Single Molecular Observation of Hop Diffusion in a Lipid Bilayer at Metallic Nanogates

Abstract

Single molecular tracking was carried out for a lipid molecule (TR-DHPE) in a self-spreading lipid bilayer (egg-PC) on a glass substrate with and without Ag nanoarchitectures. Without Ag architectures, the mean square displacement (MSD) analyses demonstrated that lipid molecules diffuse randomly within the self-spreading lipid bilayer with a diffusion coefficient of 3.1 μm2/s, which is comparable to the value for an artificial solid supported lipid bilayer. However, in the presence of the Ag architectures, TR-DHPE molecules undergo hop diffusion between two neighboring compartments surrounded by the Ag architectures. Smaller diffusion coefficients observed for the substrates with the Ag architectures are attributable to the suppressed diffusion at the gap between the Ag architectures. The escape probability from the initial compartment to the neighboring compartment estimated from the MSD analysis agreed well with the values estimated from the compartment configuration, which proves that the Ag nanoarchitectures act as a diffusion barrier.