Rsym...what's that? JPK
On Wed, Jul 18, 2012 at 9:12 AM, Edwin Pozharski <epozh...@umaryland.edu>wrote: > As has been shown recently (and discussed on this board), Rsym is not the > best measure of data quality (if any measure at all): > > http://www.sciencemag.org/content/336/6084/1030.abstract > > > > > narayan viswam wrote: > >> Hello CCP4ers, > >> In my data, the highest reolution shell 2.8-3.0 A has I/sigmaI 2.5 & > >> Rsym 224.3 % > >> for multiplicity 7.8 and completeness 98.2 %. I solved the structure by > >> MAD & refined it > >> to Rfree 27.3 %. Ths crystal belongs to P622 space group and it is not > >> twinned. The water > >> content is 68%. I loweredthe multiplicity to 4.1 by excluding few > >> images but still the > >> Rsym is > 200 % and I/sigmaI > 2.0. My rudimentary crystallography > >> knowledge makes me > >> believe it's quite Ok to use data upto 2.8 A and report the statistics. > >> Could I request > >> people's views. Thanks very much. > >> Narayan > > > > After refinement, what is R-free in the last shell? If it is > significantly > > better > > than random, say around .4 or less, that could be taken as evidence that > > there > > is data in the last shell. > > Also check the error model- Rsym >2 sort of implies the error is greater > > than > > the signal, so I/sigI 2 seems surprising. > > eab > > > > > -- > Edwin Pozharski, PhD > University of Maryland, Baltimore -- ******************************************* Jacob Pearson Keller Northwestern University Medical Scientist Training Program email: j-kell...@northwestern.edu *******************************************
