Regarding Phil's comment about the space group, check the PBD stats and you'll see that c222 is pretty rare. It occurs only in 0.24% of all cases, versus 5.1% of C2221. So i guess you could say that without doing any analysis, there's a 95% chance that a centered orthorhombic cell is c2221 rather than c222. In terms of stats, its also pretty interesting that 58% of all structures are in only 5 (low-symmetry) space groups: p212121, p21, c2, p21212 and c2221. Bert van den Berg University of Massachusetts Medical School Program in Molecular Medicine Biotech II, 373 Plantation Street, Suite 115 Worcester MA 01605 Phone: 508 856 1201 (office); 508 856 1211 (lab) e-mail: [EMAIL PROTECTED] http://www.umassmed.edu/pmm/faculty/vandenberg.cfm
________________________________ From: CCP4 bulletin board on behalf of Phil Evans Sent: Fri 7/25/2008 9:43 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] MR problem --molrep Perhaps obvious - are you sure the space group is C222 not C2221? Phil On 25 Jul 2008, at 14:19, Roger Rowlett wrote: > Carl Soja wrote: >> Dear all >> I tried to solve one structure by ccp4i molrep(resolution at 3.0 A, >> space group C222, sequence ID 30%). I can get a good Rfactor 0.528 >> at first translation function. However, the second translation >> function Rfac is 0.526, the third is 0.525, the fourth is 0.525. >> All of the translation function Rfacs are too closed. I changed >> the model and minimum resolution for search, the Rfactor closed no >> any improved. My structure estmates four molecules in the >> aymmetric unit. This is my first time found the closed Rfac by >> molrep. From the low translation function Rfac, it seems that it >> is correct solution. I checked the solution and found some clashes >> in the structure.I am not sure why the Rfactor too closed in next >> the molecule search? I know this is unusual solution by molrep. >> Does it mean the diffraction data has problem? >> Any suggestions are welcome.Thank you in advance! >> Carl soja > To be honest, I would try both Phaser and EPMR (now Open-EPMR) first > to do MR. Both especially excel at finding good MR solutions for > multimers, and are very fast as well. These programs can find > solutions that are very difficult to find using other rotation- > translation programs, including MOLREP. In my experience (using > Phaser and EPMR) reasonable MR solutions almost always have an R- > factor under 50%. > > Cheers, > > > -- > ------------------------------------------------------------------------ > Roger S. Rowlett > Professor > Colgate University Presidential Scholar > Department of Chemistry > Colgate University > 13 Oak Drive > Hamilton, NY 13346 > > tel: (315)-228-7245 > ofc: (315)-228-7395 > fax: (315)-228-7935 > email: [EMAIL PROTECTED]
