p-Benzoquinone in aqueous solution: Stark shifts in spectra, asymmetry in solvent structure

Results from a simulation of p-benzoquinone (PBQ) in water is presented. An explicit solvent representation is used together with a multiconfigurational ab initio quantum chemical method. The electronic n --> pi* transitions are studied in aqueous solution and the two such transitions are both blue-shifted but to different degree. Both non-equilibrium and many-body effects are found to have decisive influence on the solvation: despite stronger hydrogen bonding between solute and solvent in an excited state than in the ground state, there is a blue-shift, and the solvent structure around the non-polar PBQ is asymmetric, which is argued to come from special many-body effects. The unusual result of strengthened hydrogen bonds in the excited state that follows from an excitation of a non-bonding electron on a proton acceptor, is explained by the near-linear Stark shift that is present in the transition.     

Use of NAA in marine environment and in archaeology in Greece

Neutron activation analysis (NAA) is a very sensitive and accurate multielement analytical method that is widely applied to the investigation of environmental and archaeological problems. The first part of this paper is a review of pollution studies of toxic trace elements in sediments, seawater and marine organisms of Saronikos Gulf, Greece by NAA. The second part of this paper is a review of provenance studies based on minor and trace element research in ancient ceramics, obsidian, flint, limestone, marble and lead by Instrumental NAA, performed at the NCSR Demokritos.     

University-level education in nuclear and radiochemistry in Slovenia

Summary The status of education in nuclear and radiochemistry in Slovenia is reviewed and elucidated at both undergraduate and graduate levels. It is observed that both the quantity and the quality of studies have deteriorated during recent years/decades, thus following similar trends in the developed countries. Presently, no dedicated study of radioactivity is offered within the country. The main reason for this deterioration is a general decline of interest for studying nuclear sciences and the limited need for such specialization in a small country such as Slovenia.     

Recent Advances in in situ multi-spectroelectrochemistry

To consider the past, present and future of in situ spectroelectrochemistry, a review on the recent state of modern spectroelectrochemistry and trends in the development of spectroelectrochemcial techniques is presented for the combined application of different in situ spectroelectrochemcial methods like ESR spectroelectrochemistry, NMR spectroelectrochemistry, Raman spectroelectrochemistry or IR spectroelectrochemistry to electrode systems. Starting with a discussion of the first steps in spectroelectrochemistry in the past, the main part of this review is focused on the advantages of the combined application of spectroelectrochemical techniques in the analysis of electrode reactions. The spectroelectrochemical methods are demonstrated to be successful in electrode reactions both for solid structures like polymers or carbon nanotubes and for molecular structures like fullerenes and oligothiophenes. The final outlook is attributed to future developments in spectroelectrochemistry.     

Protein splicing in cis and in trans

Intein-mediated protein splicing is a self-catalytic process in which the intervening intein sequence is removed from a precursor protein and the flanking extein segments are ligated with a native peptide bond. Splice junction proximal residues and internal residues within the intein direct these reactions. The identity of these residues varies in each intein, as groups of related residues populate conserved motifs. Although the basics of the four-step protein splicing pathway are known, mechanistic details are still unknown. Structural and kinetic analyses are beginning to shed some light. Several structures were reported for precursor proteins with mutations in catalytic residues, which stabilize the precursors for crystallographic study. Progress is being made despite limitations inherent in using mutated precursors. However, no uniform mechanism has emerged. Kinetic parameters were determined using conditional trans-splicing (splicing of split precursor fragments after intein reassembly). Several groups concluded that the rate of the initial acyl rearrangement step is rapid and Asn cyclization (step 3) is slow, suggesting that this latter step is rate limiting. Understanding the protein splicing pathway has allowed scientists to harness inteins for numerous applications.     

Azobenzenes in a new light-switching in vivo

Two bands make light work: since the isomerization of azobenzenes is usually induced by UV light, its application is limited in living systems. A new azobenzene switch now operates entirely in the visible range. The new design is based on the introduction of OMe groups in the ortho positions, which splits the n-π* transition into two absorption bands. The two isomeric forms can be obtained with more than 80 % enrichment from the respective photostationary state.     

Trends in Structural Polymer Science in Industry

Plastics production has grown rapidly in the past 30 years. The versatility of plastics which is not exceeded by any other class of materials, guarantees that polymers will continue to be very important in the future. However, at present a distinct change is taking place in polymer research and development. While in the pioneering days of plastics new polymer properties were determined by the choice of suitable monomers, today the commercialization of polymers from new monomers is restricted to a few specialities with a rather modest production volume. On the other hand, the number of new polymers derived from old monomers is increasing very rapidly. The development of highly selective catalysts and advances in reactor technology have provided the means for producing new tailor-made polymers. The same is true regarding new polymer blends and alloys based on old polymers: blending immiscible polymers yields materials with property profiles superior to the features of the individual components. Using selected examples, this paper will discuss trends, possibilities and challenges for structural polymer research in industry. © 1997 John Wiley & Sons, Ltd.     

Context-dependent photodimerization in isolated thymine-thymine steps in DNA

The effect of 280 nm irradiation on a family of synthetic DNA hairpins possessing an alkane linker connecting a six-base pair stem having a single T-T step located at different positions within the hairpin has been investigated. A single adduct assigned to the product of 2+2 dimerization is obtained except in the case of a T-T step located adjacent to the linker, in which case both 2+2 and 6-4 adducts are obtained. The efficiency of dimerization is similar for three hairpins having a T-T step located within the duplex interior. Lower efficiency is observed for a T-T step located at the open end of the hairpin and in T overhangs, whereas higher efficiency is observed for the T-T step adjacent to the linker and in a single T bulge. The context-dependence of dimerization efficiency is discussed.     

我国化学生物学研究新进展

作为化学领域的一门新兴二级学科,化学生物学已经成为具有举足轻重作用的交叉研究领域,是推动未来生命和化学学科发展的重要动力。近年来,我国的化学生物学研究正在以前所未有的速度蓬勃发展,在基础建设、人才培养、研究经费支持等方面都有了长足的进步。尤其是以国家自然科学基金委"基于化学小分子探针的信号转导过程研究"重大研究计划为依托,我国的化学生物学工作者以小分子探针为工具,充分发挥化学与生命科学等多学科综合交叉的优势,对细胞信号转导中的重要分子事件和机理进行了深入的探索,在一些前沿方向上取得了突出的成绩,相关研究结果多次发表在顶级的国际期刊上。本文对近两年来我国化学生物学领域取得的突出进展加以归纳和介绍:(1)基于小分子化合物及探针的研究。利用有机化学手段,通过设计合成一系列多样化的小分子化合物,以这些探针为工具深入开展了细胞生理、病理活动的调控机制、细胞关键信号转导通路及重要靶标、抑制剂和标记物的发现、基于金属催化剂的活细胞生物分子激活等方面的研究;(2)以化学生物学技术为手段,着重发展了针对蛋白质、核酸和糖等生物大分子的合成、特异标记与操纵方法,用以揭示这些生物大分子所参与的生命活动的调控机制;(3)采用信号传导过程研究与靶标发现相结合,以实现"从功能基因到药物"的药物研发模式,发展了药物靶标功能确证与化合物筛选的联合研究策略;(4)以化学分析为手段,发展了在分子水平、细胞水平或活体动物水平上,获取生物学信息的新方法和新技术。这些研究成果极大地推动了我国化学生物学的进步。共引用63篇参考文献。     

Recent Advances in Analytical Methodology for in vivo Electrochemistry in Mammals

Electrochemistry is one of the most advanced techniques for monitoring neurochemical activities in the living brain because electrochemical approaches bear the advantageous features of high spatial and temporal resolutions, which facilitate its tremendous potential in investigating the highly spatially heterogeneous brain system and the fast dynamics of neurochemical activities. On the other hand, since brain is the most complicated organ in the sense of its numerous kinds of neurochemical species, high selectivity is always required for any analytical methods that approach the brain. In this review, we will discuss various electrochemical methodologies to achieve selective detection of neurochemicals in mammalian brain and the strategies developed mainly by our group towards selective monitoring of both electrochemically active and inactive neurochemicals. At the end, we will discuss possible solutions towards brain mapping of neurochemical species and combination of neurochemical detection strategy with electrophysiology as the direction of future development of electroanalysis in living brain.     

Conformational changes in humic acids in aqueous solutions

Conformational changes in humic acids in two different aqueous solutions (NaCl and NaOH) are studied by means of high resolution ultrasound spectrometry. The method is based on the measurement of parameters of ultrasonic waves propagating through the sample. The attenuation describes the decay of the amplitude of the ultrasonic wave with the distance travelled. The velocity is the speed of this wave and is related to the wavelength and the frequency of oscillation of the deformation. It is determined by the density and elasticity of the sample, which is strongly influenced by the molecular arrangement. The minimal velocity of ultrasound was observed at 1 g dm^?3 for lignitic humic acids and at 0.5 g dm^?3 for IHSS Leonardite standard. The values of compressibility as computed are almost constant up to humic acids?? content corresponding to the minimum velocity of ultrasound and then decrease with the increase in concentration. This shows that the organisation of particles in diluted and concentrated humic acids sols is different. The decrease in compressibility points to the formation of a more rigid structure, which could lead to the decrease in humic acids?? binding ability. It was confirmed that the method employed was very sensitive and could be utilised as an indicator of conformational changes in humic acids in solutions with varying concentrations.     

Recent development in photosensitive resin in Korea

The aim of the review is to introduce some recent progress in the photosensitive polymers in Korea. It is focused to review the research works performed recently in this country, especially in the academic world. As photosensitive polymers, cinnamates of various polymers, azides and diazido compounds, oximeesters or oxime containing polymers, and some other sensitizing polymers were treated, and also sensitizing effects were evaluated.     

Radiochemistry in chemistry and chemistry related undergraduate programmes in Argentina

Summary The evolution of education in Argentina at the university level is described. The detailed search of the educational offer shows that less than half of the universities (35 out of 92) include chemistry and chemistry related undergraduate programmes in their curriculum. The revision of the position of radiochemistry in these programmes reveals that only seven courses on radiochemistry are currently offered. Radiochemistry is included only in few programmes in chemistry and biochemistry. With respect to the programmes in chemical engineering the situation is worse. This offer is strongly concentrated in Buenos Aires and its surroundings.     

汞的环境生化分析进展

汞是一种毒性很大的环境内分泌干扰物,全球环境中存在各种形式的汞已经严重地威胁着人类的健康.因此,发展高灵敏度、高选择性检测汞的分析新方法对环境监测和临床医学研究具有十分重要的意义.对近年来环境中汞的生化分析方法进展作了综述,引用文献61篇.     

Nuclear interactions used in in vivo activation analysis

A brief review of nuclear interactions applied in in vivo activation analysis is presented. 38 interactions for the determination of 20 elements are listed. The classification of the interactions is discussed in terms of the type of interaction, radiation used for activation and objects analyzed.     

Redox indicators in titrations in aqueous nitric acid

Iron(II) in nitric acid solution can be titrated with dichromate (and vice versa), diphenylamine, N-phenylanthranilic acid, ferroin, or brucine being used as indicator. Fluoride is added when one of the first three is used, and urea if the last is used. Citric, oxalic and tartaric acids, arsenic(III) and mercury(I) interfere in the titration.     

Extra-thermodynamic relationships in chromatography enthalpy-entropy compensation in gas chromatography

The phenomenon of enthalpy-entropy compensation in gas chromatography is examined. Using 53 probe solutes that span a wide range in size (dispersive interaction), dipolarity, hydrogen-bond-donor and hydrogen-bond-acceptor strength, enthalpy-entropy compensation is not observed, while for probe solutes within a homologous series enthalpy-entropy compensation is observed as predicted by the linear salvation energy relationship methodology.     

Detection of mitochondrial caspase activity in real time in situ in live cells.

Apoptosis plays an important role in many physiological and pathological processes. The initiation and execution of the cell death program requires activation of multiple caspases in a stringently temporal order. Here we describe a method that allows real-time observation of caspase activation in situ in live cells based on fluorescent resonance energy transfer (FRET) measurement using the prism and reflector imaging spectroscopy system (PARISS). When a fusion protein consisting of CFP connected to YFP via an intervening caspase substrate that has been targeted to a specific subcellular location is excited with a light source whose wavelength matches the cyan fluorescent protein (CFP) excitation peak, the energy absorbed by the CFP fluorophore is not emitted as fluorescence. Instead, the excitation energy is absorbed by the nearby yellow fluorescent protein (YFP) fluorophore that is covalently linked to CFP through a short peptide containing the caspase substrate. Cleavage of the linker peptide by caspases results in loss of FRET due to the separation of CFP and YFP fluorophores. Using a mitochondrially targeted CFP-caspase 3 substrate-YFP construct (mC3Y), we demonstrate for the first time that there is caspase-3-like activity in the mitochondrial matrix of some cells at very late stage of apoptosis.     

钙与人体及临床

钙是宏量元素，是人体中含量较高的元素之一，体内99％的钙构成骨骼和牙齿以及维持骨骼结构，1％的钙调节人体重要生理功能。钙的含量过高或过低都与许多疾病有关，只有保持一种平衡状态，才能使机体处于正常环境。     

Determination of active titanium in titanium powder used in pyrotechnics

Possible approaches to the problem of determining active titanium in titanium powder used for pyrotechnics are discussed. A method is proposed for the determination whereby the sample is dissolved in a mixture of fluoboric and sulfurie acids and the volume of hydrogen evolved in the reaction measured. An improved eudiometer is described.