International
Tables for Crystallography Volume F Crystallography of biological macromolecules Edited by M. G. Rossmann and E. Arnold © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. F. ch. 16.1, p. 336
Section 16.1.5.2. Iterative peaklist optimization
a
Institut für Anorganisch Chemie, Universität Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany,bHauptman–Woodward Medical Research Institute, Inc., 73 High Street, Buffalo, NY 14203-1196, USA, and cLehrstuhl für Strukturchemie, Universität Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany |
An alternative approach to peak picking is to select approximately peaks as potential atoms and then eliminate some of them, one by one, while maximizing a suitable figure of merit such as The top peaks are used as potential atoms to compute . The atom that leaves the highest value of P is then eliminated. Typically, this procedure, which has been termed iterative peaklist optimization (Sheldrick & Gould, 1995), is repeated until only atoms remain. Use of equation (16.1.5.1) may be regarded as a reciprocal-space method of maximizing the fit to the origin-removed sharpened Patterson function, and it is used for this purpose in molecular replacement (Beurskens, 1981). Subject to various approximations, maximum-likelihood considerations also indicate that it is an appropriate function to maximize (Bricogne, 1998). Iterative peaklist optimization provides a higher percentage of solutions than simple peak picking, but it suffers from the disadvantage of requiring much more CPU time.
References
Beurskens, P. T. (1981). A statistical interpretation of rotation and translation functions in reciprocal space. Acta Cryst. A37, 426–430.Google ScholarBricogne, G. (1998). Bayesian statistical viewpoint on structure determination: basic concepts and examples. Methods Enzymol. 276, 361–423.Google Scholar
Sheldrick, G. M. & Gould, R. O. (1995). Structure solution by iterative peaklist optimization and tangent expansion in space group P1. Acta Cryst. B51, 423–431.Google Scholar