Structures of ruthenium-modified Pseudomonas aeruginosa azurin and [Ru(2,2'-bipyridine)(2)(imidazole)(2)]SO4 center dot 10H(2)O

The crystal structure of Ru(2,2'-bipyridine)(2)(imidazole) (His83)azurin (R uAz) has been determined to 2.3 Angstrom resolution by X-ray crystallograph y. The spectroscopic and thermodynamic properties of both the native protei n and [Ru(2,2'-bipyridine)(2)(imidazole)(2)](2+) are maintained in the modi fied protein. Dark-green RuAz crystals grown from PEG 4000, LiNO3, CuCl2 an d Tris buffer are monoclinic, belong to the space group C2 and have cell pa rameters a = 100.6, b = 35.4, c = 74.7 Angstrom and beta = 106.5 degrees. I n addition, [Ru(2,2'-bipyridine)(2)(imidazole)(2)]SO4. 10H(2)O was synthesi zed, crystallized and structurally characterized by X-ray crystallography. Red-brown crystals of this complex are monoclinic, space group P2(1)/n, uni t-cell parameters a = 13.230 (2), b = 18.197 (4), c=16.126(4)Angstrom, beta =108.65 (2)degrees. Stereochemical parameters for the refinement of Ru(2,2' -bipyridine),(imidazole) (His83) were taken from the atomic coordinates of [Ru(2,2'-bipyridine)(2)(imidazole)(2)](2+). The structure of RuAz confirms that His83 is the only site of chemical modification and that the native az urin structure is not perturbed significantly by the ruthenium label.