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Hi Jacob I agree with Juergen, and just add that your Cys and Cl might not be fully occupied. cheers Preben On 9/1/11 10:03 PM, Jacob Keller wrote: > Dear Crystallographers, > > I recently have been working with a 2.5 Ang SeMet peak wavelength > dataset which contains 2 cys's and also a couple of bona fide Cl ions > (reasonable b-factor/site is semi-buried/water does not work). In the > FFT anomalous difference map using PhiC from the refined model and > Dano, I can see the MSE's at ~10 sigma, but no Cl ions, even though Cl > should have f" = ~0.3 versus Se's f" = ~4, and no S's in the cys, > despite f" = 0.23e. There is really no anomalous peak at all--is it > just the smallness of the signal, or are the Se's somehow "swamping > out" the other signal? Perhaps the phases are tainted by the presence > of semet in the model? > > Looking for suggestions, > > Jacob Keller > > ******************************************* > Jacob Pearson Keller > Northwestern University > Medical Scientist Training Program > cel: 773.608.9185 > email: [log in to unmask] > ******************************************* -- J. Preben Morth, Ph.D Group Leader Membrane Transport Group Nordic EMBL Partnership Centre for Molecular Medicine Norway (NCMM) University of Oslo P.O.Box 1137 Blindern 0318 Oslo, Norway Email: [log in to unmask] Tel: +47 2284 0794 http://www.jpmorth.dk