Catalysis in Organic Solvents with Lipase Immobilized by Sol-Gel Technique

A series of immobilized lipases were obtained by sol-gel process, using silica prepolymers prepared from tetramethoxysilane, methyltrimethoxysilane, propyltrimethoxysilane and (3-aminopropyl)triethoxysilane. The activities of these biocatalysts were compared with the lipase adsorbed on poly(methylhydroxysiloxane) and encapsulated into a silicone rubber, lipase entrapped in nanoporous silica matrix and commercial sol-gel lipase. Model reactions were the esterification of stearic acid and Corey lactone bisalcohol (an intermediate of prostaglandin synthesis). The positive effect of hydrophobic-hydrophilic interface, created by the addition of organosilanes, on the activity of biocatalysts was partially reduced by decreasing specific surface of mesopores. Hydrophobic solvents increased the activity of the lipase entrapped in tetramethoxysilane–methyltrimethoxysilane prepolymer in the sequence acetone < toluene < benzene < decane < hexane. The activity of silicone rubber-encapsulated biocatalysts was proportional to polymer swelling in organic solvents (hexane > toluene > acetone).     

Size extensive modification of local multireference configuration interaction

We recently developed a reduced scaling multireference configuration interaction (MRCI) method based on local correlation in the internal (occupied) and external (virtual) orbital spaces. This technique can be used, e.g., to predict bond dissociation energies in large molecules with reasonable accuracy. However, the inherent lack of size extensivity of truncated CI is a disadvantage that in principle worsens as the system size grows. Here we implement an a priori size-extensive modification of local MRCI known as the averaged coupled pair functional (ACPF) method. We demonstrate that local MR-ACPF recovers more correlation energy than local MRCI, in keeping with trends observed previously for nonlocal ACPF. We test the size extensivity of local ACPF on noninteracting He atoms and a series of hydrocarbons. Basis set and core correlation effects are explored, as well as bond breaking in a variety of organic molecules. The local MR-ACPF method proves to be a useful tool for investigating large molecules and represents a further improvement in predictive accuracy over local MRCI.     

Radiological dose assessment of naturally occurring radioactive materials in concrete building materials

Previous studies have shown that the natural radioactivity contained in building materials have significantly influenced the dose rates in dwelling. Exposure to natural radiation in building has been of concerned since almost 80 % of our daily live are spend indoor. Thus, the aim of the study is to assess the radiological risk associated by natural radioactivity in soil based building materials to dwellers. A total of 13 Portland cement, 46 sand and 43 gravel samples obtained from manufacturers or bought directly from local hardware stores in Peninsular of Malaysia were analysed for their radioactivity concentrations. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied building materials samples were found to be in the range of 3.7–359.3, 2.0–370.8 and 10.3–1,949.5 Bq kg^?1 respectively. The annual radiation dose rates (μSv year^?1) received by dwellers were evaluated for 1 to 50 years of exposure using Resrad-Build Computer Code based on the activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K found in the studied building material samples. The rooms modelling were based on the changing parameters of concrete wall thickness and the room dimensions. The annual radiation dose rates to dwellers were found to increase annually over a period of 50 years. The concrete thicknesses were found to have significantly influenced the dose rates in building. The self-absorption occurred when the concrete thickness was thicker than 0.4 m. Results of this study shows that the dose rates received by the dwellers of the building are proportional to the size of the room. In general the study concludes that concrete building materials; Portland cements, sands, and gravels in Peninsular of Malaysia does not pose radiological hazard to the building dwellers.     

Zeaxanthin Production by Novel Marine Isolates from Coastal sand of India and its Antioxidant Properties

Zeaxanthin carotenoids are class of commercially important natural products and diverse biomolecules produced by plants and many microorganisms. Bacteria often produce a cocktail of polar and nonpolar carotenoids limiting their industrial applications. Marine members of the family Flavobacteriaceae are known to produce potential carotenoids such as astaxanthin and zeaxanthin. A few bacterial species have been reported for the predominant production zeaxanthin. Here, we report the molecular identification of the zeaxanthin as a major carotenoid produced by two novel bacteria (YUAB-SO-11 and YUAB-SO-45) isolated from sandy beaches of South West Coast of India and the effect of carbon sources on the production of zeaxanthin. The strains were identified based on the 16S rRNA gene sequencing as a member of genus Muricauda. The closest relatives of YUAB-SO-11 and YUAB-SO-45 were Muricauda aquimarina (JCM 11811^T) (98.9 %) and Muricauda olearia (JCM 15563^T) (99.2 %), respectively, indicating that both of these strains might represent a novel species. The highest level of zeaxanthin production was achieved (YUAB-SO-11, 1.20?±?0.11 mg g^?1) and (YUAB-SO-45, 1.02?±?0.13 mg g^?1) when cultivated in marine broth supplemented with 2 % NaCl (pH 7) and incubated at 30 °C. Addition of 0.1 M glutamic acid, an intermediate of citric acid cycle, enhanced the zeaxanthin production as 18 and 14 % by the strains YUAB-SO-11 and YUAB-SO-45 respectively. The zeaxanthin showed in vitro nitric oxide scavenging, inhibition of lipid peroxidation, and 2,2-diphenyl-1-picryl hydrazyl scavenging activities higher than the commercial zeaxanthin. The results of this study suggest that two novel strains YUAB-SO-11 and YUAB-SO-45 belonging to genus Muricauda produce zeaxanthin as a predominant carotenoid, and higher production of zeaxanthin was achieved on glutamic acid supplementation. The pigment showed good in vitro antioxidant activity, which can be exploited further for commercial applications.     

Flux line lattice symmetries in the borocarbide superconductor LuNi2B2C

We compare the results of small angle neutron scattering on the flux line lattice (FLL) obtained in the borocarbide superconductor LuNi₂B₂C with the applied field along the c- and a-axes. For H‖c the temperature dependence of the FLL structural phase transition from square to hexagonal symmetry was investigated. Above 10 K the transition onset field. H ₂(T), rises sharply, bending away from H _c2(T) in contradiction to theoretical predictions of the two merging. For H‖a a first order FLL reorientation transition is observed at H _tr=3–3.5 kOe. Below H _tr the FLL nearest neighbor direction is parallel to the b-axis, and above H _tr to the c-axis. This transition cannot be explained using nonlocal corrections to the London model.     

Dynamics of Ligand Binding to a Rigid Glycosidase**

The single-domain GH11 glycosidase from Bacillus circulans (BCX) is involved in the degradation of hemicellulose, which is one of the most abundant renewable biomaterials in nature. We demonstrate that BCX in solution undergoes minimal structural changes during turnover. NMR spectroscopy results show that the rigid protein matrix provides a frame for fast substrate binding in multiple conformations, accompanied by slow conversion, which is attributed to an enzyme-induced substrate distortion. A model is proposed in which the rigid enzyme takes advantage of substrate flexibility to induce a conformation that facilitates the acyl formation step of the hydrolysis reaction.     

Direct use of unassigned resonances in NMR structure calculations with proxy residues

We present a method that significantly enhances the robustness of (automated) NMR structure determination by allowing the NOE data corresponding to unassigned NMR resonances to be used directly in the calculations. The unassigned resonances are represented by additional atoms or groups of atoms that have no interaction with the regular protein atoms except through distance restraints. These so-called "proxy" residues can be used to generate NOE-based distance restraints in a similar fashion as for the assigned part of the protein. If sufficient NOE information is available, the restraints are expected to place the proxies at positions close to the correct atoms for the unassigned resonance, which can facilitate subsequent assignment. Convergence can be further improved by supplying additional information about the possible identities of the unassigned resonances. We have implemented this approach in the widely used automated assignment and structure calculation protocols ARIA and CANDID. We find that it significantly increases the robustness of structure calculations with regard to missing assignments and yields structures of higher quality. Our approach is still able to find correctly folded structures with up to 30% randomly missing resonance assignments, and even when only backbone and beta resonances are present! This should be of significant value to NMR-based structural proteomics initiatives.     

The Application of a Sol-Gel Technique to Preparation of a Heavy Metal Biosorbent from Yeast Cells

In this work we compared biosorbents obtained by encapsulation of polysaccharides, isolated from waste brewing biomass, in sol-gel derived silicates and an organic polymer. Biosorbents were prepared by mixing cross-linking-agents—organic or siliceous—with dried cells envelopes. Siliceous prepolymers were synthezised via transesterification and hydrolysis from tetraethoxysilane (TEOS) and methanol. Sorption of Cd2+, Cu2+ and Ag+ by biosorbent granules (0.25–0.6 mm) was examined in batch and in a packed column. The biosorbent prepared by interesterification of TEOS showed a 2–3 times higher intensity of sorption than the biosorbent cross-linked with epichlorohydrin (the most effective cross-linking organic agent) while the sorption capacity of both biosorbents was equal. The specific surface area of the silica matrix was 597 m2/g but only traces of metals were sequestered from solution with a concentration of Cd2+ of 50 mg/l. The biosorbent with a silica matrix is a heterogeneous material containing microporous matrix inclusions of thin cell walls. Its high sorption intensity and good mechanical strength will be useful in continuous metal uptake of low concentrations of metals.     

发光玻璃在X射线实时成像系统中的应用

介绍了以铽（Ｔｂ）激活的高密度发光玻璃和光导纤维发光玻璃的特性。它应用在Ｘ射线实时成像系统中,可大大改善空间分辨能力。用它做的转换屏比一般晶粒状荧光物质做的厚得多,特别适合用于高能Ｘ射线实时成像系统