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The stability of a peroxo-iron species in the second time scale when reacted with H2O2 is due to the E47A mutation in superoxide reductase (SOR) from Desulfoarculus baarsii. Further characterization on the basis of Mossbauer and spin Hamiltonian parameters shows that the peroxo-Fe(super +3) species is a high-spin side-on complex.

Density functional, broken symmetry techniques have been used to assess exchange coupling constants for di-mu-oxo-bridged copper(II) dimers with varying Cu-O-Cu bond angles. It is demonstrated that O. Kahn's antiferromagnetic term can be ferromagnetic.

An analytical expression of varDeltaP2-(Cu) for two bridged Cu(II) dimers is presented.

The structure of a spore photoproduct of the dinucleoside TpT (SPTpT) is reexamined to determine the absolute configuration of the natural SP by combining NMR measurements and density functional theory calculations. The results have shown that this natural SPTpT compound is the dinucleotide 5'->3' with an R configuration at the carbon [C.sub.5a].

A phenomenological model aimed at rationalizing variations in both average g-tensor values and effective exchange coupling constants [J.sub.eff] is derived in order to describe the great variety of magnetic properties displayed by reduced [2Fe-2S] clusters in proteins. The crystallographic structures of wild-type and mutant As ferrodoxins (Fd's) are used for describing a distribution of spin states.

The synthesis, X-ray structure, magnetic properties and successive preliminary density functional theory analysis of azido-bridged binuclear [Cu.sup.II] complex [[Cu.sub.2]([[[mu].sub.1.1-][N.sub.3]).sub.2][(im-2py).sub.2][([N.sub.3]).sub.2] is reported. A large metal-nitroxide ferromagnetic exchange coupling was noticed whose magnitude compares well with that reported for closely related complexes.