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Dear Pat, You don't say how large your ligand is, but if the occupancy is refined as a single parameter so that all the atoms in the ligand are constrained to have the same occupancy, it should be rather well-defined and not highly correlated with the B-values. By the way, I was not your referee! Best wishes, George Prof. George M. Sheldrick FRS Dept. Structural Chemistry, University of Goettingen, Tammannstr. 4, D37077 Goettingen, Germany Tel. +49-551-39-3021 or -3068 Fax. +49-551-39-22582 On Sun, 31 May 2009, Patrick Loll wrote: > Hi all, > > I'm looking for a reference to bolster my response to a referee, in which I > defend my decision not to refine the occupancy of a ligand in structure > refined at around 2 A resolution (note the ligand binding slte lies on a > two-fold crystallographic axis, so the maximum occupancy is 0.5) > > I recall reading a paper a LONG time ago (decades) in which someone described > some careful refinement experiments, and concluded that the correlation > between occupancy and B-value is so strong that it simply makes no sense to > "independently" refine both parameters (at least for light atoms, and in the > absence of super high resolution data). > > Alas, all that I recall is this take-home message. I have no idea of where the > paper appeared, or the names of the authors (or indeed, if I'm even > remembering the paper's message correctly). I've tried trolling through Acta, > without success. Does anyone have a better idea of where I might find this > paper, or one espousing a similar message? > > Thanks, > > Pat > > > ------------------------------------------------------------------------------------- > Patrick J. Loll, Ph. D. Professor of > Biochemistry & Molecular Biology > Director, Biochemistry Graduate Program > Drexel University College of Medicine > Room 10-102 New College Building > 245 N. 15th St., Mailstop 497 > Philadelphia, PA 19102-1192 USA > > (215) 762-7706 > [log in to unmask] > > > >