Real-time measurement of protein crystallization method based on optical interferometry

摘要

The growth of large and high quality protein crystals has been a bottleneck for the determination of three dimensional structures and medicines design. Failure to prepare large crystals can be partly attributed to a lack of understanding of the crystal growth process. In this paper, a real-time optical diagnostic system consisting of the Mach-Zehnder interferometer with the phase-shift device, a microscope and an image processor has been developed for the study of the kinetics of the crystal growing process. The crystallization of NaCl was investigated to simulate protein crystallization method of vapor diffusion with an oil barrier. 1) The relative refractive index could be obtained from four-step phase-shift algorithm. 2) Fourier analysis and Windowed Fourier analysis were applied in the spatiotemporal domains to extract evolution of the absolute refractive index profile, which has not appeared before as far as we know. 3) The comparison of Fourier analysis and windowed Fourier analysis in phase and velocity measurements is also presented. The experiment has a major theoretical and practical significance in the domain of crystal growth experiments and crystal optimization.