Conformational changes in cyclic (D‐Phe‐Pro‐Gly‐D‐Ala‐Pro) upon complexation with Mg++.
- 12 January 1984
- journal article
- research article
- Published by Wiley in International Journal of Peptide and Protein Research
- Vol. 23 (1) , 32-38
- https://doi.org/10.1111/j.1399-3011.1984.tb02688.x
Abstract
Upon long standing and very slow evaporation, a solution of the cyclic penta-peptide and Mg(SCN)2 in CDCl3/CD3CN produced colorless crystals of a 1:1 complex of the peptide and Mg++. X-ray diffraction analysis showed the contents of the asymmetric unit to be C24H31N5O5˙ Mg++˙ NCS-˙ HSO-4˙ 6H2O (P212121, a = 8.444 (1) A, b = 10.735 (2) A, c = 39.726 (6) A). This first example of a metal ion complex with a cyclic pentapeptide is in the form of an infinite stack with alternating peptide and Mg++ moieties. The octahedrally coordinated Mg++ makes only two ligands with the peptide carbonyls: O(3)—Mg++ above and O(1)—Mg++ below. The equatorial coordinations involve three H2O molecules and NCS-. There is a profound change in conformation upon complexation, with several ø and ø values changing by 90° to 230°. One NCS- oxidizes to HSO-4 to provide the counter-ion.Keywords
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