Zinc Complexes of Amino Acids and Peptides, 6. Zinc Complexes of Oligopeptides Containing Histidine at Both Termini

Abstract

One tripeptide, five tetrapeptides, and one pentapeptide, all containing His–Xn–His sequences and being blocked at the N and C termini with acyl and amide functions, respectively, were synthesized by solid‐phase methods. With one exception their reaction with various zinc salts led to the precipitation of 1:1 (zinc/peptide) complexes. Analytically pure compounds were obtained from zinc tetrafluoroborate and His–Gly–His (1), from zinc chloride (resp. bromide) and His–Gly –Gly–His (2), His–Ala–Gly–His (3), His–Leu–Gly–His (4), His–Pro–Gly–His (5), and His–Pro–Asn–His (6) as well as from zinc sulfate and His–Leu–Gly–His (4) and His–Ala–Pro–Gly–His (7). 1H‐NMR data, when available, indicate the coordination of both histidine units to zinc in all cases. The low solubility of the complexes points to their polymeric nature. The only 1:2 (zinc/peptide) complex in this series was obtained from zinc perchlorate and His–Gly–Gly–His (2). An EXAFS study revealed that it contains zinc symmetrically coordinated by four histidine imidazole ligands. Based on the available information it is proposed that all complexes are one‐dimensional polymers containg [–Zn–His–Xn–His–Zn–]x backbones.

Dipeptides Made up Solely from Histidine: Solution Behaviour and Zinc Complexation

“…Counting the number of donor functions available for the zinc ions in the observed compositions allows the conclusion that zinc is tetrahedrally coordinated both in the monomers and the polymers. While none of our zinc complexes of bis(histidine) oligopeptides [1,6,8] has formed crystals suitable for X-ray analysis, we could confirm the tetrahedral coordination by an EXAFS analysis for Zn(Ac-HisGlyGlyHis-NH 2 ) 2 Zn(ClO 4 ) 2 . [6] …”

“…While none of our zinc complexes of bis(histidine) oligopeptides [1,6,8] has formed crystals suitable for X-ray analysis, we could confirm the tetrahedral coordination by an EXAFS analysis for Zn(Ac-HisGlyGlyHis-NH 2 ) 2 Zn(ClO 4 ) 2 . [6] …”

X-ray absorption spectroscopic studies of zinc in the N-terminal domain of HIV-2 integrase and model compounds

“…It has been shown previously (EggersBorkenstein et al, 1989) that the major shells of the data can be satisfactorily analyzed with either empirical or theoretical (McKale et al, 1988) amplitude and phase functions. For the present simulations, however, we chose EXCURVE because it allows us to simulate and iteratively re®ne the multiple scattering of imidazole rings with restraints (Binsted et al, 1992) and because of its successful earlier application (EXCURV88; Fo È rster et al, 1996) in the simulation of Zn imidazole EXAFS spectra. The results of the present calculations were tested on the model compounds zinc(II) ethylxanthate (1) and tetrakis(imidazole)zinc(II) diperchlorate (3), which feature Zn±S (Ikeda & Hagihara, 1966) and ±imidazole (Bear et al, 1975) coordination, respectively.…”

l-Histidyl-glycyl-glycyl-l-histidine. Amino-acid structuring of the bleomycin-type pentadentate metal-binding environment capable of efficient double-strand cleavage of plasmid DNA

“…On the other hand, totally different linear polymeric coordination mode of zinc complex of Ac-HGGH-NH 2 (Fig. 9C) has been proposed based on the EXAFS study [8]. The above results does not support this type of linear polymeric Cu complex formation.…”