1H, 2H and 19F NMR spectroscopy of a novel iron(II) tetradentate cysteine-peptide complex having only one δ isomer. Detection of two isomers in coordination of CysXYCys bidentate peptide ligands to iron(II) ion

✍ Scribed by Wei-yin Sun; Norikazu Ueyama; Akira Nakamura

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 671 KB
• Volume: 31
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260311309

✦ Synopsis

Abstract

An Fe(II) complex with Z‐Ala‐CysProLeuCysGlyNHC~6~H~4~__m__F (Z = benzoxylcarbonyl) having an invariant bidentate peptide ligand, CysKYCys, in rubredoxins was synthesized. The contact‐shifted ^1^H, ^2^H and ^19^F NMR signals of (Et~4~N)~2~[Fe(ZAlacysProLeucysGlyNHC~6~H~4~__m__F)~2~] (1) in acetonitrile‐d~3~ or acetonitrile at 30°C indicate the existence of two isomers (δ and λ) in the solution of bidentate complex 1 with different orientations of the bidentate peptide ligand to a tetrahedral Fe(II) ion. A novel tetradentate cysteine‐containing peptide ligand, cis‐1,2‐cyclohexylene(COAlaCysProLeuCysGlyNHC~6~H~4~__m__F)~2~, is designed by energy minimum calculations and synthesized. Its Fe(II) complex, (Et~4~N)~2~[Fe(cis‐1,2‐cyclohexylene(CO‐Ala‐cys‐Pro‐Leu‐cys‐Gly‐NH‐C~6~H~4~‐m‐F)~2~)], showed only set of contact‐shifted ^1^H, ^2^H and ^19^F NMR signals of Cys C~β~H~2~ due to the preferable formation of the δ isomer.