[ccp4bb]: How to evaluate local coordinate error (?)

[James Stroud <James.Stroud@Colorado.EDU>]

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This is not a question directly related to ccp4 as far as I can tell, but I'm hoping someone on this list may have some insight.

We are presently working on the structure of a mutant wherein this mutant appears to have the rigid body movement of a 15 residue alpha-helix by about 1 Angstrom relative to the position of the helix in the wild-type. This movement is "detected" by the 2.5 sigma density of a simulated annealing fofc omit map. The problem is that our reflection data is 2 sigma only to about 3.2 Angstroms. So my questions are: How valid are any conclusions derived from this perceived movement? Is there a mathematical/statistical basis for such conclusions. If any person has a reference, I would be grateful. Or, almost as helpful would be for someone to restate my problem in the proper terminology so that I may do my own research. Of course a flat-out answer would be wonderful.

Thank you in advance for your help,

James
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 James C. Stroud
 Department of Chemistry and Biochemistry
 University of Colorado at Boulder
 Boulder, CO 80309

 Tel: 303-492-4503      Fax: 303-735-1347
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