Sridhar Gorti

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 (ζ-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. ζ-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, SiO 2 , Si 3 N 4 , and Al 2 O 3 , 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 μl. 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.

TRIANGULATION METHOD FOR DETERMINING CAPILLARY BLOOD FLOW AND PHYSICAL CHARACTERISTICS OF THE SKIN

A method capable of measuring blood flow at precise depths within the skin is described. The method determines the static and the dynamic properties of light that is backscattered to small areas on the surface of the skin at several contiguous locations along the expected trajectory of laser-light propagation. From observations the method has been shown to be capable of determining physical characteristics that are unique to the different layers of the skin.

Lysozyme diffusion adjacent to the (1 1 0) crystal surface

Measurements of lysozyme diffusion within the depletion zone of the (110) face of lysozyme crystals are reported. The measurements were performed using the technique of microscope light scattering, capable of measuring small sampling areas (∼2 μm 2 ). Measurements within such small areas allowed for the determination of intensity correlation functions at precise locations (at ∼ 10 μm intervals) adjacent to the (110) crystal face. From the intensity correlation functions, diffusion coefficients of lysozyme molecules adjacent to the (110) crystal face and in solution were determined. The diffusion coefficients were observed to decrease as the surface of the crystal was approached.

Macromolecular Crystallization Microarrayed Chip for Super Saturated Vapor and Liquid-Liquid Diffusion Screening

In spite of the need and effort for obtaining high quality single crystals in modern structural biology, biological macromolecules are still hard to crystallize. Here we propose an improved crystallization strategy using a Si-based microarrayed chip for allowing high yield of macromolecular crystals without changing conventional screening reagents and protocols. Some crystallization experiments using commercial proteins are also presented.