W0137

Crystallography and NMR System: a New Approach for Phasing and Refinement. Axel T. Brünger, Yale University/HHMI, Department of Molecular & Biochemistry, 434-A Bass Center, 266 Whitney Avenue, New Haven, CT 06520 USA

A new and advanced software system, termed Crystallography and NMR System (CNS), for crystallographic and NMR structure determination has been developed. The goals of CNS are: (1) to create a flexible computational framework for exploration of new approaches to structure determination, (2) to provide tools for structure solution of difficult or large structures, (3) to develop models for analyzing structural and dynamical properties of macromolecules, and (4) to integrate all sources of information into all stages of the structure determination process.

To meet these goals, algorithms were moved from the source code into a symbolic structure determination language which represents a new concept in computational crystallography. The high-level CNS computing language allows definition of symbolic target functions, data structures, procedures, and modules. The CNS program acts as an interpreter for the high-level CNS language and includes hard-wired functions for efficient processing of computing-intensive tasks. Methods and algorithms are therefore more clearly defined, and easier to adapt to new and challenging problems. The result is a multi-level system which provides maximum flexibility to the user. The CNS language provides a common framework for nearly all computational procedures of structure determination. A comprehensive set of crystallographic procedures for phasing, density modification, and refinement has been implemented in this language. Task-oriented input files written in the CNS language, which can also be accessed through an HTML graphical interface, are available to carry out these procedures.

A.T. Brünger, P. Adams, G. Clore, W. DeLano, P. Gros, R. Grosse-Kunstleve, J.-S. Jiang, J. Kuszewski, M. Nilges, N. Pannu, R. Read, L. Rice, T. Simonson, G. Warren (1998). Crystallography & NMR System (CNS): A New Software Suite for Macromolecular Structure Determination. Acta Cryst. D, in press, 1998.