About HWI What does HWI do? Leadership Fast Facts History Our Nobel Laureate HWI Building Career Opportunities Visitor Information
Medical Research Institute
1. Radiation damage in X-ray Crystallography
Radiation damage occurs when X-rays interact with matter in the crystal or mother liquor surrounding the crystal. Free radicals are formed which can migrate damaging the short-range and eventually long-range order of the crystal. To some extent this damage can be mitigated by cryocooling. Our aims are three fold;
Studies to understand radiation damage center round a model protein, xylose isomerase. Xylose isomerase has an active site that is very sensitive to the damage. Starting from data at 0.95Å resolution we have gradually incurred damage through successive data sets reducing the overall resolution to 1.20Å. The radiation causes defined structural changes in the enzyme.
2. Free radical scavengers and metalloproteins
We are currently developing Extracellular SOD (ecSOD) as a crystallization target along with Fibulin-5/DANCE, a binding protein for ecSOD. Understanding the structure and mechanism of these proteins is important in understanding many common cardiovascular diseases. We are also in the early stages of studies on P450's important in drug metabolism.
3. The development and use of neutron diffraction
Neutron diffraction does not cause radiation damage and is unique in its ability to detect deuterium at resolutions of approximately 2Å. This means, by the replacement of hydrogen with deuterium, one can determine key hydrogen positions, protonation state and study samples and physiologically relevant temperatures.
Neutron flux is weak and hence neutron diffraction has not been developed as a well used technique. However, with the use of the Laue method studies have been increasing at sources in the US, France and Japan. The Spallation Neutron Source at Oak Ridge, Tennessee is under construction and will greatly increase the available neutron flux enabling many experiments that are currently not possible. We are working on the other side of the problem by increasing crystal volume with a number of model proteins and targets for our own structural studies.
4. Macromolecular Crystal Quality
Quality in a crystal can be described as long-range or short-range. In general long-range disorder in the crystal gives rise to localized effects in reciprocal space and vice versa. For example, crystal mosaicity, which is a large-scale property in real space, causes the localized effect of broadened spots in reciprocal space whereas the effect of random disorder between adjacent unit cells is a global, resolution-dependent reduction in diffracted intensity in reciprocal space. Thus, careful measurements of the diffraction from macromolecular crystals can reveal the degree and nature of their disorder. Since macromolecular crystals are, by the standard of small molecule crystals, not very good crystals, they offer a fruitful field for the study of disorder. A better understanding of the nature and causes of disorder in macromolecular crystals can lead to the production of better crystals.
|back to top|
|700 Ellicott Street Buffalo, New York 14203-1102 Tel: 716 898 8600 Fax: 716 898 8660|