No abstract

with the known properties of Compounds I of catalase and peroxidase leads us to propose that these forms of the enzymes contain a ir-cation radical of the heme prosthetic group. METHODSThe techniques for bromine oxidations, controlled potential electrolysis, coulometry, and for optical and esr measurements (as well as for purification and preparation of materials) have been described (4). For anion-transfer reactions, a quartz esr tube was attached to an ampoule with two side arms, one of which contained a degassed solution of [Co(III) (Et)8P]2+ 2Br-in chloroform and the other dry AgCl04 isolated by a fritted disc. After the spectrum of the bromide salt was obtained, the solution was shaken in the AgCl04 compartment to form the [Co(III)(Et)8P]2+ 2C104-salt. Relative concentrations of free radicals were determined by double integration by computer of the first-derivative spectra obtained under comparable experimental conditions. The mass spectrum was recorded on an AEI MS-9 mass spectrometer operating at 70 eV, and a source temperature of 2500C. The nuclear magnetic resonance (nmr) spectra were measured in chloroform and recorded on a Varian HA-100 spectrometer, with tetramethylsilane as internal reference. Attempts to oxidize ferric porphyrins to a formal Fe(V) oxidation state were unsuccessful due to solvent breakdown encountered at the high potentials required [>1.5 V vs. aqueous saturated calomel electrode (see) ]. RESULTS

Bacteriopheophytin, the magesium-free base of bacteriochlorophyll, undergoes reversible one-electron reduction in organic solvents to yield an anionic free radical with characteristic optical and electron spin resonance spectra. The which was pumped away to codistill water, and the pigment was dried under reduced pressure (10-3 Pa) for several hours. RESULTSThe anion radical of bacteriopheophytin BPh exhibits a reversible, one electron, halfwave reduction potential E1/2 of -0.58 against NHE in CH2Cl2.