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A systematic analysis of weighting schemes for structure factors in macromolecular crystallography
Author(s) -
Vellieux F. M. D.
Publication year - 1997
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889896015592
Subject(s) - weighting , figure of merit , computation , phase (matter) , mathematics , trigonometric functions , algorithm , physics , optics , geometry , quantum mechanics , acoustics
The three weighting schemes for structure‐factor amplitudes used in macromolecular crystallography, and the products of these weighting schemes, have been analysed by comparison of the figures of merit to the cosine of the phase difference between the current phase estimate and the true phase, and by computation of the linear correlation coefficient between these figures. The results of the analysis indicate that (i) the σ A and Sim weighting schemes are superior to all others investigated (for the latter scheme, provided that Σ L has been computed by the method of Henderson & Moffat [ Acta Cryst. (1971), B 27 , 1414–1420]), (ii) all weighting schemes are an underestimate of the cosine of the phase difference, (iii) the correlation between the Rayment figures of merit and the cosine of the phase difference is quite low, indicating a poor weighting scheme, and (iv) for the figures of merit obtained by multiplication of weights, better results are obtained when the best weighting schemes, namely the σ A and Sim figures of merit, are combined.