Interaction Forces and Adhesion of Myelin Lipid Bilayers as Modulated by Myelin Basic Protein

Our SFA results indicate that myelin lipid-protein interactions, and especially the adhesion forces and minimum cytoplasmic spacings, are determined by a synergistic mechanism involving both the positively charged MBP protein and the negatively charged lipids, although other interactions such as van der Waals, hydrophobic and weak dipolar interactions between zwitterionic groups on the lipids and MBP may also be contributing to the attractive forces. In particular, both the amount and ratio (or balance) of positive charges on MBP and negative charges on the lipid headgroups act together to determine the optimum electrostatic forces, with maximum adhesion occurring when each negative group can bind to a positive arginine or lysine group on MBP. When MBP is present in excess, the bilayers swell and the excess MBP appears to form a weak and dilute gel-like structure between the surfaces that exhibits a phase transition on being compressed.