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Jason, How does the diffraction pattern look? Do you see multiple lattices or split spots? It seems to me that XDS isn't able to index it (correctly) possibly because of these things. It's always worth it to manually page through your images just to confirm. I've personally seen people just use XDS and assume everything went well, and run into similar problems. Kelly ******************************************************* Kelly Daughtry, Ph.D. Post-Doctoral Fellow, Raetz Lab Biochemistry Department Duke University Alex H. Sands, Jr. Building 303 Research Drive RM 250 Durham, NC 27710 P: 919-684-5178 ******************************************************* On Tue, May 17, 2011 at 5:43 PM, Jason Busby <[log in to unmask]> wrote: > Hi, > > I have a diffraction data-set from a hexagonal rod shaped crystal, to about > 2.0 Å. The problem comes when I try to process the data - Mosflm won't > index it, and XDS indexes it as P622, but the unit cell is too small to > contain even a single molecule of my protein. I have tried integrating it > in some different space groups that XDS suggested (P2, C2, P1) but in all > cases the Rmerge and Rmeas are worse than for P622. > > If I scale in P622 (or any of the other space groups) I get odd results > from the twinning tests. For example, the 4th moment of E (expected values > of 2 for untwinned, 1.5 for perfect twin) is around 1.1, and the L-test and > cumulative intensity distribution are unusual as well (uploaded images here: > http://tinypic.com/r/65rfr7/7 and here: http://tinypic.com/r/30adgyr/7 ) > > Has anyone else had similar issues? Any ideas would be appreciated. > > Thanks, > > Jason. > > -- > Jason Busby > PhD Student > Laboratory of Structural Biology > School of Biological Sciences > University of Auckland > Thomas Building 110 > 3a Symonds St > Private Bag 92019 > Auckland 1142 > New Zealand > > ph: +64 9 3737599 ext 83888 > fx: +64 9 3737414 >