Conformational study of glycyl-L-proline technetium complex

Abstract

Dipeptide glycyl-L-proline (gly-pro) is degradation product of collagen. This degradation product is further cleaved by prolidase and proline can be recycled in to the new collagen or other peptide. Gly-pro labeled by technetium [99mTc] may potentially allow the in vivo visualization of synthesis and degradation of collagen. The aim of our work is conformational study of potential technetium complexes with gly-pro prepared in the acid reaction medium using AMBER and ZINDO/1 molecular modeling methods. In this reaction medium technetium creates two types of complexes with schematic formula ML2 and ML3. Existence of these complexes was proved by HPLC, electrophoresis on the paper and thin layer chromatography (Silufol© UV254). Gly-pro (ligand) in these two complexes can have cis and trans configuration. This configuration depends on the torsion angle between glycine and proline in the peptide bond. ML2 and ML3 complexes are created with TcO2+ as the result of reduction of TcO4− with SnCl2. Bonds presented in ML2 complex are between technetium, two amino groups and two oxygen atoms. These four atoms and central atom form square planar configuration. The most optimal ML2 complex is axial symmetric and both ligands have cis configuration. In ML3 complex TcO2+ creates three bonds with amino groups and three bonds with oxygen atoms. The most optimal ML3 complex has two ligands with cis and one ligand with trans configuration.