Dear Sudarshan, I have the feeling the your R factor after Molrep is really high because the program has failed to produce a correct/not-partial solution, which could be due to many things, but usually the main problem is how good your search model is. The difference in spacegroups is not a problem as in MR the model will be rotated and translated inside the new cell.
The number of molecules that you need to search for is a tricky question. You need to make some educated guesses with help from analysis of, for example, crystal solvent content (e.g., Matthews program from CCP4) and/or self-rotation maps (Molrep or Polarrfn programs, also available from CCP4 suite). If you have never before used molecular replacement, however, I would advise that you get some help/guidance from some more experienced colleague/friend in the Department, since you may encounter quite a few more other problems that would perhaps be a bit too long to go through by email. Some of these problems could also be probably self-solved by looking at some tutorials on Molecular replacements. Best wishes, D From: Sudarshan Murthy [mailto:sudarshan.murthy...@gmail.com] Sent: 29 April 2014 05:11 To: ccp4bb Subject: [ccp4bb] Problem with Rfactor Dear All, I am very new to the field of crystallography, I have a few questions which are very basic and getting input from this forum would help me a lot. Firstly I am trying to solve a structure using MR Molrep. In the result the Rfactors are really high how do I reduce the same?? ..When I tried with Phaser I didnt get any solution at all.. Will der be a problem with the space group?? like the model is in monoclinic and the data which I have is processed in hexagonal. Secondly while using hexagonal space group should I search for only one monomer in Molrep?? These are very basic questions if anybody could help me out with this , I would be very happy for the same. Sudarshan .N. Murthy Crystallography Division Bangalore
