Time-averaging crystallographic refinement: possibilities and limitations using α-cyclodextrin as a test system
- 1 January 1995
- journal article
- Published by International Union of Crystallography (IUCr) in Acta Crystallographica Section D-Biological Crystallography
- Vol. 51 (1) , 85-92
- https://doi.org/10.1107/s0907444994007158
Abstract
The method of time-averaging crystallographic refinement is assessed using a small molecule, alpha-cyclodextrin, as a test system. A total of 16 refinements are performed on simulated data. Three resolution ranges of the data are used, the memory relaxation time of the averaging is varied, and several overall temperature factors are used. The most critical factor in the reliable application of time-averaging is the resolution of the data. The ratio of data to molecular degrees of freedom should be large enough to avoid overfitting of the data by the time-averaging procedure. The use of a free R-factor can aid in determining whether time-averaging can be reliably applied. Good ensembles of structures are obtained using data up to 1.0 or 2.0 A resolution. Comparison of electron-density maps from time-averaging refinement and anisotropic temperature-factor refinement indicates that the former technique yields a better representation of the exact data than the latter.Keywords
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