How simple can a model of an empty viral capsid be? Charge distributions in viral capsids

We investigate and quantify salient features of the charge distributions on viral capsids. Our analysis combines the experimentally determined capsid geometry with simple models for ionization of amino acids, thus yielding the detailed description of spatial distribution for positive and negative charge across the capsid wall. The obtained data is processed in order to extract the mean radii of distributions, surface charge densities and dipole moment densities. The results are evaluated and examined in light of previously proposed models of capsid charge distributions, which are shown to have to some extent limited value when applied to real viruses.Comment: 10 pages, 10 figures; accepted for publication in Journal of Biological Physic

Fluid-membrane tethers: minimal surfaces and elastic boundary layers

Thin cylindrical tethers are common lipid bilayer membrane structures, arising in situations ranging from micromanipulation experiments on artificial vesicles to the dynamic structure of the Golgi apparatus. We study the shape and formation of a tether in terms of the classical soap-film problem, which is applied to the case of a membrane disk under tension subject to a point force. A tether forms from the elastic boundary layer near the point of application of the force, for sufficiently large displacement. Analytic results for various aspects of the membrane shape are given.Comment: 12 page

Vesicle self-reproduction: The involvement of membrane hydraulic and solute permeabilities

Conditions for self-reproduction are sought for a growing vesicle with its growth defined by an exponential increase of vesicle membrane area and by adequate flow of the solution across the membrane. In the first step of the presumed vesicle self-reproduction process, the initially spherical vesicle must double its volume in the doubling time of the membrane area and, through the appropriate shape transformations, attain the shape of two equal spheres connected by an infinitesimally thin neck. The second step involves separation of the two spheres and relies on conditions that cause the neck to be broken. In this paper we consider the first step of this self-reproduction process for a vesicle suspended in a solution whose solute can permeate the vesicle membrane. It is shown that vesicle self-reproduction occurs only for certain combinations of the values of membrane hydraulic and solute permeabilities and the external solute concentration, these quantities being related to the mechanical properties of the membrane and the membrane area doubling time. The analysis includes also the relaxation of a perturbed system towards stationary self-reproduction behavior and the case where the final shape consists of two connected spheres of different radii

Shapes of nearly cylindrical, axisymmetric bilayer membranes

Shapes of nearly cylindrical sections of axisymmetric phospholipid membranes are studied theoretically. Describing the shape of such sections by their deviation from a reference cylinder, the well-established shape equation for axisymmetric bilayer membranes is expanded in terms of this deviation, and it is then solved analytically. The phase diagram shows the resulting stationary shapes as functions of system parameters and external conditions, i.e., the pressure difference across the membrane, the membrane tension, the difference between the tensions of the two monolayers, and the axial force acting on the vesicle. The accuracy of the approximate analytical solution is demonstrated by comparison with numerical results. The obtained analytical solution allows to extend the analysis to include shapes where numerical methods have failed

High Avidity Anti-β2-Glycoprotein i Antibodies Activate Human Coronary Artery Endothelial Cells and Trigger Peripheral Blood Mononuclear Cell Migration

Anti-β2-glycoprotein I antibodies (aβ2GPI) represent a potential pathogenic candidate for coronary artery diseases. High avidity aβ2GPI (HAv aβ2GPI) are known to be associated with thrombotic and obstetric manifestations in patients with antiphospholipid syndrome, who are also susceptible to the development of premature atherosclerosis. However, there is little information about how human coronary artery endothelial cells (HCAEC) are affected by HAv aβ2GPI. The purpose of our study was to evaluate the pathophysiological effects of HAv aβ2GPI on HCAEC and determine their influence on cytokine expression and migration of peripheral blood mononuclear cells. Following the two hit hypothesis, we co-stimulated HAv aβ2GPI-treated HCAEC in the presence and absence of the acute phase protein serum amyloid A (SAA). HAv aβ2GPI induced in vitro HCAEC dysfunction, through the ERK1/2 signaling pathway, promoted the expression of chemokines (MCP-1, GROα and IL-8) and IL-6, which led to the attraction and migration of peripheral blood mononuclear cells. These effects were potentiated and intensified in conditions with SAA, indicating that HAv aβ2GPI, in the presence of physiological concentrations of acute-phase proteins represent pathogenic autoantibodies, which could lead to the development of premature atherosclerosis and/or thrombosis development

Anti-phospholipid antibodies following vaccination with recombinant hepatitis B vaccine

This study was undertaken to evaluate the possible role of hepatitis B recombinant vaccine inducing the synthesis of IgG and IgM anti-cardiolipin antibodies (aCL), antibodies against β(2)GPI (anti-β(2)GPI), lupus anti-coagulant (LA), anti-nuclear antibodies and antibodies against extractable nuclear antigens (anti-ENA). The study population consisted of 85 healthy students (63 female, 22 male; mean age 20·8 years), vaccinated with three doses of recombinant DNA hepatitis B vaccine. One month after vaccination with the first dose of hepatitis B vaccine a minority of vaccinated individuals showed changes in IgG or IgM aCL or anti-β(2)GPI or LA activity (P < 0·001). Among subjects in whom changes of IgG anti-β(2)GPI were observed, a significantly higher number of increased (8/85) than decreased (2/85) values were found (P < 0·01). Analyses of paired data showed that differences in aCL or anti-β(2)GPI levels before vaccination or 1 month later did not reach statistical significance. In two people aCL transitorily reached medium positivity after the first dose of hepatitis B vaccine with a drop 5 months later. Similar evident anti-β(2)GPI fluctuation was also observed in one person. Another participant was initially low positive for IgG anti-β2GPI and the levels were increasing after vaccination. Two participants became positive for anti-nuclear antibodies during 6 months' follow-up. There were no sex-dependent differences in tested antibodies observed and no associations between levels of aPL and levels of anti-HBV antibodies. We conclude that HBV can induce aPL, although rarely. In genetically susceptible individuals or together with some other triggers such combination might confer the risk of developing a continuous autoimmune response in an individual