ChemInform Abstract: Copper(II) Complexes of L-Histidylglycyl-L-histidylglycine and L-Histidyl-L-histidylglycylglycine: Coordination Mode of Histidyl Residues.

ChemInform Abstract

The complex formations of the title tetrapeptides with Cu(II) ion are studied in a slightly alkaline medium by visible absorption, CD and electron spin resonance spectroscopies. His-Gly-His-Gly coordinates to Cu(II) via a terminal amino N atom, two deprotonated peptide N atoms and an imidazole N atom of the histidyl residue in the third position. The Cu(II) ion in the His-His-Gly-Gly complex is coordinated by three N donors; i.e., a terminal amino N atom, an adjacent deprotonated peptide N atom and an imidazole N atom of the histidyl residue in the second position. The imidazole N atom at the N-terminal does not participate in the chelate formation with Cu(II), but it bridges between the two monomeric complexes so that a broad ESR spectrum without the hyperfine structure is observed. The preparations of the tetrapeptides by a liquid phase method are described.