Dioxygen reduction to water by multicopper oxidases: crystal structures of several potential intermediates in the dioxygen reduction to water by multicopper oxidases: a) HoloCotA. b) CotA-H2O2 (1W8E) . c) Laccase from Trametes hirsuta  (3FPX). d) Ascorbate oxidase from Zucchini (1ASO) . e) ApoCu(I) f) reduced CotA (2BHF) .