Valorization of Oceanic Waste Biomass: A Catalytic Perspective

Efficacious waste utilization is vital in context of sustainability. The past decade has witnessed attempts of usage of land biomass and wastes for various applications, contributing towards a sustainable society. Exploitation of the marine biomass, which does not compete with habitation and food production like land biomass has been largely unnoticed and therefore not being utilized judiciously. Researchers have mainly exploited these resources as functional materials having significant potential applications. However, a catalytic perspective for the valorisation of these polymers arising from oceanic waste widens their scope and ameliorates its use. The objective of the present review is to demonstrate the effectiveness of chitin/chitosan as a catalyst and as a feedstock for deriving important fuels and chemicals. It displays all the reactions heterogeneously catalyzed by them along with the strategic methodology. Their important catalytic organic transformations attempted so far, have also been discussed. The future perspectives are also presented which if inculcated would improve the value addition of the waste, paving a way for greener and imperishable world.     

Copolymerizations of alkyl methacrylates with vinyltriacetoxysilane

Copolymerizations of methyl methacrylate (MMA) and butyl methacrylate (BMA) with vinyltriacetoxysilane (VTAS) have been carried out in bulk at 70°. The compositions of the copolymers were determined from their silicon contents; the reactivity ratios were calculated by the Kelen-Tüdős method. For MMA/VTAS, r₁ = 7.75 ± 0.31 and for BMA/VTAS, r₁ = 4.62 ± 0.15; in both systems, r₂ is zero, indicating that VTAS does not homopolymerize under the experimental conditions. The influence of the silicon comonomer on properties of the copolymers, such as solubility annd thermal behaviour, was studied.     

Gram level synthesis of lead-free solder in the nanometer length scale obtained from tin and silver compounds using silicone oil

A straightforward route to gram level synthesis of a pure phase of the Sn-Ag nanoalloy in an eutectic composition (Sn/Ag 96.5:3.5) in silicone oil is reported. The composition, morphology, and microstructure of the alloy were fully characterized. In a mixture of ethylene glycol and silicone oil, direct reduction of Sn(II) acetate and Ag(I) nitrate gave the Sn-Ag nanoalloy. The nanoalloy disintegrates by sonication and reforms by heating, leading to smaller particles with a melting point as low as 128 degrees C.     

Basic Ionic Liquid Promoted Domino Knoevenagel–Thia‐Michael Reaction: An Efficient and Multicomponent Strategy for Synthesis of 1,3‐Thiazines

An efficient, three‐component strategy for synthesis of 1,3‐thiazines with high atom economy in one‐pot mediated by room temperature basic ionic liquid is described here. The strategy involves basic ionic liquid, [bmim]OH‐catalyzed Knoevenagel condensation between ethyl cyanoacetate and aromatic aldehyde and subsequent thia‐Michael addition with substituted thioureas. The reaction sequence is smooth and quantitative under ambient temperature. [bmim]OH was recovered and reused four times without any appreciable decrease in its reactivity and product yield.     

Polyaniline–graphene oxide nanocomposites: Influence of nonconducting graphene oxide on the conductivity and oxidation‐reduction mechanism of polyaniline

The present endeavor focuses on the unusual interactions between polyaniline and graphene oxide (PANi–GO) which radically affects the properties of nanocomposites as it is an emerging material for many potential applications. A series of nanocomposites have been synthesized by varying the weight percentage of highly nonconducting GO with respect to aniline which exhibit superior properties in terms of shelf life, processability and conductivity due to the synergistic effect of GO and PANi. A comparison of the resistances of samples reveal that though as‐synthesized GO is insulating (80 MΩ), when added to PANi (283 kΩ) in small amounts yields conducting composites (50–280 Ω). Up to 5 weight % concentration, GO renders conductivity to the composite probably by increasing the doping level of PANi. Nonetheless, no further increase in conductivity observed on addition of more than 5 wt% GO in the composite has dictated us to unravel the structure property relationship between PANi and GO, where GO facilitates the formation of partially reduced phase of PANi, thereby restricting the electronic transport. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3778–3786     

Investigating the effect of antibiotics on quorum sensing with whole-cell biosensing systems

Quorum sensing (QS) allows bacteria to communicate with one another by means of QS signaling molecules and control certain behaviors in a group-based manner, including pathogenicity and biofilm formation. Bacterial gut microflora may play a role in inflammatory bowel disease pathogenesis, and antibiotics are one of the available therapeutic options for Crohn’s disease. In the present study, we employed genetically engineered bioluminescent bacterial whole-cell sensing systems as a tool to evaluate the ability of antibiotics commonly employed in the treatment of chronic inflammatory conditions to interfere with QS. We investigated the effect of ciprofloxacin, metronidazole, and tinidazole on quorum sensing. Several concentrations of individual antibiotics were allowed to interact with two different types of bacterial sensing cells, in both the presence and absence of a fixed concentration of N-acylhomoserine lactone (AHL) QS molecules. The antibiotic effect was then determined by monitoring the biosensor’s bioluminescence response. Ciprofloxacin, metronidazole, and tinidazole exhibited a dose-dependent augmentation in the response of both bacterial sensing systems, thus showing an AHL-like effect. Additionally, such an augmentation was observed, in both the presence and absence of AHL. The data obtained indicate that ciprofloxacin, metronidazole, and tinidazole may interfere with bacterial communication systems. The results suggest that these antibiotics, at the concentrations tested, may themselves act as bacterial signaling molecules. The beneficial effect of these antibiotics in the treatment of intestinal inflammation may be due, at least in part, to their effect on QS-related bacterial behavior in the gut.     

Comments on “hydromagnetic slip flow with heat transfer in an inclined channel”

The hydromagnetic slip flow of a viscous incompressible and electrically conducting fluid through an inclined channel of rectangular cross section in the presence of a transverse magnetic field has been analysed. The walls of the channel are assumed to have prescribed temperatures and finite conductivities. The boundary conditions for both velocity and temperature are properly rectified. The expressions for the velocity, induced magnetic field and the temperature are obtained both analytically and numerically.     

Facile synthesis of novel bis-derivatives of 2,5-diamino-thiadiazole/<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-thiocarbohydrazide and their biological perspective

A series of new bis derivatives of 2,5-thiadiazole and N,N′-thiocarbohydrazide along with their transition metal complexes were synthesized by green methods (sonochemical and microwave), i.e., energy and time efficient and operationally more simple than existing conventional methods. All the synthesized compounds were fully characterized by routine analytical techniques and subjected to a preliminary biological screening. These novel characterized compounds were screened for antimicrobial activities and showed promising results. A few potent compounds were also tested for antitumor activities against MDA-MB231 (human breast carcinoma cell line) and compound 5 has emerged as a potential antitumor compound followed by compound 2, 10 and 9, with IC₅₀ values of 29.48, 32.25, 32.34 and 34.34 μg/ml, respectively. To understand the binding interactions of these compounds, in silico studies were performed using the AUTODOCK 4.2 suite and found to be supportive of the experimental results.     

Discovering New Classes of <Emphasis Type="Italic">Brugia malayi</Emphasis> Asparaginyl-tRNA Synthetase Inhibitors and Relating Specificity to Conformational Change

SLIDE software, which models the flexibility of protein and ligand side chains while docking, was used to screen several large databases to identify inhibitors of Brugia malayi asparaginyl-tRNA synthetase (AsnRS), a target for anti-parasitic drug design. Seven classes of compounds identified by SLIDE were confirmed as micromolar inhibitors of the enzyme. Analogs of one of these classes of inhibitors, the long side-chain variolins, cannot bind to the adenosyl pocket of the closed conformation of AsnRS due to steric clashes, though the short side-chain variolins identified by SLIDE␣apparently bind isosterically with adenosine. We hypothesized that an open conformation of the motif 2 loop also permits the long side-chain variolins to bind in the adenosine pocket and that their selectivity for Brugia relative to human AsnRS can be explained by differences in the sequence and conformation of this loop. Loop flexibility sampling using Rigidity Optimized Conformational Kinetics (ROCK) confirms this possibility, while scoring of the relative affinities of the different ligands by SLIDE correlates well with the compounds’ ranks in inhibition assays. Combining ROCK and SLIDE provides a promising approach for exploiting conformational flexibility in structure-based screening and design of species selective inhibitors.     

Structural elucidation of propargylated products of 3-substituted-1,2,4-triazole-5-thiols by NMR techniques

Propargylation of 3-substituted-1,2,4-triazole-5-thiols, which predominantly exist as their thione tautomers, was carried out with the view to synthesize different heterocycles and study their biological activity. Three different products namely, a mono S-propargyl and two S,N-dipropargyl regioisomers, arising from N1/N2 substitution, were isolated and characterized. Unambiguous structural elucidation of the regioisomers of S,N-dipropargyl derivatives was achieved by means of (13)C-(1)H HMBC technique. The proportion of the regioisomers was found to vary with the substituent on the 1,2,4-triazole thiols. No product corresponding to N4 substitution was isolated from any of the reactions carried out.