Radiochemistry teaching and research activities in Brazil

Summary Much concern has been expressed lately about the decline of teaching and research activities in radiochemistry in many countries, as was discussed in an IAEA Technical Meeting in Antalya, Turkey, in 2002, and also at MTAA-11 in Guildford, UK. In the IAEA meeting, a survey was presented about the current situation in different regions of the world (Eastern Europe, East and West Asia, Africa, North America and Latin America) by experts of each region. In the case of Brazil, which has nuclear research reactors and also cyclotrons in operation, the teaching and research activities in radiochemistry are concentrated in the three main institutes of the Brazilian Nuclear Energy Commission, in the University of S?o Paulo and in other universities, in different regions of the country. In the present paper, a closer look is given to the radiochemistry teaching and research activities that are being conducted nowadays in Brazil, comprising: number of radiochemistry courses and students being formed, main research areas being conducted, as well as research and production of radioisotopes for nuclear medicine, using nuclear reactors and cyclotrons.     

黄鸣龙——我国有机化学的一位先驱

黄鸣龙院士(1898-1979)1919年浙江医药专科学校毕业,1924年德国柏林大学有机药物化学博士;1924-1934年任浙江医专教授、主任,卫生署化学部主任;1934-1940年在欧洲先灵公司等从事研究工作;1940年回国在昆明任中研院化学所研究员,兼任西南联大教授;1945年赴美在哈佛大学,默克公司从事研究工作。1952年绕道欧洲回国,先后在中国人民解放军医学科学院化学系和中国科学院上海有机化学研究所任研究员。1955年当选为中国科学院学部委员(院士)。黄先生一生从事有机化学的教育和研究工作,他在有机化学的“结构与机理”以及“反应和合成”二大方面都作出了在国内外具有深远影响的工作。20世纪40年代黄先生发现了变质山道年4个立体异构体的循环转变,堪称立体化学的经典之作;1948年发表了黄鸣龙还原反应;1952年归国后引领和发展了我国的甾体化学研究,带领了我国甾体药物的生产发展,是我国甾体药物工业的奠基人。黄先生治学严谨,既重视应用研究,又强调基础研究;关注学习新知识、新概念,又更重视实验技术。黄先生教书育人,身体力行,是我国有机化学发展的先驱者和奠基人。     

Investigation of the activity and stability of papain in different micellar systems

Hydrolysis of PyrPheAlaPNa, catalyzed by papain in reverse micelles of ionogenic surfactant of Aerosol OT, and in octane, was studied in the presence and in the absence of nonionogenic surfactants of a different nature. As found, the dependence of the catalytic activity of papain on the hydration degree of the surfactant in reverse micelles of AOT has two maxima, corresponding to the activity of monomeric and oligomeric forms of the enzyme. It was established that the addition of nonionogenic surfactant of a different nature to the Aerosol OT in octane leads to changes of the catalytic properties of the enzyme, in particular, to its activation in the presence of Pluronic L61. Nanoemulsions of nontoxic nonionogenic surfactant and organic solvents, lecithin and Tween 20 in eucalyptus oil were created and characterized; with the use of the photon-correlation spectroscopy technique it was shown that the size of such particles lie in the range from 34 to 266 nm, depending on the water content, nature, and the concentration of system components, and factors regarding its shape lie in the interval 20–30, suggesting the presence of particles with a rod-like shape. It is important to note that in such systems, suitable for use in medicine and cosmetology, the activity of papain was revealed.     

Research progress of graphene-based nanomaterials for the environmental remediation

Graphene is a two-dimensional nanomaterial with huge surface area,high carrier mobility and high mechanical strength.Because of its great potential in nanotechnology and environmental protection,it has attracted much attention in environmental and energy fields since its discovery in 2004.Although graphene is a star material,many reviews have introduced its use in terms of energy,the research progress in the field of environment,especially water pollution control,has been rarely reported.Here,we review exhaustively the research progress of graphene-based materials in environmental pollution remediation in the past ten years.Firstly,the advantages and classification of graphene were introduced.Secondly,the research progress and main achievements of graphene and its composites in the fields of photocatalytic degradation,pollutant adsorption and water treatment were emphatically described,and the mechanism of action in the above fields was summarized.Finally,we discuss the problems existing in the preparation and summarize the application of graphene in the environment.     

Analytical strategies to determine antibiotic residues in fish

The accelerated growth of aquaculture has resulted in a series of harmful effects to human health. The widespread and unrestricted use of antibiotics in this industry, to prevent bacterial infections, leads to remaining amounts in the aquatic environment. This has resulted in the emergence of antibiotic-resistant bacteria in aquaculture environments, in the increase in antibiotic resistance in fish pathogens as well as in the transfer of these resistance determinants to human pathogens. Moreover, the use of large amounts of antibiotics may lead to the presence of residual antibiotics in fish tissue and fish products. Fluoroquinolones, tetracyclines, penicillins, sulphonamides and other antibiotics, exhibiting activity against both Gram-positive and Gram-negative bacteria, are widely used for the treatment and prevention of diseases in fish. An extended and comprehensive review on the recent analytical methodologies concerning antibiotic residues in fish reported in the literature is provided in the present article. Emphasis is given on sample preparation regarding isolation and purification, chromatographic conditions and method validation according to legislation. Results of published assays are comparatively presented and criticised.     

Dendrimers with electroactive units in the core or in each branching centre

Interest in dendrimers is mostly focused on their capability of performing specific functions which, in their turn, derive from the possibility of incorporating in predetermined sites of the structure selected functional groups (‘pieces of information’). From a topological viewpoint we can distinguish dendrimers containing electroactive units (a) in the core, (b) in the branches, (c) in the surface, (d) in the core and in the branches, (e) in the core and in the surface, (f) in the branches and in the surface, and (g) in the core, branches and surface. In this article we review the behaviour of dendrimers with electroactive units buried in the core and dendrimers with electroactive units in each branching centre investigated in our laboratory. To cite this article: M. Venturi, P. Ceroni, C. R. Chimie 6 (2003).     

灌喂氯化汞大鼠组织中汞结合金属硫蛋白的色谱/质谱联用表征研究

通过测定大鼠脏器组织中汞的总量、金属硫蛋白(MTs)含量及利用尺寸排阻色谱(SEC)与电感耦合等离子体质谱(ICP-MS)联用技术,分析了灌喂HgCl2大鼠脏器组织中汞与MTs的积累量及金属与MTs的结合形态。结果表明,灌喂HgCl2大鼠各脏器中汞的积累量显著高于其相应的对照组,特别是在肾、肝和睾丸中汞的含量较高,表明此3个脏器受汞的危害最大。MTs的含量水平说明当大鼠脏器受汞污染时,肌体中的MTs将被大量诱导产生以对重金属进行解毒。通过SEC-ICP-MS联用技术获得了组织中的金属与MTs的结合形态,其     

大气臭氧化学研究进展

臭氧是大气化学中的核心物种。在平流层中，臭氧层可以吸收对生物有害的紫外辐射，对地球生命起保护伞作用。在对流层大气中，适量臭氧对清洁大气是有益的。但是，由于对流层中臭氧前体物排放量的增加，特别是在大城市，产生的高浓度臭氧会对大气环境造成严重污染，对人类、动植物和生态环境具有极大危害。臭氧的研究一般结合外场观测、实验室烟雾箱模拟和计算机数值模拟进行。深入开展大气臭氧化学研究，不仅有助于全面深入理解大气氧化过程以及全面掌握区域乃至全球大气自净能力，而且能为对流层污染控制提供科学依据和方案。本文总结了近年来有关臭氧化学的研究进展，论述了臭氧问题与人类当前面临的一些主要环境问题间的相互关系；重点综述了近年来有关南极臭氧空洞、中纬度地区臭氧低值和北极地区臭氧的损耗机理及其发展趋势；综述了臭氧与大气光化学和气溶胶间的耦合关系，并结合我国实际情况，提出了大气臭氧化学尚待深入开展研究的一些重要科学问题。     

Dynamics and density profile of water in nanotubes as one-dimensional fluid

The transport and structural properties of water confined in nanotubes with different diameters were studied by molecular dynamics (MD) simulation. The effects of pore size, molecule-wall interaction, and the helicity of CNT on the diffusivity, thermal conductivity, and shear viscosity as well as density profile were analyzed. For diffusivity, in model NT > in armchair CNT > in zigzag CNT at similar conditions. However in contrast to the diffusivity, the thermal conductivity and the shear viscosity increase as the pore size decreases, in zigzag CNT > in armchair CNT > (or approximately ) in model NT. The ordered layer distribution of water molecules in nanotubes is clear. It suggests the structure of fluid in the zigzag CNTs is more ordered, and more solidlike. In the nanotubes, where the molecule and the pore dimensions are of similar order of magnitude, the nature of water-water and water-wall interactions, the confinement effect of space, and the helicity of CNT become more significant.     

Liquid crystals in biology II. Origins and processes of life

Part II of this review elaborates a hypothesis presented in Part I (2003 Liq. Cryst. 30, 541) and earlier publications. This hypothesis proposes that specified naturally occurring substances in the aqueous lyotropic mesophase of the liquid crystalline state of matter possess the ability to replicate, polymerize spontaneously and engage in further transitions to form ordered two- and three-dimensional layered, cubic, helical and spherulitic structures resembling those described geochemically, and observed experimentally in elementary forms of living substance. This ability uses energy originating in the kinetics of particles showing Brownian movements, spin and tensions at liquid-liquid and solid-liquid interfaces. Energy is derived also from chemiosmosis, phosphorylation, negative entropy and bonding by covalent and electro-weak forces to build macromolecules in ordered sequences of lipids, peptides and nucleic acids. These can polymerize to form glyco- and lipo-proteins, polynucleotides, anabolic and catalytic enzymes, plausibly and causally associated with the morphogenesis, metabolism and replication of protista, plankton and other primitive forms of life observed in prebiotic pools and surfaces of the cooling litho-hydrosphere of planet earth.

Interactions in these ecological niches would undoubtedly promote biochemical evolution compatible with self-organization of diversified living processes. These phenomena reveal plausible, natural mechanisms for formation of bilayer membranes with ionic channels, and other ordered structures providing spaces in which oxidative reactions and syntheses may proceed. All of this can be linked causally to early steps in animation of matter in accordance with laws governing particle physics and chemistry, templates and the general logic of molecular memories expressed in polynucleotides and proteins. Phenomena indicative of transfer of information, cellular organization, metabolism and transmission of neural signals are identifiable additionally as mechanisms for diversification and evolution. There are, however, credibility gaps in trying to extend this reasoning to sexual reproduction, speciation, competitive survival and ontogeny in the higher plants and metazoa. Various probabilities are discussed in statistical and physico-chemical terms. It is suggested that these could justify the hypothesis in so far as natural processes are sufficient to engender conditions for emergence of primitive life and Darwinian evolution in eco-niches of terrestrial space and measurable time. But there are also, in the unique utilization of energy, exploitation of advantages and adaptive capabilities of organisms at all levels to changing environmental stresses, many indications of teleonomic forces operating in ways for which there is no explanation in accordance with the laws of physical or chemical processes. This might be because understanding of particle physics and wave mechanics is insufficiently deployed in molecular biology, or because the laws of physics are scientifically incomplete in this respect.     

The role of metrology in chemistry in the upholding of public health and food safety in Hong Kong

The Government Laboratory has been involved in the provision of analytical and advisory services since its formal establishment in 1913 in support of the needs of the community and the commitments of the Government of Hong Kong Special Administrative Region, China. One of the earliest areas of work involves the testing of food samples for maintenance of public health and food safety. Remarkable advances in technology in recent years coupled with the introduction of new policies and regulations, the launching of new international standards and requirements have all contributed to significant and ever-rising demand of accurate, specific, comparable and traceable measurements using the latest technologies for a wide variety of additives, contaminants, residues and genetically modified ingredients in food.Metrology, the science of measurement, has always played a key role in the development and validation of analytical methodologies in the Government Laboratory for the realization of its measurements to the highest level of accuracies and traceability to internationally recognized standards. Besides the application of the latest analytical technologies such as isotope dilution mass spectrometry, tandem mass spectrometry, real-time polymerase chain reactions, etc., the Analytical and Advisory Services Division of the Laboratory develops a quality assurance system in full compliance with the requirements of ISO/IEC 17025 and endeavours to ensure that every analytical methods are validated with the best applicable means and are fit for the intended purposes. In this presentation, the role and application of metrology in chemistry in the measurements pertaining to public health and food safety work undertaken by the Government Laboratory are discussed.Presented at International Symposium on Metrology in Chemistry, 2004 Beijing, China.     

Amount of sterols and triterpenoids in leaves and petioles of leaf-shedding and standard lines of cotton plant

The amount of free and bound sterols and triterpenoids in the leaf blades and petioles of the variety Tashkent-1 and the deciduous lines L-275 and L-470 in the budding-flowering, maturing, and leaf-fall phases have been compared. In the leaf blades, the maximum accumulation of free sterols in the deciduous lines is observed in an earlier phase than in the variety Tashkent-1, and this is most characteristic for sterols saturated in the C-17 side chain. The dynamics of the change in the content of unsaturated sterols is individual for each line. The nature of the change in the amount of free sterols in the petioles is typical for each line and does not depend on the nature of the sterol for the variety Tashkent-1 this index falls sharply in the leaf-fall phase while for L-275 the process is retarded between the second and third phases, and for L-470 in the same period the amount of these substances rises sharply. In the leaf blades, as a rule, the level of sterol esters changes in parallel with the levels of free sterols, and in the petioles in the antiparallel direction between the first and second phases. In all the samples free and bound amyrin was detected. The dynamics of the change in the amounts of these substances in the three lines were different.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Institute of Experimental Plant Biology, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, Vol. 6, pp. 796–805, November–December, 1989.     

Amount of sterols and triterpenoids in leaves and petioles of leaf-shedding and standard lines of cotton plant

The amount of free and bound sterols and triterpenoids in the leaf blades and petioles of the variety Tashkent-1 and the deciduous lines L-275 and L-470 in the budding-flowering, maturing, and leaf-fall phases have been compared. In the leaf blades, the maximum accumulation of free sterols in the deciduous lines is observed in an earlier phase than in the variety Tashkent-1, and this is most characteristic for sterols saturated in the C-17 side chain. The dynamics of the change in the content of unsaturated sterols is individual for each line. The nature of the change in the amount of free sterols in the petioles is typical for each line and does not depend on the nature of the sterol for the variety Tashkent-1 this index falls sharply in the leaf-fall phase while for L-275 the process is retarded between the second and third phases, and for L-470 in the same period the amount of these substances rises sharply. In the leaf blades, as a rule, the level of sterol esters changes in parallel with the levels of free sterols, and in the petioles in the antiparallel direction between the first and second phases. In all the samples free and bound amyrin was detected. The dynamics of the change in the amounts of these substances in the three lines were different. Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Institute of Experimental Plant Biology, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, Vol. 6, pp. 796–805, November–December, 1989.     

《高分子材料近代测试技术》课程教学改革初探

《高分子材料近代测试技术》是高分子材料专业的一门实用性强且有着重要学科意义的基础课程。本论文以提高教学质量、锻炼学生的专业实验能力和创新能力、培养高素质学科人才为目的,针对目前该课程存在的教学问题,在教学内容、教学方法、实践性教学及考核等方面进行了一系列的改革,并探讨了实践的效果。     

High frequency titration methods in the investigation of complex formation

High frequency titration is a valuable tool in the study of complex formation in solutions, and the breaks in the titration curves can be used, in conjunction with the results of other physical methods, to determine the composition of the complexes formed. High frequency titration and other methods have been used to study the complexes formed by thorium, indium, plutonium(V) and boron with various complexing agents, and to develop methods for the determination of thorium and yttrium in rare earth mixtures, and of indium in the presence of zinc, cadmium, aluminium, nickel and cobalt.     

Some peculiarities of metal migration in the aerobic and anaerobic conditions in the surface water bodies

The results of research on metal migration (Mn, Cu, Zn, Pb, Cr) in the surface water bodies of the different type (the Kiev and the Kanev reservoirs of the Dnieper cascade, and Verbnoye and Telbin lakes of the Kiev city) in dependence on their oxygenous regime are considered. It was shown that the metal migration in the aerobic conditions is mainly directed from water thickness to bottom sediments. In contrast, the migration of metal compounds from bottom sediments in the anaerobic conditions is increased. Manganese is mostly in a form of free ions Mn²⁺ in the pore solutions, therefore, it migrates from bottom sediments in the greatest extent. The migration of other studied metals occurs in a much smaller extent and depends on the migration mobility of organic substances which they are bound to complexes. Migration mobility of copper, lead and chromium decreases essentially when the hydrogen sulphide is in the water of bottom layer. The data on a degree of metal binding to complexes and their chemical nature in water of reservoirs and lakes are given. The greater part of metals is found to be in complex compounds with humic substances in water of the Dnieper reservoirs, whereas in the lakes a share of neutral (mainly with carbohydrates) and cationic (mainly with protein-like substances) complexes essentially increases. The distribution of metals is explained by distinction in a component composition of dissolved organic matters in the reservoirs and in the lakes.     

Structure and fluorescence properties of merocyanine dyes derived from dimethylbarbituric acid

The fluorescence properties of positively and negatively solvatochromic di-, tetra-, and hexamethinemerocyanines derived from 1,3-dimethylbarbituric acid in solvents of various polarities were studied. The range of solvatofluorochromic effect for these compounds is narrower than the range of solvatochromic effect. Extension of the polymethine chain of these compounds causes in the fluorescence spectra, in contrast to the absorption spectra, an increase in vinylene shifts, a decrease in deviations, and band narrowing. The electronic structure of the merocyanines was analyzed by the AM1 method. Transitions between the ideal states (neutral polyene, polymethine, and charged polyene) were examined. The electronic structure of the merocyanines in the excited state was found to approach the cyanine limit. Its attainment accounts for a sharp increase in the quantum yields of the fluorescence and a decrease in the Stokes shifts in going to higher vinylogs, and also with an increase in the solvent polarity for positively solvatochromic merocyanines and with its decrease for the negatively solvatochromic derivatives.     

Interactions between carbonic anhydrase and its inhibitors revealed by gel electrophoresis and circular dichroism

Structural properties, and especially the differential stability, of complexes between carbonic anhydrase (CA) and three sulfonamide inhibitors, acetazolamide, dorzolamide and methazolamide, were investigated by spectroscopic and electrophoretic techniques. These included denaturant gradient gel electrophoresis either across a urea or a steady-state transverse sodium dodecyl sulfate (SDS) gradient. Acetazolamide, the smallest and most hydrophilic of the sulfonamides, forms the most stable complex in the presence of urea, whereas dorzolamide, with a bulky and hydrophobic structure, is most stable against the effects of SDS. At pH 7.4, complexes with dorzolamide show minimal changes in mobility across the SDS gradient, as if unaffected by the detergent, both in the presence and in the absence of excess ligand in the gel. When bound to both acetazolamide and methazolamide, on the other hand, CA displays an increase in mobility above 0.05% SDS, lower in the presence than in the absence of excess ligand. The finding of a distinct pattern for the unliganded enzyme, however, suggests the complexes can still retain the ligand, although binding of the surfactant changes their charge density. Under saturating conditions and in the presence of SDS, the surface charge of all complexes is much lower than for unliganded, denatured CA. Circular dichroism (CD) spectra clearly indicate that the increase in secondary structure and the decrease in tertiary structure brought about in CA by the presence of low concentrations of SDS are largely prevented by complexing with the inhibitors. These observations point out peculiar properties of each CA inhibitor, of potential value in the definition of their biological activities and also in the potential development of novel antagonist molecules.     

Membrane lipids are both the substrates and a mechanistically responsive environment of TMEM16 scramblase proteins

Recent discoveries about functional mechanisms of proteins in the TMEM16 family of phospholipid scramblases have illuminated the dual role of the membrane as both the substrate and a mechanistically responsive environment in the wide range of physiological processes and genetic disorders in which they are implicated. This is highlighted in the review of recent findings from our collaborative investigations of molecular mechanisms of TMEM16 scramblases that emerged from iterative functional, structural, and computational experimentation. In the context of this review, we present new MD simulations and trajectory analyses motivated by the fact that new structural information about the TMEM16 scramblases is emerging from cryo-EM determinations in lipid nanodiscs. Because the functional environment of these proteins in in vivo and in in vitro is closer to flat membranes, we studied comparatively the responses of the membrane to the TMEM16 proteins in flat membranes and nanodiscs. We find that bilayer shapes in the nanodiscs are very different from those observed in the flat membrane systems, but the function-related slanting of the membrane observed at the nhTMEM16 boundary with the protein is similar in the nanodiscs and in the flat bilayers. This changes, however, in the bilayer composed of longer-tail lipids, which is thicker near the phospholipid translocation pathway, which may reflect an enhanced tendency of the long tails to penetrate the pathway and create, as shown previously, a nonconductive environment. These findings support the correspondence between the mechanistic involvement of the lipid environment in the flat membranes, and the nanodiscs. © 2019 Wiley Periodicals, Inc.     

FTIR studies of zeolite matrix effects on the properties of palladium clusters confined in the supercages of NaX and NaY

Palladium clusters have been synthesized by the "ship-in-a-bottle" approach in the supercages of NaX and NaY faujasite zeolites. In comparison with CO adsorbed on a bulk Pd electrode, the same molecule adsorbed on the Pd clusters electrodes evoked an enhanced IR absorption (EIRA). The enhancement factors have been determined to be about 38 and 51 in NaX and NaY, respectively. IR band centers of linear-bonded CO, bridge-bonded CO, and multi-bonded CO in NaX are measured, respectively, 12, 14, and 11 cm(-1) lower than those of the corresponding adsorption modes in NaY. The adsorption of CO and the oxidation of adsorbed CO in NaX matrix are faster than that in NaY matrix. These results suggest that part of the Pd2+ ions in NaX are located in sites III and III' that are near the 12-ring window of the supercage of zeolite, which lead to the formation of small Pd clusters. The present study is of significant importance in exploring the dependence of catalyst properties on structures, as well as in understanding and predicting the locations and properties of metal clusters in zeolites.