| Abstract: | The ultraviolet-visible absorbance differences spectra of Mn(II,III) and Mn(III,III) oxo-bridged carboxylate complexes are reported. The difference spectra are remarkably similar to those of the photosynthetic water-oxidation enzyme complex reported by Dekker et al. [(1984) Biochim. Biophys. Acta 764, 301-309] which were interpreted as being due exclusively to Mn(II----IV) transitions. This result indicates that certain S-state changes of the enzyme complex may instead involve Mn(II----III) transitions, and that difference spectra alone cannot be used with confidence to assign the Mn oxidation state changes during water oxidation. |
