Complexes of Peptides and Related Ligands

1 Complexes of Peptides with Non-coordinating Side Chains 

2 Complexes of Peptides with Coordinating Side Chains 

The presence of side chain donor atoms generally influences the thermodynamic stability and coordination geometry of peptide complexes significantly. The most important findings in this field have already been reviewed by several authors [63-66]. It is evident from these compilations that the effects of various donor atoms largely depend on the number and location of the extra donor atoms and also on the nature of the metal ions. Most of the data were published for the copper(II) complexes, but nickel(II) and paUadium(II) are also widely studied. 

In the case of cadmium(II), systematic studies on the role of specific amino acid residues are not available. On the basis of the analogies to other transition elements and from selected data for several systems, some general conclusions on the role of side chain residues can be predicted. 

The synthesis and studies of multihistidine peptides is a rapidly increasing field in metallopeptide chemistry because these hgands are the most promising models for biological conditions. The exclusive coordination of the imidazole-N side chain donor atoms of these ligands results in the formation of various macrochelates built 

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Coordinating properties of the amide bond. Stability and structure of metal ion complexes of peptides and related ligands. H. Sigel and R. B. Martin, Chem. Rev., 1982, 82, 385-426 (409). 

In the preferential interaction model, the equilibrium association constant, K.ISVIC, for a peptide docked to a RPC sorbent can be related via eq 6 to the changes in the preferential interaction of the solvent and water with the peptide P- the ligands L, and the peptide-ligand complex PtL as a function of solvent concentration, [3]m. The effect of preferential hydration/solvation of a peptide on k can be represented in terms of the following expression t85l... 

On the other hand, the simple complexes (hemins I and II) have a reverse relation between the ICD magnitudes in the Soret region and the ligand field strengths of the axial ligands bound to the heme for peptides and proteins. This difference between our models 199) and Urry s findings 196 198> may be partly due to the existence of the ring(s) with optically active center(s). 

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