domain to regions of negative surface curvature, i.e., the interior of the nanowells. Two different sensor architectures with and without an additional niobium oxide layer are compared for this purpose. In both cases, curvature preferential binding of IRSp53 (at around 0.025 nm(-1) and higher) can be detected qualitatively. The high refractive index niobium oxide influences the near field distribution and makes the signature for bilayer formation less clear, but the contrast for accumulation at regions of negative curvature is slightly higher. This work shows the first example of analyzing preferential binding of an average-sized and biologically important protein to negative membrane curvature in a label-free manner and in real-time, illustrating a unique application for nanoplasmonic sensors.

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  • 49.
    Essalhi, Mohamed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Khayet, M.
    Department of Structure of Matter, Thermal Physics and Electronics, Faculty of Physics, University Complutense of Madrid, Madrid, Spain; Madrid Institute for Advanced Studies of Water (IMDEA Water Institute), Madrid, Spain.
    Yavuz, A. B.
    Department of Chemistry, Agri Ibrahim Cecen University, Agri, Turkey.
    Rosa, L.R. de la
    Department of Structure of Matter, Thermal Physics and Electronics, Faculty of Physics, University Complutense of Madrid, Madrid, Spain.
    García-Payo, M. C.
    Department of Structure of Matter, Thermal Physics and Electronics, Faculty of Physics, University Complutense of Madrid, Madrid, Spain.
    Tavajohi, Naser
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Development of a Lycopodium powder-based superhydrophobic nanofiber membrane suitable for desalination2023Ingår i: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 323, artikel-id 124405Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A biobased, green, inexpensive additive, Lycopodium particles, which are spores of the “Lycopodium clavatum” plant, were incorporated in the poly(vinylidene fluoride) PVDF electrospun nanofiber membranes (ENMs) for desalination by direct contact membrane distillation (DCMD). Superhydrophobic ENMs were prepared using this additive (PVDF-ENMs-Lyc). Thanks to their morphological structure and their prominent surface superhydrophobicity (anti-wetting) character, the resulting PVDF-ENMs-Lyc exhibited an improved liquid entry pressure (LEP), a high void volume fraction (greater than 87.2%), a good salt rejection factor (greater than 99.93%) and a reasonably high permeate flux (greater than 51.76 kg·m-2·h-1) at 80 °C, which are of great practical importance for water desalination by DCMD. The optimum membrane prepared with 3 wt% Lycopodium in the dope solution demonstrated a stable permeate flux of 52.4 ± 0.6 kg·m-2·h-1 with an electrical conductivity around 4.76 ± 0.46 μS/cm (NaCl rejection factor of 99.998 ± 0.036%) during 25 h DCMD desalination experiment using 35 g/L NaCl aqueous solution (similar to seawater concentration). The presented results pave the way for superhydrophobic nanofibrous membrane engineering suitable for membrane contactors by electrospinning in a single step without surfactants, organic additives, or chemical post-treatments, just by the incorporation of a green additive like Lycopodium powder.

  • 50.
    Essalhi, Mohamed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Structure of Matter, Thermal Physics and Electronics, Faculty of Physics, University Complutense of Madrid, Avda. Madrid, Spain.
    Khayet, Mohamed
    Ismail, Norafiqah
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sundman, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Tavajohi Hassan Kiadeh, Naser
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Improvement of nanostructured electrospun membranes for desalination by membrane distillation technology2021Ingår i: Desalination, ISSN 0011-9164, E-ISSN 1873-4464, Vol. 510, artikel-id 115086Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A systematic study is carried out to determine the optimum electrospinning preparation condition to prepare an adequate electrospun nanofibrous membrane (ENM) for direct contact membrane distillation (DCMD). A structural properties investigation of ENM was carried out because of the significant impact of its architectural structure, nanofiber diameter, inter-fiber space and ENM thickness, on DCMD performance. The morphology, hydrophobicity, mechanical properties, crystallinity and DCMD desalination were investigated. A long-term DCMD experiment (100h) was carried out using 30 g/L NaCl aqueous solution, both in the feed and permeate side of the optimum ENM membrane to evaluate its potential to produce drinkable water in case of lack of distilled water, for instance in a remote area, emergency situation, and/or portable system. In this case, drinkable water could be produced after 28 h with a permeate flux of 57.5 kg/m2.h and a salt rejection factor greater than 99.9%. Another long-term DCMD experiment (65 h) was conducted using 30 g/L NaCl aquesous solution as feed but at a higher temperature and distilled water as permeate to evaluate the desalination stability, wettability and scaling of the optimum ENM. A permeate flux of 58.5 kg/m2.h was obtained with a salt rejection factor greater than 99.9%.

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