混合磷脂单分子层和双分子层的纳米尺度表面性质

Mixed distearoylphosphatidylethanolamine (DSPE) and dioleoylphosphatidylethanolamine (DOPE) monolayers and bilayers have been deposited on mica using the Langmuir-Blodgett (LB) technique, as amodel systemfor biomembranes. Investigation with atomic forcemicroscopy revealed phase-separation for both monolayers in air and bilayers in water in the form of microscopic DSPE domains embedded in a DOPE matrix. For the monolayers in air, the step height measured between the higher DSPE phase and the lowerDOPE phasewas larger than expected fromthemolecular lengths, and a significant contrast in adhesion and frictionwas observed despite identical lipid end groups. This unexpected behavior resulted primarily froma difference in the filmmechanical properties, theDOPEphase being inelastically deformed by the probe. For the bilayers in water, similar trends were found in terms of height, adhesion, and friction, but an additional short-range repulsive hydration/steric force over the DSPE phase contributed to the observed differences.