Hi Didn’t Francis Crick have something to say about this in the early 1950s? I’m sure it was published but off the top of my mind I can’t think where (one of the more “established” members of this community will be able to give chapter and verse)!
If you want to read something a little more detailed than people have mentioned here, there’s a “Methods in Enzymology” chapter by Charlie Carter (?) et al from the early part of this century on the subject - again, I can’t remember exactly who or when. Have a good break (which reminds me to register for the CCP4 Study Weekend)! Harry > On 21 Dec 2023, at 08:04, Tim Gruene <tim.gru...@univie.ac.at> wrote: > > Hi Doeke, > > you can take the coordinates of B and do a rigid body refinement > against the data from A. If this map is sufficient to reproduce model A > (including model building and more refinement cycles), then B is > isomorphous to A. You can do this the other way round, and the result > may not be the same - hence, the mathematical definition of isomorphous > is not identical to the practical use of 'isomorphous' structures when > it comes to phasing. You can repeat this for each side of the triangle > (each in two directions) in order to label the semantic triangle. > > Merry Christmas, more peace on earth and sanity for the elections in > 2024! > > Tim > > On Wed, 20 Dec 2023 20:15:17 +0000 "Hekstra, Doeke Romke" > <doeke_heks...@harvard.edu> wrote: > >> Dear colleagues, >> >> Something to muse over during the holidays: >> >> Let's say we have three crystal forms of the same protein, for >> example crystallized with different ligands. Crystal forms A and B >> have the same crystal packing, except that one unit cell dimension >> differs by, for example, 3%. Crystal form C has a different crystal >> packing arrangement altogether. What is the right nomenclature to >> describe the relationship between these crystal forms? >> >> If A and B are sufficiently different that their phases are >> essentially uncorrelated, what do we call them? Near-isomorphous? >> Non-isomorphous? Do we need a different term to distinguish them from >> C or do we call all three datasets non-isomorphous? >> >> Thanks for helping us resolve our semantic tangle. >> >> Happy holidays! >> Doeke >> >> ===== >> >> Doeke Hekstra >> Assistant Professor of Molecular & Cellular Biology, and of Applied >> Physics (SEAS), Director of Undergraduate Studies, Chemical and >> Physical Biology Center for Systems Biology, Harvard University >> 52 Oxford Street, NW311 >> Cambridge, MA 02138 >> Office: 617-496-4740 >> Admin: 617-495-5651 (Lin Song) >> >> >> >> ######################################################################## >> >> To unsubscribe from the CCP4BB list, click the following link: >> https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 >> >> This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a >> mailing list hosted by www.jiscmail.ac.uk, terms & conditions are >> available at https://www.jiscmail.ac.uk/policyandsecurity/ > > > > -- > -- > Tim Gruene > Head of the Centre for X-ray Structure Analysis > Faculty of Chemistry > University of Vienna > > Phone: +43-1-4277-70202 > > GPG Key ID = A46BEE1A > > ######################################################################## > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > > This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing > list hosted by www.jiscmail.ac.uk, terms & conditions are available at > https://www.jiscmail.ac.uk/policyandsecurity/ ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
