3 research outputs found

    Cyclotides from the Indian Medicinal Plant <i>Viola odorata</i> (Banafsha): Identification and Characterization

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    Cyclotides are cyclic cystine knotted macrocyclic plant peptides that have several promising applications. This study was undertaken to detect and identify known and new cyclotides in <i>Viola odorata</i>, a commercially important medicinal plant, from three geographical locations in India. The number of cyclotides in the plant varied with the tissue (leaves, petioles, flowers, runners, and roots) and with geographical locations in India. Using liquid chromatography coupled to Fourier transform mass spectrometry (FTMS), 166 cyclotide-like masses were observed to display cyclotide-diagnostic mass shifts following reduction, alkylation, and digestion, and 71 of these were positively identified based on automated spectrum matching. Of the remaining 95 putative cyclotides observed, de novo peptide sequencing of three new cyclotides, namely, vodo I1 (<b>1</b>), vodo I2 (<b>2</b>), and vodo I3 (<b>3</b>), was carried out with tandem mass spectrometry

    Diffusion of Solvent-Separated Ion Pairs Controls Back Electron Transfer Rate in Graphene Quantum Dots

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    In the present study, the stability of the photogenerated, solvent-separated charged states of graphene quantum dots (GQDs) in the presence of <i>N</i>,<i>N</i>-diethylaniline (DEA) has been evaluated in a series of organic solvents. The results indicate that the rate constant for back electron transfer (<i>k</i><sub>BET</sub>) from GQD radical anion to DEA radical cation is diffusion-controlled. As a result of the diffusion-controlled back electron transfer (BET), <i>k</i><sub>BET</sub> exhibits an inverse exponential relation to (a) the viscosity coefficient (η) of the solvent and (b) the average radius of the graphene quantum dots. An analytical expression for the diffusion-controlled back electron transfer rate constant has been formulated. The dependence of <i>k</i><sub>BET</sub> on the diffusion of solvent-separated ion pairs has been evaluated for the first time for quantum dot systems and the results provide an efficient method for enhancing the lifetime of the photogenerated charge-separated states from graphene quantum dots. The present findings can potentially improve the performance of GQD-based photovoltaic and optoelectronic devices
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