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 included micelles of 1, 5, 10, 20, 27, 34, 50, and 75 surfactant molecules in water, as well as an OG bilayer, and neat octane. Micelles consisting of 5 lipids were unstable, while those of 10 or more remained intact (except for rare single lipid escapes) during the 4 ns simulations. Aggregate shape and internal properties (tail length, dihedral angle distributions, and isomerization 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 larger aggregates. Micelles in the studied size range are nonspherical with rough, uneven surfaces. Their tail lengths are comparable to those in the bilayer and neat octane, indicating that packing into a compact highly curved shape does not significantly distort the tails. Instead, the preference of the tails for an extended conformation may drive the micelle to exhibit a rough surface with large hydrophobic patches.