What is the relationship between the molecules in the spacegroups - it seems likely that in the bigger cell there is a NC translation of ~(1/2,y,z)? ? (A2 ~ twice a1) That can be checked by the native Patterson..
If so that gives a class of significantly weaker reflections for h odd, and that usually does lead to higher R factors. It also means that the h00 reflections will be weak for h odd, and that the SG assignment could be either P2 2i2i or P21 2i2i - you need to test both.. However that doesnt explain the smaller R factors, unless the packing there also gave rise to a NC translation.. Again checked from the native Patterson.. Eleanor On 29 April 2013 16:14, Tim Gruene <t...@shelx.uni-ac.gwdg.de> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Hi Ed, > > just FYI: while this does not apply in the ccp4/mtz world, the fact > you might be missing is that in some refinement environments merging > is carried out by the refinement program so that the actual data can > be kept unmerged and e.g. the information you refer to does not get > lost (although scaling would smoothen it to a certain extent but at > least does not erase it as mergin does). In that case you could expand > to P1 (as far as I understand). > > best, > Tim > > On 04/29/2013 04:13 PM, Edward A. Berry wrote: > > herman.schreu...@sanofi.com wrote: > >> I would process or expand the data to P1, also expand your pdb > >> file to P1 and refine in P1 to see what happens. I would also run > >> Phaser or some other molecular replacement program on the P1 data > >> to see what comes out. > > > > > > process or expand? I don't understand how there can really be a > > choice here. If the data is expanded from higher symmetry, it will > > precisely have that higher symmetry, i.e. all reflections that were > > equivalent in the higher symmetry will be identical. Any > > information about asymmetry was lost when the data were merged in > > the higher symmetry space group. Won't refinement by minimizing a > > target function have exactly the same solution? > > > > Or not exactly, because the refinement program can introduce > > asymmetry by allowing different phases for the equivalent > > reflections. But where is the information to generate that > > asymmetry coming from? > > > > There is probably something I'm missing here, but i would > > definitely reprocess in the lower symmetry if the rotation angle > > was sufficient to give good completeness. > > > > eab > > > > - -- > - -- > Dr Tim Gruene > Institut fuer anorganische Chemie > Tammannstr. 4 > D-37077 Goettingen > > GPG Key ID = A46BEE1A > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.12 (GNU/Linux) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ > > iD8DBQFRfo5lUxlJ7aRr7hoRAkHvAJ9VRWDjbH8gcF1OW5vfprehPJDCUwCfTHoA > nv3mtZH/Em2VlbDh9IFDvoU= > =F/Om > -----END PGP SIGNATURE----- >
