Re: [ccp4bb] twinning in hexagonal system

2011-09-05 Thread Eleanor Dodson
Dear John, In a hexagonal crystal class the possible point groups are P3 (only a 3-fold axis) P321(3-fold plus 2-fold relating hkl and kh-l) P312 (3-fold and 2-fold relating (hkl and -k,-h,-l) P6 ( 6 fold axis only) P622 (6-fold plus 2-fold relating hkl and k,h,-l) pointless will tell you which

Re: [ccp4bb] twinning in hexagonal system

2011-08-31 Thread Herman . Schreuder
Dear John, It is not the sequence identity/similarity that counts, but how similar the protein folds are. For many protein families, the fold is identical although the sequence identity is very low. With 25% sequence identity and presumably a protein from the same family, I give you a good chance

Re: [ccp4bb] twinning in hexagonal system

2011-08-30 Thread Garib N Murshudov
Hello Space groups with point groups 622 and 432 merohedral twinning is not possible (they are the highest groups possible for proteins). If you could merge in 622 it means that Rmerge was very small. It is very likely that point group is either 622 or 6 with very strong rotational symmetry th