Structural properties of CHAPS micelles, studied by molecular dynamics simulations.

FERNANDO E. HERRERA; A. SERGIO GARAY; DANIEL E. RODRIGUES

Villa Carlos Paz, Córdoba

Congreso; XLII Reunión Anual de la Sociedad Argentina de Biofísica; 2013

SAB - Sociedad Argentina de Biofísica

P { margin-bottom: 0.08in; } Detergents are essential tools to study biological membranes. They are frequently used to solubilize lipids and integral membrane proteins, and to evaluate the strength of interaction of the membrane components. The nondenaturing zwiterionic detergent usually named CHAPS was designed for membrane biochemistry and integrates the effects of sulfobetaine-type detergents and bile salts. Despite of the available experimental data little is know about the molecular structure of its micelles. We performed Molecular Dynamics simulations to study the aggregation in micelles of several numbers of CHAPS (1-16) starting from an homogeneous water dilution. We developed and validated the forcefield parameters to describe the interactions of the molecule. After 50ns of simulation all the systems result in the formation of stable micelles. We characterize the molecular shape (gyrate radii, volume, surface) of the micelles. We analyzed the molecular structure (RDF, salt bridges, H-bonds, SAS) and found that the main interactions that lead to the stability of the micelles are the electrostatic ones among the polar groups of the tails and the OH´s from the rings moiety. At variant with micelles of other compounds, CHAPS- show a grain-like heterogeneity with hydrophobic micro-pockets. Our results agree with avalaible information from NMR and X-ray. The rotational diffusion of the micelles is also characterized to compare with EPR spectroscopy results.