Metal complexes of luteinizing hormone-releasing hormone (LHRH). potentiometric and spectroscopic studies

The results are reported of a potentiometric and spectroscopic study of the H+, Cu2+, and Ni2+ complexes of luteinizing hormone-releasing hormone (LHRH, HL) at 25 degrees C and an ionic strength 0.10 mol dm-3 (KNO3), since there is much evidence that the in vivo release of LHRH is influenced by the concentration of copper ions. With Cu2+ the hormone has been shown to behave similarly to the thyrotropin releasing factor, forming a very stable [CuH-1L] complex involving coordination of three nitrogen donors: the Nim atom of the imidazole side chain and the two amido-N atoms of the pyroglutamylhistidyl unit. With Ni2+, coordination proceeds differently to give four nitrogen coordination.