Faculty Publications
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Item Synthesis and antimicrobial activities of some novel 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles and 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines carrying thioalkyl and sulphonyl phenoxy moieties(2007) Karabasanagouda, T.; Vasudeva Adhikari, A.V.; Shetty, N.S.Thirty one new 6-aryl-3-{(4-substituted phenoxy) methyl}-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles (6a-s) and 6-aryl-3-{(4-substituted phenoxy methyl}-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazines (7a-l) have been synthesized from 4-thioalkyl phenols (1a-b) through a multi-step reaction sequence. Compounds 1a-b reacted with ethyl chloroacetate in presence of acetone and potassium carbonate to give ethyl [4-(thioalkyl) phenoxy] acetates (2a-b). Further, 2a was oxidized to [4-(methyl sulphonyl) phenoxy] acetate (2c) using hydrogen peroxide in acetic acid. Reactions of (2a-c) with hydrazine hydrate in alcoholic medium furnished 2-[4-thiosubstituted phenoxy] acetohydrazides (3a-b) and 2-[4-methyl sulphonyl phenoxy] acetohydrazide (3c) which on treatment with carbon disulphide and methanolic potassium hydroxide yielded corresponding potassium dithiocarbazates (4a-c). They were then converted to 4-amino-5-{(4-thioalkyl phenoxy) methyl}-4H-1,2,4-triazole-3-thiols (5a-b) and 4-amino-5-{(4-methyl sulphonyl phenoxy) methyl}-4H-1,2,4-triazole-3-thiol (5c) by refluxing them with aqueous hydrazine hydrate. The title compounds 6a-s were prepared by condensing 5a-c with various aromatic carboxylic acids in presence of phosphorus oxychloride. The intermediates 5a-c, on condensation with various substituted phenacyl bromides afforded a series of title compounds (7a-l). The structures of new compounds 2a-7l were established on the basis of their elemental analysis, IR, 1H NMR, 13C NMR and mass spectral data. All the title compounds were subjected to in vitro antibacterial testing against four pathogenic strains and antifungal screening against three fungi. Preliminary results indicate that some of them exhibited promising activities and they deserve more consideration as potential antimicrobials. © 2006 Elsevier Masson SAS. All rights reserved.Item Novel chromeno [2,3-b]-pyrimidine derivatives as potential anti-microbial agents(2010) Sankappa Rai, U.; Isloor, A.M.; Shetty, P.; Vijesh, A.M.; Prabhu, N.; Isloor, S.; Thiageeswaran, M.; Fun, H.-K.An efficient, microwave irradiated synthesis of novel chromeno[2,3-b]-pyrimidine derivatives was carried out. 2-Amino-3,4-dihydro-2H-chromene-3-carbonitrile was converted into imine using N,N-Dimethylacetaldehyde dimethylacetal to give the core intermediate, which was used for the preparation of chromenopyrimidine library, using acetic acid and different amine in microwave irradiation for 5 min. Structures of newly synthesized compounds were confirmed by spectral studies. Compound 6g was characterized by single crystal X-ray analysis. All the compounds were also screened for their anti-microbial activity. Few of the compounds are found to be potential antimicrobials. © 2010 Elsevier Masson SAS. All rights reserved.Item New polypropylene supported chitosan NF-membrane for desalination application(2011) Padaki, M.; Isloor, A.M.; Fernandes, J.; Prabhu, K.N.In the present study, a new NF membrane was prepared by coating chitosan on polypropylene fiber support, by the dissolution of chitosan in 2% acetic acid solution. The resulting membrane was characterized by thermo gravimetric analysis, water absorption, contact angle measurement and scanning electron microscopy. Prepared membrane showed two Tg peaks, one at ~90 °C that was due to chitosan and the other peak at ~170 °C that was corresponding to the supporting polypropylene membrane. The membrane showed a low swelling ratio at pH 7, 9, and 11 as compared with pH 5. The performance of the membrane was assessed out using dead end cell. Water flux was studied at different pressures. The salt rejection study was done using NaCl solution and the effect of pH on performance of the membrane was also examined. Newly prepared membrane showed improved water flux, and % of rejection is highest in acidic pH and lowest in basic pH. Hydrulic permeability coefficient and the dielectric constant confirms that the prepared membrane is nanofiltration membrane. © 2011 Elsevier B.V.Item Dual colorimetric receptor with logic gate operations: Anion induced solvatochromism(Royal Society of Chemistry, 2014) Kigga, M.; Swathi, N.; Manjunatha, J.R.; Das, U.K.; Nityananda Shetty, A.N.; Trivedi, D.R.A receptor R1 was designed and synthesised for colorimetric detection of F- ions as well as Cu2+ ions via intramolecular charge transfer mechanism. Upon addition of F- ions in dry DMSO, the color of the receptor R1 changed from pale yellow to blue. The receptor showed a unique property of solvatochromism by displaying different coloration with different solvents only in the presence of F- ions, which were applied to determine the percentage composition of binary solvent mixtures. The receptor R1 was able to detect Cu2+ ions colorimetrically where it exhibited a color change from pale yellow to orange-red. In addition, the receptor was subjected to molecular logic gate applications, wherein it showed 'ON-OFF' switching operations. © 2014 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Item New carbazole based metal-free organic dyes with D-?-A-?-A architecture for DSSCs: Synthesis, theoretical and cell performance studies(Elsevier Ltd, 2017) Naik, P.; Elmorsy, M.R.; Su, R.; Babu, D.D.; El-Shafei, A.; Vasudeva Adhikari, A.V.Herein we report the design, synthesis and photovoltaic performance studies of three new D-?-A-?-A architectured organic chromophores (N1-3) derived from (Z)-3-(9-hexyl-9H-carbazol-3-yl)-2-(thiophen-2-yl) acrylonitrile scaffold. In the new design, the electron rich carbazole unit is connected to three different electron withdrawing/anchoring species, viz. cyano acetic acid, rhodanine-3-acetic acid and barbituric acid via cyano vinyl thiophene as ?-spacer. Newly synthesized dyes were characterized by spectral, photophysical and electrochemical analyses. Their optical band-gap, GSOP and ESOP values, as calculated from the optical and CV studies were found to be in the range of 2.12–2.21, ?5.52 to ?5.43 and ?5.40 to ?3.25 eV respectively. The DFT and TD-DFT studies were performed using Turbomole 7.1V software and the results indicated the existence of proper charge separation between HOMO and LUMO levels of the dyes. Also, the results revealed good matching of theoretically generated optical spectral data with the experimental values. Finally, DSSC devices were fabricated using these three dyes and the dye N1 containing cyanoacetic acid as an acceptor unit showed better photo conversion efficiency (?) of 3.55% than the other two dyes. It's JSC, VOC, and IPCE parameters were shown to be 9.06 mA cm?2, 0.577 V and 48%, respectively. The obtained EIS data and electron lifetimes of N1–3 sensitized devices are well in accordance with experimental photovoltaic parameters. © 2017 Elsevier LtdItem Colorimetric anion sensors based on positional effect of nitro group for recognition of biologically relevant anions in organic and aqueous medium, insight real-life application and DFT studies(Elsevier B.V., 2018) Singh, A.; Sahoo, S.K.; Trivedi, D.R.A new six colorimetric receptors A1-A6 were designed and synthesized, characterized by typical common spectroscopic techniques like FT-IR, UV–Visible, 1H NMR, 13C NMR and ESI-MS. The receptor A1 and A2 exhibit a significant naked-eye response towards F? and AcO? ions in DMSO. Due to presences of the NO2 group at para and ortho position with extended ?-conjugation of naphthyl group carrying –OH as a binding site. Compared to receptor A2, A1 is extremely capable of detecting F? and AcO? ions present in the form of sodium salts in an aqueous medium. This is owed to the occurrence of –NO2 group at para position induced in increasing the acidity of –OH proton. Consequently, it easily gets deprotonated in aqueous media. The detection limit of receptor A1 was turned out to be 0.40 and 0.35 ppm for F? and AcO? ions which is beneath WHO permission level (1.0 ppm). Receptor A1 shows a solitary property of solvatochromism in different aprotic solvents in presence of AcO? ion. Receptor A1 depicts high selectivity towards AcO? ion in DMSO: HEPES buffer (9:1, v/v). Receptor A1 proved itself for real life application by detecting anion in solution and solid state. The binding mechanism of receptor A1 with AcO? and F? ions was monitored from 1HNMR titration and DFT study. © 2017 Elsevier B.V.Item Preparation, characterization and stability evaluation of ionic liquid blended chitosan tripolyphosphate microparticles(Editions de Sante editions.de.sante@wanadoo.fr, 2019) Safdar, R.; Francisco Nirmala, N.; Iyyaswami, R.; Arunagiri, A.; Papadimitriou, S.; Murugesan, M.Recently, drug delivery systems are facing several shortcomings which demand for the development of new formulations. A new drug–solvent systems may improve the characteristics and sustained release of drugs. Investigations in this domain revealed the significance of Ionic Liquids (ILs) as active pharmaceutical ingredients for pharmaceutical applications. ILs–drug assisted carriers exhibit many unique and attractive properties which are lacking in their conventional counterparts. In this work, Chitosan (CS), a natural polymer was blended with an ammonium based IL, Tetramethylammonium hydroxide (TMAOH), and microparticles (MPs) of CS–TMAOH–TPP were synthesized by cross–linking with sodium tripolyphosphate (TPP) using ionic gelation method. The addition of TMAOH to CS enhanced the stability of MPs without affecting the particle size. FTIR analysis confirmed the structural changes whereas the FE-SEM analysis showed almost similar sizes of freeze–dried MPs as determined by Zetasizer. The morphology of the CS–TMAOH–TPP MPs was mostly similar to CS–TPP MPs. The Thermogravimetric analysis indicated that these MPs exhibit good thermal resistance. Moreover, the DSC and XRD analysis of the prepared MPs were conducted to analyze thermograms and crystallographic structure respectively. Overall, the present synthesized CS–TMAOH–TPP MPs are more stable than CS–TPP MPs, which will be useful for drug delivery applications. © 2019Item Design and synthesis new colorimetric receptors for naked-eye detection of biologically important fluoride and acetate anions in organic and arsenite in aqueous medium based on ICT mechanism: DFT study and test strip application(Elsevier B.V., 2020) Singh, A.; Mohan, M.; Trivedi, D.R.Novel three colorimetric anion receptors R1, R2 and R3 have been designed and synthesized via condensation reaction and characterized using IR, MS, and NMR spectroscopic techniques. Anion sensing properties were studied using colorimetric, UV–vis titration, 1H NMR titration, and Cyclic Voltammetric Studies. Comparing the UV–visible titration data of the receptors R1 and R2, R2 showed high redshift (??max) in the mixed competitive solution (DMSO: H2O, 9: 1; v/v) of about 155 nm, 157 nm, 169 nm for Na+F?, Na+AcO?, and Na+AsO2 ? ions with LOD of 0.23 ppm, 0.18 ppm, and 0.30 ppm, respectively. The observed spectral change of receptor R2 is due to the anion-induced deprotonation of the OH proton, which is confirmed by UV–vis titration, 1HNMR titration, and cyclic voltammetric studies. Theoretical studies via DFT calculation were carried for R1 and R2 to optimize the structure and to explain the anion-binding mechanism. The application of designed receptor R2 was successfully demonstrated for the detection of F? and AsO2 ? ions using a test strip. The receptors R1 and R2 proved itself to be potentially useful for real-life application by sensing F? and AcO? ions in real samples like toothpaste, mouthwash, vinegar and seawater in a complete aqueous medium. © 2019 Elsevier B.V.Item Design and synthesis of malonohydrazide based colorimetric receptors for discrimination of maleate over fumarate and detection of F?, AcO? and AsO2 ? ions(Elsevier B.V., 2020) Singh, A.; Mohan, M.; Trivedi, D.R.In this study, we have designed and synthesized two new organic receptors R1 and R2 based on malonohydrazide for the recognition of biologically important anions. The receptor R1 capable of colorimetric discrimination of maleate over fumarate ion, exhibit significant color change from pale yellow to wine red due to intermolecular hydrogen bond between the R1 and maleate ion, supported by 1HNMR titration, where the peak at ?12.0 ppm attributed to the NH proton experiences a downfield shift upon binding with maleate ion. Receptor R1, equipped with two electron-withdrawing [sbnd]NO2 moieties as the chromogenic signaling unit enhance the hydrogen bonding tendency and acidity, and thus when comparing with receptor R2, R1 displayed substantial higher redshift (??max) of 148 nm, 143 nm, and 140 nm towards F?, AcO?, and maleate anion in the DMSO. In addition, the synthesized receptors R1 and R2 are able to detect F?, AcO?, and AsO2 ? ions as their sodium salts in an aqueous solution with visual color change. Receptor R1 exhibit electrochemical response towards F? and AcO? ions. The receptors R1 and R2 are successfully applied for quantitative detection of F? ion in the toothpaste solution in an aqueous medium. Additionally, R1 and R2 exhibit fluorescence enhancement towards F? and AcO? ions in the DMSO. As well, R1 and R2 demonstrate to be potentially useful colorimetric chemosensor for sensing maleate ion using the test strip. The theoretical calculation based on TD-DFT corroborates well with the experimental results of the receptors R1 and R2 with fluoride, acetate and maleate. © 2019 Elsevier B.V.Item Cloning, expression, purification and characterization of chitin deacetylase extremozyme from halophilic Bacillus aryabhattai B8W22(Springer Science and Business Media Deutschland GmbH, 2021) Pawaskar, G.M.; Raval, K.; Rohit, P.; Shenoy, R.P.; Raval, R.Chitin deacetylase (CDA) (EC 3.5.1.41) is a hydrolytic enzyme that belongs to carbohydrate esterase family 4 as per the CAZY database. The CDA enzyme deacetylates chitin into chitosan. As the marine ecosystem is a rich source of chitin, it would also hold the unexplored extremophiles. In this study, an organism was isolated from 40 m sea sediment under halophilic condition and identified as Bacillus aryabhattai B8W22 by 16S rRNA sequencing. The CDA gene from the isolate was cloned and overexpressed in E. coli Rosetta pLysS and purified using a Ni–NTA affinity chromatography. The enzyme was found active on both ethylene glycol chitin (EGC) and chitooligosaccharides (COS). The enzyme characterization study revealed, maximum enzyme velocity at one hour, optimum pH at 7 with 50 mM Tris–HCl buffer, optimum reaction temperature of 30 ºC in standard assay conditions. The co-factor screening affirmed enhancement in the enzyme activity by 142.43 ± 7.13% and 146.88 ± 4.09% with substrate EGC and COS, respectively, in the presence of 2 mM Mg2+. This activity was decreased with the inclusion of EDTA and acetate in the assay solutions. The enzyme was found to be halotolerant; the relative activity increased to 116.98 ± 3.87% and 118.70 ± 0.98% with EGC and COS as substrates in the presence of 1 M NaCl. The enzyme also demonstrated thermo-stability, retaining 87.27 ± 2.85% and 94.08 ± 0.92% activity with substrate EGC and COS, respectively, upon treatment at 50 ºC for 24 h. The kinetic parameters Km, Vmax, and Kcat were 3.06E?05 µg mL?1, 3.06E + 01 µM mg?1 min?1 and 3.27E + 04 s?1, respectively, with EGC as the substrate and 7.14E?07 µg mL?1, 7.14E + 01 µM mg?1 min?1 and 1.40E + 06 s?1, respectively, with COS as the substrate. The enzyme was found to be following Michaelis–Menten kinetics with both the polymeric and oligomeric substrates. In recent years, enzymatic conversion of chitosan is gaining importance due to its known pattern of deacetylation and reproducibility. Thus, this BaCDA extremozyme could be used for industrial production of chitosan polymer as well as chitosan oligosaccharides for biomedical application. © 2021, The Author(s).