ABSTRACT: Wentworth et al. [Wentworth, P., Jones, L. H., Wentworth, A. D., Zhu, X. Y., Larsen, N. A., Wilson, I. A., Xu, X., Goddard, W. A., Janda, K. D., Eschenmoser, A. & Lerner, R. A. (2001) Science 293, 1806-1811] recently reported the surprising result that antibodies and T cell receptors efficiently catalyze the conversion of molecular singlet oxygen (1O2) plus water to hydrogen peroxide (HOOH). Recently, quantum mechanical calculations were used to delineate a plausible mechanism, involving reaction of 1O2 with two waters to form HOOOH (plus H2O), followed by formation of HOOOH dimer, which rearranges to form HOO-HOOO + H2O, which rearranges to form two HOOH plus 1O2 or 3O2. For a system with 18O H2O, this mechanism leads to a 2.2:1 ratio of 16O:18O in the product HOOH, in good agreement with
