Spectroscopic analysis of tyrosine derivatives: on the role of the tyrosine-histidine covalent linkage in cytochrome c oxidase.
2'-(1-Imidazolyl)-4-methylphenol (C-N bonding in the ortho' position at the phenyl group), a model compound for a tyrosine-histidine covalent linkage, was studied with a combined electrochemical and UV-vis/IR spectroscopic approach. Electrochemical analysis of the 2'-(1-imidazolyl)-4-methylphenol model compound by the means of cyclic voltammetry yielded a potential of 0.48 vs ferrocene (1.15 V vs NHE) for the oxidation of the deprotonated form, the reaction being kinetically irreversible. A tentative assignment of the electrochemically induced Fourier transform infrared (FTIR) difference infrared spectra is presented that indicates the deprotonation of the tyrosine before oxidation and importantly the strong influence of the solvent on the spectral properties and on the mechanism of radical formation. Fluorescence lifetimes and pre-exponential factors of the tyrosine-histidine model compounds are presented and discussed in comparison to tyrosine. The tyrosine-histidine fluorescence lifetime is found to be solvent dependent. The influence of the solvent on the reaction mechanism is proposed with regard to the mechanism of electron coupled proton transfer in proteins that include covalently linked amino acid side chains, like the cytochrome c oxidase.
Voicescu
Mariana
M
Laboratoire de Spectroscopie Vibrationnelle et Electrochimie des Biomolécules, UMR 7177, Institut de Chimie, CNRS-Université de Strasbourg, 67070 Strasbourg, France.
El Khoury
Youssef
Y
Martel
David
D
Heinrich
Martine
M
Hellwig
Petra
P
D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics; D005296:Ferrous Compounds / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D006639:Histidine / Q000737:chemistry*; D000075163:Metallocenes; D015394:Molecular Structure; D017550:Spectroscopy, Fourier Transform Infrared; D013057:Spectrum Analysis; D014443:Tyrosine / Q000031:analogs & derivatives / Q000737:chemistry
D005296:Ferrous Compounds; D005609:Free Radicals; D000075163:Metallocenes; D014443:Tyrosine; D006639:Histidine; D003576:Electron Transport Complex IV; C004998:ferrocene