Highly efficient synthesis of quinoxalinone-N-oxide via tandem nitrosation/aerobic oxidative C-N bond formation

An efficient method for constructing quinoxalinone-N-oxides from cyanoacetanilides has been developed. This transformation can be achieved using inexpensive reagents and molecular oxygen under mild conditions, thus offering a practical pathway to quinoxalinone-containing pharmaceuticals such as ataquimast and opaviraline.     

Estimation of organophosphoric acid triesters in soft polyurethane foam using a concentrated sulfuric acid dissolution technique and gas chromatography with flame photometric detection.

A concentrated sulfuric acid dissolution technique and a GC method are described for the estimation of tributyl phosphate, tris(2-chloroethyl) phosphate, tris(chloropropyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate, triphenyl phosphate and tris(butoxyethyl) phosphate in soft polyurethane foam. A soft polyurethane foam sample containing organophosphoric acid triesters was dissolved in concentrated sulfuric acid. The solution was added to water, where only the polyurethane was separated out. The pH of the solution was adjusted, and organophosphoric acid triesters were extracted with toluene. After purification, the compounds were determined by GC. The detection limits of the organophosphoric acid triesters were 0.3 - 0.9 microg g(-1). The recoveries of the organophosphoric acid triesters from a 0.05 g sample of soft polyurethane foam were 80.0 - 90.0%, when the spiked amounts were 0.25 - 1 microg. The compounds were detected from soft polyurethane foam at the level of 0.4 - 23.3 microg g(-1).     

Coupled nano-plasmons

High aspect-ratio nanochannels were fabricated by irradiating polyimide films with swift heavy ions of 2.2 GeV energy and subsequently sensitising and etching the ion tracks in hydrogen peroxide and sodium hypochloride, respectively. The nanochannels were analysed by means of small angle X-ray scattering in combination with a new form factor model that considers bi-conical channel geometry. This approach allows us to tune the etching parameters for controlled channel shape adjustment.     

Small molecule affinity fingerprinting. A tool for enzyme family subclassification,target identification,and inhibitor design

Classifying proteins into functionally distinct families based only on primary sequence information remains a difficult task. We describe here a method to generate a large data set of small molecule affinity fingerprints for a group of closely related enzymes, the papain family of cysteine proteases. Binding data was generated for a library of inhibitors based on the ability of each compound to block active-site labeling of the target proteases by a covalent activity based probe (ABP). Clustering algorithms were used to automatically classify a reference group of proteases into subfamilies based on their small molecule affinity fingerprints. This approach was also used to identify cysteine protease targets modified by the ABP in complex proteomes by direct comparison of target affinity fingerprints with those of the reference library of proteases. Finally, experimental data were used to guide the development of a computational method that predicts small molecule inhibitors based on reported crystal structures. This method could ultimately be used with large enzyme families to aid in the design of selective inhibitors of targets based on limited structural/function information.     

Control of structure and particle size of iron oxide on carrier oxide by the sol-gel method using organic polydentate ligands

It was tried to control the structure and particle size of iron oxide supported on a carrier by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands. The iron oxide/carrier composites were prepared by calcining carrier oxides impregnated with organic ligands and Fe(NO₃)₃·9H₂O. When ligands were diacetone alcohol and ethanol, the structure of the iron oxide was exclusively corundum. But, with ligands such as ethylene glycol, citric acid and galacturonic acid, the structure of the iron oxide changed from corundum to spinel as the amount of ligands used increased. With both series of ring and straight chain saccharides, size of the iron oxide particles changed depending on saccharides used. It was thus concluded that the structure and particle size of iron oxide supported on a carrier can be regulated by using organic polydentate ligands.     

Catalytic enantioselective [2+2]-cycloaddition reaction of 2-methoxycarbonyl-2-cyclopenten-1-one by chiral copper catalyst

A new catalytic system for enantioselective [2+2]-cycloaddition reaction of 2-methoxycarbonyl-2-cyclopenten-1-one with thioacetylene derivatives is described. The use of a catalytic amount (20-30 mol%) of copper(II) salt with chiral bis-pyridine ligand was found to be effective in promoting the [2+2]-cycloaddition reaction, furnishing the corresponding bicyclic compound in good yield and good enantioselectivity.     

Spectrofluorometric Determination of Purine-Deoxyribonucleoside and Its Deoxyribonucleotides Using 4-Carbamoylbenzamidine

A spectrofluorometric method utilizing 4-carbamoylbenzamidine as a new fluorogenic reagent selective for 2-deoxysugars is proposed for the determination of purine-deoxyribonucleos(t)ides. The method is based on the fluorescence reaction of 4-carbamoylbenzamidine with 2-deoxy-D-ribose released from purine-deoxyribonucleos(t)ides by acid hydrolysis. The optimized method is fairly selective; ribonucleos(t)ides and pyrimidine-deoxyribonucleos(t)ides yield only weak fluorescence of which intensities correspond to 0-15% that given by deoxyadenosine at an equimolar concentration. The method is also sensitive for purine-deoxyribonucleos(t)ides and DNAs; their detection limits are approximately 0.8 nmol/ml and 1.0 μg/ml, respectively.     

Metal cation control of electroosmotic flow magnitude in phospholipid‐coated capillaries

CZE has become widespread for the separation and analysis of biomolecules such as proteins and peptides, due to factors such as, the speed of the separations, low sample volume, and high resolution associated with the technique. However, the separation of biomolecules by CZE does present a significant challenge due to the electrostatic attraction and adsorption of cationic, or cation containing, biomolecules to the capillary surface. To that end numerous methods have been developed to passivate, or protect the surface, in order to prevent the adsorption of analytes. Yet, in the process of protecting the capillary surface, the potential for further modification of the EOF, a factor crucial to effective analyte resolution, is greatly diminished. In seeking to overcome this limitation we have explored the potential of incorporating a range of metal cations into a phospholipid bilayer capillary coating. It has previously been established that the inclusion of calcium into the separation buffer with a phospholipid coating will reverse the EOF in the capillary. Here, we present our investigation of a broader range of metal cations included in the separation buffer (Ca²⁺, Mg²⁺, Co²⁺, Ni²⁺, Sr²⁺, Ba²⁺, and Ce³⁺) revealing that the choice of metal cation can drastically influence the EOF, with observed values between ?3.80 × 10^?4 and ?5.74 × 10^?5 cm²/V·s.     

Anthracene‐sensitized polymerization of vinyl ethers by onium tetrakis(pentafluorophenyl)borate initiators

Cationic photopolymerization of vinyl ethers by the sensitized photolysis of onium tetrakis(pentafluorophenyl)borate initiators has been investigated in this study. The onium borates were sensitized by anthracene and initiated the photopolymerization of the vinyl ethers. The rate of polymerization increased with the decrease in the free‐energy change from the excited singlet state of anthracene to the onium cation of the onium borates. The acid generated by the decomposition of the onium borates formed nonacidic products by heating. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 982–987, 2000     

Crystallization of cellulose microfibrils in wood cell wall by repeated dry-and-wet treatment, using X-ray diffraction technique

The purpose of this study is to investigate the effect of repeated moisture change on the crystallinity and crystal size of cellulose microfibrils (CMF) in sugi (Cryptomeria japonica D.Don) and karamatsu (Larix kaempferi Gord.) wood cell wall. Based on obtained results, we discussed the qualitative change in the fine structure of CMF caused by repeated dry-and-wet (RDW) treatments. Green quarter-sawn specimens (5 × 16 × 15 mm in thickness × length × width) and microcrystalline cellulose powder (Avicel) were prepared, and these specimens were subjected to 7 times at most of heated or unheated RDW treatments. After giving RDW treatments, specimens were seasoned to the fiber saturated point and absolutely dried. Wide angle X-ray diffraction measurements were adopted to determine the crystallinity and the crystal size in each condition. Results indicate that crystallinity and crystal size in wood specimens gradually increased with the progress of heated or unheated RDW treatments, while no such increases were observed in Avicel powder. Those results suggest that RDW treatments promote the crystallization of CMF in wood cell wall, regardless of heating. We presume that noncrystalline cellulose forms hydrogen bonding with the cellulose at the surface of crystalline region with the progress of RDW treatments, thus enlarging the crystal size. Avicel powder did not show features that were observed in wood specimens by RDW treatments, because it contained few noncrystalline cellulose.