Zinc Complexes of a Helical 22-mer Peptide with Two Histidine Donors

A new 22-mer model peptide P22 was designed for maximal α-helicity in nonpolar media, synthesized by solid-phase methods, and isolated in an analytically pure state. It contains histidine at positions 10 and 14 representing the i, i + 4 motif which is typical for metal ion binding. Treatment with zinc halides yielded the uncharged molecular complexes (P22)ZnCl2 and (P22)ZnI2 which are the first metal complexes of medium-sized peptides to be isolated in an analytically pure state and identified by mass spectrometry. The helicity of both the free peptide and its complexes was confirmed by IR and CD spectroscopy as well as by molecular mechanics calculations. This has allowed us to propose a molecular structure which shows that the complexes are viable models for zinc-binding sections in zinc finger proteins. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)