The distribution and conformation of very long-chain plant wax components in a lipid bilayer.

Plant wax contains long-chain alkanes and related components which are transported to the surface of the plant by specialized ABC transporter proteins. Here, we determine the distribution and conformation of three wax components, nonacosane, nonacosan-15-one, and nonacosan-15-ol, using unbiased and umbrella sampling molecular dynamics simulations. The molecules all partitioned to the center of the bilayer, with a free-energy difference of -70 kJ/mol between bulk water and the center of the bilayer for the alkane and -55 kJ/mol for the two more-polar molecules. All of the wax molecules were highly mobile in the bilayer, freely moving between opposite leaflets on a time scale of a few nanoseconds. Nonacosan-15-one and nonacosan-15-ol folded double to expose their hydrophilic group to the solvent, whereas nonacosane alternated between orientations spanning the full bilayer and orientations in the center of the bilayer.