Hi Ethan, Yes. My question was simply whether it calculates the statistics from completely unmerged intensities and just compare say h,k,l with -h,-k,l (or -h,-k,-l and h,k,-l) if there is a 2-fold? Although I believe so...
And what is a good number? Is 20 % OK? What about 30 % and even higher? Thanks a lot, Chen > On May 13, 2015, at 6:07 PM, Ethan A Merritt <merr...@u.washington.edu> wrote: > >> On Wednesday, 13 May, 2015 17:51:59 Chen Zhao wrote: >> Hi all, >> >> I am sorry about this question which I should have figured out earlier. For >> point group determination, does the Rmeas consider Fridel pairs >> differently? > > A Friedel pair consists of the [hkl] and [-h-k-l] reflections. > This pairing is independent of space group. > So the agreement or lack of agreement between Friedel pairs is > not informative about selection of point group or space group. > > You may be thinking of a Bijvoet pair, which consists of > [hkl] and the Friedel mate of some symmetry equivalent of [hkl] > within a particular spacegroup. > > But even in the presence of anomalous scattering I think that > Bijvoet pairs are expected to agree with each other better than > with a reflection not related by point group symmetry. > >> (although I think it should be...) This is because I saw a >> derivative dataset collected at peak (from a demo) whose Rmeas is quite >> high (>50 %) for all the space groups tested (including P1). However, the >> native dataset has only <10 % Rmeas. Should I worry about the derivative >> dataset? There seems to be multiple lattices in both datasets based on >> IDXREF. >> >> You inputs are really appreciated! >> >> Sincerely, >> Chen > -- > Ethan A Merritt > Biomolecular Structure Center, K-428 Health Sciences Bldg > MS 357742, University of Washington, Seattle 98195-7742 >
