Electron spin relaxation of CuA and cytochrome a in cytochrome c oxidase: comparison to heme, copper, and sulfur radical complexes

The method of continuous saturation has been used to measure the electron spin relaxation parameter T1T2 at temperatures between 10 and 50 K for a variety of S = % species including: CuA and cytochrome a of cytochrome c oxidase, the type1 copper in several blue copper proteins, the type 2 copper in laccase, inorganic Cu(I1) complexes, sulfur radicals, and low spin heme proteins. The temperature dependence and the magnitude of T1T2 for all of the species examined are accounted for by assuming that the Van Vleck Raman process dominates the electron spin-lattice relaxation.