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]> 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] > ******************************************* >
