9304674 Carter This is a project to adapt X-ray crystallographic phasing methods based on the theoretical work of G. Bricogne and apply them to protein structure determination. The immediate goal is to complete the structure of the monoclinic form of tryptophane synthetase using maximum entropy extrapolation and phase permutation to generate new phases and symmetrization by a known six-fold noncrystallographic redundancy to refine them. The expectation is that noncrystallographic symmetry averaging, together with techniques cited above represent sufficient potential phase information to solve the structure ab initio. %%% This proposal deals with advanced computational methods for solving crystal structures using maximum entropy methods. In particular, these studies involve the crystallographic phasing problem, especially involving deficient data sets and may lead to eliminating the need for isomorphous replacement methods. These methods will be applied to solve the structure of monoclinic tryptophanyl-t-RNA synthetase. ***
