Dear Dear Crystallographers, Thanks very much to all who replied on and off the list—I feel I have to express my continuous admiration and gratitude to the folks who respond to these questions. I am not sure where there is a listserve like CCP4BB!
Anyway, in the current issue I have gotten to complete lucidity, thanks to all who responded. I guess the summary is that the non-screw 1’s are essentially place-holders. All the best, Jacob Keller From: Ian Tickle [mailto:[email protected]] Sent: Wednesday, February 18, 2015 1:45 AM To: Keller, Jacob Cc: [email protected] Subject: Re: [ccp4bb] P3212--1's in Space Group Names? Hi Jacob If you look at SGs P312 and P321in ITC-A you'll see that they are quite different in terms of the arrangement of the a.u.s relative to the symmetry axes. So essentially the 1's are there to distinguish these. The extra 1 or 2 after the 3 of course signifies a screw axis. Note that for a rhombohedral cell SGs R312 and R321 would be identical so there is only R32. Note that the original SG names in ITC without intervening spaces were carefully designed to be unambiguous. The extra spacing that was added by the PDB is redundant (or maybe they thought that it improves readability). Hope this helps. -- Ian On Wednesday, 18 February 2015, Keller, Jacob <[email protected]<mailto:[email protected]>> wrote: > Dear Crystallographers, > > I don't understand what the 1's are doing in space group names like P3212 or > P3112--can someone fill me in? Not easy to google this one. > > JPK > > ******************************************* > Jacob Pearson Keller, PhD > Looger Lab/HHMI Janelia Research Campus > 19700 Helix Dr, Ashburn, VA 20147 > email: [email protected]<mailto:[email protected]> > ******************************************* >
