title: Model complexes suggest certain S-state changes of the photosynthetic water-oxidation enzyme may involve an Mn(II)-Mn(III) transition.
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.
mesh_terms: D008345:Manganese / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases; D010788:Photosynthesis; D045332:Photosystem II Protein Complex; D013056:Spectrophotometry, Ultraviolet
chemical_list: D045332:Photosystem II Protein Complex; D008345:Manganese; D010088:Oxidoreductases