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Hello all I have data that I'm trying to see if it is a pseudo-merohedral twin. The data process well in C2 or P1 but it does flag R32. I tried to process in R32 but it didn't work so I processed in both C2 and P1. C2 cell: 104.4 61.6 96.9 90.0 112.9 90.0; P1 cell: 60.7 60.6 95.5 107.1 91.9 118.9. I tried MR in both unit cells looking for 2 mol/ASU in C2 or 4 mol/ASU in P1 and got nothing. I tried Phaser, molrep, epmr and no solutions was given for any of these programs using both C2 or P1. I use a complete model as well as a trimmed model (obtained from SMM) and didn't work either. I used a monomer as well as a combination of dimers as seen in other published models for this protein, again no solution. I also ran an SDS-gel of these crystals and it showed the same MW as the protein I placed for crystallization. So I looked at back posts from the mail list and I ran phenix.xtriage with C2.mtz and P1.mtz. Both runs resulted in no pseudo-translation nor -symmetry found. However, in P1 there is a pseudo-merohedral twin operator: k, h, -h-k-l and the Britton analysis gives 0.441, H-test gives 0.450 and ML gives 0.458. This is not shown on C2 analysis. In the P1 analysis it recommends to process data in C2 so I'm guessing that's why in the C2 analysis there was no similar twin operator. But it makes me think that perhaps I don't have a twin crystal since I'm assuming that if it was twin, it should have been shown on C2 analysis, am I making the right assumptions? I tried to reprocess the data using the unit cell recommended in the P1 analysis which is the same as the C2 cell except that beta=126.76 but it doesn't index well. This is my first encounter with a possible twin data, could you please look at the attached logs files and please tell me if I read them correctly? And if it is not twin, not pseudo-translated nor -symmetry, what other things could be hindering the structure solving? Thank you for your kind suggestions/answers. Teresa Teresa De la Mora-Rey Ph.D. Dept. Medicinal Chemistry University of Minnesota 8-101 Weaver-Densford Hall 308 Harvard St. SE, Minneapolis, MN 55455 Lab phone (612) 626-5226 "If you never did you should. These things are fun and fun is good" Dr. Seuss