Low temperature 65Cu NMR spectroscopy of the Cu+ site in azurin.

Copper is a ubiquitous component of living systems. It fulfills a vital role in many enzymes, particularly redox enzymes, and more generally in electron transfer. As might be anticipated from the chemistry of the element, the primary redox couple involved in biological redox processes is Cu+/ Cu2+. However, multinuclear copper centers1,2 and mixed metal centers3 give it the ability to participate in multielectron processes. Copper sites in proteins have been classified into several types: type-14 , type-25 , and type-31 copper, as well as the dinuclear CuA center6. Among the best studied are the type-1 sites, characterized by a strong absorbtion in the orange region of the visible spectrum. The blue copper proteins, a class of relatively small, one-electron transfer proteins found in bacteria and plants, notably employs type-1 copper sites.