Biological oxidation methods

As seen in the above equations, the aqueous oxidation processes convert sulfur in the feed to dissolved sulfate, while arsenic is oxidized and precipitated as ferric arsenate compounds. So, problems of the emission of sulfur and arsenic oxides caused by roasting are avoided in the aqueous oxidation processes. The two different industrial methods which achieve the oxidation reactions are pressure oxidation and biological oxidation. 

The functionality associated with N-1 of the vindoline portion of the bisindole alkaloids confers much biological diversity to these compounds. This property is exemplified by the differences in the cellular pharmacology, antitumor efficacy, and toxicity of vinblastine (1) and vincristine (2). Since 1 is isolated from extracts of Catharanthus in approximately 10-fold greater yield, it is not surprising that several oxidative methods have... 

Allison, L.E. Scarseth, G.D. (1942) A biological reduction method for removing free iron oxides from soils and colloidal days. J. Am. Soc. Agr. 34 616-623... 

Air oxidation of synthetic fully reduced co-conotoxin GVIA (9) (Scheme 4), a 27-residue peptide, 64 generated a main product that possessed the identical biological activities as the natural product whose cystine framework was determined with the synthetic compound. 65 The choice of buffer system and peptide concentration can, however, dramatically affect the folding efficiency when the DMSO-mediated oxidation method was applied. 661... 

The problems above mostly involve homogeneous oxidations. Another objective of this symposium was to find out how similar are the mechanisms and reactions in homogeneous oxidations to those in heterogeneous catalysis and biological systems. So far it seems that they are not very similar because neither ordinarily involves free radicals. However, the methods used to study biological oxidations have much in common with those used by physical-organic chemists in homogeneous oxidations. 

The use of ester-cleaving enzymes is probably going to be one of the most useful biological-chemical methods in the synthetic laboratory. No example of this type of reaction has hitherto been published in the Organic Syntheses series of procedures. So far, the only biological-chemical Organic Synfheses-procedures are two yeast reductions,4 5 one oxidation with horse-liver-alcohol-dehydrogenase,6 and a disaccharide synthesis catalyzed by emulsin.7 The procedure described here is... 

The combination of radiolabeled sulfide and the bimane-HPLC method is particularly powerful because one of the main obstacles to the use of labeled sulfide is, that aside from radioactive decay, the compound is subject to rapid oxidation in the presence of air. The breakdown products of chemical sulfide oxidation are the same as those of biological oxidation. Previously it has been impossible to check routinely the purity of the purchased isotope and its subsequent purity during a series of experiments. It is our experience that newly purchased sodium sulfide sometimes contains up to 10% thiosulfate as well as traces of sulfite and sulfate (Figure 2), and that the sulfide once hydrated readily oxidizes if stored in a normal refrigerator. 

Although cotinine is one of the important tobacco alkaloids and is known as the first metabolite of nicotine in the human body, the conventional chemical methods for its synthesis from nicotine are not always satisfactory. On the other hand, the oxygenation of nicotine 60 to cotinine 61 by using the electroreduetively generated superoxide anion has been studied, since it has been mentioned that the anion may have a similar reactivity to the biological oxidation 41 The maximum yield (65.2%) was obtained when the electroreduction was carried out at —0.9 V in aerating DMF with a carbon rod anode. 

An important environmental issue is the fate of cyanide. HCN, if spilled, evaporates quite readily. That which does not evaporate is soon decomposed or rendered nonhazardous by complexing with iron in the soil, by biological oxidation or by degradation from photolysis129. Several methods for treatment and disposal of cyanide compounds are described in references 129 and 133. 

Oxidation States of Alcohols and Related Functional Groups 467 11-2 Oxidation of Alcohols 469 11-3 Additional Methods for Oxidizing Alcohols 472 11-4 Biological Oxidation of Alcohols 474 11-5 Alcohols as Nucleophiles and Electrophiles Formation ofTosylates 476... 

The determination of urinary cresols, particularly o-cresol, has been proposed as a biological monitoring method for toluene, as a fraction of the inhaled vapor is oxidized at the aromatic ring with the production of cresols. 

Cyanides are commonly treated by chemical or biological oxidation. Of lesser importance is the precipitation of cyanide ion as complex iron cyanide, or by the direct atmospheric release of hydrogen cyanide by acidification and aeration. The oxidation methods, however, have found widest acceptance chemical oxidation is preferred for all but the more dilute cyanides free from other toxics, which may be diluted or treated biologically. Biological treatment of cyanides offers the possibility... 

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