-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Dear Andrea,
unless you are desperately longing for resolution, I normally cut the resolution where I/sigI > 2.0. You should, however, make up your own rules as to how to determine I/sigI: it must be computed in resolution shells, and if you choose the shells wide enough the strong data might cover up for the weak ones. I usually run XSCALE or xprep and use their preset resolution shells (e.g. the shells in CORRECT.LP are wider than those in XSCALE). Rmerge is obsolete, and I always encourage people to use Rmeas (aka Rrim, not Rpim!) instead. Publishing Rmerge is a little bit like saying, we have always gone for lunch at 1pm, so we will stick to that - it's a habit despite better knowledge. I do not consider Rmerge/Rmeas in order to descide about the resolution cut-off and I have used data with Rmeas > 200% provided I/sigI > 2.0 The completeness does not really say much in terms of data quality: with a little tweaking of the parameters, most integration programs would give you about 99.9% completeness even if their is mostly noise on the detector! The method suggested by Karplus and Diederichs works well, i.e. checking various resolution ranges, e.g. in steps of 0.2A, and looking at the maps - but it is time consuming and I would only apply it at low resolution where +/- 0.1A can make quite a difference (actually in both directions: if you include too much noise, the maps become more difficult to interpret). Best, Tim P.S.: Your question is not embarrassing, it is an ongoing discussion with no definite answer. On 06/13/2013 05:15 PM, Andrea Edwards wrote: > Hello group, I have some rather (embarrassingly) basic questions > to ask. Mainly.. when deciding the resolution limit, which > statistics are the most important? I have always been taught that > the highest resolution bin should be chosen with I/sig no less than > 2.0, Rmerg no less than 40%, and %Completeness should be as high as > possible. However, I am currently encountered with a set of > statistics that are clearly outside this criteria. Is it acceptable > cut off resolution using I/sig as low as 1.5 as long as the > completeness is greater than 75%? Another way to put this.. if % > completeness is the new criteria for choosing your resolution limit > (instead of Rmerg or I/sig), then what %completeness is too low to > be considered? Also, I am aware that Rmerg increases with > redundancy, is it acceptable to report Rmerg (or Rsym) at 66% and > 98% with redundancy at 3.8 and 2.4 for the highest resolution bin > of these crystals? I appreciate any comments. -A > - -- - -- 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/ iD8DBQFRue6rUxlJ7aRr7hoRAleBAKDnYEA+eMoGoyS6vWD6HfU+XG+fhwCgqMG2 F2AnLH6B1rPTbqeJ9wM9FjE= =EoSr -----END PGP SIGNATURE-----
