Phospholipid Epitaxial Assembly Behavior on a Hydrophobic Highly Ordered Pyrolytic Graphite Surface

Abstract

Supported lipid bilayers (SLBs) are excellent models of cell membranes. However, most SLBs exist in the form of phospholipid molecules standing on a substrate, making it difficult to have a side view of the phospholipid membranes. In this study, the phospholipid striped lamella with the arrangement of their alkane tails lying on highly ordered pyrolytic graphite (HOPG) was constructed by a spin coating method. Atomic force microscopy and molecular dynamics simulations are utilized to study the self-assembly of phospholipids on HOPG. Results show that various phospholipids with different packing parameters and electrical property are able to epitaxially adsorb on HOPG. 0.1 mg/mL Plasm PC (0.1 mg/mL) could form a striped monolayer with a width of 5.93 ± 0.21 nm and form relatively stable four striped layers with the concentration increasing to 1 mg/mL. The width of the DOPS multilayer is more than that of electroneutral lipids due to the static electrical repulsion force. This universal strategy sheds light on direct observation of the membrane structure from the side view and modification of 2D materials with amphiphilic biomolecules.

Structure and thermodynamics of supported lipid membranes on hydrophobic van der Waals surfaces

“…Only recently has the use of hydrophobic carbon substrates such as graphite and its monolayer counterpart graphene been introduced as supports for the formation of lipid membranes. 21–26 In this case, lipids immersed in water from stable monolayers with the tails adjacent to the solid interface and the head groups pointing away from the hydrophobic surface towards the water. It has been predicted that subsequent lipid bilayers might then form on top of the first interfacial monolayer.…”