Molecular replacement using electron diffraction data

Brandeis University, Waltham MA

Investigators

Linked publications & trials

Abstract

We propose to develop enhanced use of diffraction data in the electron crystallography of 2-D crystals. Provided that well-ordered 2-D crystals are available., collecting and processing of there are many fewer factors that degrade the quality of electron diffraction data. Thus, to accelerate electron crystallographic structure determination, we will pursue the following aims. (1) We will develop methods of integrating and processing electron diffraction data to improve their accuracy. (2) We will adapt methods from x-ray crystallography for rapid determination and refinement of phase information. The evolution of proteins, including membrane proteins, has generated large families of polypeptides with related folds, and molecular replacement the use of one structure to determine phases of diffraction data from crystals of a related structure is therefore a especially powerful tool. We will develop the application of this approach to 2-D crystals of membrane proteins, and we will also explore ways to exploit fine sampling among lattice lines, multiple crystal forms, and non-crystallographic symmetry to refine and extend phases. We will use bacteriorhodopsin as a test specimen to develop the computational techniques. (3) We will apply these procedures in eicosanoid and glutathione metabolism) families. Members of both families are known to form large and very well ordered 2-D crystals, and sufficient data are available for the proposed molecular replacement and phase extension techniques.