Electron-Transfer Chemistry of Ru−Linker−(Heme)-Modified Myoglobin:  Rapid Intraprotein Reduction of a Photogenerated Porphyrin Cation Radical

We report the synthesis and characterization of RuC7, a complex in which a heme is covalently attached to a [Ru(bpy)3]2+ complex through a −(CH2)7− linker. Insertion of RuC7 into horse heart apomyoglobin gives RuC7Mb, a Ru(heme)−protein conjugate in which [Ru(bpy)3]2+ emission is highly quenched. Th...

Full description

Saved in:
Bibliographic Details
Published in:Inorganic chemistry 2004-06, Vol.43 (12), p.3593-3596
Main Authors: Immoos, Chad E, Di Bilio, Angel J, Cohen, Michael S, Van der Veer, Wytze, Gray, Harry B, Farmer, Patrick J
Format: Article
Language:English
Subjects:
Animals
Apoproteins - chemistry
Cations - chemistry
Electron Transport
Free Radicals
Heme - chemistry
Horses
Molecular Structure
Myoglobin - chemistry
Oxidation-Reduction
Porphyrins - chemistry
Protein Structure, Secondary
Ruthenium - chemistry
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We report the synthesis and characterization of RuC7, a complex in which a heme is covalently attached to a [Ru(bpy)3]2+ complex through a −(CH2)7− linker. Insertion of RuC7 into horse heart apomyoglobin gives RuC7Mb, a Ru(heme)−protein conjugate in which [Ru(bpy)3]2+ emission is highly quenched. The rate of photoinduced electron transfer (ET) from the resting (Ru2+/Fe3+) to the transient (Ru3+/Fe2+) state of RuC7Mb is >108 s-1; the back ET rate (to regenerate Ru2+/Fe3+) is 1.4 × 107 s-1. Irreversible oxidative quenching by [Co(NH3)5Cl]2+ generates Ru3+/Fe3+:  the Ru3+ complex then oxidizes the porphyrin to a cation radical (P•+); in a subsequent step, P•+ oxidizes both Fe3+ (to give FeIVO) and an amino acid residue. The rate of intramolecular reduction of P•+ is 9.8 × 103 s-1; the rate of ferryl formation is 2.9 × 103 s-1. Strong EPR signals attributable to tyrosine and tryptophan radicals were recorded after RuC7MbM3+ (M = Fe, Mn) was flash-quenched/frozen.
ISSN:0020-1669
1520-510X
DOI:10.1021/ic049741h