Showing papers by "North Eastern Hill University published in 2017"

Natural fiber reinforced polymer composites

Abstract: Hybrid composites of epoxy matrix and four mixed fibers were prepared. The epoxy matrix is from BADGE and the hardener PPA-7040 mixed in 1:1 volume ratio. The four mixed fibers used for reinforcement are (i) murta bast + jute, (ii) murta bast + luffa, (iii) murta bast + coir, and (iv) murta bast + betel nut fiber. The hybrid composites were analyzed and characterized on the basis of density, water absorption, thermal gravimetric analysis, tensile/flexural/compressive/impact strengths and hardness studies. Murta and jute form the best mixture for making hybrid composite as this composite possess superior physical and mechanical properties. The amount of water absorbed by a hybrid composite does not appear to have any correlation with the chemical composition of the fibers used for reinforcement.

Bioinformatic Approaches Including Predictive Metagenomic Profiling Reveal Characteristics of Bacterial Response to Petroleum Hydrocarbon Contamination in Diverse Environments.

Abstract: Microbial remediation of oil polluted habitats remains one of the foremost methods for restoration of petroleum hydrocarbon contaminated environments. The development of effective bioremediation strategies however, require an extensive understanding of the resident microbiome of these habitats. Recent developments such as high-throughput sequencing has greatly facilitated the advancement of microbial ecological studies in oil polluted habitats. However, effective interpretation of biological characteristics from these large datasets remain a considerable challenge. In this study, we have implemented recently developed bioinformatic tools for analyzing 65 16S rRNA datasets from 12 diverse hydrocarbon polluted habitats to decipher metagenomic characteristics of the resident bacterial communities. Using metagenomes predicted from 16S rRNA gene sequences through PICRUSt, we have comprehensively described phylogenetic and functional compositions of these habitats and additionally inferred a multitude of metagenomic features including 255 taxa and 414 functional modules which can be used as biomarkers for effective distinction between the 12 oil polluted sites. Additionally, we show that significantly over-represented taxa often contribute to either or both, hydrocarbon degradation and additional important functions. Our findings reveal significant differences between hydrocarbon contaminated sites and establishes the importance of endemic factors in addition to petroleum hydrocarbons as driving factors for sculpting hydrocarbon contaminated bacteriomes.

Organotin(IV) complexes derived from proteinogenic amino acid: synthesis, structure and evaluation of larvicidal efficacy on Anopheles stephensi mosquito larvae

Abstract: Five new organotin(IV) complexes of composition [Bz2SnL1]n (), [Bz3SnL1H⋅H2O] (), [Me2SnL2⋅H2O] (), [Me2SnL3] () and [Bz3SnL3H]n () (where L1 = (2S)-2-{[(E)-(4-hydroxypentan-2-ylidene)]amino}-4-methylpentanoate, L2 = (rac)-2-{[(E)-1-(2-hydroxyphenyl)methylidene]amino}-4-methylpentanoate and L3 = (2S)- or (rac)-2-{[(E)-1-(2-hydroxyphenyl)ethylidene]amino}-4-methylpentanoate) were synthesized and characterized using 1H NMR, 13C NMR, 119Sn NMR and infrared spectroscopic techniques. The crystal structure of reveals a distorted trigonal-bipyramidal geometry around the tin atom where the oxygen atoms of the carboxylate ligand and a water ligand occupy the axial positions, while the three benzyl ligands are located at the equatorial positions. On the other hand, the analogous derivative of enantiopure L3H () consists of polymeric chains, in which the ligand-bridged tin atoms adopt the same trans-Bz3SnO2 trigonal-bipyramidal configuration and are now coordinated to a phenolic oxygen atom instead of H2O. In , the OH hydrogen of the ketoimine substituent has moved to the nearby nitrogen atom while in the salicylidene derivative , the OH is located almost midway between the phenolic oxygen atom and the nitrogen atom of the C[DOUBLE BOND]N group. For the dibenzyltin derivative , a polymeric chain structure is observed as a result of a long intermolecular Sn⋅⋅⋅O bond involving the exocyclic carbonyl oxygen atom from the tridentate ligand of a neighbouring tin-complex unit. The tin atom in this complex has distorted octahedral coordination geometry. In contrast, the racemic dimethyltin(IV) complexes and display discrete monomeric structures with a distorted octahedral- and trigonal-bipyramidal geometry, respectively. The structures show that the coordination mode of the Schiff base ligand depends primarily on the number of bulky benzyl ligands (R) at the tin atom, as indeed found in the structures of related complexes where R = phenyl. With three bulky R groups, the tridentate chelating O,N,O coordination mode is preferred, whereas with fewer or less bulky R ligands, only the carboxylate and hydroxy groups are involved, which leads to polymers. Larvicidal efficacies of two of the new tribenzyltin(IV) complexes ( and ) were assessed on the second larval instar of Anopheles stephensi mosquito larvae and compared with two triphenyltin(IV) analogues, [Ph3SnL1H]n and [Ph3SnL3H]n. The results demonstrate that the compounds containing Sn–Ph ligands are more effective than those with Sn–Bz ligands. Copyright © 2016 John Wiley & Sons, Ltd.

Half-sandwich ruthenium, rhodium and iridium complexes featuring oxime ligands: Structural studies and preliminary investigation of in vitro and in vivo anti-tumour activities

Abstract: Half‐sandwich ruthenium, rhodium and iridium complexes (1–12) were synthesised with aldoxime (L1), ketoxime (L2) and amidoxime (L3) ligands. Ligands have the general formula [PyC(R)NOH], where R = H (L1), R = CH3 (L2) and R = NH2 (L3). Reaction of [{(arene)MCl2}2] (arene = p‐cymene, benzene, Cp*; M = Ru, Rh, Ir) with ligands L1–L3 in 1:2 metal precursor‐to‐ligand ratio yielded complexes such as [{(arena)MLκ2(N∩N)Cl}]PF6. All the ligands act as bidentate chelating nitrogen donors in κ2 (N∩N) fashion while forming complexes. In vitro anti‐tumour activity of complexes 2 and 10 against HT‐29 (human colorectal cancer), BE (human colorectal cancer) and MIA PaCa‐2 (human pancreatic cancer) cell lines and non‐cancer cell line ARPE‐19 (human retinal epithelial cells) revealed a comparable activity although complex 2 demonstrated greater selectivity for MIA PaCa‐2 cells than cisplatin. Further studies demonstrated that complexes 3, 6, 9 and 12 induced significant apoptosis in Dalton's ascites lymphoma (DL) cells. In vivo anti‐tumour activity of complex 2 on DL‐bearing mice revealed a statistically significant anti tumour activity (P = 0.0052). Complexes 1–12 exhibit HOMO–LUMO energy gaps from 3.31 to 3.68 eV. Time‐dependent density functional theory calculations explain the nature of electronic transitions and were in good agreement with experiments.

Cosmological dynamics of mimetic gravity

Abstract: We present a detailed investigation of the dynamical behavior of mimetic gravity with a general potential for the mimetic scalar field. Performing a phase-space and stability analysis, we show that the scenario at hand can successfully describe the thermal history of the universe, namely the successive sequence of radiation, matter, and dark-energy eras. Additionally, at late times the universe can either approach a de Sitter solution, or a scaling accelerated attractor where the dark-matter and dark-energy density parameters are of the same order, thus offering an alleviation of the cosmic coincidence problem. Applying our general analysis to various specific potential choices, including the power-law and the exponential ones, we show that mimetic gravity can be brought into good agreement with the observed behavior of the universe. Moreover, with an inverse square potential we find that mimetic gravity offers an appealing unified cosmological scenario where both dark energy and dark matter are characterized by a single scalar field, and where the cosmic coincidence problem is alleviated.

Studies on secondary metabolite profiling, anti-inflammatory potential, in vitro photoprotective and skin-aging related enzyme inhibitory activities of Malaxis acuminata, a threatened orchid of nutraceutical importance

Abstract: Malaxis acuminata D. Don., a small, terrestrial orchid, is endemic to tropical Himalayas at an altitude of 1200-2000m asl. The dried pseudobulbs are important ingredients of century old ayurvedic drug 'Ashtavarga' and a polyherbal immune-booster nutraceutical 'Chyavanprash', known to restore vigour, vitality and youthfulness. Considering tremendous medicinal importance of this threatened orchid species, a detailed study was undertaken for the first time to address its antioxidant potential, secondary metabolite contents and biological activities against skin-aging related enzymes (anti-collagenase, anti-elastase, anti-tyrosinase and xanthine oxidase) and anti-inflammatory activity (5-lipoxygenase and hyaluronidase) in different plant parts of wild and in vitro-derived plants of M. acuminata. Methanolic leaf and stem extracts were further evaluated for in vitro photoprotective activity against UV-B and UV-A radiations. Furthermore, secondary metabolite profiling of various plant parts was carried out by Gas Chromatography Mass Spectrometry (GC-MS). A significantly higher antioxidant potential (DPPH, metal chelating and ABTS•+) with a comparative higher yield of secondary metabolites was observed in in vitro-derived plantlets as compared to the wild plants. Among various solvent systems used, methanolic leaf and stem extracts showed promising inhibitory activity against major skin aging-related enzymes and anti-inflammatory potential. Methanolic leaf and stem extracts of both wild and in vitro-derived plants showed promising photoprotective activity against UV-B and UV-A radiations in vitro with comparatively higher sun protection factor (SPF). Furthermore, GC-MS analysis of methanolic extracts of leaves and stems of wild as well as in vitro-derived plantlets revealed presence of many bioactive metabolites such as, dietary fatty acids, α-hydroxy acids, phenolic acids, sterols, amino acids, sugars and glycosides which substantially explain the use of M. acuminata as one of the potential rejuvenator and anti-aging ingredient in many Ayurvedic formulations.

Distant Phe345 mutation compromises the stability and activity of Mycobacterium tuberculosis isocitrate lyase by modulating its structural flexibility.

Abstract: Isocitrate lyase (ICL), a potential anti-tubercular drug target, catalyzes the first step of the glyoxylate shunt. In the present investigation, we studied the conformational flexibility of MtbICL to better understand its stability and catalytic activity. Our biochemical results showed that a point mutation at Phe345, which is topologically distant (>10 A) to the active site signature sequence (189KKCGH193), completely abolishes the activity of the enzyme. In depth computational analyses were carried out for understanding the structural alterations using molecular dynamics, time-dependent secondary structure and principal component analysis. The results showed that the mutated residue increased the structural flexibility and induced conformational changes near the active site (residues 170–210) and in the C-terminal lid region (residues 411–428). Both these regions are involved in the catalytic activity of MtbICL. Upon mutation, the residual mobility of the enzyme increased, resulting in a decrease in the stability, which was confirmed by the lower free energy of stabilization in the mutant enzyme suggesting the destabilization in the structure. Our results have both biological importance and chemical novelty. It reveals internal dynamics of the enzyme structure and also suggests that regions other than the active site should be exploited for targeting MtbICL inhibition and development of novel anti-tuberculosis compounds.

Ethnozoological study of animals based medicine used by traditional healers and indigenous inhabitants in the adjoining areas of Gibbon Wildlife Sanctuary, Assam, India.

Abstract: India has an immense faunal, floral, as well as cultural diversity with many ethnic communities who are primarily dependent on the traditional medicinal system for their primary health care. Documentation and evaluation of this indigenous remedial knowledge may be helpful to establish new drugs for human health. The present study is intended to look into different zootherapeutic medicinal uses in the traditional health care system among the native inhabitants adjacent to the Gibbon Wildlife Sanctuary, Assam, India. Field survey was carried out from March 2015 to August 2015 by personal interviews through semi-structured questionnaires. In some cases where participants were uncomfortable with the questionnaires, informal interviews and open group discussions were conducted with a total of 62 indigenous respondents (43 male and 19 female) who provided the information regarding various medicinal uses of animals and their products (local name of animal, mode of preparation, application etc). The study recorded a total of 44 different species, 44 genera and 36 families of animals which are used for the treatment of 40 different ailments. Insects occupied the highest uses (30.9%), followed by mammals (23.8%), fishes (16.7%), reptiles (11.9%), amphibians (7.1%), annelids (4.8%) and gastropods (4.8%). Further, some zootherapeutic animals i.e. cockroach (Periplaneta americana), praying mantis (Mantis religiosa) and earthworms (Metaphire houletti, Pheretima posthum) are used for the treatment of asthma, otorrhoea and cancer respectively. The findings suggest that the traditional zootherapeutic remedial measures followed by the native people adjacent to Gibbon Wildlife Sanctuary plays an important role in their primary health care. The documentation of this indigenous knowledge on animal based medicines should be very helpful in the formulation of strategies for sustainable management and conservation of bio-resources as well as providing potential for the novel drugs discovery.

Internet of Things: challenges and research opportunities

Abstract: Faster development of sensor and network technologies is facilitating immense deployment of Internet of Things (IoT) towards creating a smart world. In IoT, a massive number of heterogeneous resource–constraint devices communicate with each other without any human intervention and generate a huge amount of data. Unique research challenges posed by IoT are fascinating the research community. This paper presents some of the critical issues along with state of the art solutions towards them. In-depth discussion is provided on various key issues like heterogeneity and interoperability, scalability, QoS, and security. Directions for further researches in those areas are also pointed out.

Highly selective light-up Al3+ sensing by a coumarin based Schiff base probe: Subsequent phosphate sensing DNA binding and live cell imaging

Abstract: A coumarin based simple fluorescent “turn-on” probe, 4-Hydroxy-3-[(2-hydroxy-5-methoxybenzylidene)-amino]-chromen-2-one (HMC), to detect metal ion based on the chelation enhanced fluorescence (CHEF), was synthesized by condensing 3-amino-4-hydroxycoumarin and 2-hydroxy-5-methoxybenzaldehyde. It was found to be highly selective and sensitive sensor for Al3+ in 90% aqueous methanol (MeOH: 0.01 M HEPES Buffer; 9:1; v/v) at pH 7.4 in fluorescence spectroscopy. Fluorescence intensity enhancement along with 10 nm blue shift was observed only in the presence of Al3+. The HMC binds Al3+ in 1:1 stoichiometry with a binding constant, Ka = (9.9 ± 0.04) × 103 M−1 and the detection limit was calculated to be as low as 1.62 μM. The binding mode of interaction with Al3+ and the chelate complex formation was supported with the help of a 1H NMR spectroscopy titration, ESI–MS and also by theoretical studies. Moreover, the HMC·Al3+ ensemble subsequently detected the biologically important phosphate ions and nucleotides via fluorescence quenching. The live cell imaging study indicated that HMC is highly efficient in the detection of exogenous Al3+ in living cell.

Highly Sensitive Bifunctional Probe for Colorimetric Cyanide and Fluorometric H2S Detection and Bioimaging: Spontaneous Resolution, Aggregation, and Multicolor Fluorescence of Bisulfide Adduct

Abstract: A 4-methylbenzothiazole linked maleimide-based single molecular bifunctional probe 1 has been synthesized for the colorimetric and fluorometric detection of highly competitive H2S and cyanide ion in aqueous DMSO media. The probe 1 selectively detected CN– under the UV–vis spectroscopy through the rapid appearance of deep pink color. The bright pink color developed due to ICT in the moderately stable cyano substituted enolate intermediate. The absorbance titration of 1 with CN– revealed a new band at 540 nm and the nonlinear curve fitting analysis showed good fit with 1:1 model. In fluorescence channel, 1 was found to be highly selective to H2S in 50% aqueous buffer (pH 7). It exhibited ∼16-fold fluorescence intensity enhancement at 435 nm after reaction with 1 equiv of H2S due to the inhibition of PET. The 1-SH adduct showed TICT phenomenon and behaved like molecular rotor. It further displayed aggregation behavior at higher concentration and excitation wavelength dependent multicolor emission properties....

In Silico Identification of Mimicking Molecules as Defense Inducers Triggering Jasmonic Acid Mediated Immunity against Alternaria Blight Disease in Brassica Species.

Abstract: Alternaria brassicae and Alternaria brassicicola are two major phytopathogenic fungi which cause Alternaria blight, a recalcitrant disease on Brassica crops throughout the world, which is highly destructive and responsible for significant yield losses. Since no resistant source is available against Alternaria blight, therefore , efforts have been made in the present study to identify defense inducer molecules which can induce Jasmonic acid (JA) mediated defense against the disease. It is believed that JA triggered defense response will prevent necrotrophic mode of colonization of Alternaria brassicae fungus. The jasmonate receptor, COI1 is one of the potential targets for triggering jasmonic acid mediated immunity through interaction with jasmonate signal. In the present study, few mimicking compounds more efficient than naturally occurring jasmonic acid in terms of interaction with COI1 were identified through virtual screening and molecular dynamics simulation studies. A high quality structural model of COI1 was developed using the protein sequence of Brassica rapa . This was followed by virtual screening of 767 analogs of jasmonic acid from ZINC database for interaction with COI1. Two analogs viz. ZINC27640214 and ZINC43772052 showed more binding affinity with COI1 as compared to naturally occurring jasmonic acid. Molecular dynamics simulation of COI1and COI1-jasmonic acid complex, as well as best screened interacting structural analogs of jasmonic acid with COI1 was done for 50 ns to validate the stability of system. It was found that ZINC27640214 possesses efficient, stable, and good cell permeability properties. Based on the obtained results and its physicochemical properties, it is capable of mimicking jasmonic acid signalling and may be used as defense inducers for triggering JA mediated resistance against Alternaria blight, only after further validation through field trials.

Native microorganisms as potent bioinoculants for plant growth promotion in shifting agriculture (Jhum) systems

Abstract: Microorganisms native to shifting cultivation were isolated and screened for plant growth promotion (PGP) properties. The bacterial and fungal isolates that exhibed production of indole compounds, siderophores, and ammonia; phosphate solubilization; and catalase activity, were selected and tested for their ability to promote the early growth of upland rice plants. Potential isolates from a preliminary seed germination assay carried out in plates were further tested in pots under greenhouse conditions. Observations after two and four weeks of growth indicated that all treated rice plants had higher shoot and root length than those in the control group. Of the isolates used in the experiment, the bacterial isolate SB5 and the fungal isolate SF4 exhibit higher growth activity, with growth increases of 26.20% and 15.87% respectively, over the control group. These isolates are being explored for consortium development as bioinoculants, in an attempt to restore the fertility of jhum fallows

Flood induced vulnerability to poverty: Evidence from Brahmaputra Valley, Assam, India

Abstract: This paper attempts to assess household vulnerability to poverty due to flood in Assam. Whether coping measures can reduce vulnerability and what factors affect such coping has also been examined. Applying vulnerability as expected poverty (VEP) approach to data collected through a primary survey of 476 households in 2013, the study finds that almost 83% of these households are vulnerable to poverty due to flood. The results show that incidence of poverty, flood height and use of coping strategies play significant role in determining households’ vulnerability to poverty. The study also suggests that institutional factors, household's socio-economic conditions and community characteristics determine the use of coping strategies at the household level.

Ruthenium(II) Complex-Based Luminescent Bifunctional Probe for Ag+ and Phosphate Ions: Ag+-Assisted Detection and Imaging of rRNA

Abstract: A new bis-heteroleptic Ru(II) complex (1) of benzimidazole-substituted 1,2,3-triazole pyridine ligand has been designed and constructed for the photoluminescent detection of cationic and anionic analytes, Ag+ and phosphate ions. Compound, 1[PF6]2 was fully characterized by various spectroscopic techniques and the solid-state structure was determined via single-crystal X-ray diffraction. The cation and anion sensing properties in 50% aqueous buffer (pH 9.2) and pure acetonitrile were carefully examined in photoluminescence (PL) spectroscopy. The 1[PF6]2 was found to be highly selective to pyrophosphate; PPi/HP2O73– and H2PO4– ions in CH3CN. It showed ∼10-fold PL intensity enhancement at 583 nm in the presence of only 1 and 2 equiv of PPi and H2PO4– ions, respectively. The PL titrations of 1[PF6]2 with PPi and H2PO4– in CH3CN furnished the association constant (Ka = 3.3 × 103 M–1 and 6.8 × 103 M–1) and the detection limit was as low as 5.73 and 5.19 ppb, respectively. The 1[PF6]2 also selectively detected A...

The Impact of Corporate Governance Attributes on Environmental Disclosures: Evidence from India:

Abstract: This article empirically investigates the impact of corporate governance attributes on companies’ decision to disclose environmental information since corporate governance ensures fair, res

Pyrene based D–π–A architectures: synthesis, density functional theory, photophysics and electron transfer dynamics

Abstract: Pyrene derivatives show immense potential as sensitizers for dye-sensitized solar cells (DSCs). Therefore, this work focuses on the impact of π-spacers on the photophysical, electrochemical and photovoltaic properties of pyrene based D-π-A dyes, since the insertion of π-spacers is one of the doable strategies to improve the light harvesting properties of the dye. In this respect, three new pyrene based D-π-A dyes have been synthesized and characterized by 1H, 13C NMR, and elemental analyses and EI-MS spectrometry. The selected π-spacers are benzene, thiophene and furan. Compared with a benzene spacer, the introduction of a heterocyclic ring spacer reduces the band gap of the dye and brings about the broadening of the absorption spectra to the longer wavelength region through intramolecular charge-transfer (ICT). Combined experimental and theoretical studies were performed to investigate the ICT process involved in the pyrene derivatives. The profound solvatochromism with increased nonradiative rate constants (knr) has been construed in terms of ICT from the pyrene core to rhodanine-3-acetic acid via conjugated π-spacers. Electrochemical data also reveal that the HOMO and LUMO energy levels are fine-tuned by incorporating different π-spacers between pyrene and rhodanine-3-acetic acid. On the basis of the optimized DSC test conditions, the best performance was found for PBRA, in which a benzene group is the conjugated π-spacer. The divergence in the photovoltaic behaviors of these dyes was further explicated by femtosecond fluorescence and electrochemical impedance spectroscopy.

Structure elucidation and in silico docking studies of a novel furopyrimidine antibiotics synthesized by endolithic bacterium Actinomadura sp. AL2

Abstract: On screening of endolithic actinobacteria from a granite rock sample of Meghalaya for antibacterial compound, a novel antibacterial compound CCp1 was isolated from the fermentation broth of Actinomadura sp. AL2. On purification of the compound based on chromatographic techniques followed by characterization with FT-IR, UV–visible, 1H NMR, 13C NMR and mass spectrometry, the molecular formula of the compound was generated as C20H17N3O2, a furopyrimidine derivative. In vitro antibacterial activity of the compound was evaluated against both Gram positive and negative bacteria by agar well diffusion assay. The compound had lowest MIC (2.00 µg/ml) for Bacillus subtilis and highest MIC (> 64 µg/ml) for Staphylococcus epidermidis and Pseudomonas aeruginosa. The study revealed that the compound has potential antibacterial activity. The mode of action of the antibacterial compound was evaluated through in silico studies for its ability to bind DNA gyrase, 30S RNA molecules, OmpF porins and N-Acetylglucosamine-1-phosphate uridyltransferase (GlmU). The antibacterial compound demonstrated more favorable docking with DNA gyrase, 30S RNA molecules and OmpF porins than GlmU which support the antibacterial compound CCp1 can be as a promising broad spectrum antibiotic agent with “multitarget” characteristics.

The effect of temperature, composition and alcohols on the microstructures of catanionic mixtures of sodium dodecylsulfate and cetyltrimethylammonium bromide in water

Abstract: The influence of mixing protocol, composition, temperature, ageing and added alcohols on the characteristics of the microstructures of sodium dodecylsulfate (SDS) + cetyltrimethylammonium bromide (CTAB) mixtures has been investigated in this paper. In this catanionic mixture (1 weight% total surfactant content) temperature induced microstructural transition occurs, which is (i) a micelle-to-vesicle transition (MVT) if αSDS (mole fraction of SDS) = 0.7, 0.8 or 0.9 and (ii) a vesicle-to-micelle transition (VMT) if αSDS = 0.1, 0.2 or 0.3. In the mixture of αSDS = 0.7, specific conductivity and dynamic light scattering measurements also support the occurrence of MVT. Transition electron microscopy and small angle neutron scattering measurements were also made to assess the characteristics of the microstructures. Alcohols added to the mixture of αSDS = 0.7 reduced the size of the vesicle, while only monohydric alcohols suppressed the temperature induced transition indicating that the number and location of -OH groups of the alcohols have a dramatic modulating influence on the structural transition occurring in catanionic mixtures. The influence of the alcohols is explained in terms of changes produced in the dielectric constant and hydrophobicity of the medium.

Antimicrobial nature and healing behavior of plasma functionalized polyester sutures

Abstract: This study deals with the development of bioactive poly(ethylene terephthalate) surgical suture by adopting the immobilization route with bioactive nanogels and chlorhexidine. Carbon dioxide plasma...