You need to provide a bit more information. First of all about the data processing..
Is the space group correct? ways of being misled are: Non-crystallographic translations with a shift of ~0.5 along an axis - say a. This will generate absences in the odd h 0 0 reflections and can make the space group appear to be P 21 21 21 whilst it is really P 2 21 21.. Perfect twinning can have the same effect. In an orthorhombix space group this can usually only occur if two axes have approximately the same length, but the data processing stats can indicate if that is the case. Then - re PHASER. The packing rejection criteria may be set too severely - that seems the case for your solution. Best check on any MR solution is: does it refine - give it 20 cycles of mindless refinement and see if the R and FreeR go down. Then look at the maps and see if there are obvious corrections to be made.. Eleanor On 18 September 2017 at 14:59, Satvik Kumar <kumarsatvi...@gmail.com> wrote: > Dear Crystallographers, > > I am trying to solve a structure in the space group P212121. Based on > Matthews coefficient, there are 4 molecules in the asymmetric unit. > > Based on my limited reading about using of Phaser, I understand that a > single chain should be used as search model even though many copies are > present in asymmetric unit. Am I correct? > > So when I use a single chain as search model and ask Phaser to search for > 4 molecules, Phaser identifies a single solution with a warning "The top > solution from a TF rescoring did not pack" and a warning "Search request > requires more scattering than defined in composition. Composition > increased to accommodate search components". But the final values reported > "PAK=2 > LLG=1065 TFZ==22.6" indicate that phaser has solved the problem. > > Can anyone please explain the meaning of the warning. > > When I inspect the arrangement of the chains (attachment), I observe > minimal contact between the chains and a large cavity in the center. Can a > crystal form this way? > > I have also tried using the dimer as search model and asking phaser to > search for 2 molecules. Even in this case, Phaser finds a single solution > but the warning and the advisory still appear as before. The numbers > reported reduce a bit to "PAK=1 LLG=722 TFZ==29.2". > > Please help me in understanding these results. > > Thanks, > Satvik > > >
