Hi Tim:
Thanx for your response and sorry for late acknowledgment . You are right, the peptide is forming an oligomer. I have used Xia2 and pipeline 3dii with small_molecule=true option as suggested earlier by Pierre. Now the space group is P-1. I will check for SHELXT. So far the molecular replacement is a problem for me. However, I am on it. Regards Prasun ________________________________ From: Tim Gruene <[email protected]> Sent: 05 March 2019 10:02:53 To: Prasun Kumar Cc: [email protected] Subject: Re: [ccp4bb] Racemic crystallography and structure solving problem Dear Prasun, in case you get atomic resolution (better than about 1.2A), you should be able to solve the structure with direct methods, e.g. SHELXT. You may want to check the processing if the cell is really this big. Unless you have several copies in the asymmetric unit, one might expect a smaller cell for only 30 residues. You can also try alternative programs, like XDS - start with XDSGUI in case you are not familiar with XDS from the command line. Best, Tim On Monday, March 4, 2019 4:33:20 PM CET Prasun Kumar wrote: > Hi All: > > I have performed racemic crystallography and got crystals that diffracted. > The automatic processing softwares, XIA2 DIALS, (available in Diamond, UK) > gives the space group as P1 and cell dimension > 42.78 52.16 54.49 114.11 92.16 92.31. > > Challanges start from here: > > 1) How much I should be assured of the space group as I expect my peptides > to get crystallized in the same group, but by default we get the same space > group. 2) Is there any seperate method for processing the raw images in my > case. > > I used the merged .mtz file for phasing. However, I always get the warning > that eLLG score is low and it is difficult to fit a single copy of the > ensemble. CC1/2 and I/SigI are in acceptable range. Completeness is also > more than 95%. > > My peptides, 30 residues long, form an oligomer. However, I do not have > reliable model of oligomers to start with. I have taken a single helix of > length 24, 12 and 6 residues to phase, but no luck so far. Any guidelines > will be really helpful. > > I am happy to provide any other relevant information, if one wants. > > Thanx in advance > Prasun > > ######################################################################## > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 -- -- Tim Gruene GPG Key ID = A46BEE1A ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1
