Articles written in Journal of Chemical Sciences

    • 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).

    • Colorimetric and fluorescence signalling of thioesculetin in presence of oxidising agent


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      Thioesculetin (TE) is a sulfur analogue of esculetin. The UV-Vis absorption maximum of TE at 470 nm shifted to 357 nm in the presence of oxidising agent such as m-chloroperoxy benzoic acid (m-CPBA).With gradual increase in the m-CPBA concentration, the absorption band at 470 nm decreases while the band at 357 nm increases. The same system shows gradual increase in the fluorescence signal at 463 nm in the presence of m-CPBA. The fluorescence signal was unaffected in the presence of common anions and metal cations. Themechanism for optical signalling was due to the conversion of weakly fluorescent TE to fluorescent esculetin through desulfurization reaction. 13C-NMR shows strong evidence in support of the chemical conversion of TE to esculetin. TE may find applications to probe the redox environment in various chemical and biochemical processes.

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