Faculty Publications

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    Enhancement and bias removal of optical coherence tomography images: An iterative approach with adaptive bilateral filtering
    (Elsevier Ltd, 2016) Sudeep, P.V.; Issac Niwas, S.; Ponnusamy, P.; Rajan, J.; Xiaojun, Y.; Wang, X.; Luo, Y.; Liu, L.
    Optical coherence tomography (OCT) has continually evolved and expanded as one of the most valuable routine tests in ophthalmology. However, noise (speckle) in the acquired images causes quality degradation of OCT images and makes it difficult to analyze the acquired images. In this paper, an iterative approach based on bilateral filtering is proposed for speckle reduction in multiframe OCT data. Gamma noise model is assumed for the observed OCT image. First, the adaptive version of the conventional bilateral filter is applied to enhance the multiframe OCT data and then the bias due to noise is reduced from each of the filtered frames. These unbiased filtered frames are then refined using an iterative approach. Finally, these refined frames are averaged to produce the denoised OCT image. Experimental results on phantom images and real OCT retinal images demonstrate the effectiveness of the proposed filter. © 2016 Elsevier Ltd.
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    Design and: In vitro biological evaluation of substituted chalcones synthesized from nitrogen mustards as potent microtubule targeted anticancer agents
    (Royal Society of Chemistry, 2017) Sabina, X.J.; Karthikeyan, J.; Velmurugan, G.; Muthu Tamizh, M.M.; Nityananda Shetty, A.N.
    A new series of p-[N,N-bis(2-chloroethyl)amino]benzaldehyde substituted chalcone derivatives were designed and synthesized, and their structures were characterized by spectroscopic techniques and single crystal XRD studies. Compounds 3a-f crystallized in the triclinic system with a centrosymmetric space group P1, except for crystal 3c which crystallized in the monoclinic crystal system with a centrosymmetric space group P21/c. Molecular docking studies were utilized to reveal the binding mode of the derivatives to identify new tubulin inhibitors. Density functional theory calculations were performed to understand the structural and electronic properties of these chalcones. The DFT results show that the HOMOs of all the chalcones lie in the range of -5.65 to -6.17 eV and the LUMOs in the range of -2.01 to -3.21 eV. The experimental results are well supported by the theoretical structural analysis. The biological activity of these compounds showed high potency of growth inhibitory effects with sub-micromolar IC50 values ranging from 0.089 to 0.200 ?M against A549 and HepG2 cancer cell lines. Furthermore, these compounds exhibited a strong inhibitory effect on tubulin polymerization. 3e showed the highest mean activity against both the cancer cells and in tubulin inhibition. This correlated well with the theoretical results from the pharmacophore binding model. Hence, these six compounds, particularly 3e, could be considered as potential leads in the development of new anticancer agents. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2017.
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    Effects of substituents on the enrichment of the optical limiting action of novel imidazo[2,1-: B] [1,3,4]thiadiazole fused thiophene-based small molecules
    (Royal Society of Chemistry, 2019) Kakekochi, V.; Udayakumar, D.; Nikhil, P.P.; Chandrasekharan, K.
    The imidazo[2,1-b][1,3,4]thiadiazole (ITD) ring is a fused, planar aromatic heterocyclic system consisting of four heteroatoms with a bridgehead nitrogen atom. In this study, three new donor-acceptor-donor (D-A-D)-type organic molecules (ThITD1-ThITD3) were designed and synthesized, wherein ITD was an electron acceptor unit and the thiophene/phenyl moieties were electron donor units that produced a D-A-D configuration. The thiophene-ITD core structure comprises three different groups viz., thiophene-2-acetonitrile (ThITD1), phenylacetonitrile (ThITD2) and rhodanine-3-acetic acid (ThITD3), and the effect of substituents on the optical and electrochemical properties have been discussed based on structural modifications. The third-order nonlinear optical (NLO) properties analyzed by the Z-scan technique reveal that the molecules exhibit effective two photon absorption (TPA) with ThITD3 possessing substantially higher effective TPA coefficient (?eff) than ThITD1 and ThITD2, which is comparable to the reported ?eff values. The results unravel that ITD as an acceptor with an appropriate ?-linker will be a promising candidate for application in the field of optoelectronics/photonics. Herein, the thiophene-ITD ring system was explored for NLO applications and reported for the first time. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
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    Effect of hydrophobic and hydrogen bonding interactions on the potency of ß-alanine analogs of G-protein coupled glucagon receptor inhibitors
    (John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2020) Venugopal, P.P.; Das, B.K.; Soorya, E.; Chakraborty, D.
    G-protein coupled glucagon receptors (GCGRs) play an important role in glucose homeostasis and pathophysiology of Type-II Diabetes Mellitus (T2DM). The allosteric pocket located at the trans-membrane domain of GCGR consists of hydrophobic (TM5) and hydrophilic (TM7) units. Hydrophobic interactions with the amino acid residues present at TM5, found to facilitate the favorable orientation of antagonist at GCGR allosteric pocket. A statistically robust and highly predictive 3D-QSAR model was developed using 58 ?-alanine based GCGR antagonists with significant variation in structure and potency profile. The correlation coefficient (R2) and cross-validation coefficient (Q2) of the developed model were found to be 0.9981 and 0.8253, respectively at the PLS factor of 8. The analysis of the favorable and unfavorable contribution of different structural features on the glucagon receptor antagonists was done by 3D-QSAR contour plots. Hydrophobic and hydrogen bonding interactions are found to be main dominating non-bonding interactions in docking studies. Presence of highest occupied molecular orbital (HOMO) in the polar part and lowest unoccupied molecular orbital (LUMO) in the hydrophobic part of antagonists leads to favorable protein-ligand interactions. Molecular mechanics/generalized born surface area (MM/GBSA) calculations showed that van der Waals and nonpolar solvation energy terms are crucial components for thermodynamically stable binding of the inhibitors. The binding free energy of highly potent compound was found to be ?63.475 kcal/mol; whereas the least active compound exhibited binding energy of ?41.097 kcal/mol. Further, five 100 ns molecular dynamics simulation (MD) simulations were done to confirm the stability of the inhibitor-receptor complex. Outcomes of the present study can serve as the basis for designing improved GCGR antagonists. © 2019 Wiley Periodicals, Inc.
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    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.
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    Porous graphene-NiCo2O4 nanorod hybrid composite as a high performance supercapacitor electrode material
    (Royal Society of Chemistry, 2020) Sethi, M.; Shenoy, U.S.; Bhat, D.K.
    The template free low temperature solvothermal synthesis of high capacitive porous graphene-NiCo2O4 nanorod composites has been carried out. Solvothermal synthesis followed by calcination in air led to the development of a highly porous hybrid nanocomposite, which acts as a buffering channel for fast ion diffusion and provides robust mechanical strength. Advantages of using porous graphene to enhance the capacitance of the material were studied theoretically using First principles calculations. High capacitance values of 1533 F g-1 at a scan rate of 5 mV s-1 and 1684 F g-1 at a current density of 1 A g-1 are obtained from cyclic voltammetry data and galvanostatic charge discharge data, respectively. The electrode material possesses good cyclic stability with the retention of 94% of its initial capacitance even after 10000 charge-discharge cycles at a current density of 8 A g-1 in 2 M KOH electrolyte. The fabricated supercapacitor exhibited a high energy density of 45.3 W h kg-1 and a high power density of 17843.5 W kg-1 due to the synergistic effect of the composite components. The enhanced electrochemical function of the composite makes it a potential candidate for supercapacitor application and future studies. This journal is © 2020 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
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    Enhanced photocatalytic efficiency of layered CdS/CdSe heterostructures: Insights from first principles electronic structure calculations
    (Institute of Physics Publishing helen.craven@iop.org, 2020) Shenoy, S.; Tarafder, K.
    Metal sulfides are emerging as an important class of materials for photocatalytic applications, because of their high photo responsive nature in the wide visible light range. In this class of materials, CdS with a direct band gap of 2.4 eV, has gained special attention due to the relative position of its conduction band minimum, which is very close to the energies of the reduced protons. However, the photogenerated holes in the valence band of CdS are prone to oxidation and destroy its structure during photocatalysis. Thus constructing a CdS based heterostructure would be an effective strategy for improving the photocatalytic performance. In this work we have done a detail theoretical investigation based on hybrid density functional theory calculation to get insight into the energy band structure, mobility and charge transfer across the CdS/CdSe heterojunction. The results indicate that CdS/CdSe forms type-II heterostructure that has several advantages in improving the photocatalytic efficiency under visible light irradiation. © 2020 IOP Publishing Ltd.
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    Synthesis, characterization and electroluminescence studies of cyanopyridine-based ?-conjugative polymers carrying benzo[: C] [1,2,5]thiadiazole and naphtho[1,2- c:5,6- c ?]bis([1,2,5]thiadiazole) units
    (Royal Society of Chemistry orders@rsc.org, 2020) Pilicode, N.; Naik, P.; Acharya, M.; Vasudeva Adhikari, A.V.
    Four new donor-acceptor type cyanopyridine-based conjugative polymers, i.e.TDPy1-4, carrying different electron-donating aromatic/heteroaromatic moieties in the backbone were synthesized from their respective co-monomers by using the Suzuki cross-coupling polycondensation protocol. These polymers were designed to possess good control of color emission and to have balanced charge injection, and transport properties. Their structures were confirmed by spectroscopic studies and their thermal stability was evaluated using the TGA technique. The photophysical, electrochemical and electroluminescence properties of these materials were established in order to assess their suitability for PLED applications. DFT-based computational studies were performed to verify and elucidate the above-said properties. Evidently, they demonstrate good green fluorescence with optical band gap (Eg) values of 2.14-2.27 eV. Finally, new PLEDs based on TDPy1-4 were fabricated with a structure of ITO/PEDOT:PSS/polymer/Al, wherein they are able to act as green light emitters with stable electroluminescence behaviors. © 2020 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
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    Fe-porphyrin on Co(001) and Cu(001): A Comparative Dispersion-augmented Density Functional Theory Study
    (Wiley-VCH Verlag info@wiley-vch.de, 2020) Azuri, I.; Ali, M.E.; Tarafder, K.; Oppeneer, P.M.; Kronik, L.
    We present a comparative density functional theory (DFT) investigation of the interaction of the iron porphyrin (FeP) molecule with the metallic Co(001) and Cu(001) surfaces, with the aim of elucidating the effect of different choices for the treatment of dispersion. We compare a GGA+U approach, several flavors of dispersion-augmented terms, and two variants of the vdW-DF approach, which treats long-range correlation explicitly. For the Co surface, we find that all approaches predict chemisorption and a high-spin state, although vdW-DF functionals generally predict weaker bonds and weaker chemisorption. For the Cu surface, we find that the functionals augmented by pair-wise dispersion once again predict chemisorption and a preferred HS state, but the vdW-DF functionals predict physisorption and a LS state. These results demonstrate the importance of careful assessment of the level of theory at which dispersion is treated, as this may have significant quantitative and even qualitative effects on the predictions made. The results also call for additional experimental data for these systems. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Syntheses, quantum mechanical modeling, biomolecular interaction and in vitro anticancer – Tubulin activity of thiosemicarbazones
    (Academic Press Inc. apjcs@harcourt.com, 2020) Xavier, J.S.; Karthikeyan, K.; Ragavendran, V.; NityanandaShetty, A.
    A new series of thiosemicarbazones were designed and synthesized. Their structures were confirmed by spectral characterization and single crystal XRD studies. Compounds MTSC-2 and ETSC-3 crystallized in the orthorhombic crystal system with space group Pbc21 andPca21respectively. Density functional theory computational studies were performed on MTSC-2 and ETSC-3 along with natural bond orbital analysis and Mulliken population analysis to study the structural and electronic properties of the thiosemicarbazones. The HOMOs of the two thiosemicarbazones are ?5.2943 and ?5.1133 eV respectively while the LUMOs are ?1.6879 and ?1.6398 eV respectively. The energy gap is 3.6064 and 3.4736 eV respectively. Molecular docking studies were performed to determine the binding mode of the thiosemicarbazones against ?-tubulin. The theoretical studies were further supplemented with tubulin polymerization inhibition assay. All the four thiosemicarbazones proved effective in inhibiting the polymerization of ?- and ?-tubulin heterodimers into microtubules. The anticancer activity of these compounds showed their extreme potency against A549 and HepG2 cancer cell lines with IC50 values of 0.051 – 0.189 µm and 0.042 – 0.136 µm respectively. Compound PTSC-4 showed the highest activity both against tubulin and the two cancer cell lines. This was in correlation with the theoretical studies. Hence, these four compounds, specifically PTSC-4, can be considered to be potential leads in the development of non-metallic anticancer agents. © 2020 Elsevier Inc.