Microhardness measurements of poly(methyl methacrylate) and poly(vinylidene fluoride) polyblends

The preparation of polymer blends of poly(methyl methacrylate) and poly(vinylidene fluoride) in different weight percentages is described. Vickers microhardness measurements have been made to study the effects of load and compositional ratio of the two polymers in polyblend. It is observed that poly(vinylidene fluoride) acts as a plasticizer for poly(methyl methacrylate). Evidence of increasing and decreasing strength of polyblends has been obtained for different compositional ratios of the two polymers.     

Extraction-spectrophotometric determination of uranium(VI) with PAR and N-octylacetamide

A new and simple method for selective spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol (PAR) and N-octylacetamide into benzene over pH 7.0–9.0 is described. The molar absorptivity of the complex with 9 different amides is in the range of (0.40–3.2)·10⁴ 1·mol^–1·cm^–1 at the absorption maximum. Out of these, the most sensitive compound N-octylacetamide (OAA) was chosen for detailed studies in the present investigation. The detection limit of the method is 0.008 g U·ml^–1. The system obeys Beer's law in the range of 0–5 g U·ml^–1. The method is free from interferences of most of the common metal ions except vanadium(V) and copper(II), which are masked by proper masking agents. The composition of the complex is determined by curve-fitting method. The method has been applied for the recovery of the metal from rock samples and synthetic mixtures.     

Mode of action and synergism of cellulases fromPenicillium funiculosum

A 1,4-β-d-glucan cellobiohydrolase (EC 3.2.1.91) and l,4-β-d-glucan glucanohydrolase (EC 3.2.1.4) were purified from the culture filtrates ofPenicillium funiculosum by using preparative isoelectric focusing. Both the enzymes were homogeneous on polyacrylamide gel with and without sodium dodecyl sulphate. The mol wt of the cellobiohydrolase and endoglucanase were 14,400 and 25,000 respectively. The purified enzymes were free of β-glucosidase activity. Acting in isolation, the cellobiohydrolase had little capacity for solubilizing Avicel or Walseth cellulose, but showed increased rates of hydrolysis when combined with endoglucanase. Cellobiose inhibition (50%) was observed in the initial rate of the hydrolysis of Walseth cellulose. It was also observed that cellobiohydrolase initiates the attack on crystalline cellulose. † NCL communication no. 3898.     

An Aldehyde Responsive,Cleavable Linker for Glucose Responsive Insulins

A glucose responsive insulin (GRI) that responds to changes in blood glucose concentrations has remained an elusive goal. Here we describe the development of glucose cleavable linkers based on hydrazone and thiazolidine structures. We developed linkers with low levels of spontaneous hydrolysis but increased level of hydrolysis with rising concentrations of glucose, which demonstrated their glucose responsiveness in vitro. Lipidated hydrazones and thiazolidines were conjugated to the LysB29 side-chain of HI by pH-controlled acylations providing GRIs with glucose responsiveness confirmed in vitro for thiazolidines. Clamp studies showed increased glucose infusion at hyperglycemic conditions for one GRI indicative of a true glucose response. The glucose responsive cleavable linker in these GRIs allow changes in glucose levels to drive the release of active insulin from a circulating depot. We have demonstrated an unprecedented, chemically responsive linker concept for biopharmaceuticals.     

Site-selective C–H nitration of N-aryl-7-azaindoles under palladium(II) catalysis

The site-selective C–H nitration reaction of 7-azaindoles with t-butyl nitrite under palladium catalysis is described. This protocol provides an efficient method for the construction of ortho-nitrated N-aryl-7-azaindoles with excellent site-selectivity and functional group compatibility. The formed 7-azaindole derivatives can be readily transformed into 7-azaindoles containing an aniline functional group under palladium-catalyzed hydrogenation conditions.     

Identification of Druggable Targets for Acinetobacter baumannii Via Subtractive Genomics and Plausible Inhibitors for MurA and MurB

Emergence of the multidrug-resistant pathogens has rendered the current therapies ineffective thereby, resulting in the need for new drugs and drug targets. The accumulating protein sequence data has initiated a drift from classical drug discovery protocols to structure-based drug designing. In the present study, in silico subtractive genomics approach was implemented to find a set of potential drug targets present in an opportunist bacterial pathogen, Acinetobacter baumannii (A. baumannii). Out of the 43 targets identified, further studies for protein model building and lead-inhibitor identification were carried out on two cell-essential targets, MurA and MurB enzymes (of A. baumannii designated as MurA_Ab and MurB_Ab) involved in the peptidoglycan biosynthesis pathway of bacteria. The homology model built for each of them was further refined and validated using various available programs like PROCHECK, Errat, ProSA energy plots, etc. Compounds showing activity against MurA and MurB enzymes of other organisms were collected from the literature and were docked into the active site of MurA_Ab and MurB_Ab enzymes. Three inhibitors namely, T6361, carbidopa, and aesculin, showed maximum Glide score, hydrogen bonding interactions with the key amino acid residues of both the enzymes and acceptable ADME properties. Furthermore, molecular dynamics simulation studies on MurA_Ab–T6361 and MurB_Ab–T6361 complexes suggested that the ligand has a high binding affinity with both the enzymes and the hydrogen bonding with the key residues were stable in the dynamic condition also. Therefore, these ligands have been propsed as dual inhibitors and promising lead compounds for the drug design against MurA_Ab and MurB_Ab enzymes.     

Grafting Vinyl Monomers onto Wool Fibers. VII. Graft Copolymerization of Methyl Methacrylate onto Wool Using Peroxydiphosphate-Thiourea Redox System

Graft copolymerization of methyl methacrylate onto wool was investigated in aqueous solution using the potassium peroxy-diphosphate-thiourea redox system as the initiator. The rate of grafting was determined by varying the monomer, peroxydi-phosphate ion, temperature, and solvent. The graft yield increases with increasing peroxydiphosphate ion up to 80 × 10^?-⁴ mol/L, and with further increase of peroxydiphosphate ion the graft yield decreases. The graft yield increases with increasing monomer concentration. The percentage of grafting decreases with increasing thiourea concentration. The rate of grafting increases with an increase of temperature. The effect of acid and water-soluble solvent and certain salts on graft yield has been investigated and a suitable rate expression has been derived.     

Siloxane polymers containing azo moieties synthesized by click chemistry for photo responsive and liquid crystalline applications

Three new types of siloxane‐based photoactive liquid crystalline polymers containing azo side groups were synthesized through the click chemistry route. The polymers having molecular weight range of 14,000–34,000 g mol^?1 were soluble in most of the polar solvents like chloroform, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, and dichloromethane. The photoresponsive trans–cis photoisomerization under UV radiation and cis–trans relaxation process in dark for the polymers were studied. The isomerization rate constants were found to be 0.01–0.04 sec^?1 and 1.16*10^?4–4.67*10^?4 sec^?1, respectively. It has been noted that the polymers showed high intensity absorption for n‐π* in chloroform. Both trans and cis forms of azide monomers having azo moiety exhibited molar extinction coefficient ( ? _max) in the range of 22,000–33,000 L mol^?1 cm^?1. The thermotropic behavior of the polymers was studied by polarizing optical microscope (POM) and differential scanning calorimetry (DSC) experiments. Polymer P1 showed liquid crystalline textures of nematic droplets, whereas P2 showed smectic focal conic texture and nematic droplets. Polymer P1 was also studied for photomechanical bending on exposure to UV radiation. The polymers showed initial degradation temperature in the range of 210–275°C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Click chemistry‐based synthesis of azo polymers for second‐order nonlinear optics

Four linear polymers containing pendant azo moiety were synthesized through click chemistry for second‐order nonlinear optical study. The polymers were found soluble in most of the polar organic solvents such as tetrahydrofuran (THF), chloroform, and dimethyl formamide (DMF). The polymers showed thermal stability up to 300 °C and glass transition temperatures (T_g) in the range of 120–140 °C. The molecular weights (M_w) of these polymers (measured by gel permeation chromatography) were in the range 37,900–55,000 g/mol. The polymers were found to form optically transparent films by solution casting from THF solution. Order parameters were calculated from UV–vis absorption spectra. The morphology changes in the films after poling were characterized by atomic force microscopy. The angular dependence, temperature dependence, and time dependence of second harmonic generation (SHG) intensity were obtained by using 1064 nm Nd:YAG laser. The SHG intensity remained unchanged up to 95 °C. At room temperature, it remained stable up to 8 days after initial drop of about 14%. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012