Trends in development of the educational system in the Republic of Kazakhstan

At present, the system of education in Kazakhstan is in the transition state. It is difficult to give an unambiguous assessment of the achieved level of education as yet. It is necessary to wait for a certain period of time for the performed modernization to have a positive impact on the educational system outcomes.     

Role of the special pair in the charge-separating event in photosynthesis

We synthesized special-pair/electron-acceptor systems consisting of a complementary slipped cofacial dimer of imidazolyl-substituted zinc porphyrin, bearing pyromellitdiimide as the electron acceptor. In the case of the dimer, the first and second oxidation potentials were split into a total of four peaks in the differential pulse voltammetry measurement. Furthermore, the shift values of the first oxidation potentials obtained by changing the solvent polarity for the dimer were almost half of those observed for the monomer. These results indicate that the radical cation is delocalized over the whole pi system of the dimer. Time-resolved transient absorption measurements revealed that, relative to the corresponding monomer, the dimer accelerated the charge separation rate, but decelerated the charge recombination rate. The smaller reorganization energy of the slipped cofacial dimer relative to that of the monomeric system demonstrates the significance of the special-pair arrangement for efficient charge separation in photosynthesis.     

Protection of the carboxy group in the form of the 2-cyanoethyl ester in synthesis of peptides

With the aim of studying the suitability of the 2-cyano group for the protection of carboxylic functions in peptide synthesis, we have obtained the 2-cyanoethyl esters of a number of amino acids and have studied their behavior under the conditions of peptide synthesis. The synthesis of the pentapeptide leucine-enkaphalin has been performed with the use of 2-cyanoethyl protection for C-terminal carboxy groups throughout. The physicochemical characteristics of the compounds synthesized are given.All-Union Scientific-Research Institute of Molecular Biology Kol'tsovo, Novosibirsk oblast Vector Scientific Industrial Association of the USSR Minmedbioprom, Novosibirsk. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 412–416, May–June, 1988.     

Application of IR spectroscopy in the analysis of the woody-fibrous mass in the process of hydrolysis

The possibility has been shown of using IR spectroscopy in the investigation of the changes in the polysaccharide component of wood in the process of acid hydrolysis. The method of determining the relative optical density (ROD) was used for the quantitative evaluation of the changes in the functional groups of the lignocellulose.     

Experiences with the Application of QSAR in the Routine of the Notification Procedure

Abstract

On behalf of the Umweltbundesamt the Fraunhofer Gesellschaft has developed a software system (SAR-system) comprising more than 90 estimation models for endpoints relevant in environmental risk assessment. These estimation models are based on the approach of quantitative structure-activity relationships (QSAR). All models were checked for their validity and application range. In the last months the Umweltbundesamt started to test the applicability of some models concerning the endpoints fish acute toxicity, daphnia acute toxicity and ready (i.e., ultimate) biodegradability in the daily routine of the notification procedure. For testing these models the corresponding confidential data given in the dossiers of substances notified 1993 in Germany, were used. We were able to make calculations for 36% of the notified substances. For the remaining 64% of the chemicals it was impossible to accomplish SAR estimations due to several reasons, e.g., ionic structure of the compounds. Different results for the applicability of the mentioned endpoints are obtained. The predictions of the fish and Daphnia toxicity are in sufficient agreement with the experimental results, in case of the fish toxicity we receive 58% agreement, for the Daphnia toxicity 56% The corresponding values which were obtained in the US EPA/E.C. Joint Project on the evaluation of (quantitative) structure activity relationships were 82.3% and 70.9% About 300 different models were used for the calculations of these endpoints within the framework of the EPA/EC project. The SAR-system presented here contains 8 models for estimating the fish toxicity and 6 models for the Daphnia toxicity. For the prediction of the biodegradability the results obtained with the SAR-system are rather poor and have to be improved. Meanwhile the SAR-system is commercially available and can be ordered at the Fraunhofer Institute for Environmental Chemistry and Ecotoxicology, Schmallenberg (Germany).     

Catalytic currents in the oxidation of pyridine N-oxide in the presence of alcohols

Catalytic currents were observed in the oxidation of pyridine N-oxide in acetonitrile at a glassy-carbon electrode in the presence of methyl and isopropyl alcohols. It is assumed that the pyridine N-oxide radical cation is a one-electron oxidizing agent reacting with alcohol according to a mechanism of H-atom abstraction from the alcohol molecule.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2441–2445, November, 1989.The authors thank A. E. Shilov for cooperation in the study and for discussion of a number of questions mentioned in the paper.     

Application of capillary gas chromatography in the analysis of hydrocarbons in the environment

Summary Hydrocarbons are emitted into the environment in quantity and diversity. Some of these can be detrimental in low concentration, many can be active in photochemical smog production. For combatment there is also interest in the sources of hydrocarbons in the atmosphere. For source recognition fine-structured chromatographic fingerprints are essential. This also holds for oil pollution. A complicating factor in the determination of hydrocarbon pollutants may arise from the occurrence of recently biosynthesized hydrocarbons. For distinguishing between these two types the application of capillary gas chromatography is preferred to packed column gc. It will be clear that the application of capillary gc in the analysis of hydrocarbons in the environment is of great practical value. The modified Grob method used by us for the analysis of hydrocarbons in air is discussed. For the characterization and source recognition of oil pollution in water and soil application of capillary gc fingerprinting is essential; in this way valuable information can be gathered about weathering of oil pollution. Sources of oil pollution in water areas and harbour regions can be traced in certain cases. Also the possibility of measurement of residence time is present. Typical examples are given.Publication No. 601 of the TNO Research Institute for Environmental Hygiene.     

Variation of the composition of asphaltenes in the course of bitumen aging in the presence of antioxidants

Chemical aging of BND 40/60 bitumen in the presence of an oxidation inhibitor under the conditions of heating in a thin film at 163°C for 5, 10, 15, and 20 h was studied. An increase in the asphaltene content, associated with the new formation of a colloid-unstable high-molecular-weight fraction A1 of increased aromaticity, was observed to a lesser extent than in the straight bitumen.     

Mechanistic Studies on the Roles of the Oxidant and Hydrogen Bonding in Determining the Selectivity in Alkene Oxidation in the Presence of Molybdenum Catalysts

When the molybdenum oxo(peroxo) acetylide complex [CpMo(O? O)(O)C?CPh] is used as a catalyst for the oxidation of olefins, completely different product selectivity is obtained depending on the oxidant employed. When tert‐butyl hydroperoxide (TBHP, 5.5 M ) in dodecane is used as the oxidant for the oxidation of cyclohexene, cyclohexene oxide is formed with high selectivity. However, when H₂O₂ is used as the oxidant, the corresponding cis‐1,2‐diol is formed as the major product. Calculations performed by using density functional theory revealed the nature of the different competing mechanisms operating during the catalysis process and also provided an insight into the influence of the oxidant and hydrogen bonding on the catalysis process. The mechanistic investigations can therefore serve as a guide in the design of molybdenum‐based catalysts for the oxidation of olefins.     

A DFT study of the origins of the stereoselectivity in the aldol reaction of bicyclic amino ketones in the presence of water

Experimental diastereoselectivities of the direct solvent-less (neat) aldol reactions of tropinone (8-methyl-8-azabicyclo[3.2.1]octan-3-one) and granatanone (pseudopelletierine, 9-methyl-9-azabicyclo[3.3.1]nonan-3-one) in the presence of catalytic amounts of water are most accurately reproduced by thermodynamic distributions of isomeric products calculated in the gas phase at the B3LYP/6-31g(d) level of theory. Less than 30% systematic errors, on average, exist in the predicted anti/syn-diastereomeric ratio (dr) for the solvent-less reaction of tropinone with several aromatic aldehydes. The CPCM-B3LYP/6-31g(d) method reproduces the anti/syn-diastereomeric ratio of the aqueous aldol reaction of tropinone with several aromatic aldehydes with reasonable deviation (0-88%), excellent (0-10)% agreement was found for the reactions of tropinone and granatanone with benzaldehyde. Qualitatively satisfactory agreement was also found for dr values in different solvents (DMF, THF, and Et₃N). The density functional theory (DFT) results support the notion of the thermodynamic control of the reaction.     

Application of IR spectroscopy in the analysis of the woody-fibrous mass in the process of hydrolysis

The possibility has been shown of using IR spectroscopy in the investigation of the changes in the polysaccharide component of wood in the process of acid hydrolysis. The method of determining the relative optical density (ROD) was used for the quantitative evaluation of the changes in the functional groups of the lignocellulose.Deceased.Siberian Scientific Research Institute of Cellulose and Board, Bratsk. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 683–687, September–October, 1990.     

Photometric Endpoint Detection in the Edta Titration of Zinc in the Presence of Manganese

Abstract

A method has been developed for the simultaneous determination of manganese and zinc or just zinc in the presence of manganese using a photometric technique for determination of the zinc end-point. The accuracy of the results is comparable to that obtained with conventional methods but, in most cases, there is a slight increase in precision. The endpoint is much easier to determine photometrically.     

Consecutive processes in the photolysis of dimethyl-s-tetrazine molecules in the vapor phase

Experimental studies of the variation of the fluorescence yield and photochemical product yield are presented for dimethyl-s-tetrazine (DMT) at 0.6 Torr and 300 K. Results are also reported for the variation of these yields upon adding argon buffer gas. The fluorescence yield decreases with increasing excitation energy (0 to 4200 cm^?1 vibrational energy excess in the first excited singlet state) but the decrease is insufficient to account for the corresponding increase in product yield. Added gas (600 Torr argon) quenches the photochemistry but not the fluorescence. The results imply that the photo-dissociation involves a bottleneck (B) in the non-radiative singlet decay. The molecules in B can be relaxed by collisions, relax to photostable DMT molecules without collisions, or undergo photodissociation.     

Application of the iodine-azide postcolumn reaction in RP-HPLC for the determination of thioguanine in urine

The study focuses on the analysis of a sensitive, selective, and simple postcolumn detection method for thioguanine determination, based on the sensitizing induction of thioguanine on iodine-azide reaction and the combination technique of HPLC. The analysis was accomplished in the optimum conditions for iodine-azide detection system and HPLC separation. The values for the linear range, the LOD, and DOQ amounted to 0.8-1.7, 0.4, and 0.5 nmol/mL urine, respectively.     

Effect of base on the state of palladium in the synthesis of styrene in the heck reaction

An extremely important role is shown for the tertiary amine in the reduction of Pd(II) formed as result of the reductive transformations of the aryl halide in the Heck reaction. The dependence of the rate on the nature of the base is explained.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, p. 208, January, 1991.     

脂质组学分析中样品前处理技术的研究进展

脂质不仅是细胞膜的主要组成部分,还参与一些生命活动如能量存储、信号传导等,在生命体中发挥着重要作用。近年来,越来越多的研究表明脂质的变化与一些重大疾病的发生发展密切相关,脂质组学研究对理解疾病的发生机制及过程具有重要意义。在脂质分析过程中,由于样品基质的干扰或被分析物浓度的限制,通常需要对样品进行前处理,以得到最佳的分析性能。该文综述了脂质组学分析中的样品前处理技术,包括脂质的提取方法（如液液萃取、固相萃取等）和针对不同类脂质的化学衍生化技术在各领域,尤其是生命分析和代谢组学中的应用,并对脂质组学分析中的样品前处理技术的发展进行了展望。     

The role of the HOOO(-) anion in the ozonation of alcohols: large differences in the gas-phase and in the solution-phase mechanism

The mechanism of the ozonation of isopropyl alcohol was investigated for the gas and the solution phase using second-order many body perturbation theory and density functional theory (DFT) with the hybrid functional B3LYP and a 6-311++G(3df,3pd) basis set. A careful analysis of calculated energies (considering thermochemical corrections, solvation energies, BSSE corrections, the self-interaction error of DFT, etc.) reveals that the gas-phase mechanism of the reaction is dominated by radical or biradical intermediates while the solution-phase mechanism is characterized by hydride transfer and the formation of an intermediate ion pair that includes the HOOO(-) anion. The product distribution observed for the ozonation in acetone solution can be explained on the basis of the properties of the HOOO(-) anion. General conclusions for the ozonation of alcohols and the toxicity of ozone (inhaled or administered into the blood) can be drawn.     

Detecting spoiled fruit in the house of the future

An electronic nose based on acoustic wave sensors has been developed to detect spoilt fruit. Different varieties of fruits, edible and rotten, were analysed. Starting from six sensors, the minimum number of sensors capable of discriminating between spoiled and unspoiled fruit was found. The discrimination capability of the sensor array was studied separately for each fruit variety, as well as for the whole set. Mathematical models were built to classify the fruits within a fruit variety, in an objective and clear way. The models were able to distinguish between edible and rotten fruits with 100% success for New Hall oranges, Golden apples, Kiwis and William pears, and with 97.2% of success for the Starking apples. Without forming fruit variety subsets, discrimination between edible and rotten fruit was achieved with 95% success.     

Study of the early deactivation in pyrolysis of polymers in the presence of catalysts

In this work, the early degradation step of the pyrolysis of some polymers in the presence of certain catalysts has been studied using thermogravimetric analysis (TGA). Three commercial polymers (PE, PP and EVA) and three catalysts were studied (ZSM-5, MCM-41a, and MCM-41b), and the MCM-41a catalyst has been selected for the analysis of the earlier steps of the pyrolysis process carried out in the presence of catalysts. Several cycles of heating–cooling were performed using a thermobalance, in order to analyze the influence of the first stages of decomposition on the activity of the more accessible active sites involved. In this way, the behaviour of the polymer–catalyst mixtures (20% (w/w) of catalyst) was studied and compared with that observed in the corresponding thermal degradation as well as in the pyrolysis in the presence of catalysts, in a single heating cycle.The results obtained clearly show the existence of an early degradation step. For a polymer–catalyst system with low steric hindrances such as PE-MCM-41, this early degradation step causes a noticeable decrease of the catalyst activity for the main decomposition step (i.e., cracking of the chain). The decrease of the catalytic activity is lower for a polymer–catalyst system with higher steric restrictions, as occurs in the EVA-MCM-41 degradation process. However, in this case, the catalyst activity in the first decomposition step (i.e., the loss of the acetoxi groups) is noticeable decreased after one pyrolysis run, thus reflecting that the active sites involved are mainly the most accessible ones.