Hazardous and other element characterization of new and used domestic plastic food containers using INAA and AAS

Instrumental Neutron Activation Analysis (INAA) and Atomic Absorption Spectroscopy methodology was developed to characterize the hazardous and other inorganic trace element constituents in new and used domestic plastic food containers. INAA due to its non destructive, highly sensitive, multielement and low detection limits characteristics was found to be a good technique for the characterization of polymeric products. Through the variation of irradiation, cooling and counting protocols Al, Ba, Br, Co, Cr, Eu, Fe, Hg, K, Mn, Na, Nd, Sb, Sc, Th, Ti, V and Zn were determined, while Atomic Absorption Spectroscopy was used as complementary technique to quantify toxic inorganic elements such as Cd, Pb and Cu. These elements are thought to originate from the polymer manufacturing processes. It was found that there was gradual increase in the concentration of most of these elements from new to used plastic samples. Moreover it was also observed that these inorganic elements are present in higher concentrations in the lower grade containers as compared to the high quality containers. It was also observed that the good quality containers even with the long usage do not degrade to such an extent as the low quality containers.     

Manipulation of the Conformation and Enzymatic Properties of T1 Lipase by Site-Directed Mutagenesis of the Protein Core

In silico and experimental investigations were conducted to explore the effects of substituting hydrophobic residues, Val, Met, Leu, Ile, Trp, and Phe into Gln 114 of T1 lipase. The in silico investigations accurately predicted the enzymatic characteristics of the mutants in the experimental studies and provided rationalization for some of the experimental observations. Substitution with Leu successfully improved the conformational stability and enzymatic characteristics of T1 lipase. However, replacement of Gln114 with Trp negatively affected T1 lipase and resulted in the largest disruption of protein stability, diminished lipase activity and inferior enzymatic characteristics. These results suggested that the substitution of a larger residue in a densely packed area of the protein core can have considerable effects on the structure and function of an enzyme. This is especially true when the residue is next to the catalytic serine as demonstrated with the Phe and Trp mutation.     

Generation of Monoclonal Antibody for 15-deoxy-Δ12,14-Prostaglandin J2 and Development of Enzyme-Linked Immunosorbent Assay for Its Quantification in Culture Medium of Adipocytes

15-deoxy-??^12,14-Prostaglandin J₂ (15d-PGJ₂) is a biologically active molecule serving as a pro-adipogenic factor or an anti-inflammatory regulator. This compound is one of naturally occurring derivatives formed by the non-enzymatic dehydration of PGD₂. To determine the endogenous synthesis of 15d-PGJ₂, a convenient immunological approach is useful. At first, we established a cloned hybridoma cell line to secrete a monoclonal antibody specific for 15d-PGJ₂. For the development of a solid-phase enzyme-linked immunosorbent assay (ELISA), the immobilized antigen using a protein conjugate of 15d-PGJ₂ was allowed to react competitively with a monoclonal antibody in the presence of free 15d-PGJ₂. Under the optimized conditions, a sensitive calibration curve was generated able to determine the amount of 15d-PGJ₂ from 0.5?pg to 9.7?ng with 71?pg of 50% displacement in one assay. Our monoclonal antibody did not recognize other related prostanoids except PGJ₂ with cross-reaction of 4%. Our ELISA was demonstrated to be reliable for the quantification of 15d-PGJ₂ in the maturation medium of cultured adipocytes by confirming the accuracy and specificity of its determination. The application of our assay revealed that the non-enzymatic formation of 15d-PGJ₂ became more evident after several hours of incubation with authentic PGD₂ at 37?°C. The results indicate the usefulness of our developed solid-phase ELISA with the monoclonal antibody for further studies on the endogenous synthesis of 15d-PGJ₂ and its roles in various cells and tissues.     

Practical syntheses of proposed and revised manzacidin B and their congeners

A concise and highly stereoselective total synthesis of manzacidin B and its congeners has been developed following chelation-controlled syn-epoxidation and Lewis acid catalyzed intramolecular regioselective epoxide ring opening to generate the quarternary amine center. Elaboration of the triol moiety to the target molecule was achieved in good overall yield, representing practical total syntheses of manzacidin B and its congeners. From the XRD, NMR, and analytical data, the correct structure of natural manzacidin B, (4R,5R,6R)-6, was confirmed.     

Simultaneous determination of two major snow crab aeroallergens in processing plants by use of isotopic dilution tandem mass spectrometry

Snow crab is a major fishery in the North Atlantic region. During crab processing the proteins are aerosolized and some are responsible for development of occupational asthma. Tropomyosin and arginine kinase have recently been reported as major snow crab allergens. A liquid chromatographic tandem mass spectrometric method has been developed for simultaneous analysis of these two proteins in air samples collected from processing plants. These proteins were initially isolated then characterized by use of mass spectrometry to determine their primary structure and signature peptides. The signature peptides were chemically synthesized in light and heavy forms and used as standards for developing the multiple-reaction monitoring transitions to monitor allergen levels. A validation study was performed; precision and accuracy were 1.8–8% and 91–104%, respectively. Replicate air samples were collected on air filters from two crab-processing plants in Newfoundland and Labrador (NL) and four located in Quebec. In NL, measured levels of both tropomyosin and arginine kinase were between 1 and 20 ng m⁻³. In Quebec plants, however, levels were found to be much higher at 2–2400 ng m⁻³. Significant differences were also observed among the plants and individual processing workstations. For the first time arginine kinase has been detected in its aerosolized form in processing plants. In general, levels of the allergens were highest in the butchering and cooking areas; plant design can, however, have a significant effect on levels of the allergens.     

Effect of NiO nanofiller concentration on the properties of PEO-NiO-LiClO4 composite polymer electrolyte

Composite polymer electrolyte films comprising polyethylene oxide (PEO) as the polymer host, LiClO₄ as the dopant, and NiO nanoparticle as the inorganic filler was prepared by solution casting technique. NiO inorganic filler was synthesized via sol-gel method. The effect of NiO filler on the ionic conductivity, structure, and morphology of PEO-LiClO₄-based composite polymer electrolyte was investigated by AC impedance spectroscopy, X-ray diffraction, and scanning electron microscopy, respectively. It was observed that the conductivity of the electrolyte increases with NiO concentration. The highest room temperature conductivity of the electrolyte was 7.4?×?10^?4 S cm^?1 at 10 wt.% NiO. The observation on structure shows the highest conductivity appears in amorphous phase. This result has been supported by surface morphology analysis showing that the NiO filler are well distributed in the samples. As a conclusion, the addition of NiO nanofiller improves the conductivity of PEO-LiClO₄ composite polymer electrolyte.     

The prenylated dioxopiperazine alkaloid Cristatin A has selective telomeric DNA G-quadruplex stabilising properties

Cristatin A (1a/b), a prenylated dioxopiperazine alkaloid, has been shown to bind selectively to telomeric quadruplex DNA using a FRET-based DNA melting assay. Crucially, the molecule is more drug-like than most previously identified quadruplex-binding agents, and provides a unique chemical scaffold for future chemical biology and drug discovery studies.     

Preparation and characterization of blended solid polymer electrolyte 49% poly(methyl methacrylate)-grafted natural rubber:poly(methyl methacrylate)–lithium tetrafluoroborate

The preparation and characterization of blended solid polymer electrolyte 49% poly(methyl methacrylate)-grafted natural rubber (MG49):poly(methyl methacrylate) (PMMA) (30:70) were carried out. The effect of lithium tetrafluoroborate (LiBF₄) concentration on the chemical interaction, structure, morphology, and room temperature conductivity of the electrolyte were investigated. The electrolyte samples with various weight percentages (wt.%) of LiBF₄ salt were prepared by solution casting technique and characterized by Fourier transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy. Infrared analysis demonstrated that the interaction between lithium ions and oxygen atoms occurred at symmetrical stretching of carbonyl (C=O) (1,735 cm^?1) and asymmetric deformation of (O–CH₃) (1,456 cm^?1) via the formation of coordinate bond on MMA structure in MG49 and PMMA. The reduction of MMA peaks intensity at the diffraction angle, 2θ of 29.5° and 39.5° was due to the increase in weight percent of LiBF₄. The complexation occurred between the salt and polymer host had been confirmed by the XRD analysis. The semi-crystalline phase of polymer host was found to reduce with the increase in salt content and confirmed by XRD analysis. Morphological studies by SEM showed that MG49 blended with PMMA was compatible. The addition of salt into the blend has changed the topological order of the polymer host from dark surface to brighter surface. The SEM analyses supported the enhancement of conductivity with the addition of salt. The conductivity increased drastically from 2.0 to 3.4?×?10^?5 S cm^?1 with the addition of 25 wt.% of salt. The increase in the conductivity was due to the increasing of the number of charge carriers in the electrolyte. The conductivity obeys Arrhenius equation in higher temperature region from 333 to 373 K with the pre-exponential factor σ _o of 1.21?×?10^?7 S cm^?1 and the activation energy E _a of 0.46 eV. The conductivity is not Arrhenian in lower temperature region from 303 to 323 K.     

Utilization of compressed natural gas for the production of carbon nanotubes

The present work aims at utilizing compressed natural gas (CNG) as carbon source for the synthesis of carbon nanotubes (CNTs) over CoOMoO/Al2O3 catalyst via catalytic chemical vapor deposition (CCVD) method. The as-produced carbonaceous product was characterized by thermal gravimetric analyzer (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The experimental finding shows that CNTs were successfully produced from CNG while carbon nanofibers (CNFs) were formed as the side products. In addition, the catalytic activity and lifetime were found sustained and prolonged, as compared with using high purity methane as carbon source. The present study suggests an alternative route which can effectively produce CNTs and CNFs using low cost CNG.     

Dynamic Stability Analysis of Shells Using a Finite Element Based Reduction Method

A finite element formulation of a reduction method for dynamic stability analysis of imperfection-sensitive shell structures is presented. The reduction method makes use of a perturbation approach, initially developed for static buckling and later extended to dynamic buckling analysis. The single mode dynamic buckling analysis and its extension to parametric excitation analysis are described. The approach is available within a general purpose finite element code. Characteristic results for the parametric excitation analysis of a composite cylindrical shell are shown. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)