| Abstract
| - We simulated micelles of 40 (M40), 54 (M54), and 65 (M65) dodecylphosphocholine (DPC) lipids in waterfor up to 15 ns and analyzed the system energetics, structure of the water/lipid interface, structure and dynamicsof the lipid tails, and overall size and shape of the micelles. M54 and M65 are similar, being mostly sphericalin shape with comparable tail order parameters, atom distributions, and solvent accessible areas, whereasM40 assumes a prolate ellipsoid shape with a larger hydrophobic solvent accessible area per lipid and morerestricted lipid packing. A comparison of the lipid chain structure and dynamics with those of decane anddipalmitoylphosphatidylcholine (DPPC) shows that the trans dihedral fractions are comparable, but that thedihedral transition rate is considerably slower in the micelles than in decane or DPPC, in agreement with aprevious simulation of the sodium dodecyl sulfate micelle but in contrast with a recent simulation of DPC.The relaxation behavior of the CH2 segments in the lipid chains is complex, and the overall and internalmotions of the lipids cannot be separated. The full orientational autocorrelation function of the CH vectorsis calculated and found to decay to zero within a few nanoseconds, which is fast compared to overall micellarrotation. From a direct calculation of the spectral densities, 13C T1 and T2 relaxation times of the tail carbonsare calculated and found to agree well with experimental measurements for the lipid chain carbons, but lesswell for the headgroup.
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