Hi all A genuine question; I'm wondering how well Phaser (or other MR programs) deals with achiral space groups and the presence of both hands of a molecule (just because you can have both hands of a chiral molecule related crystallographically in a crystal, you don't need a centrosymmetric space group - note that not all achiral space groups are not centrosymmetric...).
Harry -- Dr Harry Powell > On 7 Mar 2019, at 10:11, Prasun Kumar <prasun.ku...@bristol.ac.uk> wrote: > > 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 <tim.gru...@posteo.net> > Sent: 05 March 2019 10:02:53 > To: Prasun Kumar > Cc: CCP4BB@jiscmail.ac.uk > 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 ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1
