Time-of-flight neutron diffraction study of bovine γ-chymotrypsin at the Protein Crystallography Station.

The overarching goal of this research project is to determine, for a subset of proteins, exact hydrogen positions using neutron diffraction, thereby improving H-atom placement in proteins so that they may be better used in various computational methods that are critically dependent upon said placement. In order to be considered applicable for neutron diffraction studies, the protein of choice must be amenable to ultrahigh-resolution X-ray crystallography, be able to form large crystals (1 mm(3) or greater) and have a modestly sized unit cell (no dimension longer than 100 Å). As such, γ-chymotrypsin is a perfect candidate for neutron diffraction.

Decreased sensitivity to changes in the concentration of metal ions as the basis for the hyperactivity of DtxR(E175K).

The metal-ion-activated diphtheria toxin repressor (DtxR) is responsible for the regulation of virulence and other genes in Corynebacterium diphtheriae. A single point mutation in DtxR, DtxR(E175K), causes this mutant repressor to have a hyperactive phenotype. Mice infected with Mycobacterium tuberculosis transformed with plasmids carrying this mutant gene show reduced signs of the tuberculosis infection.

A preliminary neutron diffraction study of gamma-chymotrypsin.

The crystal preparation and preliminary neutron diffraction analysis of gamma-chymotrypsin are presented. Large hydrogenated crystals of gamma-chymotrypsin were exchanged into deuterated buffer via vapor diffusion in a capillary and neutron Laue diffraction data were collected from the resulting crystal to 2.0 A resolution on the LADI-III diffractometer at the Institut Laue-Langevin (ILL) at room temperature.

Malonate: a versatile cryoprotectant and stabilizing solution for salt-grown macromolecular crystals.

Collection of quality data on high-energy synchrotron sources requires the selection of a cryoprotectant that allows protein crystals to be cryocooled without damage to the crystal and with suppression of ice formation. The use of sodium malonate as a versatile cryoprotectant for salt-grown protein crystals is presented here. In addition to its useful cryoprotectant properties, sodium malonate can also function as a versatile stabilizing solution that allows the manipulation, derivatization and ligand soaking of crystals grown from salt that may not be possible in the crystal mother liquor.