Molecular dynamics simulations of DPPC, DHPC, DMPC and DTPC lipid bilayers in water: A detailed study of the water distribution at the interface

GARAY, ALBERTO S.; NICASTRO, ALCIDES; RODRIGUES, DANIEL E.

Rosario, Argentina

Congreso; XXXV Reunión Anual de la Sociedad Argentina de Biofísica; 2006

SAB

<!-- @page { size: 8.5in 11in; margin: 0.79in } P { margin-bottom: 0.08in } --> A detailed comparative study of lipid bilayers of DPPC, DHPC, DMPC and DTPC in water has been performed using Molecular Dynamics (MD) simulations. We obtained different sets of atomic charges of the lipid polar head using quantum mechanical calculations on several molecular conformations. These molecular conformations are obtained from previous MD simulations and classified using cluster statistical methods. For different molecular conformations the atomic charges on the C=O group of the Sn-1 and Sn-2 chains can differ up to 0.1|e|. These differences are enough to affect the results of the MD simulation (e.g. Atomic density profiles, hydrogen bond number and distribution). The structure of the intra- and inter-molecular hydrogen bonds, and their relation with the atomic density profiles are analyzed. Our results give support to the existence of a dynamical charge effect at the polar head that affects the lipid-water interaction. The model would explain the long sustained debate about the origin of several peaks in each isotope component of the IR spectra C=O stretching bands in lipids labeled with 13C=O substitution on Sn-1 or Sn-2.