Surface-potential controlled Si-microarray devices for heterogeneous protein crystallization screening

Fundamental investigations of protein crystallization using microarrayed multiple cell Si-devices were proposed for achieving heterogeneous nucleation/crystallization and also for screening experiments. Surface-potential (C-potential) controlled nucleation and crystallization sites made from deposited thin-film semiconductor and insulating materials were fabricated on the surface of each crystal growth cell. zeta -potential measurement using the electrophoretic light scattering spectrophotometric method showed that both of ionic strength and pH values had a great influence on the potential of solid material surfaces, such as n/P-Si, SiO2, Si3N4, and Al2O3, and also protein ones. Isoelectric point of protein was influenced and shifted with the ionic strength, but point of zero charge of our solid material surface was still unchanged. Then the conventional microarrayed configuration was adopted in our device, but each unit well was composed of single reservoir and paired multiple crystal growth cells to prepare the protein droplets of different buffer and precipitant concentrations. The number of our multiple growth cells in a unit well was at least 2, and the available volume for protein drop ranged from 1 to 10 mul. This cell configuration and sample preparation was expected to cover the whole effective pH and concentration regions for heterogeneous nucleation and crystallization and accordingly accelerate the screening experiments without changing conventional reagents and protocols. (C) 2001 Elsevier Science B.V. All rights reserved.