Figure 14.

Typical conformation and potential of mean force for adsorbed PEG molecules. (A,B) Simulation snapshots of PEG molecule adsorbed onto Ld and Lo bilayer. The color code for the lipids is blue for DOPC, orange for DPPC, and red for cholesterol. The PEG molecules consist of 180 monomers corresponding to the average molecular weight used in the experiments. Each lipid membrane is immersed in about 27,000 water molecules (not shown). (C,D) Potential of mean force (PMF) for Ld and Lo membranes as a function of the separation z between the polymer's center-of-mass and the bilayer midplane. The potential wells are relatively broad, with a width of about 4 nm, because the polymer end groups can adsorb even for relatively large z-values. The binding free energy of a single PEG chain is about 4 kJ/mol or 1.6 k_BT for both types of membranes. Reprinted with permission from Liu et al. (2016). Copyright (2016) American Chemical Society.