Unless you have a degree in maths, the IUCr's "Little Dictionary of Crystallography" by A. Authier and G. Chapuis (2014) defies comprehension on this matter (it's all to do with set / group theory, I think, and there are many more morphisms covered in about 6 pages: homo, epi, mono, endo, auto).
Having discussed this with Ian Tickle, about 10 or 12 years ago, the formal (?) definition of isomorphous simply means that the unit cells of two or more crystals are the same, but the structure/molecule/compound/mineral, etc, does not even have to be the same. A sensible definition for dumb biologists might be to say that A and B are isomorphous, but C isn't. Best wishes, Jon Cooper. jon.b.coo...@protonmail.com Sent from Proton Mail mobile -------- Original Message -------- On 20 Dec 2023, 20:15, Hekstra, Doeke Romke 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 ######################################################################## 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/
