2,5-Dinitrosalicylic acid groups

The PG activity was measured [10] by detecting the increase of reducing groups during the depolymerisation of 1 % (w/v) polygalacturonic acid buffered solutions, by a colorimetric method based on the 3,5-dinitrosalicylic acid. 

For enzyme uptake studies, 0.1 g of substrate (corn flour or carboxym-ethylcellulose) and 24 mL of buffer were added to a 40-mL jacketed reactor. The temperature was maintained at 52 2°C using a water bath. A 1.5-mL "blank" sample was collected from the reaction mixture and added to 3 mL of the dinitrosalicylic acid (DNS) reagent. Then 500 pL of the soluble enzyme was added to the reactor to initiate the reaction. Samples were collected every 3 min, and the DNS assay (4) was performed for all the samples. One unit of enzyme releases 1 pmol of reducing groups/min, the absorbance of which can be measured at 540 nm. Thus, the amount of activity transferred to the support can be determined from the sugar pro-... 

Dinitrosalicylic acid proved to be an excellent oxidizing agent for measuring very low amylase activities. The colorimetric response results from the conversion of 3,5-dinitrosalicylic acid to 3-amino-5-nitro-salicylic acid. The color produced by this reduction reaction is proportional to the actual number of reducing groups generated. 

Methyl ethers of D-fructose, difficult to estimate by any other means (especially those having the hydroxyl groups at C-1 and C-3 methylated), have been estimated by the alkaline 3,5-dinitrosalicylic acid reagent proposed by Bell and coworkers, and differentiation of the conformation of these methyl ethers was made possible by the addition of borate to the urea-phosphoric acid spray of Dedonder. 

New sensitive assays for dextranase activity are based on the use of Sephadex substituted with either 2,4,6-trinitrophenyl groups (for spectrophotometric assay) or fluorescamine groups (for fluorometric assay). 3,5-Dinitrosalicylic acid has been used in automated assays to determine the reducing sugars released on hydrolysis of the appropriate substrates with soluble or insoluble dextranases and other polysaccharide hydrolases. ... 

A quantum-chemical study of the mechanism of the condensation reaction between propanoic acid and aniline has been made. The mechanism of proton-transfer reactions of 3,5-dinitrosalicylic acid (41) has been the subject of a review (50 references). A successful correlation has been obtained between dissociation of a variety of acids in different solvents and quantum self-similarity measures of the CO2H fragment. The substituent effects of the isopropyl group in 2- (42), 3- (43), and 4-isopropylbenzoic acid (44) have been evaluated from their enthalpies of formation, gas-phase acidities, acidities in MeOH and in DMSO, and their IR spectra in tetrachloromethane. Particular attention was given to the influence of variable conformation on the observed steric effect. In contrast to 2-r-butylbenzoic acid and similarly to 2-methylbenzoic acid, 2-isopropylbenzoic acid exists in two planar conformations (42a,b) in equilibrium. Owing to this conformational freedom, the... 

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