Utilization of a high-speed computer in the analysis of mixtures of organophosphorus compounds by IR spectra

Summary Using a mixture of two organothiophosphorus compounds with diacetyl sulfide as an example, it was demonstrated that systems composed of three components can be analyzed by IR spectra with an accuracy of up to 3% by utilizing the high-speed computer Strela.The authors are extremely grateful to L. N. Drozdov-Tikhomirov for discussion of the results and to A. I. Dmitriev for assistance with the calculations.     

Photoresponsive liposomal nanohybrid cerasomes

An innovative photoresponsive cerasome is fabricated by sol-gel process in combination of self-assembly technique from a molecularly designed organoalkoxysilylated lipid containing an azobenzene unit, which is able to operate as a "valve" with an "on-off" function under specific stimuli to control the release of loaded guest molecules from the liposomal membrane.     

脱铝沸石羟基窝的表征

NH4Y和NaY沸石用草酸溶液脱铝制备的样品，用红外光谱测定了表征“羟基窝”的3710cm-1处的背底吸光度（A3710）．并考察了其热稳定性；用DTA和TGA建立了定量测定“羟基窝”的方法，并测定了各样品的“羟基窝”浓度，样品的“羟基窝”浓度与其实际脱铝数相对应     

Moment of inertia, backbending, and molecular bifurcation

We predict an anomaly in highly excited bending spectra of acetylene with high vibrational angular momentum. We interpret this in terms of a vibrational shape effect with moment of inertia backbending, induced by a sequence of bifurcations with a transition from "local" to "orthogonal" modes.     

Synthesis of new arylidene derivatives of 3-aminorhodanine

The synthesis of new arylidene derivatives of 3 -aminorhodanine has been effected. It has been established that the condensation of 3-aminorhodanine with aldehydes in an alcoholic medium gives 3-arylidene derivatives. Similar reactions in an ammoniacal medium lead to 5-derivatives of 3-aminorhodanine. 3, 5-Diarylidene derivatives can be obtained by condensing 3-aminorhodanine with an excess of an aldehyde in glacial acetic acid, except for the salicylidene and 9-anthrylidene derivatives, the synthesis of which can be carried out only in two stages.     

Calculating the Electrochemical Activity of Porous Electrodes of a Filled-up Type with an Immobilized Enzyme

The electrochemical activity of porous electrodes of a filled-up type with an immobilized enzyme is calculated with the aid of computer-aided modeling. The percolation properties of two-component (a mixture of dispersed particles of the substrate and the enzyme) and three-component (a carrier of a gas reactant is added) models of a porous electrode are investigated. Taking into account specific features inherent in the forming macroscopic clusters (collections of particles of one sort or another connected with one another), i.e. an electron cluster and a gas cluster, makes it possible to determine the concentration of an active catalyst which is capable of taking part in the electrochemical process. The calculation of the electrochemical activity is performed in two-component structures, where the process of the current generation is limited by diffusion limitations, and in three-component structures, where the process of the current generation is limited by ohmic limitations. Estimates of the current are performed using an oxygen porous electrode with Nafion and an enzyme as an example. The electrochemical characteristics of this model electrode are close to those obtained on laccase. Introducing a hydrophobizing agent into the active layer of the porous electrode (passing from two-component structures to three-component structures) produces a positive effect. Although the number of active molecules of the enzyme drops in this case by an order of magnitude, the liquidation of diffusion limitations eventually raises the magnitude of the current by approximately threefold. Calculations show that it is quite feasible to obtain currents of 0.2 A cm^–2 on a porous electrode 16 m thick at an overvoltage of 30 mV.     

Atom States and Interatomic Interactions in Complex Perovskite-Like Oxides: XV.1 Magnetic Susceptibility of La0.67Ca0.33MnO3-LaAlO3 Solid Solutions

Magnetic susceptibility of diluted solid solutions of manganites with perovskite structure having a colossal magnetoresistivity was studied. It was found that the systems are characterized by ferromagnetic type strong exchange interactions, which are characterized by an exchange parameter varying with temperature.     

High-performance anion-exchange chromatographic study of desialylated human alpha 1-acid glycoprotein variants. Development of a fractionation method for the protein slow variants

The three main desialylated variants (F1, S and A) of human alpha 1-acid glycoprotein (AAG), a serum acute-phase reactant, were analysed by high-performance anion-exchange chromatography in order to determine their optimum separation conditions. The analysis consisted of three steps, as follows: (1) A desialylated commercial AAG was separated into one "fast"- and one "slow"-migrating fraction by preparative isoelectrofocusing. The "fast" and "slow" fractions were shown to contain the F1 variant and a mixture of the S and A variants, respectively. (2) The pH titration curves of these two fractions were then measured by strong anion-exchange chromatography with several buffer systems of increasing pH. From the data obtained, it was not possible to select the optimum conditions to separate the "fast" variant F1 from the "slow" variants A and S. However, the S and A variants were shown to ionize very differently. (3) The specific fractionation of the S and A variants was therefore carried out by anion-exchange chromatography under operating conditions based on the data obtained from the study of their pH titration curves. This was performed both with the "slow"-migrating fraction obtained by preparative isoelectrofocusing of commercial AAG and with an AAG (containing only variants S and A) purified from an individual serum on immobilized Cibacron Blue F3G-A. Identification of the fractionated proteins was achieved by analytical isoelectrofocusing.     

Conformational and receptor-binding properties of the insect neuropeptide proctolin and its analogues

Summary Proctolin (Arg-Tyr-Leu-Pro-Thr) was the first insect neuropeptide to be chemically characterised. It plays an essential role in insect neurophysiology and is involved in muscular contraction and neuromodulation. Elements of secondary structure in solution have been studied by comparing data obtained from NMR and molecular dynamics simulations. Different secondary structural requirements are associated with agonist and antagonist activities. A favoured conformation of proctolin has an inverse -turn, comprising an intramolecular hydrogen bond near the C-terminal end between Thr NH and Leu CO. Antagonists have a more compact structure resembling a paperclip loop, containing an intramolecular hydrogen bond between Tyr NH and Pro CO, possibly stabilised by a salt bridge between the N- and C-terminal groups. A cyclic analogue retains antagonist activity and resembles a -bulge loop, also comprising intramolecular hydrogen bonds between Tyr NH and Pro CO and Thr CO. These models may offer feasible starting points for designing novel compounds with proctolinergic activity.     

The use of SEM for multielement analysis in small volumes and low concentrations

Summary A preparation method is described for analysing size classified rain drops by SEM (scanning electron microscopy), equipped with an energy-dispersive detection system. The concentration is determined by addition of an internal standard. This allows the quantitative analysis of samples with a volume of 2 l and a concentration of 1 g/l. The time of measurement is 100 s.Dedicated to Professor Dr. V. Krivan on the occasion of his 60th birthday     

Application of an image scanner for determination of boron in glass by a nuclear track technique

For boron concentration in the range of 010%, a 600 g²⁵²Cf neutron source was used for thermal neutron irradiation. As for the track counting technique, a visual observation method by human eye and an automatic counting method with an image scanner showed a good agreement between the determinations by both methods. The latter is useful for improving accuracy in elemental determination by using the nuclear track technique because it gives reproducible count values which are free from human error in comparison with the former.     

Light-triggered reversible assemblies of azobenzene-containing amphiphilic copolymer with β-cyclodextrin-modified hollow mesoporous silica nanoparticles for controlled drug release

Hollow mesoporous silica nanoparticles (HMSs) were modified by β-cyclodextrin via a "click" reaction, an amphiphilic copolymer with a trans-azobenzene structure was then assembled onto β-cyclodextrin to cover the surface of the HMSs. The prepared nanocomposites can release drugs in a "release-stop-release" manner by converting light irradiation.     

Synthesis and Reaction of 4-Methyl-3,4-epithiotetrahydropyran with α-Amino Acids

4-Methyl-3,4-epithiotetrahydropyran was synthesized by the recyclization of 4-methyl-3,4-epoxytetrahydropyran by the action of thiourea. The product reacts with -amino acids in an alkaline medium with regioselective opening of the thiirane ring at the least substituted carbon atom.     

Host-guest chemistry at interface for photoswitchable bioelectrocatalysis

Photoswitchable bioelectrocatalysis of glucose with glucose oxidase in an "On-Off" state is fabricated from host-guest chemistry at an interface by using the photocontrolled reversible immobilization and detachment of ferrocene-labeled redox-polymer as mediator.     

Preparation and Surface Modification of Novel Vesicular Nano-Particle “Cerasome” with Liposomal Bilayer and Silicate Surface

A novel class of nano-hybrid materials, Cerasome, bearing a liposomal bilayer structure and a ceramic surface, has been developed by a sol-gel reaction of a double-chain proamphiphile having an trialkoxysilane in the head moiety and followed self-assembling. In the present work, we developed new methods for preparation of the Cerasomes forming under various pH conditions and their surface modification by employing appropriate alkoxysilane compounds. When the proamphiphilic alkoxysilane was hydrolyzed in an acidic ethanol and then injected into an aqueous media at various pH, the morphologically stable Cerasomes were obtained in a wide pH range. On the other hand, an acid treatment of the proamphiphile in ethanol in the presence of tetraethoxysilane gave the Cerasome with highly developed siloxane networks on its vesicular surface. Surface modification of the Cerasome with amino groups was readily achieved in the similar manner by replacing tetraethoxysilane to 3-aminopropyltriethoxysilane. The Cerasomes thus prepared were characterized by means of dynamic light scattering and zeta potential measurements.     

A radiogaschromatographic separation of some aliphatic ethers

Unsolvated methyl cations, generated by spontaneous -decay of multitritiated methane, have been allowed to react with some aliphatic ethers. The reaction mixtures contain various products, mainly aliphatic ethers, that have been separated by gaschromatography and continuously counted in an ionization chamber. A mechanism involving different reaction channels can provide an explanation of the results.     

Determination of beryllium in plants by means of flameless atomic absorption with zirconium-coated and non-coated graphite tubes

Summary After removing the major part of the matrix elements and other accompanying ions from the digested plants by an extraction with acetylacetone/methylisobutyl-ketone in presence of EDTA, subsequently followed by a reextraction with nitric acid, this element can be determined interference-free by means of flameless atomic absorption with non-coated and zirconium-coated graphite tubes as electrothermal atomizers. During the above mentioned extraction-reextraction procedure only very small amounts of aluminium and iron are coextracted and did not interfere with the determination of beryllium. Recovery analyses confirmed that the whole analytical procedure was quantitative. The detection limit of beryllium was found to be 1.5 g/l reextract. As an example, roots, stems and leaves of Calluna vulgaris were analyzed.

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Bestimmung von Beryllium in Pflanzen durch flammenlose AAS unter Verwendung von Graphitrohren mit und ohne Zr-Beschichtung

     

Powder dilution as a new method of elimination of interelement effects in energy-dispersive X-ray fluorescence analysis

Summary If the concentration of elements with Z>22 (Ti) is to be determined in mineral samples and if the concentration of any of these elements is greater than 1%, the sample is diluted by grinding it together with an appropriate amount of quartz powder in an agate mortar mill. The diluted sample is measured in powdered form in a spectro-cup at practically infinite thickness by energy-dispersive X-ray fluorescence; the counting rates are corrected by means of the Compton scattering peak and evaluated by use of calibration curves obtained by measuring standards on the basis of silica gel. The applicability of this method is established by measuring the concentrations of 12 elements with Z>22 in 14 mineral samples of varying composition.We thank the Bundesministerium für Forschung und Technologie for financial support and the Uranerzbergbau GmbH, Bonn, for supplying the mineral samples.     

Electrokinetic Properties of the Methylated Surface of Quartz Capillaries

The surface charge and electrokinetic potential of quartz capillaries with hydrophobized (methylated) surface are measured. It is shown that, during the flow of an electrolyte solution through the capillary, the potential lowers with time due to formation of gas bubbles on the surface screening the surface charge. In a certain period of time, drastic jump of the potential to its initial value is observed, which is interpreted as a detachment of bubbles by the flowing solution. The formation of bubbles is provoked by the roughness of the methylated surface with asperities of up to 20 nm in height. The profiles of the methylated surface were obtained by the atomic force microscopy. An addition of a nonionic surfactant hydrophilizing the hydrophobic surface to the electrolyte solution lowers the -potential, which could be caused by the suppression of the slip effect. Estimations made on the basis of an earlier developed theory lead to the values of slip coefficient that are close to those measured for micron-sized hydrophobic capillaries.