Dear Guangyu Zhu, if this is not a hypothetical case you can refine both structures in each crystal form separately using whatever software and compare them later. The structure can be refined also in both crystal forms simultaneously using the multi crystal NCS refinement as implemented in MAIN http://www-bmb.ijs.si/ and thereby double the data to parameter ratio when compared to the one crystal form data set refinement.
best regards, dusan On Mar 16, 2013, at 1:00 AM, CCP4BB automatic digest system <lists...@jiscmail.ac.uk> wrote: > Date: Thu, 14 Mar 2013 20:27:44 -0400 > From: Guangyu Zhu <g...@hwi.buffalo.edu> > Subject: Resolution and data/parameter ratio, which one is more important? > > I have this question. For exmaple, a protein could be crystallized in two > crystal forms. Two crystal form have same space group, and 1 molecule/asymm. > One crystal form diffracts to 3A with 50% solvent; and the other diffracts to > 3.6A with 80% solvent. The cell volume of 3.6A crystal must be 5/2=2.5 times > larger because of higher solvent content. If both data collecte to same > completeness (say 100%), 3.6A data actually have higher data/parameter ratio, > 5/2/(3.6/3)**3= 1.45 times to 3A data. For refinement, better data/parameter > should give more accurate structure, ie. 3.6A data is better. But higher > resolution should give a better resolved electron density map. So which > crystal form really give a better (more reliable and accurate) protein > structure?
