Reduction of methemerythrin by dithionite ion

Binuclear oxygen carriers: hemerythrin

“…The structure of the semimet form of hemerythrin obtained by reduction of the full met form has been delineated from a variety of physicochemical studies. Mossbauer and EPR data23 have established that in sulfidosemimethemerythrin the individual iron atoms are Fe(III), S = 5/2, and Fe(II), S = 2 in their oxidation and spin states, as originally suggested by Harrington et al 19 Furthermore, they are antiferromagnetically coupled, to a resultant spin of S = 3/2. Chemical ti-trations21 as well as EPR measurements22-24 also indicate that almost all the iron pairs in octametric semimethemerythrin are in the hybrid oxidation state [FenFeni).…”

Role of mixed oxidation states in the oxidation of hemerythrin species by ferricyanide ion

“…be delineated. Furthermore, the results can be compared with those obtained by ferricyanide oxidation of a semi-met form which has been recently obtained by a one-electron reduction of the met form using dithionite (Harrington et al, 1978) and which we now term (semi-met)R. (b) A comparison of the kinetic behavior of the deoxy and oxy forms will determine whether oxidation of the latter occurs directly or via the deoxy form with which it is in dissociative equilibrium, (c) Finally, the observation of further absorption changes following rapid oxidation of hemerythrin species is a distinct possibility since the geometries of, and even the nature of, the ligands attached to the iron sites in the iron(II) forms are likely to be quite different from those in the iron(III) species (Kurtz et al, 1977). Conformational adjustments will be necessary following the oxidation, and these might be reflected in spectral changes.…”

Hydroxide binding equilibrium in hemerythrin

“…The various anion adducts of methemerythrin tend to fall into three classes of bound ligand. Aquom~themerythrin is characterized by monophasic formation from oxyhemerythrin (Bradic, et al, 1980) and a biphasic reduction by dithionite (Harrington, et al, 1978). Another class, which includes azide, cyanide, and cyanate, can be characterized by biphasic formation from oxyhemerythrin (Bradic, et al, 1980) and no or very slow reduction by dithionite (Olivas, et al, 1979).…”