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  • 1.
    Johagen, Daniel
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Svenmarker, Pontus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Jonsson, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine. Department of Biomedical Engineering and Informatics, Umeå University, Umeå, Sweden.
    Svenmarker, Staffan
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    A microscopic view of gaseous microbubbles passing a filter screen2017In: International Journal of Artificial Organs, ISSN 0391-3988, E-ISSN 1724-6040, Vol. 40, no 9, p. 498-502Article in journal (Refereed)
    Abstract [en]

    Purpose: The aim of this study was to investigate the filtration efficacy of a 38-µm 1-layer screen filter based on Doppler registrations and video recordings of gaseous microbubbles (GME) observed in a microscope.

    Methods: The relative filtration efficacy (RFE) was calculated from 20 (n = 20) sequential bursts of air introduced into the Plasmodex® primed test circuit.

    Results: The main findings indicate that the RFE decreased (p = 0.00), with increasing flow rates (100-300 mL/min) through the filter screen. This reaction was most accentuated for GME below the size of 100 µm, where counts of GME paradoxically increased after filtration, indicating GME fragmentation. For GME sized between 100-250 µm, the RFE was constantly >60%, independently of the flow rate level. The video recording documenting the GME interactions with the screen filter confirmed the experimental findings.

    Conslusions: The 38-µm 1-layer screen filter investigated in this experimental setup was unable to trap gaseous microbubbles effectively, especially for GME below 100 µm in size and in conjunction with high flow rates.

  • 2. Spaulding, Caitlin N.
    et al.
    Schreiber, Henry Louis
    Zheng, Weili
    Dodson, Karen W.
    Hazen, Jennie E.
    Conover, Matt S.
    Wang, Fengbin
    Svenmarker, Pontus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luna-Rico, Areli
    Francetic, Olivera
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hultgren, Scott
    Egelman, Edward H.
    Functional role of the type 1 pilus rod structure in mediating host-pathogen interactions2018In: eLIFE, E-ISSN 2050-084X, Vol. 7, article id e31662Article in journal (Refereed)
    Abstract [en]

    Uropathogenic E. coli (UPEC), which cause urinary tract infections (UTI), utilize type 1 pili, a chaperone usher pathway (CUP) pilus, to cause UTI and colonize the gut. The pilus rod, comprised of repeating FimA subunits, provides a structural scaffold for displaying the tip adhesin, FimH. We solved the 4.2 Å resolution structure of the type 1 pilus rod using cryo-electron microscopy. Residues forming the interactive surfaces that determine the mechanical properties of the rod were maintained by selection based on a global alignment of fimA sequences. We identified mutations that did not alter pilus production in vitro but reduced the force required to unwind the rod. UPEC expressing these mutant pili were significantly attenuated in bladder infection and intestinal colonization in mice. This study elucidates an unappreciated functional role for the molecular spring-like property of type 1 pilus rods in host-pathogen interactions and carries important implications for other pilus-mediated diseases.

  • 3.
    Stangner, Tim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Dahlberg, Tobias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Svenmarker, Pontus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zakrisson, Johan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wiklund, Krister
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Oddershede, Lene B.
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cooke-Triplet-Tweezers: More compact, robust and efficient optical tweezers2018In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, no 9, p. 1990-1993Article in journal (Refereed)
    Abstract [en]

    We present a versatile three-lens optical design to improve the overall compactness, efficiency, and robustness for optical tweezers based applications. The design, inspired by the Cooke–Triplet configuration, allows for continuous beam magnifications of 2–10× , and axial as well as lateral focal shifts can be realized without switching lenses or introducing optical aberrations. We quantify the beam quality and trapping stiffness and compare the Cooke–Triplet design with the commonly used double Kepler design through simulations and direct experiments. Optical trapping of 1 and 2 μm beads shows that the Cooke–Triplet possesses an equally strong optical trap stiffness compared to the double Kepler lens design but reduces its lens system length by a factor of 2.6. Finally, we demonstrate how a Twyman–Green interferometer integrated in the Cooke–Triplet optical tweezers setup provides a fast and simple method to characterize the wavefront aberrations in the lens system and how it can help in aligning the optical components perfectly.

  • 4.
    Svenmarker, Pontus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Department of Physics, Lund University.
    Xu, Can T.
    Liu, Haichun
    Wu, Xia
    Andersson-Engels, Stefan
    Multispectral guided fluorescence diffuse optical tomography using upconverting nanoparticles2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, no 7, p. 073703-Article in journal (Refereed)
    Abstract [en]

    We report on improved image detectability for fluorescence diffuse optical tomography using upconverting nanoparticles doped with rare-earth elements. Core-shell NaYF4 : Yb3+/Er3+ @ NaYF4 upconverting nanoparticles were synthesized through a stoichiometric method. The Yb3+/Er3+ sensitizer-activator pair yielded two anti-Stokes shifted fluorescence emission bands at 540 nm and 660 nm, here used to a priori estimate the fluorescence source depth with sub-millimeter precision. A spatially varying regularization incorporated the a priori fluorescence source depth estimation into the tomography reconstruction scheme. Tissue phantom experiments showed both an improved resolution and contrast in the reconstructed images as compared to not using any a priori information.

  • 5.
    Zakrisson, Johan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Singh, Bhupender
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Svenmarker, Pontus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wiklund, Krister
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hakobyan, Shoghik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Detecting the presence of surface organelles at the single cell level, a novel cell sorting approachManuscript (preprint) (Other academic)
  • 6.
    Zakrisson, Johan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Singh, Bhupender
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Svenmarker, Pontus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wiklund, Krister
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zhang, Hanqing
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hakobyan, Shoghik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Detecting Bacterial Surface Organelles on Single Cells using Optical Tweezers2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 18, p. 4521-4529Article in journal (Refereed)
    Abstract [en]

    Bacterial cells display a diverse array of surface organelles that are important for a range of processes such as: intercellular communication, motility and adhesion leading to biofilm formation, infections and bacterial spread. More specifically, attachment to host cells by Gram-negative bacteria are mediated by adhesion pili, which are nm wide and µm long fibrous organelles. Since these pili are significantly thinner than the wavelength of visible light, they cannot be detected using standard light microscopy techniques. At present, there is no fast and simple method available to investigate if a single cell expresses pili while keeping the cell alive for further studies. In this study, we present a method to determine the presence of pili on a single bacterium. The protocol involves imaging the bacterium to measure its size, followed by predicting the fluid drag based on its size using an analytical model, and thereafter oscillating the sample while a single bacterium is trapped by an optical tweezer to measure its effective fluid drag. Comparison between the predicted and the measured fluid drag thereby indicate the presence of pili. Herein, we verify the method using polymer coated silica microspheres and Escherichia coli bacteria expressing adhesion pili. Our protocol, can in real time and within seconds assist single cell studies by distinguishing between piliated and non-piliated bacteria.

  • 7. Zheng, Weili
    et al.
    Spaulding, Caitlin N.
    Schreiber, Henry L.
    Dodson, Karen W.
    Conover, Matt S.
    Wang, Fengbin
    Svenmarker, Pontus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luna-Rico, Areli
    Francetic, Olivera
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hultgren, Scott J.
    Egelman, Edward H.
    Cryo-Em Structure of Type 1 Pilus2018In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 114, no 3, p. 370a-370aArticle in journal (Other academic)
    Abstract [en]

    Urinary tract infections (UTIs) are caused by a wide range of pathogens, but the most common causative agent of UTIs is uropathogenic Escherichia coli (UPEC). Virtually all uropathogenic strains of E. coli encode filamentous surface adhesive organelles called type 1 pili, which are a subset of Chaperone-usher pathway (CUP) pili. CUP pili are also ubiquitously expressed on the surface of many other Gram-negative bacterial pathogens. They are important virulence factors facilitating host-pathogen interactions that are crucial for the establishment and persistence of an infection, and involved in regulating other key processes such as biofilm formation. We have solved the 4.2 Å resolution cryo-EM structure of the type 1 pilus, which was present as a background contaminant in a prep of type 4 pili. We have taken advantage of the strength of cryo-EM to separate different molecules and conformations present in solution to show that filament images which might otherwise have been discarded as a contaminant can actually be used to build an atomic model. The model reveals the residues that allow a long chain of FimA subunits, linked by the insertion of a β-strand of one subunit into the β-sheet of an adjacent subunit, to coil into a rigid rod. We show that site-specific mutation of these residues reduces the force needed to unwind the rod. Strikingly, one mutation (A22R) which showed the greatest reduction in unwinding force, eliminated bladder infections in a mouse model. This is presumably due to the fact that the altered mechanics of the A22R pilus rod cannot withstand the shear forces due to urinary flow in the bladder and bacteria harboring this mutation are cleared from the bladder. This provides new insights into the important role of pili mechanics in bacterial pathogenesis.

  • 8. Zheng, Weili
    et al.
    Spaulding, Caitlin
    Schreiber, Henry
    Dodson, Karen
    Conover, Matt
    Wang, Fengbin
    Svenmarker, Pontus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luna-Rico, Areli
    Francetic, Olivera
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hultgren, Scott J
    Egelman, Edward H.
    Cryo-Em Structure of Type 1 Pilus2018In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 114, no 3Article in journal (Other academic)
1 - 8 of 8
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  • nn-NO
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