199Hg NMR investigation on the solution structure of Hg(II) complexes of oligopeptides containing cysteine and histidine residues
摘要:
The Hg(II) complexes of cysteine, histidine-containing oligopeptides, Hg2Cl3(Z-cis-his-OMe) (1), Hg2Cl3(Z-cys-Ala-Ala-his-OMe) (2), Hg2Cl3(Z-cys-Ala-Pro-his-OMe) (3) and Hg2Cl3(Z-cys-Pro-Val-his-OMe) (4), were synthesized from HgCl2 and the corresponding S-acetamidomethyl-protected peptides. Hg-199 NMR studies suggested that Hg(II) ions rapidly exchange even at -55-degrees-C between cysteine thiolate and histidine imidazole groups in solution. The Hg-199 NMR signals are observed at higher field from Me2Hg in the order of chemical shift values; 1 > 4 > 2 > 3. Self exchange of two Hg(II) occurs through an intermediate of peptide chelating coordination to one of the two Hg(II) ions. The energy-minimum calculations (Biograf) of the peptide complexes support the structure of the proposed intermediate. The observed Hg-199 NMR chemical shifts are correlated with the (S,N)-chelating ability of the oligopeptides at the cysteine and histidine residues.
A general and versatile route to “zinc finger” templates
摘要:
The basic zinc finger template is formed in a single step from PNHCys[S-CH2NHAc]HisOMe and zinc chloride by a tandem complexation deprotection sequence.