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  • 1.
    Andersson, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Björnham, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Bullitt, Esther
    Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany St., Boston MA, USA.
    Svantesson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Differentiating pili expressed by enterotoxigenic and uropathogenic escherichia coli with optical tweezersManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Enterotoxigenic Escherichia coli (ETEC) attach to the host epithelium in the intestinal tract via specific adhesion organelles expressed on the cell membrane. We investigate, by force measuring optical tweezers, the intrinsic biomechanical properties and kinetics of the colonization factor I (CFA/I) at a single pilus level. The measurements indicate that CFA/I pili are helix-like structures that can both be unraveled to a linearized polymer by applying a small external force, 7.5 ± 1.5 pN but also regain its helix-like structure when the applied force is reduced. The data confirm that layer-to-layer interactions, that stabilize the helix-like structure, are much weaker than the interactions found in pili expressed by Uropathogenic Escherichia coli (UPEC). It is also found, contrary to previous results assessed from UPEC pili, that the CFA/I undergo in some cases a sudden structural change, a force drop of ~2 pN, when unraveled from the helix-like configuration to an open helical linearized fiber. These data suggest a rotation of the filament about its helical axis, followed by a region in which the force required to extend the pili further increases rapidly. During this final elongation to a super-extended fiber, CFA/I pili do not show any structural transition as seen for UPEC pili. In addition, the CFA/I pili show faster kinetics than UPEC pili that allows for a larger dynamic regime of in vivo shear forces. The unfolding and refolding possibility points toward an organelle that has evolved to allow for dynamic damping of external forces and handling of harsh motion without breaking.

  • 2.
    Axner, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Björnham, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Castelain, Mickaël
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Klinth, Jeanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Koutris, Efstratios
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Assessing bacterial adhesion on an individual adhesin and single pili level using optical tweezers 2011Ingår i: Bacterial adhesion: chemistry, biology and physics / [ed] D. Line and A. Goldman, Berlin: Springer Berlin/Heidelberg, 2011, s. 301-313Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Optical tweezers (OT) are a technique that, by focused laser light, can both manipulate micrometer sized objects and measure minute forces (in the pN range) in biological systems. The technique is therefore suitable for assessment of bacterial adhesion on an individual adhesin-receptor and single attachment organelle (pili) level. This chapter summarizes the use of OT for assessment of adhesion mechanisms of both non-piliated and piliated bacteria. The latter include the important helix-like pili expressed by uropathogenic Escherichia coli (UPEC), which have shown to have unique and intricate biomechanical properties. It is conjectured that the large flexibility of this type of pili allows for a redistribution of an external shear force among several pili, thereby extending the adhesion lifetime of bacteria. Systems with helix-like adhesion organelles may therefore act as dynamic biomechanical machineries, enhancing the ability of bacteria to withstand high shear forces originating from rinsing flows such as in the urinary tract. This implies that pili constitute an important virulence factor and a possible target for future anti-microbial drugs.

  • 3.
    Axner, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Björnham, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Castelain, Mickael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Koutris, Efstratios
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Fällman, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Unraveling the secrets of bacterial adhesion organelles using single-molecule force spectroscopy2010Ingår i: Single molecule spectroscopy in chemistry, physics and biology: Nobel symposium / [ed] Gräslund, Astrid, Rigler, Rudolf & Widengren, Jerker, Springer, 2010, s. 337-362Konferensbidrag (Refereegranskat)
    Abstract [en]

    Many types of bacterium express micrometer-long attachment organelles (so-called pili) whose role is to mediate adhesion to host tissue. Until recently, little was known about their function in the adhesion process. Force-measuring optical tweezers (FMOT) have since then been used to unravel the biomechanical properties of various types of pili, primarily those from uropathogenic E. coli, in particular their force-vs.-elongation response, but lately also some properties of the adhesin situated at the distal end of the pilus. This knowledge provides an understanding of how piliated bacteria can sustain external shear forces caused by rinsing processes, e.g., urine flow. It has been found that many types of pilus exhibit unique and complex force-vs.-elongation responses. It has been conjectured that their dissimilar properties impose significant differences in their ability to sustain external forces and that different types of pilus therefore have dissimilar predisposition to withstand different types of rinsing conditions. An understanding of these properties is of high importance since it can serve as a basis for finding new means to combat bacterial adhesion, including that caused by antibiotic-resistance bacteria. This work presents a review of the current status of the assessment of biophysical properties of individual pili on single bacteria exposed to strain/stress, primarily by the FMOT technique. It also addresses, for the first time, how the elongation and retraction properties of the rod couple to the adhesive properties of the tip adhesin.

  • 4.
    Axner, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Björnham, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Castelain, Mickaël
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Koutris, Efstratios
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Fällman, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Unraveling the secrets of bacterial adhesion organelles using single molecule force spectroscopy2010Ingår i: Springer series in chemical physics: single molecule spectroscopy in chemistry, physics and biology, Springer Verlag , 2010, 96, s. 337-362Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    Many types of bacterium express micrometer-long attachment organelles (so called pili) whose role is to mediate adhesion to host tissue. Until recently, little was known about their function in the adhesion process. Forcemeasuring  ptical tweezers (FMOT) have since then been used to unravel the  iomechanical properties of various types of pili, primarily those from uropathogenic E. coli, in particular their force-vs.-elongation response, but lately also some properties of the adhesin situated and the distal end of the pilus. This knowledge provides an understanding of how piliated bacteria can sustain external shear forces caused by rinsing processes, e.g. urine flow. It has been found that anytypes of pilus exhibit unique and complex force-vs.-elongation responses. It has been conjectured that their dissimilar properties impose significant differences in their ability to sustain external forces and that different types of pilus therefore have dissimilar predisposition to withstand different types of rinsing conditions. An understanding of these properties is of high importance since it can serve as a basis for finding new means to combat bacterial adhesion, including that caused by antibiotic-resistance bacteria. This work presents a review of the current status of the assessment of biophysical properties of individual pili on single bacteria exposed to strain/stress, primarily by the FMOT technique. It also addresses, for the first time, how the elongation and retraction properties of the rod couple to the adhesive properties of the tip adhesin.

  • 5.
    Björnham, Oscar
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    A study of bacterial adhesion on a single-cell level by means of force measuring optical tweezers and simulations2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The intriguing world of microbiology is nowadays accessible for detailed exploration at a single–molecular level. Optical tweezers are a novel instrument that allows for non–invasive manipulation of single cells by the sole use of laser light and operates on the nano– and micrometer scale which corresponds to the same length scale as living cells. Moreover, forces within the field of microbiology are typically in the picoNewton range which is in accordance with the capability of force measuring optical tweezers systems. Both these conformabilities imply that force measuring optical tweezers is suitable for studies of single living cells. This thesis focuses on the mechanisms of bacterial attachments to host cells which constitute the first step in bacterial infection processes. Bacteria bind specifically to host receptors by means of adhesins that are expressed either directly on the bacterial membrane or on micrometer–long adhesion organelles that are called pili. The properties of single adhesin–receptor bonds that mediate adherence of the bacterium Helicobacter pylori are first examined at various acidities. Further on, biomechanical properties of P pili expressed by Escherichia coli are presented to which computer simulations, that capture the complex kinetics of the pili structure and precisely replicate measured data, are applied. Simulations are found to be a powerful tool for investigations of adhesive attributes of binding systems and are utilized in the analyses of the specific binding properties of P pili on a single–pilus level. However, bacterial binding systems generally involve a multitude of adhesin–receptor bonds. To explore bacterial attachments, the knowledge from single–pilus studies is brought into a full multipili attachment scenario which is analyzed by means of theoretical treatments and simulations. The results are remarkable in several aspects. Not only is it found that the intrinsic properties of P pili are composed in an optimal combination to promote strong multipili bindings. The properties of the pili structure itself are also found to be optimized with respect to its in vivo environment. Indeed, the true meaning of the attributes derived at a single–pilus level cannot be unraveled until a multipili–binding system is considered. Whereas detailed studies are presented for the helix–like P pili expressed by Gram–negative Escherichia coli, conceptual studies are presented for the open coil–like T4 pili expressed by Gram–positive Streptococcus pneumoniae. The structural and adhesive properties of these two types of pili differ considerably. These dissimilarities have far–reaching consequences on the adhesion possibilities at both single–pilus and multipili levels which are discussed qualitatively. Moreover, error analyses of conventional data processing methods in dynamic force spectroscopy as well as development of novel analysis methods are presented. These findings provide better understanding of how to perform refined force measurements on single adhesion organelles as well as how to improve the analyses of measurement data to obtain accurate parameter values of biomechanical entities. In conclusion, this thesis comprises a study of bacterial adhesion organelles and the way they cooperate to establish efficient attachment systems that can successfully withstand strong external forces that acts upon bacteria. Such systems can resist, for instance, rinsing effects and thereby allow bacteria to colonize their host. By understanding the complexity, and thereby possible weaknesses, of bacterial attachments, new targets for combating bacterial infections can be identified.

  • 6.
    Björnham, Oscar
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Catch-Bond behavior of bacteria binding by slip bonds2010Ingår i: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 99, nr 5, s. 1331-1341Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is shown that multipili-adhering bacteria expressing helix-like pili binding by slip bonds can show catch-bond behavior. When exposed to an external force, such bacteria can mediate adhesion to their hosts by either of two limiting means: sequential or simultaneous pili force exposure (referring to when the pili mediate force in a sequential or simultaneous manner, respectively). As the force is increased, the pili can transition from sequential to simultaneous pili force exposure. Since the latter mode of adhesion gives rise to a significantly longer bacterial adhesion lifetime than the former, this results in a prolongation of the lifetime, which shows up as a catch-bond behavior. The properties and conditions of this effect were theoretically investigated and assessed in some detail for dual-pili-adhering bacteria, by both analytical means and simulations. The results indicate that the adhesion lifetime of such bacteria can be prolonged by more than an order of magnitude. This implies that the adhesion properties of multibinding systems cannot be directly conveyed to the individual adhesion-receptor bonds.

  • 7.
    Björnham, Oscar
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Multipili Attachment of Bacteria with Helix–like Pili Exposed to Stress2009Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 130, s. 235102-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A number of biomechanical properties of various types of pili expressed by Escherichia coli, predominantly their force–vs.–elongation behavior, have previously been assessed in detail on a single pilus level. In vivo, however, bacteria bind in general to host cells by a multitude of pili, which presumably provides them with adhesion properties that differs from those of single pili. Based upon the previously assessed biomechanical properties of individual pili, this work presents a theoretical analysis of the adhesion properties of multipili–attaching bacteria expressing helix–like pili exposed to an external force. Expressions for the adhesion lifetime of dual– and multipili–attaching bacteria are derived and their validity is verified by Monte Carlo simulations. It is shown that the adhesion lifetime of a multipili–binding bacterium depends to a large degree on the cooperativity of the attaching pili, which, in turn, depends strongly on their internal biomechanical properties, in particular their helix–like structure and its ability to elongate, which, in turn, depend on the intrinsic properties of the bonds, e.g. their lengths and activation energies. It is shown, for example, that a decrease in the length of a layer–to–layer bond in the rod of P pili, expressed by E. coli, by 50 % leads to a decrease in the adhesion lifetime of a bacterium attaching by 10 pili and exposed to a force of 500 pN by three orders of magnitude. The results indicate moreover that the intrinsic properties of the rod for this particular type of pili are optimized for multipili attachment under a broad range of external forces and presumably also to its in vivo environment. Even though the results presented in this work apply quantitatively to one type of pilus, they are assumed to apply qualitatively to all helix–like pili systems expressing slip bonds.

  • 8.
    Björnham, Oscar
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Modeling of the elongation and retraction of Escherichia coli P pili under strain by Monte Carlo simulations2008Ingår i: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 37, nr 4, s. 381-391Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    P pili are fimbrial adhesion organelles expressed by uropathogenic Escherichia coli in the upper urinary tract. They constitute a stiff helix-like polymer consisting of a number of subunits joined by head-to-tail bonds. The elongation and retraction properties of individual P pili exposed to strain have been modeled by Monte Carlo (MC) simulations. The simulation model is based upon a three-state energy landscape that deforms under an applied force. Bond opening and closure are modeled by Bells theory while the elongation of the linearized part of the pilus is described by a worm-like chain model. The simulations are compared with measurements made by force measuring optical tweezers. It was found that the simulations can reproduce pili elongation as well as retraction, under both equilibrium and dynamic conditions, including entropic effects. It is shown that the simulations allow for an assessment of various model parameters, e.g. the unfolding force, energy barrier heights, and various distances in the energy landscape, including their stochastic spread that analytical models are unable to do. The results demonstrate that MC simulations are useful to model elongation and retraction properties of P pili, and therefore presumably also other types of pili, exposed to strain and/or stress. MC simulations are particularly suited for description of helix-like pili since these have an intricate self-regulating mechanical elongation behavior that makes analytical descriptions non-trivial when dynamic processes are studied, or if additional interactions in the rod or the behavior of the adhesion tip needs to be modeled.

  • 9.
    Björnham, Oscar
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Bugaytsova, Jeanna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Borén, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Dynamic force spectroscopy of the Helicobacter pylori BabA-Lewis b binding2009Ingår i: Biophysical Chemistry, ISSN 0301-4622, E-ISSN 1873-4200, Vol. 143, nr 1-2, s. 102-105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The binding strength of the Helicobacter pylori adhesin–receptor complex BabA-ABO/Lewis b has been analyzed by means of dynamic force pectroscopy. High-resolution measurements of rupture forces were performed in situ on single bacterial cells, expressing the high-affinity binding BabA adhesin, by the use of force measuring optical tweezers. The resulting force spectra revealed the mechanical properties of a single BabA–Leb bond. It was found that the bond is dominated by one single energy barrier and that it is a slipbond. The bond length and thermal off-rate were assessed to be 0.86±0.07 nm and 0.015±0.006 s−1, respectively.

  • 10.
    Björnham, Oscar
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fällman, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ohlsson, J.
    Nilsson, U.J.
    Borén, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Measurements of the binding force between the Helicobacter pylori adhesin BabA and the Lewis b blood group antigen using optical tweezers2005Ingår i: Journal of Biomedical Optics, ISSN 1560-2281 (Online), Vol. 10, nr 4, s. 044024-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Helicobacter pylori is a world-wide spread bacterium that causes persistent infections and chronic inflammations that can develop into gastritis and peptic ulcer disease. It expresses several adhesin proteins on its surface that bind to specific receptors in the gastric epithelium. The most well-known adhesin is BabA, which has previously been shown to bind specifically to the fucosylated blood group antigen Lewis b (Leb). The adhesion forces between BabA and the Leb antigen are investigated in this work and assessed by means of optical tweezers. A model system for in situ measurements of the interaction forces between individual bacteria and beads coated with Leb is developed. It is found that the de-adhesion force in this model system, measured with a loading rate of approximately 100 pNs, ranges from 20 to 200 pN. The de-adhesion force appears predominantly as multiples of an elementary force, which is determined to 25+/-1.5 pN and identified as the unbinding force of an individual BabA-Leb binding. It is concluded that adhesion in general is mediated by a small number of bindings (most often 1 to 4) despite that the contact surface between the bacterium and the bead encompassed significantly more binding sites.

  • 11.
    Björnham, Oscar
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nilsson, Håkan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Physical properties of the specific PapG–galabiose binding in E. coli P pili-mediated adhesion2009Ingår i: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 38, nr 2, s. 245-254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Detailed analyses of the mechanisms thatmediate binding of the uropathogenic Escherichia coli tohost cells are essential, as attachment is a prerequisite forthe subsequent infection process. We explore, by means offorce measuring optical tweezers, the interaction betweenthe galabiose receptor and the adhesin PapG expressed byP pili on single bacterial cells. Two variants of dynamicforce spectroscopy were applied based on constant andnon-linear loading force. The specific PapG–galabiosebinding showed typical slip-bond behaviour in the forceinterval (30–100 pN) set by the pilus intrinsic biomechanicalproperties. Moreover, it was found that the bondhas a thermodynamic off-rate and a bond length of2.6×10-3 s-1 and 5.0 Å , respectively. Consequently, thePapG–galabiose complex is significantly stronger thanthe internal bonds in the P pilus structure that stabilizes thehelical chain-like macromolecule. This finding suggeststhat the specific binding is strong enough to enable the Ppili rod to unfold when subjected to strong shear forces inthe urinary tract. The unfolding process of the P pili rodpromotes the formation of strong multipili interaction,which is important for the bacterium to maintain attachmentto the host cells.

  • 12.
    Björnham, Oscar
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Methods and error estimations of uncertainties in single-molecule dynamic force spectroscopy2009Ingår i: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 38, nr 7, s. 911-922Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In dynamic force spectroscopy, access to the characteristic parameters of single molecular bonds requires non-trivial measurements and data processing as the rupture forces are found not only to be distributed over a wide range, but are also dependent on the loading rate. The choice of measurement procedure and data processing methods has a considerable impact on the accuracy and precision of the final results. We analyse, by means of numerical simulations, methods to minimize and assess the magnitude of the expected errors for different combinations of experimental and evaluation methods. It was found that the choice of fitting function is crucial to extract correct parameter values. Applying a Gaussian function, which is a common practice, is equivalent to introducing a systematic error, and leads to a consequent overestimation of the thermal off-rate by more than 30%. We found that the precision of the bond length and the thermal off-rate, in presence of unbiased noise, were improved by reducing the number of loading rates for a given number of measurements. Finally, the results suggest that the minimum number of measurements needed to obtain the bond strength, with acceptable precision, exceeds the common number of ~100 reported in literature.

     

  • 13.
    Bugaytsova, Jeanna A.
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Björnham, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Swedish Defence Research Agency, 906 21 Umeå, Sweden.
    Chernov, Yevgen A.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Gideonsson, Pär
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Henriksson, Sara
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Mendez, Melissa
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Sjöström, Rolf
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Mahdavi, Jafar
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. School of Life Sciences, CBS, University of Nottingham, NG7 2RD Nottingham, UK.
    Shevtsova, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Ilver, Dag
    Moonens, Kristof
    Quintana-Hayashi, Macarena P.
    Moskalenko, Roman
    Aisenbrey, Christopher
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Bylund, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Schmidt, Alexej
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap.
    Åberg, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Brännström, Kristoffer
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Koeniger, Verena
    Vikström, Susanne
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Rakhimova, Lena
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap.
    Hofer, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Ögren, Johan
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Avdelningen för medicin.
    Liu, Hui
    Goldman, Matthew D.
    Whitmire, Jeannette M.
    Åden, Jörgen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Younson, Justine
    Kelly, Charles G.
    Gilman, Robert H.
    Chowdhury, Abhijit
    Mukhopadhyay, Asish K.
    Nair, G. Balakrish
    Papadakos, Konstantinos S.
    Martinez-Gonzalez, Beatriz
    Sgouras, Dionyssios N.
    Engstrand, Lars
    Unemo, Magnus
    Danielsson, Dan
    Suerbaum, Sebastian
    Oscarson, Stefan
    Morozova-Roche, Ludmilla A.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Olofsson, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Gröbner, Gerhard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Holgersson, Jan
    Esberg, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Strömberg, Nicklas
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Landström, Maréne
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap.
    Eldridge, Angela M.
    Chromy, Brett A.
    Hansen, Lori M.
    Solnick, Jay V.
    Linden, Sara K.
    Haas, Rainer
    Dubois, Andre
    Merrell, D. Scott
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Remaut, Han
    Arnqvist, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Berg, Douglas E.
    Boren, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Helicobacter pylori Adapts to Chronic Infection and Gastric Disease via pH-Responsive BabA-Mediated Adherence2017Ingår i: Cell Host and Microbe, ISSN 1931-3128, E-ISSN 1934-6069, Vol. 21, nr 3, s. 376-389Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The BabA adhesin mediates high-affinity binding of Helicobacter pylori to the ABO blood group antigen-glycosylated gastric mucosa. Here we show that BabA is acid responsive-binding is reduced at low pH and restored by acid neutralization. Acid responsiveness differs among strains; often correlates with different intragastric regions and evolves during chronic infection and disease progression; and depends on pH sensor sequences in BabA and on pH reversible formation of high-affinity binding BabA multimers. We propose that BabA's extraordinary reversible acid responsiveness enables tight mucosal bacterial adherence while also allowing an effective escape from epithelial cells and mucus that are shed into the acidic bactericidal lumen and that bio-selection and changes in BabA binding properties through mutation and recombination with babA-related genes are selected by differences among individuals and by changes in gastric acidity over time. These processes generate diverse H. pylori subpopulations, in which BabA's adaptive evolution contributes to H. pylori persistence and overt gastric disease.

  • 14.
    Bugaytsova, Jeanna
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Chernov, Yevgen A
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Gideonsson, Pär
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Mendez, Melissa
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Henriksson, Sara
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Mahdavi, Jafar
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. School of Life Sciences, CBS, University of Nottingham, Nottingham, UK..
    Quintana-Hayashi, Macarena
    Department of Biochemistry and Cell biology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden..
    Shevtsova, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Sjöström, Rolf
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Moskalenko, Roman
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Department of Pathology, Medical Institute, State University, Sumy, Ukraine.
    Aisenbrey, Christopher
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Université de Strasbourg, Institut de Chimie, Strasbourg, France.
    Moonens, Kristof
    Structural and Molecular Microbiology, VIB Department of Structural Biology, Belgium.
    Björnham, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. FOI Totalförsvarets Forskningsinstitut, Umeå, Sweden..
    Brännström, Kristoffer
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Bylund, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Königer, Verena
    Max von Pettenkofer Institute of Hygiene and Medical Microbiology, LMU, Munich, Germany.
    Vikström, Susanne
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Schmidt, Alexej
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap.
    Rakhimova, Lena
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Hofer, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Ögren, Johan
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Ilver, Dag
    Department of Biochemistry and Cell biology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
    Liu, Hui
    Department of Medicine, USUHS, Bethesda, MD, USA.
    Goldman, Matthew
    Department of Pediatrics, USUHS, Bethesda, MD, USA.
    Whitmire, Jeannette M
    Department of Microbiology and Immunology, USUHS, Bethesda, MD USA.
    Kelly, Charles G
    King's College London, Dental Institute, London, UK.
    Gilman, Robert H
    Department of International Health, John Hopkins School of Public Health, Baltimore, MD, USA.
    Chowdhury, Abhijit
    Centre for Liver Research, School of Digestive and Liver Diseases, Institute of Post Graduate Medical Education & Research, Kolkata, India.
    Mukhopadhyay, Asish K
    Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India.
    Nair, Balakrish G
    Translational Health Science and Technology Institute, Haryana, India.
    Papadakos, Konstantinos S
    Hellenic Pasteur Institute, Athens, Greece.
    Martinez-Gonzalez, Beatriz
    Hellenic Pasteur Institute, Athens, Greece.
    Sgouras, Dionyssios N
    Hellenic Pasteur Institute, Athens, Greece.
    Engstrand, Lars
    Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
    Unemo, Magnus
    Department of Laboratory Medicine, Microbiology, Örebro University Hospital, Örebro, Sweden.
    Danielsson, Dan
    Department of Laboratory Medicine, Microbiology, Örebro University Hospital, Örebro, Sweden.
    Sebastian, Suerbaum
    Institute for Medical Microbiology and Hospital Epidemiology Hannover Medical School, Hannover, Germany.
    Oscarson, Stefan
    Centre for Synthesis and Chemical Biology, School of Chemistry, University College Dublin, Dublin, Ireland.
    Morozova-Roche, Ludmilla
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Gröbner, Gerhard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Holgersson, Jan
    Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska Academy, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden.
    Strömberg, Nicklas
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Esberg, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Eldridge, Angela
    Department of Pathology and Laboratory Medicine, University of California Davis School of Medicine, Sacramento, CA, USA.
    Chromy, Brett A
    Department of Pathology and Laboratory Medicine, University of California Davis School of Medicine, Sacramento, CA, USA.
    Hansen, Lori
    Departments of Medical Microbiology and Immunology, Center for Comparative Medicine, University of California Davis, Davis, CA, USA.
    Solnick, Jay
    Departments of Medical Microbiology and Immunology, Center for Comparative Medicine, University of California Davis, Davis, CA, USA.
    Haas, Rainer
    Max von Pettenkofer Institute of Hygiene and Medical Microbiology, LMU Munich, Munich, Germany.
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Lindén, Sara K
    Department of Biochemistry and Cell biology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
    Dubois, Andre
    Department of Medicine, USUHS, Bethesda, MD, USA.
    Merrell, D. Scott
    Department of Microbiology and Immunology, USUHS, Bethesda, MD, USA.
    Remaut, Han
    Structural and Molecular Microbiology, VIB Department of Structural Biology, VIB, Brussels, Belgium.
    Arnqvist, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Berg, Douglas E
    Department of Medicine, University of California San Diego, La Jolla, CA, USA.
    Borén, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Acid Responsive Helicobacter pylori Adherence: Implications for Chronic Infection and DiseaseManuskript (preprint) (Övrigt vetenskapligt)
  • 15.
    Castelain, Mickaël
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Koutris, Efstratios
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wiklund, Krister
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Björnham, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Characterization of the Biomechanical Properties of T4 Pili Expressed by Streptococcus pneumoniae – A Comparison between Helix-like and Open Coil-like Pili2009Ingår i: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 10, nr 9-10, s. 1533-1540Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bacterial adhesion organelles, known as fimbria or pili, are expressed by Gram–positive as well as Gram–negative bacteria families. These appendages play a key role in the first steps of the invasion and infection processes, and they therefore provide bacteria with pathogenic abilities. To improve the knowledge of pili-mediated bacterial adhesion to host cells and how these pili behave under the presence of an external force, we first characterize, using force measuring optical tweezers, open coil-like T4 pili expressed by Gram–positive Streptococcus pneumoniae with respect to their biomechanicalproperties. It is shown that their elongation behavior can be well described by the worm-like chain model and that they possess a large degree of flexibility. Their properties are then compared with those of helix-like pili expressed by Gram–negative uropathogenic Escherichia coli (UPEC), which have different pili architecture. The differences suggest that these two types of pili have distinctly dissimilar mechanisms to adhere and sustain external forces. Helix-like pili expressed by UPEC bacteria adhere to host cells by single adhesins located at the distal end of the pili while their helix-like structures act as shock absorbers to dampen the irregularly shear forces induced by urine flow and to increase the cooperativity of the pili ensemble. Open coil-like pili expressed by S. pneumoniae adhere to cells by a multitude of adhesins distributed along the pili. It is hypothesized that these two types of pili represent different strategies of adhering to host cells in the presence of external forces. When exposed to significant forces, bacteria expressing helix-like pili remain attached bydistributing the external force among a multitude of pili, whereas bacteria expressing open coil-like pili sustain large forces primarily by their multitude of binding adhesins.

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