Photoelectron spectra of some antibiotic building blocks: 2-azetidinone and thiazolidine-carboxylic Acid

X-ray photoelectron spectra of the core and valence levels of the fundamental building blocks of β-lactam antibiotics have been investigated and compared with theoretical calculations. The spectra of the compounds 2-azetidinone and the 2- and 4-isomers of thiazolidine-carboxylic acid are interpreted in the light of theoretical calculations. The spectra of the two isomers of thiazolidine-carboxylic acid are rather similar, as expected, but show clear effects due to isomerization. Both isomers are analogues of proline, which is well-known to populate several low energy conformers in the gas phase. We have investigated the low energy conformers of thiazolidine-4-carboxylic acid theoretically in more detail and find some spectroscopic evidence that multiple conformers may be present. The measured valence levels are assigned for all three compounds, and the character of the frontier orbitals is identified and analyzed.     

Hydrogen-bonding-driven self-assembly of PEGylated organosilica nanoparticles with poly(acrylic acid) in aqueous solutions and in layer-by-layer deposition at solid surfaces

PEGylated organosilica nanoparticles have been synthesized through self-condensation of (3-mercaptopropyl)trimethoxysilane in dimethyl sulfoxide into thiolated nanoparticles with their subsequent reaction with methoxypoly(ethylene glycol) maleimide. The PEGylated nanoparticles showed excellent colloidal stability over a wide range of pH in contrast to the parent thiolated nanoparticles, which have a tendency to aggregate irreversibly under acidic conditions (pH < 3.0). Due to the presence of a poly(ethylene glycol)-based corona, the PEGylated nanoparticles are capable of forming hydrogen-bonded interpolymer complexes with poly(acrylic acid) in aqueous solutions under acidic conditions, resulting in larger aggregates. The use of hydrogen-bonding interactions allows more efficient attachment of the nanoparticles to surfaces. The alternating deposition of PEGylated nanoparticles and poly(acrylic acid) on silicon wafer surfaces in a layer-by-layer fashion leads to multilayered coatings. The self-assembly of PEGylated nanoparticles with poly(acrylic acid) in aqueous solutions and at solid surfaces was compared to the behavior of linear poly(ethylene glycol). The nanoparticle system creates thicker layers than the poly(ethylene glycol), and a thicker layer is obtained on a poly(acrylic acid) surface than on a silica surface, because of the effects of hydrogen bonding. Some implications of these hydrogen-bonding-driven interactions between PEGylated nanoparticles and poly(acrylic acid) for pharmaceutical formulations are discussed.     

Wide-aperture CO2 lasers pumped with an electron-beam-controlled discharge

This review paper presents the results obtained during the development and study of three high-power wide-aperture CO ₂ lasers (λ=10.6 μm) pumped with a discharge controlled by an electron beam. In developing these lasers, the method of formation of a space discharge at elevated pressures due to uniform ionization of the working mixture by an electron beam with an energy of some hundreds of kiloelectron-volts was used, which was proposed by researchers at the Instute of High-Current Electronics (IHCE). Institute of High-Current Electronics, Siberian Division of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 5–11, April, 2000.     

Magnus wind turbine. 3. Calculated characteristics of the windwheel

On the basis of experimental data for a windwheel with large-aspect-ratio (up to 14) cylinders, a method making it possible to determine optimal parameters and main characteristics of a windwheel (power, highspeed) is proposed. Effects due to number of cylinders, their aspect ratio and speed of rotation, stream velocity, and generator load are analysed.     

Potentialities of low-temperature chlorination of aluminum and its alloys with uranium

Potentialities of low-temperature (300–500°C) chlorination to remove the aluminum cladding of fuel elements and separate uranium and aluminum were studied.     

Interaction of <Emphasis Type="Italic">L</Emphasis>-cysteine with selenious and selenic acids: A study by the density functional theory method

Using the density functional theory method at the B3LYP/6-31G(d,p) theory level, the formation of hydrogen bonded complexes of L-cysteine with selenious and selenic acids is studied. In both cases, complexes formed through the carboxyl group of cysteine mostly arise, their enthalpy of formation being of -19kcal/mol to -21 kcal/mol and the free energy of -6kcal/mol to -9kcal/mol. The primary act of interaction in the system of hydroxyl-containing selenium compound — α-aminoacid, including the mutual orientation of reactant molecules and the formation of intermolecular hydrogen bonds is likely to a serve as prerequisite for the thiol group to be able to participate in the next stages (including deeper chemical transformations) of biologically significant reactions.     

Obtaining Mannanoligosaccharide Preparations by Means of the Mechanoenzymatic Hydrolysis of Yeast Biomass

A new method of obtaining biologically active mannanoligosaccharides is proposed. It involves mechanical activation of the enzymatic hydrolysis of components forming the supramolecular structure of the cell wall. Processes that take place during mechanical treatment and enzymatic hydrolysis of yeast biomass and lead to an increase in the availability of mannanoligosaccharides of the yeast cell walls are investigated. The efficiency of the use of mechanoenzymatic approach to obtaining mannanoligosaccharide preparations is evaluated.     

The aza Arndt–Eistert reaction based on N-trifluoromethylsulfonylarenecarboximidoyl chlorides

The aza analogues of carboxylic acids chlorides containing the NSO₂CF₃ and NSO₂CH₃ groups instead of oxygen atom were used in the Arndt–Eistert reaction. It was found that N-trifluoromethylsulfonyl-(4-fluorophenyl)-carboximidoyl chloride 1 reacts with diazomethane vigorously even at ?70 °C with formation of 1-trifluoromethylsulfonylamino-2-(4-fluorophenyl)-2,3-dimorpholine-4-yl-propane 3, 2-trifluoromethylsulfonylamino-2-(4-fluorobenzyl)-7-oxa-4-azonia-spiro[3.5]nonane 4, 2-trifluoromethylsulfonylamino-2-(4-fluorobenzyl)-1,3-dimorpholine-4-yl-propane 5 and 1-trifluoromethylsulfonylamino-2-(4-fluorobenzyl)-2,3-dimorpholine-4-yl-propane 6. Reaction of N-methylsulfonylbenzcarboximidoyl chloride 8 with diazomethane proceeds at ?15 °C yielding 4-chloro-4-methylsulfonylaminomethyl-3-phenyl-4,5-dihydro-1H-pyrazoline 9.