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ing the distance between two charge groups: the conjugate acid and its specific counter anion. This is equivalent to a 1 : 1 electrolyte. However, it must be remembered that the protein, by virtue of its ionic groups, is itself a polyelectrolyte.This electrically neutral molecule contains a large number of positive and negative centers, and instead of analyzing the charge state as a 1 : 1 electrolyte, it should be analyzed as a polyelectrolyte. For this purpose, the positive charge of the conjugate acid can be visualized to be located at some fixed point in the electrostatic field. With respect to the conjugate acid the electrostatic field will have one excess negative charge. In comparison to the order in a crystal of an ionic compound, the protein may be considered as a random matrix of fixed charges. The center of negative charge density with respect to the conjugate acid will be a contribution of the nearest negative groups, and this negative charge density does not have to be located at the same point as the negative group. The distance from the cation to the center of negative charge density of the electrostatic field is equal to the rc + ra term. This means that with respect to the conjugate acid each protein conformation will have a certain center of negative charge density, and consequently, the resulting change in electrostatic interaction energy will induce a change in excitation energy.

Iron I 7100 Aqueous Fe IV =O: Spectroscopic Identification and Oxo-Group Exchange. -[(H2O)5Fe=O] 2+ species are generated from [Fe(H2O)6] 2+ and O3 in aqueous solution at pH 1 and characterized by Moessbauer spectroscopy, XANES, DFT calculations, and chemical reactions with Me2SO. Criteria are developed that make it possible to distinguish between hydroxyl radicals and aqueous ferryl-oxo species. [(H2O)5Fe IV =O] 2+ can be unambiguously ruled out as a crucial Fenton intermediate in acidic and neutral aqueous solutions. -(PESTOVSKY, O.; STOIAN, S.; BOMINAAR, E. L.; SHAN, X.; MUENCK*, E.; QUE, L. J.; BAKAC, A.; Angew. Chem., Int. Ed. 44 (2005) 42, 6871-6874; Dep. Chem., Carnegie Mellon Univ., Pittsburgh, PA 15213, USA; Eng.) -W. Pewestorf 02-025

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