Molecular dynamics simulations of octyl glucoside micelles: Structural properties

Molecular dynamics simulations were used to explore the effect of aggregate size on structural properties of octyl glucoside (OG) micelles. Systems in cluded micelles of 1, 5, 10, 20, 27, 34, 50, and 75 surfactant molecules in water, as well as an OCT bilayer, and neat octane. Micelles consisting of 5 lipids were unstable, while those of 10 or more remained intact (except f or rare single lipid escapes) during the 4 ns simulations. Aggregate shape and internal properties (tail length, dihedral angle distributions, and iso merization rates) change little with size. In contrast, surface properties (hydrophobic accessible surface area and headgroup cluster size) vary with size, a consequence of the decreasing surface area-to-volume ratio in large r aggregates. Micelles in the studied size range are nonspherical with roug h, uneven surfaces. Their tail lengths are comparable to those in the bilay er and neat octane, indicating that packing into a compact highly curved sh ape does not significantly distort the tails. Instead, the preference of th e tails for an extended conformation may drive the micelle to exhibit a rou gh surface with large hydrophobic patches.