• Hari Mohan

      Articles written in Journal of Chemical Sciences

    • Effect of electron-withdrawing power of the substituted group onOH radical reaction with substituted aryl sulphides: A pulse radiolysis study

      Hari Mohan

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      In neutral aqueous solution of (phenylthio)acetic acid, hydroxyl radical is observed to react with a bimolecular rate constant of 7.2 × 10-1 dm3 mols and the transient absorption bands are assigned toOH radical addition to benzene and sulphur with a rough estimated values of 50 and 40% respectively. The reaction of theOH radical with diphenyl sulphide (k = 4.3 × 108 dm3 mol−1 s−1) is observed to take place with formation of solute radical cation, OH-adduct at sulphur and benzene with estimated values of about 12, 28 and 60% respectively. The transient absorption bands observed on reaction ofOH radical, in neutral aqueous solution of 4-(methylthio)phenyl acetic acid, are assigned to solute radical cation (λmax = 550 and 730 nm), OH-adduct at sulphur (λmax = 360 nm) and addition at benzene ring (λmax = 320 nm). The fraction ofOH radical reacting to form solute radical cation is observed to depend on the electron-withdrawing power of substituted group. In acidic solutions, depending on the concentration of acid and electron-withdrawing power, solute radical cation is the only transient species formed on reaction ofOH radical with the sulphides studied.

    • Effect of NaCl on the spectral and kinetic properties of cresyl violet (CV)-sodium dodecyl sulphate (SDS) complex

      K I Priyadarsini Hari Mohan

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      Effect of added NaCl on the spectral and kinetic properties of cationically charged dye (cresyl violet) and anionically charged surfactant (sodium dodecyl sulphate) were studied in the pre-micellar and micellar regions. Addition of 0.2 M NaCl to dye-surfactant solution decreased the critical micellar concentration for the micellization of the dye in sodium dodecyl sulphate to 1.2 × 10−3 M. Time-resolved studies using a stopped-flow spectrometer showed that NaCl influences the dynamics of micellisation. Addition of NaCl during the dye-surfactant complex formation converted the complex into micellized form at NaCl concentration of 0.01 to 0.05 M. In contrast, much higher concentration of NaCl (2 M) is required for the salting-out effect of the dye-surfactant complex for conversion to the micellized form

    • Fluorescence spectroscopic studies on binding of a flavonoid antioxidant quercetin to serum albumins

      Beena Mishra Atanu Barik K Indira Priyadarsini Hari Mohan

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      Binding of quercetin to human serum albumin (HSA) was studied and the binding constant measured by following the red-shifted absorption spectrum of quercetin in the presence of HSA and the quenching of the intrinsic protein fluorescence in the presence of different concentrations of quercetin. Fluorescence lifetime measurements of HSA showed decrease in the average lifetimes indicating binding at a location, near the tryptophan moiety, and the possibility of fluorescence energy transfer between excited tryptophan and quercetin. Critical transfer distance (Ro) was determined, from which the mean distance between tryptophan-214 in HSA and quercetin was calculated. The above studies were also carried out with bovine serum albumin (BSA).

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