In a nutshell ============= Is there a way to make solve/resolve behave reasonably if the data is twinned? Is there a recommended alternative path to clean up and maybe even auto-trace a map with 4-fold NCS but twinned data? Maybe Pirate/Buccaneer?
In detail ========= I'm fighting with a structure that is probably/maybe in P4(2). 2.6A data 98% complete Rmerge = 0.07 in P4 Rmerge = 0.16 in P422 (note the disturbingly low value) Pointless is 88% confident it's P4(2). Laue Group Lklhd NetZc Zc+ Zc- CC CC- Rmeas R- = 1 P 4/m *** 0.916 4.68 9.36 4.67 0.94 0.47 0.09 0.30 10 P 4/m m m 0.000 6.83 6.83 0.00 0.68 0.00 0.20 0.00 Truncate says the data is twinned, with a twinning fraction of 0.25. That is consistent with the bad-but-not-awful Rmerge in P422, right? I have a promising initial MR solution in P4(2) with four monomers in the a.s.u. It refines to R/Rfree = 0.36/0.38 in refmac but only if I enable the twinned data option. Twinning fraction refines to Twin fractions = 0.4322 0.5678 My thought was to use the 4-fold NCS and solvent flattening in resolve to clean up and ideally auto-trace into the initial mediocre maps. The resolution is not great, but the 4-fold NCS should help a lot. Unfortunately, so far as I can figure out resolve ignores the twinning and is stuck dealing with R > 0.60 and extremely poor maps. I tried de-twinning the data, but this was not a great success. Should I believe the truncate estimate of 25% twinning fraction or the refmac estimate of 43%? Neither? In any case, feeding the supposedly detwinned data to either refmac or resolve produces worse results that I was getting before attempted detwinning. Any advice? -- Ethan A Merritt Biomolecular Structure Center University of Washington, Seattle 98195-7742
