Marco,indeed, as Fred says, the space group I422 may not be the correct one for the large cell. Use the model from the small cell for molecular replacement in the large cell. You may try I4(1)22, I4(1), I4 first, then lower symmetries: look into the International Tables what subgroups of I422 are; I can think of I222, F222, P422, P4 A "lazy way" would be P1 and then let the symmetry be sorted out by Garib's Zanuda server, but that requires that you collected 180° of data (or at least expand to P1).
HTH, Kay -------- Original Message -------- Subject: Re: XDS question Date: Mon, 13 Jun 2011 17:43:50 +0200 From: Vellieux Frederic <frederic.velli...@ibs.fr> "the space group is I422" "do you have any other suggestion?" Yes, how certain are you of the space group? For myself, I'm never entirely certain of the space group until I have solved the structure... I always keep in mind the other possibilities for space group assignment, if need be. And sometimes the "obvious space group" is not the space group of the "final" structure. The computer programs we use only give hints of the solution, but these are only hints. Remember that crystals "behave as they want", the fact for example that I(equiv.1) is approximately equal to I(equiv.2) is approximately equal to I(equiv.3) etc does not mean that the relationship between intensities is in fact an equality, it can be just an approximation... With crystals I have learned, everything is possible. It might be an idea to enclose parts of relevant XDS output files for our perusal. Using "standard" input parameters (for spot selection) as well as your spot selection input parameters. Fred. Marco Lolicato wrote:
Thank you to all! @FredericI have a problem with the following sentence: "if I collect all spots I get good map, but it is impossible to solve the structure by molecular replacement" - if you have a good map (I assume electron density map) then the structure is solved... for me a good map is a map I can interpret.You're right, I said "good map" instead of "good output values". @KonstantinIt is possible to process diffraction spots from both crystals using XDS. The procedure is described here (under 'Index and integrate multiple-crystal diffraction'): http://strucbio.biologie.uni-konstanz.de/xdswiki/index.php/Tips_and_TricksI tried but with no success! :( @Kay and all the others The following links are the images: http://www.facebook.com/photo.php?fbid=2127189780277&set=o.136323896385679&type=1&theater http://www.facebook.com/photo.php?fbid=2127189180262&set=o.136323896385679&type=1&theater http://www.facebook.com/photo.php?fbid=2127188820253&set=o.136323896385679&type=1&theater ...then a little bit more details... so, if I process only the strong spots I have those cell parameters: a=b=96.66 c=112.26 alpha=beta=gamma= 90 f I process all the spots I have those cell parameters: a=b=216.4 c=112.4 alpha=beta=gamma= 90 In both cases the space group is I422. Thank you again to all, do you have any other suggestion? Marco
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