[Modeling the dynamics of polyunsaturated lipids in biological membranes]

Molecular dynamics simulations were performed for the docosahexaene C22H34 and docosan C22H46 chains, which are typical components of phospholipids in biological membranes. The calculations were carried on at two temperatures of 276 K and 320 K. The time of each computation covered 600 ps. The torsion angles variations phi i(t), i = 1, 2, ..., 21 has been analysed. It has been demonstrated that in docosan phi i(t) are oscillating with the amplitudes of 10-15 degrees, which are slightly increasing with the temperature. The average torsion angle positions correspond to the rotation-isomeric model. In docosahexaene chain the amplitudes of the torsion angles oscillations around a simple bond, connected to a double one, are about twice greater and their frequencies are about 3.5 times less then the docosan have. It has been noted that these angles also possess states, living up to 5 ps, which do not correspond to the regions of the minimum potential energy of molecular fragments. Average frequency of conformational transitions in docosahexaene chain is about six times greater than in the docosan one.