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Anju Chadha
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Anju Chadha
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Anju Chadha
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Chadha, A.
Chadha, Anju
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59 results
Now showing 1 - 10 of 59
- PublicationSimplified procedure for TEMPO-catalyzed oxidation: Selective oxidation of alcohols, α-hydroxy esters, and amides using TEMPO and calcium hypochlorite(01-12-2012)
;Reddy, Sabbasani Rajasekhara ;Stella, SelvarajA wide range of primary and secondary multifunctional alcohols, α-hydroxyamides, and α-hydroxyesters were oxidized to their corresponding aldehydes, ketones, α-ketoamides, and α-ketoesters under mild reaction conditions using 2,2,6,6-tetramethylpiperidine-1-oxyl as a catalyst with calcium hypochlorite as an oxidant [TEMPO-Ca(OCl) 2]. This simplified method does not require any transition metals, acids, or bases and demonstrates controlled and selective oxidation of structurally diverse alcohols, affording moderate to excellent yields at room temperature. © 2012 Taylor & Francis Group, LLC. - PublicationA fourier transform infrared spectroscopy (FTIR) based assay for Candida parapsilosis ATCC 7330 mediated oxidation of aryl alcohols(19-06-2015)
;Sudhakara, SnehaWe present an FTIR based assay to monitor the whole cell mediated oxidation of aryl alcohols by measuring the characteristic IR absorption of the hydroxyl group [OH] of the substrate and the carbonyl group [CO] of the corresponding oxidized product. This method expedites the analysis of whole cell mediated catalysis which is usually done by GC and/or HPLC. The FTIR assay had linearity with R2≥0.980 and sensitivity up to 10μM. The accuracy and precision of FTIR assay was found ≥81% and ≥94%, respectively. This assay was validated by GC which exhibited ≥82% accuracy and ≥79% precision. The time of analysis taken by this assay was 2-3min per sample in comparison with 20-40min by GC. - PublicationCallus and cell suspension culture of Viola odorata as in vitro production platforms of known and novel cyclotides(01-08-2017)
;Narayani, M.; Cyclotides are unique plant cyclic-peptides that can serve as agrochemicals, pharmaceutical scaffolds for drug delivery, and therapeutic agents. Currently, cyclotides are obtained only via direct extraction from limited plants. Hence, they serve as valuable candidates for synthesis via plant cell bioprocesses. In this study, callus lines (47 in total) were successfully induced from the leaf and petiole explants of the Indian medicinal plant, V. odorata, on a solidified woody plant medium (WPM) supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) (4.5 mg/l). Two fast growing callus lines, VOP-4 and VOL-44, were selected for the development of cell suspension cultures having a doubling time of 8 and 6 days, respectively. Further, known (15) and novel (9) cyclotides were identified for the first time in the callus and cell suspension cultures of V. odorata, using liquid chromatography and Fourier transform mass spectrometry. The cyclotides were identified based on their monoisotopic mass (2.5–4 kDa), hydrophobic nature, disulfide bonds, circular structure and amino acid sequence. Some of the cyclotides identified in the study (vodo I96, vodo I97, vodo I98) were exclusively produced in callus/cell suspension cultures and not in the parent plant. The study revealed that besides germplasm conservation, plant cell bioprocessing of V. odorata could be a potential alternative for in vitro production of known and novel cyclotides. - PublicationBiocatalytic deracemisation of aliphatic β-hydroxy esters: Improving the enantioselectivity by optimisation of reaction parameters(01-02-2015)
;Venkataraman, SowmyalakshmiOptically pure aliphatic β-hydroxy esters were prepared from their racemates by deracemisation using the biocatalyst Candida parapsilosis ATCC 7330. High optical purity (up to >99 %) and good yields (up to 71 %) of the product secondary alcohols were obtained. This study highlights the importance of optimization of reaction conditions using ethyl-3-hydroxybutanoate as the model substrate to improve the enantioselectivity (enantiomeric excess from 9 to 98 %). The present study emphasises the broad substrate scope of the biocatalyst towards deracemisation. This is the first report of Candida parapsilosis ATCC 7330-mediated deracemisation of various alkyl-3-hydroxybutanoates to produce either the (R)-enantiomers (methyl, ethyl, propyl, butyl, t-butyl, allyl-3-hydroxybutanoates) or (S)-enantiomers (pentyl, iso-amyl and iso-propyl-3-hydroxybutanoates). - PublicationKinetic studies of base-catalyzed transesterification reactions of non-edible oils to prepare biodiesel: The effect of Co-solvent and temperature(21-07-2011)
;Kumar, Gobbaka Ravi; The non-edible oils of mahua and jatropha were transesterified using methanol and 1 wt % KOH as the catalyst. The effect of co-solvent and the kinetic study of the transesterification of mahua oil is being reported here for the first time. Kinetics, modeled as a single-step reaction, revealed that the order of the reaction is 2 with respect to the triglyceride concentration and 1 with respect to the methanol concentration in both oils. In the presence of co-solvent, tetrahydrofuran (THF), methanolysis of mahua oil resulted in the increase of the rate constants from 0.08 to 1.17 L2 mol-2 min-1 at 28 °C and from 0.43 to 3.18 L2 mol -2 min-1 at 45 °C. The corresponding values for jatropha oil were found to be 0.50 and 2.76 L2 mol-2 min-1 at 28 °C and 1.26 and 4.56 L2 mol-2 min-1 at 45 °C. © 2011 American Chemical Society. - PublicationPackaged bulk micromachined triglyceride biosensor(03-05-2010)
;Mohanasundaram, S. V. ;Mercy, S. ;Harikrishna, P. V. ;Rani, Kailash; Estimation of triglyceride concentration is important for the health and food industries. Use of solid state biosensors like Electrolyte Insulator Semiconductor Capacitors (EISCAP) ensures ease in operation with good accuracy and sensitivity when compared to conventional sensors. In this paper we report on packaging of miniaturized EISCAP sensors on silicon. The packaging involves glass to silicon bonding using adhesive. Since this kind of packaging is done at room temperature, it cannot damage the thin dielectric layers on the silicon wafer unlike the high temperature anodic bonding technique and can be used for sensors with immobilized enzyme without denaturing the enzyme. The packaging also involves a teflon capping arrangement which helps in easy handling of the bio-analyte solutions. The capping solves two problems. Firstly, it helps in the immobilization process where it ensures the enzyme immobilization happens only on one pit and secondly it helps with easy transport of the bio-analyte into the sensor pit for measurements. © 2010 Copyright SPIE - The International Society for Optical Engineering. - PublicationSynthesis and aggregation properties of dansylated glycerol-based amphiphilic polyether dendrons(01-09-2010)
;Vuram, Prasanna K. ;Subuddhi, Usharani ;Krishnaji, Subrahmanian Tarakkad; Glycerol-based amphiphilic polyether mono azide third-generation dendrons were synthesized through a divergent strategy. A repetitive synthetic sequence of O-alkylation and isopropylidene deprotection reaction was adopted for the synthesis, pentamethylene was used as spacer. Dansyl chloride was attached to the focal point as a fluorophore. The photophysical property in aqueous solution of the protected dendrons showed self-association behaviour from second generation onwards even at a very low concentration (1×10-8 M). A hypsochromic shift of around 60 nm in the emission maximum, significant increase in fluorescence intensity, almost ten-fold increase in the fluorescence anisotropy and a fourfold increase in average fluorescence lifetime of dansyl moi-ety were observed on going from first generation dendron to higher generation dendrons in aqueous medium. The absence of such behavior in the corresponding unprotected, relatively hydrophilic dendritic units clearly indicated that the aggregation is due to the presence of hydrophobic isopropylidene end groups. Quenching studies of the dendrimers in aqueous solution using a hydrophilic quencher Ag+ revealed that the dansyl moiety in protected higher generations dendritic units is significantly shielded from the surroundings, which further rendered support to the fact that higher order dendrons undergo aggregation in aqueous medium. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. - PublicationDisaggregation induced solvatochromic switch: A study of dansylated polyglycerol dendrons in binary solvent mixture(15-07-2014)
;Subuddhi, Usharani ;Vuram, Prasanna K.; A reversal in solvatochromic behaviour was observed in second and third generation glycerol based dansylated polyether dendrons in water on addition of a second solvent like methanol or acetonitrile. Below a certain percentage of the nonaqueous solvent there is a negative-solvatochromism observed and above that there is a switch to positive-solvatochromism. The negative-solvatochromism is attributed to the progressive disaggregation of the dendron aggregates by the nonaqueous solvent component. Once the disaggregation process is complete, positive-solvatochromism is exhibited by the dendron monomers. Higher the hydrophobicity of the dendron more is the amount of the second solvent required for disaggregation. © 2014 Elsevier B.V. All rights reserved. - PublicationWhole resting cells vs. cell free extracts of Candida parapsilosis ATCC 7330 for the synthesis of gold nanoparticles(01-12-2016)
;Krishnan, Saravanan ;Narayan, ShobaThe cell free extracts of Candida parapsilosis ATCC 7330 are more efficient than the whole resting cells of the yeast in the synthesis of directly usable gold nanoparticles as revealed by this systematic study. Cell free extracts yielded gold nanoparticles of hydrodynamic diameter (50–200 nm). In this study, the total protein concentration influences the nanofabrication and not only the reductase enzymes as originally thought. Powder X-ray diffraction studies confirm the crystalline nature of the gold nanoparticles. Fourier Transform Infra Red spectroscopy and thermal gravimetric analysis suggests that the biosynthesized gold nanoparticles are capped by peptides/proteins. Dispersion experiments indicate a stable dispersion of gold nanoparticles in pH 12 solutions which is also confirmed by electron microscopic analysis and validated using a surface plasmon resonance assay. The effectiveness of the dispersed nanoparticles for the reduction of 4-nitrophenol using sodium borohydride as a reductant further confirms the formation of functional gold nanoparticles. It is also reported that gold nanoparticles with mean particle diameter of 27 nm are biosynthesized inside the whole cell by transmission electron microscopy analysis. With optimized reaction conditions, maximum gold bioaccumulation with the 24 h culture age of the yeast with cellular uptake of ~1010 gold atoms at the single cell level is achieved but it is not easy to extract the gold nanoparticles from the whole resting cells. - PublicationMeasurement and reliability issues in resonant mode cantilever for bio-sensing application in fluid medium(06-07-2016)
;Kathel, G. ;Shajahan, M. S. ;Bhadra, P. ;Prabhakar, A.; Cantilevers immersed in liquid experience viscous damping and hydrodynamic loading. We report on the use of such cantilevers, operating in the dynamic mode with, (i) frequency sweeping and (ii) phase locked loop methods. The solution to reliability issues such as random drift in the resonant peak values, and interference of spurious modes in the resonance frequency spectrum, are explained based on the actuation signal provided and laser spot size. The laser beam spot size and its position on the cantilever were found to have an important role, on the output signal and resonance frequency. We describe a method to distinguish the normal modes from the spurious modes for a cantilever. Uncertainties in the measurements define the lower limit of mass detection (m min). The minimum detection limits of the two measurement methods are investigated by measuring salt adsorption from phosphate buffer solution, as an example, a mass of 14 pg was measured using the 14th transverse mode of a m × 100 μm × 1 μm silicon cantilever. The optimized measurement was used to study the interaction between antibody and antigen.