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      Volume 129, Issue 12

      December 2017,   pages  1794a-1940

    • Table of Contents

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    • Advances in trifluoromethylation or trifluoromethylthiolation with copper CF₃ or SCF₃ complexes


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      The copper CF₃ or SCF₃ complexes as the fluoride sources for the synthesis of trifluoromethylated or trifluoromethylthiolated compounds are reviewed. Compared with the ordinary fluoride reagents, the addition of reactant species in the reaction systems of copper trifluoromethyl or trifluoromethylthio complexes were less, so the reaction systems are relatively simple and easy to operate. In most cases, the trifluoromethylated or trifluoromethylthiolated products were obtained in moderate to excellent yields.

    • Harnessing cell-material interaction to control cell fate: design principle of advanced functional hydrogel materials


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      Physical (topography, stiffness) and chemical instructions encoded in the extracellular environment govern cell behaviour. Understanding these interactions as they operate in native extracellular matrix and capturing the complexity of the spatiotemporal presentation of multiple such signals in synthetic scaffolds is a key to develop advanced functional materials for tissue engineering applications. This review discusses the advancement in engineered hydrogel materials as such scaffold to control cell fate.

    • Detergent-induced aggregation of an amyloidogenic intrinsically disordered protein


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      Intrinsically disordered proteins (IDPs) belong to an important class of proteins that do not fold up spontaneously. The conformational flexibility of IDPs allows them to adopt a wide range of conformations depending upon their biochemical environment. Many IDPs undergo profound conformational conversion thatis often coupled to amyloid aggregation in the presence of negatively charged lipid membranes. Here, we show the effect of a well-known anionic lipid mimetic, sodium dodecyl sulfate (SDS), on the aggregation mechanism of a model amyloidogenic IDP, namely, bovine κ-casein. In the absence of SDS, the aggregation kinetics of reduced and carboxymethylated (RCM) κ-casein followed a nucleation dependent polymerization model that comprises both lag- and assembly phases. On the contrary, in the presence of sub-micellar concentration of SDS, the aggregation kinetics did not exhibit a lag phase and appears to follow a non-nucleation pathway. Additionally, the morphologies of the aggregates formed in the absence and presence of SDS were found to be different. In the absence of SDS, κ-casein aggregation proceeded to typical amyloid fibrils, whereas, in the presence of SDS, the aggregation yielded large oligomers. Our results provide important molecular insights into the aggregation mechanism that can be utilized for the designing of novel protein/amyloid based nanomaterialswith desired properties.

    • Fluorescent vinyl and styryl coumarins: A comprehensive DFT study of structural, electronic and NLO properties


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      Nonlinear optical properties of 3-styryl and 3-vinyl coumarin dyes have been investigated with Density Functional Theory (DFT) using global hybrid (GH) and range-separated hybrid (RSH) functionals. The performance of GHs - B3LYP, BHHLYP, PBE0, M06, M06L, M062X, and M06HF and RSHs - CAM-B3LYP,HISSbPBE, HSEH1PBE, wB97, wB97X, and wB97XD in combination with 6-311++G(d,p) basis set has been analyzed. Estimated (hyper) polarizability (α0, β0) obtained from the GHs - M06, M062X and PBE0 are in agreement with each other. The RSHs - wB97 and wB97X estimate very close values of β0. The β0 value of 3-styryl and 3-vinyl coumarins reaches the maximum as the bond length alternation and bond order alternation parameters tend to zero. Natural bond orbital analysis shows there is extensive charge transfer in the excitedstate leading to large value of β0. The vibrational contribution to α0 and β0 is significantly less when the donor is methoxy group and acceptor is nitro group in the 3-styryl coumarin. The dye, (E)-7-(diethylamino)-3-(4-nitrostyryl)-2H-chromen-2-one (3c) is found to give the highest NLO response. An increasing electrophilicity originating from the decreased HOMO-LUMO band gap leads to an increase in α0 and β0 in all the cases.

    • Does alkali cation binding to aromatic ring retard the fluxional haptotropic migration? Evidences from density functional study


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      DFT calculations were performed on the sandwich complexes of naphthalene (MNC) with alkali metal cation (Li⁺ /Na⁺ /K⁺) on one π face and the tripodal Cr(CO)₃ moiety on the other with a view to explore the role of cation on haptotropic migration. Cation binding not only enhances the complex interaction energy but also delicately affects the fluxionality in the molecule by increasing the barrier to haptotropic shift of Cr(CO)₃. The competing nature of the bifacial acids with sandwiched aromatic ring is established. In line with Pearson’s HSAB principle, LiNC system with highest interaction energy is found to be the most stable one among all the systems under study.

    • Surfactant free metal chalcogenides microparticles consisting of nano size crystallites: room temperature synthesis driven by the supersaturated condition


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      A versatile methodology for the production of organic surfactant-free metal chalcogenide microparticles consisting of nano crystallites at room temperature in a short time is described. The reaction of various metal sources with LiBH4 in the presence of either S or Se yielded their corresponding CuS, Cu₂S, CdS and Cu₂-zSe microparticles. These micron size particles are aggregates of nano crystallites. The reactivity of LiBH4 and supersaturated condition helped in the formation nanocrystals. The first observation of metal source dependent morphology of particles produced under identical reaction condition is also discussed. The morphology of CuS particles obtained in these reactions was varying with the change of metal source used in the reaction. Interestingly, the reactions producing metal chalcogenide microparticles also yielded borane (BH₃) as a side product.

    • Syntheses, structures and properties of two coordination polymers of Cadmium(II) pseudohalide containing an in situ generated bidentate Schiff base: Control of dimensionality by varying pseudohalides

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      Two neutral coordination polymers of Cadmium(II) pseudohalide of the type [Cd(LL)(μ₁, ₅-dca) ₂]n (1) and [Cd(LL)(μ₁, ₃-NCS) ₂] n (2) (LL = phenyl(pyridin-2-yl)methanimine and dca = dicyanamide) have been isolated using a 1:1:1:2 molar ratio of CdCl₂.H₂O, 2-aminopyridine (ap), 2-benzoylpyridine (bp) and Na(dca)/NH₄SCN in alcoholic solvent at room temperature. X-ray structural study reveals that in the condensation reaction of ap and bp some degradation occurs in presence of the metal ion to afford an in situ generated bidentate Schiff base (LL) in the complexed form. Each Cadmium(II) center in both 1 and 2 adopts an octahedral geometry with a CdN₆ chromophore in 1 and a CdN4S₂ chromophore in 2. In 1, each metal(II) center is connected to four other metal(II) centers through four different μ₁, ₅-dca bridges affording a three-dimensional network structure, whereas each Cd(II) center in 2 is linked with neighbouring Cd(II) centers through bibridged end-to-end (EE) thiocyanates to form a non-ending linear 1D zig-zag chain. Further, in crystalline state 1D chains in 2 are stabilized through weak intermolecular C-H…S hydrogen bond interaction promoting 2D sheet structure. Thermally stable compounds 1 and 2 show intraligand 1(π-π∗) fluorescence in DMF solution at room temperature.

    • Influence of alkene substituent in dictating the reaction course to form carbocycles or oxacycles during ring closing metathesis of acyclic trienes


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      Ring closing metathesis of acyclic trienes that can provide oxacycles or carbocycles has been investigated. It was found that a substituent on one of the alkene units determines the reaction course to provide either oxacycles or carbocyles exclusively irrespective of the ring size of the resulting compounds.

    • A new procedure for synthesis of α-aminophosphonates by aqueous formic acid as an effective and environment-friendly organocatalyst


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      Aqueous formic acid (37%) as a green organocatalystwas used to synthesis of α-aminophosphonates in one-pot, three-component Kabachnik–Fields reaction. The structures of compounds were determined by FTIR, ¹H-NMR and ¹³C-NMR spectroscopy. After optimization of the experimental conditions, the reaction was carried out at 65 ◦C under solvent- free condition. Use of a nontoxic effective organocatalyst, easy work up process and low-cost cleaning procedure are from the main advantages of this research.

    • Deactivation mechanism of the simultaneous removal of carbonyl sulphide and carbon disulphide over Fe–Cu–Ni/MCSAC catalysts


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      The deactivation mechanism of the simultaneous removal of COS and CS ₂ over a Fe–Cu– Ni/MCSAC catalyst was investigated using SEM/EDS, XPS and in situ DRIFTS methods. The results show that the catalytic hydrolysis of COS and CS ₂ over the Fe–Cu–Ni/MCSAC catalyst involves two steps: hydrolysis of COS/CS ₂ and oxidation of H ₂S. The SEM/EDS and XPS results indicate that that catalytic hydrolysis of CS ₂ can be achieved by the actions of alkaline groups and active components. When O ₂ was introduced into the system, oxidation of H ₂S occurred via H ₂S → S → SO ²⁻ ₄ /sulphate. In situ DRIFTS experiments indicated that the formation of sulphate may occur as follows: (a) H ₂S + O ₂ → S + H ₂O, (b) S+O ₂ → S–O, (c) – COO+H ₂S →–CH+S–O, (d) C–OH+H ₂S →–CH+S–O. The in situ DRIFTS experiments also indicated that the C–OH groups, –COO groups and O ₂ played important roles in the deactivation of the catalyst, which was consistent with the XPS results. Meanwhile, the SO ²⁻ ₄ /sulphate content increased during the reaction, which led to its occupancy of the catalyst’s surface activity sites. Additionally, the alkaline groups and active components were removed, which could also result in the deactivation of the catalysts.

    • Pharmacologically significant tetraaza macrocyclic metal complexes derived from isatin and 3,4-diaminobenzophenone: Synthesis, spectral studies and comparative in vitro biological assessment


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      The 12-membered Schiff base macrocyclic complexes, [Dichloro [5,6;11,12-dibenzophenone- 1,4,7,10-tetraazacyclododeca-1,3,7,9-tetraene-2,3,8,9-diindole] metal(II) [M = Co(II), 1; Ni(II), 2; Cu(II), 3 and Zn(II), 4] were synthesized via template condensation of isatin and 3,4-diaminobenzophenone. Thesefour complexes were characterized employing the analytical, spectral viz., FTIR, NMR, Mass, UV-Vis, EPR, TGA/DTAand SEM. The formation of metal complexes has been confirmed on account of the characteristic band positions in FTIR spectra and resonance signals in NMR spectra while the absorption bands in UV-Vis spectra and magnetic moment analysis signify the geometry of the complexes. However, the EPR study inferred distorted octahedral geometry in Cu(II) complex. The binding profile of the metal complexes (1–4) with CT-DNA wasmonitored by fluorescence and circular dichroism (CD) spectroscopy coupled with molecular docking studies. The binding constants were found to be highest for complex 3. Further, the hypothesis of preferential binding in the minor groove of double-stranded DNA is supported by CD and docking results. The antioxidative properties showed substantial radical scavenging potency of the complex 3. The comparative in vitro antibacterial study of the metal complexes against different pathogenic microbes (S. aureus, E. coli and C. albicans) revealed enhanced activity for complex 3 which is further certified by its efficacy to resist biofilm formation as investigated by XTT reduction assay.

    • Indicators for suicide substrate inactivation: A kinetic investigation


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      Suicide substrate kinetic pathway and a proposed set of indicators, some theoretical and a few practical ones, that can decisively conclude enzyme inactivation are considered. Steady-state approximation is assumed not only when a catalytic amount of enzyme is used but also for any substrate-enzyme ratio. In each situation, adequacy of the approximation is numerically tested. An equation for the rate of inactivation of the enzyme has been derived and employed under suitable approximations to estimate various indicators.Progressive curves for such indicators via numerical simulation are shown that decide impromptu inactivation too. The scheme though is a traditional one, the findings are novel.

    • Frequency upconversion in catechin assisted LaF₃: Yb³⁺-Er³⁺ square nanoplates


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      Yb ³⁺ -Er³⁺ codoped lanthanum upconverting nanostructures with varying concentration of dopants have been synthesized by catechin method. The prepared upconverting nanostructures were characterized through XRD,TEM,XPS, NIR absorption,TGAandDSCanalysis.TEMstudy confirms the formation of squareshaped nanoplates with size less than 100 nm. XPS peaks around 830–854eV further reveal the formation of LaF ₃ in the prepared samples. Frequency upconversion spectra from the developed nanostructures corresponding to the ²H₁₁/₂, ⁴S₃/₂ → ⁴ I₁₅/₂ and ⁴F₉/₂ → ⁴I₁₅/₂ transitions upon 980nm excitation are reported. Enhancement in the upconversion emission of catechin-based lanthanum nanostructures has been observed when compared with that prepared by ammonium di-n-octadecyldithiophosphate (AODTP) method.

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