 |
 |
Hi Francisco, If your real mosaic spread is quite a bit larger than the oscillation width (which I guess is likely) then you have either fine or very finely sliced data. I would be tempted to give this a go with a 3D profile fitting program, for example XDS or d*TREK, which are more optimally designed for this kind of work. This was not, however, your question. For mosflm, if you include the command "postref fix mosaic" and set the mosaic at what you believe to be a sensible value then you should find all of your spots being predicted. There are a couple of reasons why this problem could be happening - - your crystal is slipping - the lattice symmetry is wrong - it just is (spot backgrounds causing it or something...) For the first one, you can look at the missetting angles. If they are wondering all over the place then there is something odd happening - allowing postrefinement during integration may help this. For the second, you could try refining the cell in P1 and see what the refined cell parameters look like. I guess you could also be misindexing the diffraction pattern, so I would also give it a go using Labelit to autoindex the diffraction pattern as this includes refinement of the direct beam over quite a large range. I assume that you managed to get a fine enough oscillation width to prevent too many overlaps... If you decide you want to give XDS a go, and you have never run it before, you may find it easier to install xia2 and use this to run XDS for you (if you have Labelit installed, it will use this too...) Regarding going for a different crystal form, I look forward to seeing the other responses! Good luck, Graeme ________________________________ From: CCP4 bulletin board on behalf of [log in to unmask] Sent: Thu 22/05/2008 3:47 PM To: [log in to unmask] Subject: [ccp4bb] Mosflm : data process of crystal with huge unit cell Dear All I am processing data from a crystal for a large macromolecular complex with mosflm. Cell dimensions are around 120 x 150 x 650, with a p222 spacegroup. To avoid overlaps, we have collected data with a oscillation of 0.1 degrees. When I try to process the data with mosflm, mosaicity decreases along the processing to a very low values (0.05 to 0.1 depending on the images). The result is that I miss a lot of spots from the images. I would appreciate any help regarding : 1.- What's is the best strategy to process such a dataset ? 2.- Which are the critical parameters in mosflm to avoid these problems, and how to modify them ? 3.- and finally, can I use this data or your advice is to try to get crystals in a different spacegroup ? Many thanks Best regards Francisco ----------------------------------------- Francisco J. Enguita, Ph.D. Macromolecular Crystallography Laboratory ITQB EAN, Av. da República 2781-901 Oeiras Portugal Phone : +351-21-4469663 Fax : +351-21-4433644 E-mail : [log in to unmask] -----------------------------------------