The Study of the Mechanism of Protein Crystallization in Space by Using Microchannel to Simulate Microgravity Environment

Abstract

Space is expected to be a convection-free, quiescent environment for the production of large-size and high-quality protein crystals. However, the mechanisms by which the diffusion environment in space improves the quality of the protein crystals are not fully understood. The interior of a microfluidic device can be used to simulate a microgravity environment to investigate the protein crystallization mechanism that occurs in space. In the present study, lysozyme crystals were grown in a prototype microchannel device with a height of 50 µm in a glass-polydimethylsiloxane (PDMS)-glass sandwich structure. Comparative experiments were also conducted in a sample pool with a height of 2 mm under the same growth conditions. We compared the crystal morphologies and growth rates of the grown crystals in the two sample pools. The experimental results showed that at very low initial supersaturation, the morphology and growth rates of lysozyme crystals under the simulated microgravity conditions is similar to that on Earth. With increasing initial supersaturation, a convection-free, quiescent environment is better for lysozyme crystal growth. When the initial supersaturation exceeded a threshold, the growth of the lysozyme crystal surface under the simulated microgravity conditions never completely transform from isotropic to anisotropic. The experimental results showed that the convection may have a dual effect on the crystal morphology. Convection can increase the roughness of the crystal surface and promote the transformation of the crystal form from circular to tetragonal during the crystallization process.

Real-Time Measurement of Protein Crystal Growth Rates within the Microfluidic Device to Understand the Microspace Effect

“…Generally, microfluidic devices of 100 μm in depth can be regarded as the microgravity environment. Several research groups reported the microfluidic device for protein crystal growth in microgravity and the typical optical microscope-based crystal growth analysis. , However, the mechanism and kinetics of protein crystal growth in the microfluidic device was not elucidated in detail due to limitations in measuring the crystal growth process within the device. To overcome the problem, we demonstrated real-time spectroscopy-based measurement of the protein crystal growth in the microfluidic device.…”

Flow Instabilities of Coupled Rotation and Thermal-Solutal Capillary Convection of Binary Mixture in Czochralski Configuration

“…In the material processing industry, the crystal growth process is an important example that the qualities of the crystal materials are closely affected by the flow instabilities resulting from the buoyancy and thermal-solutal convections, since the oscillatory flow induces impurity striations in the crystals [3,4]. Especially, under microgravity conditions, the effect of gravity is minimized [5] and the effect of thermal-solutal capillary flow generated by surface tension gradient is highlighted [6][7][8]. Czochralski (Cz) crystal growth technology is an important method for producing crystals, where a rod-mounted seed crystal dipped into melt and carefully pulled out by controlling the thermal and concentration gradients, crystal rotation and pulling rates [9,10].…”