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Re: [ccp4bb] Proportion of MR in PDB |
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CCP4bb navigationCCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999Subject: Re: Proportion of MR in PDB From: James Holton JMHolton {- at -} LBL {- dot -} GOV Date: 2010-04-20 For once, I actually agree with Ian! I too refer to the process as "molecular replacement", even if you don't run a "molecular replacement program". For those who are interested in more than one opinion, other popular "method used to determine the structure" in the PDB that I still call "MR" are: 2639 fourier synthesis 447 difference fourier 96 rigid body refinement 39 rigid body 37 difference fourier plus refinement 31 isomorphous 31 difference fourier methods 25 refinement 21 rigid-body refinement 17 direct replacement 15 refmac 15 molecular substitution 15 molecular replacemen 15 difference map 14 native model phases 14 molrep 13 isomorphous molecular replacement 11 direct refinement 10 isomorphous with pdb entry xxxx 10 fourier difference 9 known phases 8 refined directly 8 isostructural to xxxx 8 difference fourier method 7 phaser 7 isomorphous to native 7 difference fourier from previously determined, related structure 6 rigid body refinement into new data 5 used previously- determined structure 5 direct based on known model 5 difference fourier maps 4 starting model was used without molecular replacement 4 protein structure is known in this cell -James Holton MAD Scientist Ian Tickle wrote: > I would say it should still be classed as MR: the distinguishing > feature of MR is surely that it uses an known structure as a starting > model, not that it does a rotation/translation search. In any case > the distinction between a rigid-body search and RB refinement is moot. > At Astex our automated scripts routinely do a limited MR search for > all our protein-ligand structures, even though it may not be necessary > in all cases. This is because we have found from experience that RB > refinement alone is often not sufficient: presumably the degree of > non-isomorphism induced by soaking and/or freezing the crystals (e.g. > we often see 5-10% changes in cell parameters) takes it beyond the > radius of convergence of the refinement. We use a limited search MR > to avoid issues of finding symmetry-related or origin-shifted > solutions. > > Cheers > > -- Ian > > On Mon, Apr 19, 2010 at 3:06 PM, Edward A. Berry > >> Quite a lot of structures in the PDB involve minor variations on structures >> that have already been solved (different ligands, mutants, high res), so the >> "solution" involves refining the previous structure against the new data, >> perhaps starting with rigid body refinement to correct minor variations >> in cell parameters. >> Would you include this in "molecular replacement"? >> >> Ed >> >> Nicholas Keep wrote: >> >>> Thanks to several people for helpful comments to my question on the >>> Proportion of MR in the PDB. >>> >>> I got two very detailed responses one from the OCA team at the Weizmann >>> which went to the Bulletin Board >>> >>> "This is what OCA has: From un total of 64,623 PDB structure files, >>> 30,784 have 'MOLECULAR REPLACEMENT' as Method for Structure Determination. >>> >>> However, you must remember that we have a large number of false negatives >>> Several reasons: >>> >>> - Only 47,557 structure files from the total of 64,623 report which >>> method was used for structure determination. For example, 1CRY whose >>> title reports using the MR method does not include the info in the >>> proper REMARK. >>> >>> - Users are allowed to write almost anything as the METHOD USED TO >>> DETERMINE >>> THE STRUCTURE, making it difficult an accurate report. OCA found PDB >>> italian >>> speaking structure files reporting 'MOLECULARE REPLACEMENT' ... >>> This and other problems are being reported to RCSB." >>> >>> >>> >>> and one from U of Virginia >>> >>> "Based on information from Remark200 lines, 31761 structures were solved >>> using MR, what comprise for 56.8% of all X-RAY structures (55843). >>> Considering structures which were determined using 'primitive MR' the >>> number grows to 34949 (62.6%). There are also some structures determined >>> using combination of MR with SAD, MAD, SIR and MIR. If we would add them, >>> the number will increase to 35258 (63.1%)." >>> >>> Thanks again >>> Nick >>> >>> >>> CCP4bb navigationCCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999 |
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