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      Volume 131, Issue 2

      February 2019

    • Table of Contents

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    • ROS dependent antitumour activity of photo-activated iron(III) complexes of amino acids

      S BINITA CHANU MD KAUSAR RAZA SAMYA BANERJEE POOJA RANI MINA DULAL MUSIB MITHUN ROY

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      Several amino acid-based photo-active monomeric iron(III) complexes of the general formula,[Fe(L)2]PP-, where L= Schiff base ligands (salisalidene arginine, salicylidenetryptophan, 3,5-di-tert-butyl benzalidine arginine and salicylidene tryptophan) were synthesized, characterized and explored for photoactivated anticancer activity to Chang Liver Cells, HeLa and MCF-7 cells. Complexes exhibited remarkable photo-cytotoxicity with IC50 value to the extent of 0.7 μM to Chang Liver Cells in visible light and there wasa 40-fold enhancement in cytotoxicity in comparison to the cytotoxicity in dark. Complexes were non-toxic to MCF-10A (normal cells) in dark and visible light (IC50 > 100 μM in dark; IC50 > 80 μM in visible light) signifying target-specific nature of the anti-tumour activity of the complexes. Increased ROS concentration,as probed by DCFDA assay, in the cancer cells was responsible for apoptotic cell death. Decarboxylation or phenolate-Fe(III) charge transfer of photo-activated iron(III) complexes generating • OH radicals (ROS) were responsible for the apoptosis. Overall, the tumour-selective photo-activated anticancer activity of the amino acidbased iron(III) complexes have shown a promising aspect in developing iron-based photo-chemotherapeutics as the next generation PDT agents.

    • A novel benzophenone-based colorimetric chemosensor for detecting Cu2+ and F-

      DONGJU YUN JU BYEONG CHAE CHEAL KIM

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      A novel selective colorimetric chemosensor ANBP ((E)-(2-(((8-hydroxy-2,3,6,7-tetrahydro-1H,5Hpyrido[3,2,1-ij]quinolin-9-yl)methylene)amino)-5-nitrophenyl)(phenyl)methanone), based on the combination of benzophenone group and julolidine chromophore, was synthesized. Sensor ANBP showed rapid colorimetric responses toward Cu2+ (pale orange to pink) and F- (orange to blue). The detection limit by ANBP to Cu2+(6.82 µM) was far below WHO guideline value (31.3 µM). Moreover, ANBP could quantify Cu2+ in aqueoussamples. 1:1 binding mode between ANBP and Cu2+ or F- was proposed by ESI-mass analyses and Job plots. The remarkable color changes with Cu2+ and F - resulted from the intramolecular charge transfer (ICT) effect, which was demonstrated by theoretical calculations.

    • Determination of gallic acid using poly(glutamic acid): graphene modified electrode

      J JENCY FEMINUS R MANIKANDAN S SRIMAN NARAYANAN P N DEEPA

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      Gallic acid (GA) is one of the main phenolic components occurring naturally in plants and has been a subject of increasing interest owing to its antioxidant, anti-mutagenic and anti-carcinogenic properties. The present work describes a rapid and cost-effective analytical procedure for the determination of gallic acid. Poly-Glu/rGO electrode was fabricated by the electro-polymerisation of glutamic acid on reduced graphene oxide (rGO) modified paraffin impregnated graphite electrode (PIGE). The modified electrode was characterized by SEM, AFM and ATR-IR. The electrochemical behavior of gallic acid at the modified sensor was studied by voltammetric and amperometric techniques under optimized conditions in pH 5 acetate buffer. The electrode showed good linear response towards the determination of gallic acid over the range of 0.03–480 µM with 0.01 µM as the detection limit for voltammetric technique and the amperometric technique showed a linear range of 1–17 µM with 0.33 µM as the detection limit. The electrode also showed good stability and reproducibility with a sensitivity of 0.97 µM/µA. The proposed method can be applied to detect GA in real samples withsatisfactory results.

    • New organotin(IV) chlorides derived from N-(2-hydroxyphenyl)aryloxy sulfamates. Synthesis, characterization and DSC investigation

      ALI AKREMI ADEL NOUBIGH

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      Three monomeric pentacoordinate organotin complexes were prepared by the reaction of dimethyltin dichloride with three N-(2-hydroxy)phenyl substituted aryloxy sulfamates in alkaline medium. The newly synthesized compounds were characterized on the basis of their infrared, CPMAS NMR, powder XRD diffractionand elemental analysis. The XRD powder analyses revealed a tetragonal system for two complexes, whereas the third one was crystallized in the hexagonal system. The thermal decomposition behavior of the synthesized complexes have been investigated and all the organotin compounds have a similar order of thermal stability.

    • Construction of metal oxide decorated g-C3N3 materials with enhanced photocatalytic performance under visible light irradiation

      T VINODKUMAR P SUBRAMANYAM K V ASHOK KUMAR BENJARAM M REDDY CH SUBRAHMANYAM

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      Herein we report the synthesis and photocatalytic evaluation of heterostructure WO3/g-C3N4 (WMCN) and CeO2/g-C3N4(CMCN) materials for RhB degradation and photoelectrochemical studies. These materials were synthesized by varying the dosages of WO3 and CeO2 on g-C3N4 individually and were characterized with state-of-the-art techniques like XRD, BET surface area, FT-IR, UV–Vis DRS, TGA, SEM, TEM and XPS. A collection of combined structural and morphological studies manifested the formation of bare g-C3N4, WO3, CeO2, WO3/g-C3N4 and CeO2/g-C3N4 materials. From the degradation results, we found that the materialwith 10 wt% WO3 and 15 wt% CeO2 content on g-C3N4 showed the highest visible light activity. The first order rate constant for the photodegradation performance of WMCN10 and CMCN15 is found to be 5.5 and 2.5times, respectively, greater than that of g-C3N4. Photoelectrochemical studies were also carried out on the above materials. Interestingly, the photocurrent density of WMCN10 photoanode achieved 1.45 mA cm − 2 at 1.23 V (vs.) RHE and this is much larger than all the prepared materials. This enhanced photoactivity of WMCN10 is mainly due to the cooperative synergy of WO3 with g-C3N4, which enhanced the visible light absorption and suppresses the electron–hole recombination

    • An organometallic ruthenium nanocluster with conjugated aromatic ligand skeleton for explosive sensing

      PRANAV DAVE BHAVESH AGRAWAL JAYDEV THAKARDA SAGAR BHOWMIK PRASENJIT MAITY

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      9-Ethynylphenanthrene (EPT) bound to highly monodispersed Ruthenium (Ru) nanocluster (Ru:EPT) with mean diameter of 1.5 ± 0.2 nm and mol wt. of ~8600 Da was synthesized via a facile and high yield biphasic ligand exchange protocol using similar sized ethylene glycol (EG)-stabilized Ru clusters (Ru:EG) as precursor. The synthesized organometallic nanocluster was meticulously analyzed to understand its size distribution, oxidation state, crystallinity, optical and luminescence behavior and metal–ligand interfacial structure. Contrary to the extensive quenching of ligand emission by metalcore as usually observed, the ruthenium core here acts as a conductor, which conjugates surface ligands with strong emission property courtesy to an unusual vinylidene-binding motif. Thus, the synthesized nanocluster shows good luminescence property (φ= ~7%) originated from the ligand skeleton and the spherical metal core restricts lateral overlap of phenanthrene moiety to cause any excimer emission. This nanocluster showed high sensitivity for solution phase detection of nitroaromatic explosives through luminescence quenching method (KSVup to 498×10.4M -1) andmimic the mechanism like conjugated organic polymer. We propose that dynamic χ−χ interaction between Ru bound phenanthrene moiety and nitroaromatic compounds followed by photoinduced electron transfer (PET), as well as Förster Resonance Energy Transfer (FRET), are the possible mechanisms behind this luminescence quenching.

    • Quantum chemical studies of structures and spin Hamiltonian parameters of iron transferrin using isolated and embedded clusters models

      LOKPATI MISHRA MAHESH SUNDARARAJAN

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      Density functional theory (DFT) based calculations using large cluster models are used to elucidate the ground state electronic structure of iron bound transferrin. Explicit incorporation of second coordination amino acid residues and crystallographic water molecules anchors the active site. Our calculations clearlysuggest that tyrosine amino acid (Tyr188) residue is bound to iron when the structures are optimized within the continuum solvation model. However, in the gas phase optimized structure, we note that Tyr188 is unbound to Fe (by more than 3 Å). The Mössbauer isomer shift (δ) and quadrupolar splitting (ΔEq) of iron transferrin are in line with the experimental data only when Tyr188 is bound to Fe(III). Further, the computed oxygen hyperfine coupling constant value is very large (−14.5 MHz) when bound to iron which can be verified through 17O NMR experiments. We propose that Tyr188 is strongly bound to Fe(III) at physiological pH, which needs to be protonated (acidic pH) to weaken this bond, thus the metal release pathway can be possible only in acidic conditions.

    • Molecular dynamics based antimicrobial activity descriptors for synthetic cationic peptides

      MALAY RANJAN BISWAL SANDHYA RAI MEHER K PRAKASH

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      There is an urgent need to identify novel antimicrobial drugs in light of the development of resistance by the bacteria for a broad spectrum of antibiotics. Antimicrobial peptides are proving to be an effective remedy to which bacteria have not been able to develop resistance easily. With the goal of progressing towards a rational design of AMPs, we developed a neural network based quantitative model relating their physicochemical properties to their activity. A set of synthetic cationic polypeptides (CAMEL-s) (Mee et al. in J. Peptide Res.49:89, 1997) which were studied systematically in experiments was used in the development of our model. Intuitive variables derived from short molecular dynamics simulations in octanol were used as descriptors, resulting in a good prediction of activity and underscoring the possibility of a rational design.

    • Correction to: ROS dependent antitumour activity of photo-activated iron(III) complexes of amino acids

      S BINITA CHANU MD KAUSAR RAZA SAMYA BANERJEE POOJA RANI MINA DULAL MUSIB MITHUN ROY

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