Long-timescale motions in glycerol-monopalmitate lipid bilayers investigated using molecular dynamics simulation

The occurrence of long-timescale motions in glycerol-1-monopalmitate (GMP) lipid bilayers is investigated based on previously reported 600 ns molecular dynamics simulations of a 2×8×8 GMP bilayer patch in the temperature range 302-338 K, performed at three different hydration levels, or in the presence of the cosolutes methanol or trehalose at three different concentrations. The types of long-timescale motions considered are: (i) the possible phase transitions; (ii) the precession of the relative collective tilt-angle of the two leaflets in the gel phase; (iii) the trans-gauche isomerization of the dihedral angles within the lipid aliphatic tails; and (iv) the flipping of single lipids across the two leaflets. The results provide a picture of GMP bilayers involving a rich spectrum of events occurring on a wide range of timescales, from the 100-ps range isomerization of single dihedral angles, via the 100-ns range of tilt precession motions, to the multi-μs range of phase transitions and lipid-flipping events.