Rapid solubility measurement of protein crystals as a function of precipitant concentration with micro-dialysis cell and two-beam interferometer

Abstract

A novel dialysis-based technique was developed for the rapid and sample-saving determination of the precipitant dependence of protein solubility. We developed a unique thin dialysis cell which permits both the direct optical measurement of protein concentration and the observation of concentration gradients around a crystal via two-beam interferometry. Interferograms around a lysozyme crystal under the desired concentrations of precipitant (NaCl) and lysozyme were observed to determine whether the crystal is growing or dissolving. This technique enables the precipitant dependent solubility curve of lysozyme crystal to be obtained in two days using a small sample (total amount: 7 mg lysozyme).