Resonance Raman spectra (RR) are reported for bovine adrenodoxin (Ado) and ferredoxin (Fd) from Porphyra umbilicalis, with 34S substituted at the bridging positions of the Fe2S2 cluster. All of the Fe-S stretching modes are assigned on the basis of the 34S isotope shifts and the previous analysis of analogue spectra. Appreciable frequency variations are seen, which can be explained on the basis of stronger Fe-S bonds, both bridging and terminal, in the proteins. This strengthening is attributable to protein compression effects or to H-bond interactions which reduced the negative charge on the iron-sulfur complex. In addition the Fe frequencies suggest an alteration in the Fe-S-C-C dihedral angles which induce mixing of the terminal Fe-S stretches with the S-C-C bending coordinate. The RR spectrum of the Porphyra umbilicalis Fd is identical with that of Fd isolated from Spirulina platensis, for which the crystal structure has been reported, as well as that of spinach Fd. RR spectra have also been obtained for a red paramagnetic protein (RPP) from Clostridium pasteurianum. Its frequencies suggest weakened Fe-S bridge bonding. RR spectra of reduced protein have been obtained for Ado and RPP, but not for Fd. The reduced protein spectra differ strongly from those of the oxidized proteins, and can be accounted for on the basis of a 30% reduction of the Fe-S force constants on the Fe11 side of the Fe2S2 cluster.

Steam gasification of chars from the pyrolysis of a Japanese bamboo and cedar was studied using a reactor that enabled experimental definition of the gas composition in the vicinity of gasifying char particles. Intraparticle diffusion of neither steam nor the product gases influenced the kinetics of gasification. The chars underwent noncatalytic and catalytic gasification in parallel. The noncatalytic gasification, in which kinetic parameters were successfully defined by those for the gasification of the acid-washed char, was first-order with respect to the amount of residual carbon over the entire range of char conversion. In consequence of this, contribution of the catalytic gasification was quantified as a function of the char conversion. Among the inherent alkali and alkaline earth metallic species, potassium (K) played the major catalytic role and its overall activity changed via a maximum in the course of gasification, suggesting the presence of optimum sizes of clusters or particles of K catalyst. The noncatalytic and catalytic reactions obeyed respective Langmuir−Hinshelwood mechanisms that involved inhibition by H2.

We reported evidence that horseradish peroxidase (HRP) and chloroperoxidase (CPO) catalyze oxygen transfer from H2O2 to thioanisoles [Kobayashi, S., Nakano, M., Goto, T., Kimura, T., & Schaap, A. P. (1986) Biochem. Biophys. Res. Commun. 135, 166-171]. In the present paper, the reaction mechanism of this oxygen transfer is discussed. The oxidation of para-substituted thioanisoles by HRP compound II showed a large negative rho value of -1.46 vs. the sigma + parameter in a Hammett plot. These results are in accord with the formation of a cation radical intermediate in the rate-determining step. Hammett treatments for HRP- and CPO-dependent S-oxygenations did not provide unequivocal proofs to judge the reaction mechanism, because of the poor correlations for sigma + and sigma p parameters. Different behavior was found in kinetics and stereoselectivity between the two enzymes. Results in the present study and recent studies strongly suggested the formation of a cation radical intermediate. The oxygen atom would transfer by reaction of compound II and the cation radical intermediate. Although involvement of the cation radical was not confirmed in the CPO system, a similar mechanism was proposed for CPO.

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Nascent volatiles from the pyrolysis of a type of woody biomass were reformed in a bed of charcoal at 750À850 °C. While the volatiles passed through the bed together with air at an air ratio of 0.115, the concentration of heavy tar (bp > 336 °C) decreased from 910 000 to 6À1020 mg/Nm 3 dry . This rapid and almost total decomposition of the tar can be ascribed to its deposition onto the charcoal surface, forming coke. The coke formation leads to the loss of the charcoal micropores that provide active sites. Therefore, simultaneous creation of micropores by gasification is necessary to maintain the charcoal activity. Steam played the role of gasifying agent, while O 2 was consumed mainly by gas-phase oxidation that supplied the heat for the reaction.