Chapter One - Charged Particles can Mediate Attraction Between Equally Charged Membranes—Theoretical Study

Abstract

Electrostatic interactions are one of the leading interactions in all biological systems. In this chapter, we present a possible mechanism which can lead to attractive interaction between two like-charged biological surfaces. We show three different modeled systems of charged biological surfaces in the solution containing charged macro-ionic particles which were inspired by experimental observations. In our proposed mechanism, we take into consideration the orientational entropy of the system. Namely, when the macro-ionic particles in solution have distinctive internal distribution of charge, the additional degrees of freedom for rotation are involved in the entropic contribution to the total free energy. The contribution is negative and thus lowers the free energy. Under certain conditions, this can lead to attractive force between like-charged surfaces. In the study, we use analytical as well as numerical methods—modifications of Poisson–Boltzmann equation and Monte Carlo simulations. We studied rod-like and spherical geometry of particles which can mediate the attraction. The macro-ionic particles can represent different kinds of proteins or various metallic nanoparticles in aqueous surrounding.