Fluorescence correlation spectroscopy and Brownian dynamics simulation of protein diffusion under confinement in lipid cubic phases

Abstract

The diffusion coefficient of protein lysozyme confined in lipid monoolein cubic phases was measured by fluorescence correlation spectroscopy. From the ratio of the diffusion coefficient of confined lysozyme to the one in a bulk solution, the barrier of confined diffusion was estimated to be about 3–4k_BT at 20 °C. The origin of the barrier was investigated using Brownian dynamics simulations with model cubic phase structures based on so-called infinite periodic minimal surfaces. The simulations suggested a structure of the confinement as well as the importance of the hydrodynamic interaction between a particle and walls.