Electron addition to the active site of Cancer magister haemocyanins. An ESR study of cu(II) centres after gamma-radiolysis.

Exposure of aqueous glasses of Cancer magister haemocyanin to 60Co gamma-rays at 77 K results in a novel paramagnetic centre with ESR features showing hyperfine coupling to one strongly coupled 63/65 Cu nucleus and possibly one weakly interacting 63/65 Cu nucleus. Addition of electron scavengers showed that this centre is formed by electron addition. It is suggested that addition occurs at Cu2+-O2-Cu2+ units to give Cu2+-O2Cu+ centres. If this is correct, then electron-transfer between the two copper ions is slow or non-existent, possibly indicating that they are inequivalent. The centre is unstable, the signals being lost irreversibly on heating to approx. 270 K. The g parallel and A parallel (63/65Cu) data place this centre into the type I classification.