Depolymerization and chemical modification of lignite coal byPseudomonas cepacia strain DLC-07

Applied Biochemistry and Biotechnology - Coal metabolizingPseudomonas cepacia DLC-07 was isolated from soil and shown to use soluble lignite coal as a carbon/energy source.Pseudomonas modified coal...     

Synthesis of azido arylselenides and azido aryldiselenides: a new class of selenium-nitrogen compounds

We present here our results of the efficient synthesis of azido arylselenides and azido aryldiselenides under mild conditions. Starting from nitrogen-substituted benzenes, we incorporated selenium atom at aromatic ring and obtained amino arylselenides and diselenides in satisfactory yields. Treatment of these compounds with iso-pentyl nitrite (i-C₅H₁₁ONO) and azido trimethylsilane (Me₃SiN₃) in THF affords a variety of azido arylselenides and diselenides in good to excellent yields.     

A bar impact tester for dynamic fracture testing of ceramics and ceramic composites

A bar impact test was developed to study the dynamic fracture responses of precracked ceramic bars, Al₂O₃ and 15/29-percent volume SiC_w/Al₂O₃. Crack-opening displacement was measured with a laser-interferometric displacement gage and was used to determine the crack velocity and the dynamic stress-intensity factorK _I ^dyn . The crack velocity andK _I ^dyn increased with increasing impact velocity while the dynamic-initiation fracture toughness,K _Id, did not vary consistently with increasing impact velocities.Paper was presented at the 1992 SEM Spring Conference on Experimental Mechanics held in Las Vegas on June 8–11.     

Chiral seleno-amines from indium selenolates. A straightforward synthesis of selenocysteine derivatives

A simple and efficient procedure for the synthesis of chiral beta-seleno-amines derivatives from a one-pot indium(I) iodide-mediated aziridine ring opening with diorganoyl diselenides has been developed. As an application, the synthesis of selenocysteine and selenotreonine derivatives has been accomplished.     

Organocatalytic asymmetric epoxidation and tandem epoxidation/Passerini reaction under eco-friendly reaction conditions

An eco-friendly synthesis of highly functionalized epoxides and their incorporation into an organocatalytic multicomponent approach are reported. For this, a modified class of diarylprolinol silyl ethers was designed to enable high catalytic activity in an environmentally benign solvent system. The one-pot procedure showed great efficiency in promoting stereoselective multicomponent transformations in a tandem, 'green' fashion. Because of its non-residual, efficient and selective character, this synthetic design shows promise for large-scale applications in both diversity and target-oriented syntheses.     

Novel method for immobilization of enzymes to magnetic nanoparticles

The value of coupling biological molecules such as enzymes to solid materials has long been recognized. To date, protein immobilization onto such surfaces often involves covalent coupling, encapsulation, or non-specific adsorption techniques. Here we demonstrate the feasibility of specifically attaching a haloalkane dehalogenase enzyme to silica-coated or uncoated iron oxide superparamagnetic nanoparticles using affinity peptides. The enzyme was cloned from Xanthobacter autotrophicus strain GJ10 into Escherichia coli to produce fusion proteins containing dehalogenase sequences with C-terminal polypeptide repeats that have specific affinity for either silica or iron oxide. The fusion proteins serve dual functions, allowing for specific inorganic surface binding and for enzymatic activity. The degree of fusion protein adsorption to nanoparticle surfaces was found to exceed that of enzymes that had not been activated with affinity sequences, particularly for iron-oxide nanoparticles. The ability to specifically adsorb cloned affinity-tagged dehalogenase was further demonstrated by selectively adsorbing dehalogenase fusion proteins containing an iron-oxide affinity tripeptide directly from cell lysate. The retention of enzymatic activity was found to be dependent upon the surface chemistry of the nanoparticles. An increase in activity was observed after adsorption of fusion proteins onto the surface of nanoparticles modified by treatment with hydrophilic polyethylene glycol or 3-glycidoxypropyltrimethoxysilane molecules. As a result of this work, it is possible to tag an active enzyme with specific peptides that bind to inorganic nanoparticle surfaces. Because the conjugates self assemble, the novel surface-specific conjugate formation procedure is highly efficient and easily scalable for use in large-scale applications.     

Lignin biotransformations by an aromatic aldehyde oxidase produced byStreptomyces viridosporus T7A

Streptomyces viridosporus produces an intracellular aromatic aldehyde oxidase that oxidizes aromatic and α, β-unsaturated aromatic aldehydes to their corresponding acids. It also produces extracellular oxidase as shown by zones of clearing when grown on agar containing insoluble dehydrodivanillin (DHDV). This extracellular form may be responsible for oxidizing aldehyde groups in lignin. The extracellular oxidase was expressed maximally after 3 d growth in medium containing only yeast extract. However, higher levels were produced when lignocellulose was in the medium. The enzyme was partially purified and its molecular weight was approximated to be about 80,000 daltons. Mutant cultures that had lost the ability to produce zones of clearing on DHDV-containing agar solubilized smaller quantities of lignin as compared to the wild type, except for one strain. A partially purified oxidase preparation was shown to oxidize a natural lignocellulose substrate.     

Ionic liquid: an efficient and reusable media for seleno- and thioester synthesis promoted by indium

A series of thio and selenoesters were efficiently obtained employing stable diorganyl chalcogenides, acyl chlorides, and In as reducing agent in BMIM·PF₆. Recycling of the ionic liquid was also performed, which was reused three times.     

Utilization of a Fluorescent Dye Molecule as a Proton and Electron Reservoir

Fluorescent dyes have been widely utilized as chemical sensors and in photodynamic therapy, but exploitation of their redox‐active nature in chemical reactions has remained mostly unexplored. This report describes the isolation of a 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY)‐based radical. The redox‐active nature of the BODIPY compound can be utilized in combination with a guanidine center, the basicity of which can be manipulated by greater than 14 pK_a units, to promote the conversion of protons and electrons into H‐atoms for transfer to substrate molecules.     

Efficient synthesis of diorganyl selenides via cleavage of Se-Se bond of diselenides by indium(III) catalyst and zinc

A simple and efficient procedure for the synthesis of unsymmetrical diorganyl selenides from an one-pot indium(III) catalyzed procedure, in the presence of zinc, has been developed. Various organic halides and even the unreactive organic chlorides underwent the reaction efficiently. Also diaryl and dialkyl diselenides underwent the coupling reaction.