Ruthenium-azurin

In a sense, the comparative studies that were performed in the ruthenium derivatives of plastocyanin and azurin are also related to this kind of approach [152]. 

A variety of physical methods has been used to ascertain whether or not surface ruthenation alters the structure of a protein. UV-vis, CD, EPR, and resonance Raman spectroscopies have demonstrated that myoglobin [14, 18], cytochrome c [5, 16, 19, 21], and azurin [13] are not perturbed structurally by the attachment of a ruthenium complex to a surface histidine. The reduction potential of the metal redox center of a protein and its temperature dependence are indicators of protein structure as well. Cyclic voltammetry [5, 13], differential pulse polarography [14,21], and spectroelectrochemistry [12,14,22] are commonly used for the determination of the ruthenium and protein redox center potentials in modified proteins. 

Gradinaru C, Crane BR. Comparison of intra- vs intermolecular long-range electron transfer in crystals of ruthenium-modified azurin. I Phys Chem B 2006 110 20073-6. 

Ill (140). The ET reaction is initiated by photogenerated [Ru(bpy)3], which rapidly reduces the surface ruthenium. The [Ru(bpy)3] + is then scavenged by EDTA before it can back react with a5Ru(II)(histidine). Electron transfer to the protein metal center is then monitored spectroscopically. In the case of a heme (FeP), a fast increase in absorbance because of direct reduction of Fe(III)P by [Ru(bpy)3] is followed by a slower increase in absorbance due to reduction of Fe(III)P by the Ru(II) on the protein surface. Control flash experiments with unmodified proteins show only the fast initial increase in absorbance resulting from Fe(III)P reduction by [Ru(bpy)3]-. Such control experiments demonstrate for horse heart cytochrome c (140), azurin (93), and sperm whale myoglobin (30) that slow reduction of the heme by the EDTA radical produced in the scavenging step does not occur in competition with intramolecular ET. For C. krusei cytochrome c, however, the control experiment shows evidence for slow EDTA radical reduction of the heme after initial fast reduction by [Ru(bpy)3p (164). 

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