199Hg NMR investigation on the solution structure of Hg(II) complexes of oligopeptides containing cysteine and histidine residues

✍ Scribed by Hayamitsu Adachi; Norikazu Ueyama; Akira Nakamura

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 754 KB
• Volume: 198-200
• Category: Article
• ISSN: 0020-1693
• DOI: 10.1016/s0020-1693(00)92426-5

✦ Synopsis

The Hg(I1) complexes of cysteine, histidine-containing oligopeptides, Hg,Cl,(Z-cis-his-OMe) (l), Hg,Cl,(Z-cys-Ala-Ala-his-OMe) (2), Hg,Cl,(Zcys-Ala-Pro-his-OMe) (3) and Hg,Cl,(ms-Prc+Val-his-OMe) (4), were synthesized from HgCl, and the corresponding S-acetamidomethyl-protected peptides. '?-Ig NMR studies suggested that Hg(I1) ions rapidly exchange even at -55 "C between cysteine thiolate and histidine imidazole groups in solution. The "?Hg NMR signals are observed at higher field from MgHg in the order of chemical shift values; 1 > 4 > 2 > 3. Self exchange of two Hg(I1) occurs through an intermediate of peptide chelating coordination to one of the two Hg(I1) ions. The energy-minimum calculations (Biograf) of the peptide complexes support the structure of the proposed intermediate. The observed rWHg NMR chemical shifts are correlated with the (S,N)-chelating ability of the oligopeptides at the cysteine and histidine residues. "cys and his represent the Cys and His residues coordinating to Hg(I1). Z refers to benzyloxycarbonyl.