Formazan, formation

Formazane formation 335 f. Frieswell-Green mechanism 400 f. Fullerenes, reaction with ArNj 188 6-Fulvenone 136 Furan... 

The reaction mechanism of formazan formation has been studied by many researchers. The fundamental work of Busch and his coworkers and the studies by Hiinig and Boes, and by Hauptmann and Perissd, merit special mention. A host of other authors have endeavored to widen the sphere of application of the formazan reaction, and have extended it successfully to the 4,4-iV-diarylsemicarbazonesi and guanylhydrazones, -i respectively. 

These sugar compounds show all the characteristic properties of the formazans a brilliant red color, complexing with salts of heavy metals, and ready oxidation to colorless compounds. Nevertheless, further evidence was sought, in order to prove that they really belong to the formazan group. According to all current views on the mechanism of formazan formation, secondary phenylhydrazones, such as a 2-methyl-2-phenyl-... 

To decide as to the usefulness of the simplified reaction for aldose identification, formazan formation from the corresponding aldoses has... 

A comparison of their curves shows that mutarotation and formazan formation are parallel processes and that, consequently, it is not the lacto-nization of the carboxyl group, but the aldo-cyclo isomerization that plays the decisive role. 

Fig. 11.— Lower Curve Mutarotation of n-Galacturonic Acid Phenylhydrazone (pyridine-ethanol, 1 1 by vol.) Upper Curve n-Galacturonic Acid Af.AT -Diphenyl-formazan Formation.

Of these proposed structures, only that of the n-glucose l-(A -methyl-V -phenyl)-2-(A -phenyl)osazone, suggested by Voto6ek and Vondrafek for mixed osazone B, is theoretically unsuited for formazan formation since... 

Formazan formation, the presence of two 0-acetyl groups in the acetylation product of the osazone formazan obtained, and the comparative study of the ultraviolet spectra, are all in harmony with formula XXII proposed by Hardegger and Schreier i and afford evidence of its correctness. 

Since mutarotation, spectral displacement, and formazan formation after evaporation of the solvent are, in the redissolved substance, repetitive proc-... 

Fig. 16.—Upper Curves Mutarotation of n-Glucose Phenylosazone in Pyridine-ethanol (1 1 by vol.) Lower Curves, n-Glucose Phenylosazone Formazan Formation (-----initial substance,.recovered substance).

From the formazan formation, it is possible to conclude the structure of the oxidized polysaccharides and their phenylhydrazones. 

Nishikimi et al., (1972) developed an assay for superoxide dismutase, using phenazine methosulfate which is structurally related to flavin. In this assay phenazine methosulfate is reduced by NADH, and on reoxidation, O2 was generated. The O2 was detected with nitroblue tetrazolium, and maximum inhibition of blue formazan formation by superoxide dismutase was 95% indicating that 5% of the reduction was due to direct interaction between the nitroblue tetrazolium and the reduced phenazine methosulfate. Addition of around 30 ng copper/zinc superoxide dismutase resulted in 50% inhibition of formazan formation. The assay was also used to locate the enzyme on polyacrylamide gels. 

As in isolated mitochondria, the permeability transition pore was opened in mitochondria in Morris hepatoma ICl cells, leading to depolarization [49]. Adverse effects on mitochondrial metabolism by yessotoxin appear unlikely, however since this substance, even at micromolar concentrations, did not inhibit formazan formation from 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetra-zolium in rat glioma C6 cells [55], a process that requires the presence of functional mitochondrial reductases [56]. Yessotoxin did not cause membranal depolarization in the BE(2)-M17 human neuroblastoma cell line [57]. 

Ephedrine/phenylephedrine IO4- Use of stopped-fiow mixing. Absorbance resulting from formazan formation was monitored at 620 nm. Method of proportional equations... 

Top view of isoenzyme pattern after formazan formation... 

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