anisotropy

zbyszek otwinowski zbyszek at cyberramp.net
Thu Apr 23 20:43:31 EST 1998


> realized that my average bfactor had also gone up from 37 to 53.  I
> was a little worried about the value
> being 37, but 53 really scares me.

First, arthmetic average of B-factors is almost meaningless for
proteins. Atoms that are highly disordered,
when properly refined will have very large Bs, 200-500 range is quite
reasonable. For example,
B factor 500 corresponds to atom position uncertainty of 4.5A. Few atoms
with large Bs will
skew the average, but will not contribure at all to most reflections.,

Second, average B is not meaningfull when overall anisotropic factor is
applied to the data.
Separation of B into overall component and individual atom B component
is completely
arbitrary, only the sum of them is important. York correction matrix
seems to apply
about 10-15Asquared to individual atomic Bs.

Zbyszek Otwinowski





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