Sorry, I meant to write "note that not all achiral space groups are centrosymmetric", since most are. However, even as written it's true, but less obvious...
Harry -- Dr Harry Powell > On 7 Mar 2019, at 10:23, CCP4BB <hrp-ccp...@virginmedia.com> wrote: > > 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
