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Hello, you do not state whether you did any model building. Did you look at the map? what does the difference map show? A different ligand may induce minor or major conformational changes which would lead to a non-perfect search model and hence increased R/Rfree values. I remember a case with the identical protein crystallised in a different space group and it had to be chopped into three parts for successful molecular replacement due to conformational changes. And this with the physical and chemical environment not changing. It just crystallised in P65 instead of C2. Tim -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen GPG Key ID = A46BEE1A On Fri, 10 Mar 2006 [EMAIL PROTECTED] wrote: > *** For details on how to be removed from this list visit the *** > *** CCP4 home page http://www.ccp4.ac.uk *** > > > Dear all, > > Sorry for non ccp4-related question. > > I am trying to solve structure of an inhibitor-enzyme complex at 2.6A > resolution. > The enzyme complex bound to other ligand has been determined previously at > 2.4A resolution > and has space group C2. > Our complex crystallized with similar condition to "C2 form" > but have a defferent space group by process using d*trek which indicates > P3(1)12 or P3(2)12. > (Rmerge=7.1(35.2)%, Completeness=97.6(96.6)%, parenthness is last shell > [2.71-2.60] ) > In P3(2)12, the structure was successfully deterimined by MR using C2 form as > a search model. > There is one molecule in the asymmetric unit which makes dimer structure > related with crystallographic 2-fold axis. > > After one cycle refinement using simulated annealing, positinal minimization > and B individual in CNS, > R and Rfree value dropped down only 36.0% and 41.5% respectively. > Twin is not deteced from cumulative intensity distribution and 2nd moment of > intensity of > TRUNCATE(ccp4). > > Does anyone have the same experience and please any comments about this! > > Regards, > > Masaichi Warizaya > Astallas Pharma Inc. > mailto: [EMAIL PROTECTED] > >
