Modulation of elasticity and interactions in charged lipid multibilayers: monovalent salt solutions

We have studied the electrostatic screening effect of NaCl solutions on the interactions between anionic lipid bilayers in the fluid lamellar phase using a Poisson-Boltzmann based mean-field approach with constant charge and constant potential limiting charge regulation boundary conditions. The full DLVO potential, including the electrostatic, hydration and van der Waals interactions, was coupled to thermal bending fluctuations of the membranes via a variational Gaussian Ansatz. This allowed us to analyze the coupling between the osmotic pressure and the fluctuation amplitudes and compare them both simultaneously with the measured dependence on the bilayer separation, determined by the small-angle X-ray scattering experiments. High-structural resolution analysis of the scattering data revealed no significant changes of membrane structure as a function of salt concentration. Parsimonious description of our results is consistent with the constant charge limit of the general charge regulation phenomenology, with fully dissociated lipid charge groups, together with a four-fold reduction of the membranes' bending rigidity upon increasing NaCl concentration.Comment: 18 pages, 5 figures, improved discussions of the steric parameter (or penetration coefficient) c, vestigial osmotic pressure and salt-induced reduction of bending rigidity of charged lipid bilayers, Langmuir (2016

Poincaré-invariant constituent quark model for light mesons: capabilities and constraints

We present a brief survey of some results on electroweak properties of com- posite systems that are obtained in the frameworks of our version of the instant form of relativistic quantum mechanics (RQM). Our approach describes well the π- and the ρ- mesons in wide range of momentum transfers Q2. At large Q2 the obtained pion form factor asymptotics coincides with that of QCD predictions. The method permits to per- form analytic continuation of pion form factor to complex plane of momentum transfers that is in accordance with predictions of quantum field theory