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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. 13.1, p. 265
Section 13.1.4.1. The cross-rotation function
aBiophysics Group, Blackett Laboratory, Imperial College of Science, Technology & Medicine, London SW7 2BW, England |
The rotation function can be used in the generalized case to compare the Patterson functions of different crystals. When used in this way, it is called the cross-rotation function. In the most usual case, information providing some kind of structural model is available for one of the crystals.
The power of the cross-rotation function may be greatly improved by removing all intermolecular vectors from the `model' Patterson function. This may be done by constructing an imaginary crystal structure in which a single copy of the structural model is placed in a unit cell that is large enough for all intermolecular vectors to be longer than the longest intramolecular vector of the model. In this cell, the self-Patterson vectors may be completely isolated and used for comparison with the Patterson function of a crystal containing a molecule of unknown orientation.
