A membrane crystallization method using ultrafiltration was investigated to obtain high-quality protein crystals for structural analysis. Membrane surface concentrations, which could not be measured, can be estimated by simulation. The membrane surface concentration increased rapidly during initial pressurization at any pressure, which was found to be the initial stage of crystal formation.

Abstract

High-quality single crystals are necessary for structural analysis of proteins. However, it is difficult to obtain high-quality single crystals in a short time. Therefore, a membrane crystallization method was applied in which lysozyme is concentrated on the membrane surface using an ultrafiltration membrane. Membrane surface concentrations, which cannot be measured, were calculated based on the measurable permeation flux. At all operating pressures, the measured and simulated permeation fluxes were in close agreement, allowing the membrane surface concentration to be estimated. The membrane surface concentration increased rapidly at all pressures during the initial pressurization, indicating that crystals were formed at an early stage.