Abstract: Modeling approaches have been used to develop insight into the nature of the redox active site of the freeradical-containing copper metalloenzyme galactose oxidase. The optical spectrum of the free radical generated by low-temperature UV irradiation of (methy1thio) cresol is nearly identical to that observed for the free-radical site in metal-free apo galactose oxidase, supporting the assignment of the protein radical to a novel ...