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Have you looked at a self rotation function? Is there a clear 3-fold axis perhaps? Eleanor On 27 April 2017 at 10:45, Mark J van Raaij <[log in to unmask]> wrote: > Does the self-rotation function suggest presence of NCS axes? If so, this > may help you figure out the symmetry inside the a.u.. > If you haven't done so already, try diffracting a crystal at room > temperature, to make sure cryo-protection and freezing did not affect the > diffraction. > In any case, at 3.65Å I would recommend not to spend too much of your time > on this dataset. > Just set your computer(s) to try MR with different parameters, numbers of > copies to search for etc. Instead of 40 copies at 50% solvent, you may have > down to 20 copies with 75% solvent (or maybe even less). Or more than 40 > with less solvent (perhaps less likely). Even then, judging whether an MR > solution is really correct might still not be that easy. > And in the meantime spend your own time to try to get derivatives and > better-diffracting crystals. At better than 2.5Å resolution it will all be > much easier, for instance auto-building with your input sequence will allow > much better identification of correct MR solutions. > And if you are lucky, a heavy atom soaking experiment might actually > improve the crystal. > If you haven't already, I'd also try to get some complementary information > on whether your protein forms stable complexes. EM, SAXS and AUC come to > mind. > > Good luck! > > Mark J van Raaij > Dpto de Estructura de Macromoleculas > Centro Nacional de Biotecnologia - CSIC > calle Darwin 3 > E-28049 Madrid, Spain > tel. (+34) 91 585 4616 <+34%20915%2085%2046%2016> > http://wwwuser.cnb.csic.es/~mjvanraaij > > On 26 Apr 2017, at 21:34, Jademilson Santos <[log in to unmask]> > wrote: > > Greetings all, > > I am having trouble with a data set and would like to know if somebody can > help. I'm working with a protein of approximately 50 kDa, which I have > successfully crystallized. The crystals diffracted at a resolution of 3,65 > angstroms and upon initial processing using XDS i obtained the following > information: > > space group: P21 > ISA = 33.3 > cell unit: a=285.2, b=135.9, c= 287.5, α=90, β=117.5, γ=90 > > Matthews coefficient indicates that there are 40 molecules in the > asymmetric unit > > I am currently running the program Phaser (Phenix) to determine the phase > via molecular replacement with a model that has 49% homology and query > coverage of 94% and the program is taking extremly long to finish. In this > case in which there is an extremly high number of molecules in the > asymmetric unit, is this actually possible? Does someone know how to work > with these values and is there a specific strategy which i must follow? > > Regards > > > > *Jademilson Celestino dos Santos* > > *Laboratory of Applied Structural Biology* > > > *Department of MicrobiologyInstitute of Biomedical SciencesUniversity of > São Paulo- USP* > > >