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Updated: Jul 28, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
Calcium binding cyclic hexapeptide. Crystal structure of cyclo-(L-prolyl-glycyl)3 calcium complex
Abstract:
The synthetic cyclic hexapeptide (L-prolyl-glycyl)3 forms a 2:1 complex with Ca2+ ion. The cation is sandwiched between the two peptide molecules. The glycyl carbonyls from each of the peptides are octahedrally coordinated to the cation with an average calcium oxygen coordination distance of 2.26A. Both the molecules coordinating to the calcium ion have three fold symmetry, but show significant conformational differences. In one of the peptides of the sandwich, the alternate carbonyls point to the opposite sides of the peptide ring while in the other, all the six carbonyls point to the same side of the ring. Three NH ... O hydrogen bonds between the peptides add to the stability of the sandwich.
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