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In the “good old days” we used to refer to “atomic resolution” as higher than 1.0 Å (or more specifically, at least 0.8 Å resolution), e.g. the resolution obtained by most small molecule structures, where you get at least 10 times the number of observables per refined parameter, and thus could do full matrix least squares refinement of your model (including anisotropic thermal parameter refinement on all non-hydrogen atoms). But then, I guess that just shows my age, Diana ************************************************** Diana R. Tomchick Professor Departments of Biophysics and Biochemistry University of Texas Southwestern Medical Center 5323 Harry Hines Blvd. Rm. ND10.214A Dallas, TX 75390-8816 [log in to unmask]<mailto:[log in to unmask]> (214) 645-6383 (phone) (214) 645-6353 (fax) On Jan 11, 2018, at 1:59 PM, Thomas Edwards <[log in to unmask]<mailto:[log in to unmask]>> wrote: Dear Jacob, Ah... this old chestnut! Current EM people say that they are at atomic resolution because they are building atomic models (naive??). I have been criticised in the past for using the term with say 2.2A diffraction data. By co-authors and reviewers alike. When I was young and naive. My (current) definition would be yours - visible with data. I think 1.5A is about right for X-ray. Maybe higher res? I’m sure there are lots of rigorous ways to think. I probably haven’t taken that route. However, I think it is a semantic problem that might benefit from some disambiguation rather than rigour. It depends why you are asking the question... Sorry..! Ed is: Out and about... Sent from iPhone6sPlus. On 11 Jan 2018, at 19:31, Keller, Jacob <[log in to unmask]<mailto:[log in to unmask]>> wrote: Dear Crystallographers, Has there been a consensus as to what is meant by “atomic resolution?” Seems like the term is taken by various practitioners to mean different things. A related question: at what resolution are atoms “visible” using only the data? I have an empirical feeling that this would be around 1.5 Ang Bragg spacings, but on the other hand, one can contour up most maps and see individual atom peaks. I would be interested to hear a more rigorous way to think about this. All the best, Jacob Keller +++++++++++++++++++++++++++++++++++++++++++++++++ Jacob Pearson Keller Research Scientist / Looger Lab HHMI Janelia Research Campus 19700 Helix Dr, Ashburn, VA 20147 (571)209-4000 x3159 +++++++++++++++++++++++++++++++++++++++++++++++++ The content of this email is confidential and intended for the recipient specified in message only. It is strictly forbidden to share any part of this message with any third party, without a written consent of the sender. If you received this message by mistake, please reply to this message and follow with its deletion, so that we can ensure such a mistake does not occur in the future. ________________________________ UT Southwestern Medical Center The future of medicine, today.