6-Feb-2017 Dear Pavel & Tim, For a very good visualization & description of “Resolution”, please see the Proteopedia page created primarily by Eric Martz at: http://www.proteopedia.org/w/Resolution it includes a pointer to James Holton’s movie showing an Electron Density Map vs. Resolution (with model overlay) going from 0.5Å to 5.Å resolution. best regards Joel
-------------------------------------------------------------------------------- Prof. Joel L. Sussman joel.suss...@weizmann.ac.il<mailto:joel.suss...@weizmann.ac.il> www.weizmann.ac.il/~joel<http://www.weizmann.ac.il/~joel> Dept. of Structural Biology tel: +972 (8) 934 6309 www.proteopedia.org<http://www.weizmann.ac.il/~joel> Weizmann Institute of Science fax: +972 (8) 934 6312 Rehovot 76100 ISRAEL mob: +972 (50) 510 9600 --------------------------------------------------------------------------------- On 5Feb, 2017, at 23:44, Tim Gruene <tim.gru...@psi.ch<mailto:tim.gru...@psi.ch>> wrote: Dear Pavel, I believe words have a meaning, but they are not defined. This may make languages a little more demanding than mathematics, since you have to deal with a variety of a few hundred thousand to millions, depending how popular the language in question is, but personally I enjoy the challenge. W.r.t. the thread, 3.8A resolution is poorer than 1.8A. I understand this is what John meant to clarify. Best, Tim On Sunday, February 5, 2017 11:12:10 AM CET Pavel Afonine wrote: Hi Tim, hi Natesh, one expression is mathematically, the other one is technically 'more correct'. I favour the terms poor and good resolution to avoid confusion, or explicitly list the values. just out of curiosity.. what's your definition of 'poor' and 'good' resolutions? I suspect there are as many definitions as many subscribers to this list are -;) One way to quantify resolution is that what kind of detail you can see in the map, like for example: - deformation density (~0.7A and higher) = ultra-high, sub-atomic, sub-Angstrom; - H atoms (~0.9A and higher) = not sure what the name is; - individual non-H atoms (~1.2A and higher) = atomic; - hole in rings (~2A and higher?) = high; - medium; - still can see side chains (up to 4.5A); - no side-chains but SS elements (such as tubes of density for helices) = low - no SS, molecular envelopes = very low. Note, resolution alone is not a good measure though. Data completeness is similarly important, e.g. a map corresponding to 2A resolution may look like a 3ish A resolution if you miss some low-resolution data or high-resolution end is severely incomplete (Acta Cryst. (2014). D70, 2593-2606). Low resolution --> worse than 2.7 A Ultra high resolution --> better than 0.95 A Looking into this in some systematic way one can define low-resolution as 6A and lower, and ultra-high resolution as 0.7A and higher (Page 1291: Acta Cryst. (2009). D65, 1283–1291). All the best, Pavel -- -- Paul Scherrer Institut Tim Gruene - persoenlich - OFLC/102 CH-5232 Villigen PSI phone: +41 (0)56 310 5297 GPG Key ID = A46BEE1A
