Istituto di Chimica Generale ed Inorganica Facoltà di Farmacia, Università degli Studi di Firenze Via G. Capponi 7, Firenze, Italy
Abstract:
17O NMR studies of 17O enriched water solutions containing superoxide dismutase have been performed between pH 7.5 and 11.7. Whereas T1 measurements do not reveal any interaction between 17O and the paramagnetic copper center, the linewidth results appreciably increased with increasing pH with an apparent pKa of 11.3. Comparison with 1H NMR relaxation studies allows to interpret the present data as due to binding to the copper ion of an OH? anion at high pH. The binding position should be of “equatorial” type, not involving the binding position of the coordinated water.