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Johansson, Lennart B-Å
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Publications (10 of 62) Show all publications
Mikaelsson, T., Ådén, J., Wittung-Stafshede, P. & Johansson, L.-Å. B. (2014). Macromolecular crowding effects on two homologs of ribosomal protein S16: protein-dependent structural changes and local interactions. Biophysical Journal, 107(2), 401-410.
Open this publication in new window or tab >>Macromolecular crowding effects on two homologs of ribosomal protein S16: protein-dependent structural changes and local interactions
2014 (English)In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 107, no 2, 401-410 p.Article in journal (Refereed) Published
Abstract [en]

Proteins function in cellular environments that are crowded with biomolecules, and in this reduced available space, their biophysical properties may differ from those observed in dilute solutions in vitro. Here, we investigated the effects of a synthetic macromolecular crowding agent, dextran 20, on the folded states of hyperthermophilic (S16T(herme)) and mesophilic (S161homologs of the ribosomal protein S16. As expected for an excluded-volume effect, the resistance of the mesophilic Meso, protein to heat-induced unfolding increased in the presence of dextran 20, and chemical denaturation experiments at different fixed temperatures showed the macromolecular crowding effect to be temperature-independent. Forster resonance energy transfer experiments show that intramolecular distances between an intrinsic Trp residue and BODIPY-labeled S16 Meso depend on the level of the crowding agent. The BODIPY group was attached at three specific positions in S16me, allowing measurements of three intraprotein distances. All S16meso variants exhibited a decrease in the average Trp-BODIPY distance at up to 100 mg/mL dextran 20, whereas the changes in distance became anisotropic (one distance increased, two distances decreased) at higher dextran concentrations. In contrast, the two 516-rhermo mutants did not show any changes in Trp-BODIPY distances upon increase of dextran 20 concentrations. It should be noted that the fluorescence quantum yields and lifetimes of BODIPY attached to the two S16 homologs decreased gradually in the presence of dextran 20. To investigate the origin of this decrease, we studied the BODIPY quantum yield in three protein variants in the presence of a tyrosine-labeled dextran. The experiments revealed distinct tyrosine quenching behaviors of BODIPY in the three variants, suggesting a dynamic local interaction between dextran and one particular S16 variant.

National Category
Biophysics
Identifiers
urn:nbn:se:umu:diva-91835 (URN)10.1016/j.bpj.2014.05.038 (DOI)000339148500016 ()
Available from: 2014-08-29 Created: 2014-08-18 Last updated: 2017-12-05Bibliographically approved
Mikaelsson, T., Ådén, J., Johansson, L.-Å. B. & Wittung-Stafshede, P. (2013). Direct Observation of Protein Unfolded State Compaction in the Presence of Macromolecular Crowding. Biophysical Journal, 104(3), 694-704.
Open this publication in new window or tab >>Direct Observation of Protein Unfolded State Compaction in the Presence of Macromolecular Crowding
2013 (English)In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 104, no 3, 694-704 p.Article in journal (Refereed) Published
Abstract [en]

Proteins fold and function in cellular environments that are crowded with other macromolecules. As a consequence of excluded volume effects, compact folded states of proteins should be indirectly stabilized due to destabilization of extended unfolded conformations. Here, we assess the role of excluded volume in terms of protein stability, structural dimensions and folding dynamics using a sugar-based crowding agent, dextran 20, and the small ribosomal protein S16 as a model system. To specifically address dimensions, we labeled the protein with BODIPY at two positions and measured Trp-BODIPY distances under different conditions. As expected, we found that dextran 20 (200 mg/ml) stabilized the variants against urea-induced unfolding. At conditions where the protein is unfolded, Förster resonance energy transfer measurements reveal that in the presence of dextran, the unfolded ensemble is more compact and there is residual structure left as probed by far-ultraviolet circular dichroism. In the presence of a crowding agent, folding rates are faster in the two-state regime, and at low denaturant concentrations, a kinetic intermediate is favored. Our study provides direct evidence for protein unfolded-state compaction in the presence of macromolecular crowding along with its energetic and kinetic consequences.

Place, publisher, year, edition, pages
Cell Press, 2013
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-65815 (URN)10.1016/j.bpj.2012.12.020 (DOI)
Available from: 2013-02-12 Created: 2013-02-12 Last updated: 2017-12-06Bibliographically approved
Krishnan, K. S., Bengtsson, C., Good, J. A., Mirkhanov, S., Chorell, E., Johansson, L.-Å. B. & Almqvist, F. (2013). Synthesis of fluorescent ring-fused 2-pyridone peptidomimetics. Journal of Organic Chemistry, 78(23), 12207-12213.
Open this publication in new window or tab >>Synthesis of fluorescent ring-fused 2-pyridone peptidomimetics
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2013 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 78, no 23, 12207-12213 p.Article in journal (Refereed) Published
Abstract [en]

Thiazolino fused 2-pyridones peptidomimetics are of significant biological importance due to their ability to interfere with adhesive fiber formation in uropathogenic Escherichia coli and oligomerization of amyloid fibres. We have developed an efficient synthetic route to fluorescent BODIPY analogues, with structural diversification from a key intermediate enabling introduction of C-2 substituents and late incorporation of the BODIPY moiety. A mild lithium halide mediated hydrolysis enabled preparation of peptidomimetic fluorophores with useful photophysical properties for further chemical biology applications.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2013
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-82342 (URN)10.1021/jo401844y (DOI)24161000 (PubMedID)
Funder
Swedish Research Council, 621-2010-4730
Available from: 2013-10-30 Created: 2013-10-30 Last updated: 2017-12-06Bibliographically approved
Chorell, E., Pinkner, J. S., Bengtsson, C., Edvinsson, S., Cusumano, C. K., Rosenbaum, E., . . . Almqvist, F. (2012). Design and Synthesis of Fluorescent Pilicides and Curlicides: Bioactive Tools to Study Bacterial Virulence Mechanisms. Chemistry - A European Journal, 18(15), 4522-4532.
Open this publication in new window or tab >>Design and Synthesis of Fluorescent Pilicides and Curlicides: Bioactive Tools to Study Bacterial Virulence Mechanisms
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2012 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 15, 4522-4532 p.Article in journal (Refereed) Published
Abstract [en]

Pilicides and curlicides are compounds that block the formation of the virulence factors pili and curli, respectively. To facilitate studies of the interaction between these compounds and the pili and curli assembly systems, fluorescent pilicides and curlicides have been synthesized. This was achieved by using a strategy based on structure-activity knowledge, in which key pilicide and curlicide substituents on the ring-fused dihydrothiazolo 2-pyridone central fragment were replaced by fluorophores. Several of the resulting fluorescent compounds had improved activities as measured in pili- and curli-dependent biofilm assays. We created fluorescent pilicides and curlicides by introducing coumarin and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) fluorophores at two positions on the peptidomimetic pilicide and curlicide central fragment. Fluorescence images of the uropathogenic Escherichia coli (UPEC) strain UTI89 grown in the presence of these compounds shows that the compounds are strongly associated with the bacteria with a heterogeneous distribution.

Place, publisher, year, edition, pages
Berlin: Wiley-VCH Verlagsgesellschaft, 2012
Keyword
antivirulence, biological activity, coumarin, fluorescence, structure–activity relationships
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-53543 (URN)10.1002/chem.201103936 (DOI)22431310 (PubMedID)
Available from: 2012-04-02 Created: 2012-04-02 Last updated: 2017-12-07Bibliographically approved
Stefl, M., Sachl, R., Humpolickova, J., Cebecauer, M., Machan, R., Kolarova, M., . . . Hof, M. (2012). Dynamics and size of cross-linking-induced lipid Nanodomains in model Membranes. Biophysical Journal, 102(9), 2104-2113.
Open this publication in new window or tab >>Dynamics and size of cross-linking-induced lipid Nanodomains in model Membranes
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2012 (English)In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 102, no 9, 2104-2113 p.Article in journal (Refereed) Published
Abstract [en]

Changes of membrane organization upon cross-linking of its components trigger cell signaling response to various exogenous factors. Cross-linking of raft gangliosides GM1 with cholera toxin ( CTxB) was shown to cause microscopic phase separation in model membranes, and the CTxB-GM1 complexes forming a minimal lipid raft unit are the subject of ongoing cell membrane research. Yet, those subdiffraction sized rafts have never been described in terms of size and dynamics. By means of two-color z-scan fluorescence correlation spectroscopy, we show that the nanosized domains are formed in model membranes at lower sphingomyelin (Sph) content than needed for the large-scale phase separation and that the CTxB-GM1 complexes are confined in the domains poorly stabilized with Sph. Forster resonance energy transfer together with Monte Carlo modeling of the donor decay response reveal the domain radius of similar to 8 nm, which increases at higher Sph content. We observed two types of domains behaving differently, which suggests a dual role of the cross-linker: first, local transient condensation of the GM1 molecules compensating for a lack of Sph and second, coalescence of existing nanodomains ending in large-scale phase separation.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-56217 (URN)10.1016/j.bpj.2012.03.054 (DOI)000303547700012 ()
Available from: 2012-06-12 Created: 2012-06-12 Last updated: 2017-12-07Bibliographically approved
Humpolickova, J., Stefl, M., Sachl, R., Cebecauer, M., Machan, R., Johansson, L.-Å. B. & Hof, M. (2012). Dynamics and size of crosslinking-induced lipid nanodomains in model membranes. Biophysical Journal, 102(3), 294a.
Open this publication in new window or tab >>Dynamics and size of crosslinking-induced lipid nanodomains in model membranes
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2012 (English)In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 102, no 3, 294a- p.Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

Changes of membrane organization upon crosslinking of its components trigger cellsignaling response to various exogenous factors. Crosslinking of raft gangliosides GM1with cholera toxin (CTxB) was demonstrated to cause microscopic phase separation inmodel membranes and the CTxB-GM1 complexes forming a minimal lipid raft unit aresubject of ongoing cell membrane research. Yet, those subdiffraction sized rafts havenever been described in terms of size and dynamics. By means of two-color z-scanfluorescence correlation spectroscopy, we show that the nano-sized domains are formedin model membranes at lower sphingomyelin content than needed for the large scalephase separation and that the CTxB-GM1 complexes are confined in the domains poorlystabilized with sphingomyelin. Fluorescence resonance energy transfer together withMonte Carlo modeling of the donor decay response reveal the domain radius ofapproximately 8 nm, which increases at higher sphingomyelin content. We observed twotypes of differently behaving domains, which suggests a dual role of the crosslinker: first,local transient condensation of the GM1 molecules compensating lack of sphingomyelinand second, coalescence of existing nanodomains ending in large scale phase separation.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-52464 (URN)10.1016/j.bpj.2011.11.1628 (DOI)
Note

Kompletteras 2012-09

Available from: 2012-02-22 Created: 2012-02-22 Last updated: 2017-12-07Bibliographically approved
Sachl, R., Johansson, L.-Å. B. & Hof, M. (2012). Förster Resonance Energy Transfer (FRET) between Heterogeneously Distributed Probes: Application to Lipid Nanodomains and Pores. International Journal of Molecular Sciences, 13(12), 16141-16156.
Open this publication in new window or tab >>Förster Resonance Energy Transfer (FRET) between Heterogeneously Distributed Probes: Application to Lipid Nanodomains and Pores
2012 (English)In: International Journal of Molecular Sciences, ISSN 1422-0067, E-ISSN 1422-0067, Vol. 13, no 12, 16141-16156 p.Article in journal (Refereed) Published
Abstract [en]

The formation of membrane heterogeneities, e.g., lipid domains and pores, leads to a redistribution of donor (D) and acceptor (A) molecules according to their affinity to the structures formed and the remaining bilayer. If such changes sufficiently influence the Förster resonance energy transfer (FRET) efficiency, these changes can be further analyzed in terms of nanodomain/pore size. This paper is a continuation of previous work on this theme. In particular, it is demonstrated how FRET experiments should be planned and how data should be analyzed in order to achieve the best possible resolution. The limiting resolution of domains and pores are discussed simultaneously, in order to enable direct comparison. It appears that choice of suitable donor/acceptor pairs is the most crucial step in the design of experiments. For instance, it is recommended to use DA pairs, which exhibit an increased affinity to pores (i.e., partition coefficients K(D,A) > 10) for the determination of pore sizes with radii comparable to the Förster radius R(0). On the other hand, donors and acceptors exhibiting a high affinity to different phases are better suited for the determination of domain sizes. The experimental setup where donors and acceptors are excluded from the domains/pores should be avoided.

Place, publisher, year, edition, pages
MDPI, 2012
Keyword
Formylacetic esters, Ozonolysis, Solid phase scavenging, Heterocycles
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-63342 (URN)10.3390/ijms131216141 (DOI)23203189 (PubMedID)
Available from: 2013-01-02 Created: 2013-01-02 Last updated: 2017-12-06Bibliographically approved
Opanasyuk, O., Mikaelsson, T., Ryderfors, L., Mukhtar, E. & Johansson, L.-Å. B. (2012). On the analyses of fluorescence depolarisation data in the presence of electronic energy migration.: II. Applying & Evaluating Two-Photon Excited Fluorescence. Physical Chemistry, Chemical Physics - PCCP, 14, 1917-1922.
Open this publication in new window or tab >>On the analyses of fluorescence depolarisation data in the presence of electronic energy migration.: II. Applying & Evaluating Two-Photon Excited Fluorescence
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2012 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, 1917-1922 p.Article in journal (Refereed) Published
Abstract [en]

Electronic energy migration within a bifluorophoric molecule has been studied by time-resolved two-photon excited (TPE) fluorescence depolarisation experiments. Data were analysed by using a recently developed quantitative approach [Opanasyuk, O. & Johansson, L. B.-Å., On the Analyses of Fluorescence Depolarisation Data in the Presence of Electronic Energy Migration. I. Theory & General Description. Phys. Chem. Chem. Phys., Submitted.]. The energy migration occurs between the 9-anthrylmethyl groups of the bifluorophoric molecule, bis-(9-anthrylmethylphosphonate) bisteroid. These groups undergo local reorientations, while overall tumbling of the bisteroid is strongly hampered in the used viscous solvent, 1,2-propanediol. To solely obtain information about local reorientations of the 9-anthrylmethyl group, also the mono-(9-anthrylmethylphosphonate) bisteroid was studied, which enabled modelling of the ordering potential shape. The analysis of data is partly performed in the Fourier domain and the best-fit parameters are determined by using an approach based on a Genetic Algorithm. The energy migration process was described by an extended Förster theory (EFT). A reasonable value of the distance between the 9-anthrylmethyl groups is found, as well as for the mutual orientation of the ordering potentials. Furthermore, values of the two-photon tensor components were obtained.

Keyword
Extended Förster theory, Genetic algorithms, Monte Carlo simulations, two-photon excitation
National Category
Physical Chemistry Atom and Molecular Physics and Optics
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-50049 (URN)10.1039/C2CP23177H (DOI)
Available from: 2011-11-24 Created: 2011-11-24 Last updated: 2017-12-08Bibliographically approved
Opanasyuk, O. & Johansson, L.-Å. B. (2012). On the analyses of fluorescence depolarisation data in the presence of electronic energy migration: Part I. Theory and general description. Physical Chemistry, Chemical Physics - PCCP, 14, 1907-1916.
Open this publication in new window or tab >>On the analyses of fluorescence depolarisation data in the presence of electronic energy migration: Part I. Theory and general description
2012 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, 1907-1916 p.Article in journal (Refereed) Published
Abstract [en]

A new and general procedure is described for a detailed analysis of time-resolved fluorescence depolarisation data in the presence of electronic energy migration. An isotropic ensemble of bifluorophoric molecules (D1-R-D2) has been studied to demonstrate its utility. Intramolecular donor-donor energy migration occurs between the two donor groups (D), which are covalently connected to a rigid linker group (R). These groups undergo restricted reorientational motions with respect to the R group. The analysis of depolarisation data basically involves the search for best-fit parameters which describe the local reorienting motions, the intermolecular D1-D2 distance, as well as the mutual orientations of the donors. For this, the analysis is partly performed in the Fourier domain and the best-fit parameters are determined by using an approach based on a Genetic Algorithm. The energy migration process has been described by using Monte Carlo simulations and an extended Förster theory (EFT). It is found that the EFT provides the least time-consuming computational method. Since one-photon and two-photon excited fluorescence experiments can be applied for energy migration studies, a general and unified theoretical formulation is given.

Place, publisher, year, edition, pages
Cambridge: RSC Publishing, 2012
Keyword
Extended Förster theory, Genetic algorithm, Monte Carlo simulations, two-photon excitation
National Category
Physical Chemistry Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-50048 (URN)10.1039/c1cp22483b (DOI)
Available from: 2011-11-24 Created: 2011-11-24 Last updated: 2017-12-08Bibliographically approved
Langhals, H., Walter, A., Rosenbaum, E. & Johansson, L.-Å. B. (2011). A versatile standard for bathochromic fluorescence based on intramolecular FRET. Physical Chemistry, Chemical Physics - PCCP, 13(23), 11055-11059.
Open this publication in new window or tab >>A versatile standard for bathochromic fluorescence based on intramolecular FRET
2011 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 23, 11055-11059 p.Article in journal (Refereed) Published
Abstract [en]

A perylene and a terrylene tetracarboxylic bisimide dyad was prepared in which an efficient energy transfer from the former to the latter is observed. The absorption spectrum of this compound covers a broad range. Bathochromic fluorescence with a high quantum yield was obtained independent of excitation wavelengths (λ < 655 nm). The dyad can be recommended for the use of calibrating fluorescence spectrometers, as well as a fluorescence standard in the bathochromic region.

Place, publisher, year, edition, pages
RSC Publishing, 2011
Identifiers
urn:nbn:se:umu:diva-43882 (URN)10.1039/c1cp20467j (DOI)21562665 (PubMedID)
Available from: 2011-05-16 Created: 2011-05-16 Last updated: 2017-12-11Bibliographically approved
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