Glycolate and Thioglycolate Complexes of Rhenium and Their Oxidative Elimination of Ethylene and of Glycol

Selenium dioxide and osmium tetroxide are effective reagents and catalysts for olefin oxidation, although, owing to their toxicity, reservations remain as to their applicability.^[1] We are therefore seeking more easily handled metal oxides that are soluble in organic solvents and that are as effective as osmium tetroxide in carrying out stereospecific cis hydroxylation of olefins. The rhenium(VII ) oxide 1 , which has meanwhile become readily accessible, is a favorable candidate.^[2]     

Rotation and contraction of native and regenerated cellulose fibers upon swelling and dissolution: the role of morphological and stress unbalances

Upon swelling and dissolution, native cellulose fibers such as cotton hairs or wood fibers are rotating and contracting. Regenerated cellulose fibers are only contracting, not rotating. Cotton hairs show two rotation mechanisms, a well known untwisting, not seen in wood fibers, due to the unwinding of the twists initially induced by the desiccation that occurs at the end of the growth, and a “microscopic rotation” that can also be slightly observed in wood fibers. In addition to these rotation mechanisms, cotton hairs and wood fibers show a rolling up of their primary wall that is due to the higher elongation of the external layers as compared to the internal layers arising during the elongation phase of the cell. Contraction originates from the fact that the cellulose chains are in an extended conformational state due to the spinning process for the regenerated fibers and to the bio-deposition process for native fibers. The contraction is related to the relaxation of the mean conformation of cellulose chains from an extended state to a more condensed state. Physical as well as mechanical modeling will support the experimental observations.     

Catalytic Synthesis of Organolithium and Organomagnesium Compounds and of Lithium and Magnesium Hydrides—Applications in Organic Synthesis and Hydrogen Storage

A recent development in homogeneous catalysis is the discovery of catalysts that are active for the lithiation of 1-alkenes to alkenyllithium compounds and lithium hydride as well as for the hydrogenation of lithium and magnesium under mild conditions. The catalytically prepared magnesium hydride is highly reactive and adds to 1-alkenes to give diorganomagnesium compounds and can also be used in the preparation of, for example, silane and “active” magnesium. The use of metal hydrides in hydrogen storage is discussed: hydrogenation/dehydrogenation experiments show that the catalytically prepared magnesium hydride (which can be doped with a second metal) can be used as a high-temperature hydrogen storage material.     

广山药中16种元素的分析比较

用原子吸收法和分光光度法测定了5个产地的广山药及怀山药中16种元素的含量，并进行了比较。发现广山药及怀山药中均含有Mn,Fe,Zn,Ca,Cu,Mg,P,Se等元素，5个产地的广山药中的Cu/Zn值均低于正常人血清的Cu/Zn，这些元素可能是怀山药，广山药具有补脾养胃，生津益肺，补肾涩精，治疗糖尿病等功效的物质基础之一；广山药长期作为山药的一个品种同等入药，食用是有科学根据的；广山药，怀山药中含有一定量的As,Hg。     

Synthesis and thermal characterization of new ternary chelates of piroxicam and tenoxicam with glycine and DL-phenylalanine and some transition metals

The ternary chelates of piroxicam (Pir) and tenoxicam (Ten) with Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) in the presence of various amino acids such as glycine (Gly) or dl-phenylalanine (PhA) were prepared and characterized with different physicochemical methods. IR spectra confirm that Pir and Ten behave as a neutral bidentate ligand coordinated to the metal ions via the pyridine-N and carbonyl group of the amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its deprotonated carboxylic group. In addition, PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its deprotonated carboxylic and amino groups. The solid reflectance spectra and magnetic moment measurements confirm that all the chelates have octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. Thermal behaviour of the complexes is extensively studied using TG and DTA techniques. TG results show that water molecules (hydrated and coordinated) and anions are removed in the first and second steps while Gly, PhA, Pir and Ten are decomposed in the next and subsequent steps. The pyrolyses of the chelates into different gases are observed in the DTA curves as exo- or endothermic peaks. Also, phase transition states are observed in some chelates. Different thermodynamic parameters are calculated using Coats-Redfern method and the results are interpreted.     

Toxic and Phototoxic Properties of the Protozoan Pigments Blepharismin and Oxyblepharismin*

Abstract— The toxic and phototoxic properties of blepharismin and oxyblepharismin that were purified from the pigments of a ciliated protozoan, Blepharisma japonicum, by thin-layer chromatography, were investigated in detail. The toxicity was tested against the ciliated protozoan Dileptus margaritifer, which is relatively sensitive to blepharismin. Although oxyblepharismin has been believed to be neither toxic nor phototoxic, it was found that oxyblepharismin is toxic in the dark and is also phototoxic. This shows that oxyblepharismin can act as a photosensitizer. The toxicity and phototoxicity of these pigments were compared with those of hypericin, which is known to be a typical, strong photosensitizer from plants. It was concluded that blepharismin and oxyblepharismin have strong intrinsic toxicities in the dark compared with hypericin, but their phototoxicities are slightly weaker than that of hypericin. This strong intrinsic toxicity supports our proposal that blepharismin acts as a defensive device against predators in the dark as well as in the light. The decrease in the defensive ability and the increase in the resistance to photokilling of Blepharisma concomitant with its color change from red to blue-purple in response to weak illumination can be explained by the decrease in toxicity and phototoxicity of the pigment itself and by the decrease in amount of the pigment.     

Reactivities and biological functions of iron-sulfur clusters

Iron-sulfur clusters are prevalent in biological systems. Through studies of iron-sulfur proteins and synthetic model clusters, it was realized early on that these clusters functioned as facile electron transfer agents. Until recently it was widely thought that they served exclusively in that capacity. However, in the last decade, it has become clear that their reactivities and biological functions are much more diverse. It is now apparent that these clusters can serve as the active sites of enzymes, as well as in the regulation of enzymatic activity. Synthetic clusters, which have been shown to undergo a variety of core rearrangements or structural changes, have provided insight into possible mechanisms of cluster formation or activity regulation in enzymes. Rigid tripodal ligands have been constructed which capture synthetic iron-sulfur clusters in a cavity which permits controlled reactivity studies. In this article, we review these recent developments and suggest some future directions the field may take.     

Interpenetrating and pseudo-interpenetrating polymer networks of polyethylacrylate and zeolite 13X

Free radical polymerization of liquid ethylacrylate in the presence of zeolite 13X yielded PIPNs without crosslinker and IPNs if the crosslinker ethylene glycol dimethacrylate was present. We studied these materials both unextracted as well as partially extracted with a variety of solvents using DSC, SEM as well as Small Angle X-ray Scattering (SAXS). These studies suggest that in the composites polyethylacrylate chains entered the internal pores of the zeolite. These chains had an extended state and did not exhibit a bulk glass transition, a similar behavior to that previously reported for polystyrene/zeolite 13X composite. © 1996 John Wiley & Sons, Inc.     

Infrared and Raman spectra of 8-azaguanine and 8-azaadenine

The IR and Raman spectra of 8-azaguanine and 8-azaadenine have been studied. The spectra of 8AG have been critically examined and compared with those of guanine and 9-methylguanine. Similarly, the spectra of 8-azaadenine have been examined and compared with those of adenine and 9-methyladenine. It has been possible to refute or accept the assignments for certain frequencies proposed earlier in the parent molecules by other workers, and thus almost unambiguous assignments for several frequencies in guanine and adenine as well as in 8AG and 8AA have been obtained. Several frequencies have been explained as combinations involving a 130 cm⁻¹ vibration which has been assigned to the ring-folding mode. It is found that not as many combination bands involving this mode occur in 8AA as those in 8AG. These observations indicate that guanine and 8AG are geometrically more flexible than adenine and 8AA.     

Knotting and threading of molecules: chemistry and chirality of molecular knots and their assemblies

How and why do molecules tangle or thread? Investigations of molecular knots (knotanes) may shed some light on the mechanisms of (supra)molecular templation and the folding of molecules that result in intertwining. The topological chirality of these fascinating molecules leads to new types of isomerism and paves the way to nanosized molecular motors. Their preparation and derivatization makes high demands on modern synthetic methods and analytical separation since molecular knots are formed in a more or less planned design based on metal coordination or hydrogen‐bonding patterns. This Review describes the development of templation techniques for the synthesis of knotanes and their chiral resolution as well as their selective functionalization and use as building blocks in the synthesis of higher knotane assemblies. Such assemblies can possess linear, branched, or even macrocyclic structures which, on the one hand, introduce unprecedented isomeric compositions that arise from multiple topological stereogenic units and, on the other, define new types of artificial macromolecules beyond polymers and dendritic species.     

Electron localization and radiation chemistry of amides

Alkylamides (such as N,N'-dimethylformamide, N,N'-diethylformamide, and N,N'-dimethylacetamide) are aprotic solvents that are widely used in organic synthesis. These polar molecules have no electron affinity, and it is believed that irradiated liquid and solid amides stabilize excess electrons as cavity-type species analogous to hydrated and ammoniated electrons. In this study, we use isotope substitution and EPR spectroscopy to demonstrate that, in frozen amides, the suspected "cavity electron" is, in fact, a solvent-stabilized monomer anion. Our observations call into question other attributions of such features in the literature, both in low temperature solids and room temperature liquids. We also provide a general scheme describing amide radiolysis, as the related amides are used as metal ion extracting agents in nuclear separations.     

Chemistry and biology of wortmannin

Recent synthetic and biological studies of the viridin class of steroidal furans have revealed multiple opportunities for fundamental discoveries as well as advanced drug design. Wortmannin is a potent enzyme inhibitor that binds to the ATP site of important regulatory kinases such as PI-3 kinase and Polo-like kinase. The natural product shares a unique mechanism-based biological activation pathway with other viridins. Furthermore, while there have been several encouraging approaches toward the total synthesis of these compounds, there is still ample room for improvements in synthetic strategies and tactics, and the development of structurally simplified analogs that exert more specific biological effects and are devoid of toxicity issues that have thwarted the clinical development of the parent compounds.     

药物和蛋白质与聚己内酯分层复合纳米纤维的微观结构与力学特性

应用同轴共纺技术制得芯质和表层为两种不同材料的分层复合纳米纤维.分别以乙酰螺旋酶素片剂和明胶蛋白质为芯质材料,以可生物降解的聚己内酯作为表层材料,研究了这种分层复合纳米纤维的微观结构与力学特性.结果表明,尽管药物与表层聚合物材料的溶解溶剂互不相同,但仍可以将药物包覆在壁厚小于100nm的超细纤维中.这种纤维可用作体内手术伤口缝合线或大面积创伤如烧伤伤口的敷布.在实验范围内,纤维膜的力学性能随芯质内溶质含量的提高而降低.     

Synthesis and MALDI-TOF-MS of PS-PMA and PMA-PS block copolymers

The synthesis of well-defined block copolymers from styrene and methyl acrylate via ATRP is discussed in this contribution. Kinetic studies on these block copolymerizations as well as characterization studies were performed to investigate the monomer composition in the respective PS and PMA blocks. MALDI-TOF-MS was performed to clarify the exact number of repeating units of each block and the total number of units in the block copolymer. Block copolymers up to 22 kDa could be analyzed by MALDI-TOF-MS, whereby polymers with PMA as first block showed a large second distribution corresponding to PMA homopolymers. However, SEC demonstrated that only a small amount of homopolymer was present indicating that care needs to be taken with interpreting MALDI-TOF-MS data, which is a qualitative rather than a quantitative technique.     

水分散体系中苯乙烯和甲基丙烯酸甲酯梯度共聚物的合成与表征

以2-溴代异丁酸乙酯(EBiB)为引发剂,CuBr/CuBr₂/1,10-邻二氮菲(phen)为复合催化剂,十二烷基磺酸钠(SLS)为乳化剂,考察了水分散体系中苯乙烯(St)和甲基丙烯酸甲酯(MMA)的原子转移自由基共聚合的可控性和相对反应活性.在此基础上,通过反应进料法在水分散体系中进行了St和MMA的梯度共聚合,反应表现出“活性”聚合的特征,即所得共聚物的数均分子量随着单体转化率的增加而增大,分子量分布较窄(M_w/M_n<1.50).用¹HNMR跟踪分析了聚合反应过程中共聚物微观组成的变化规律,结果表明,共聚物链中MMA链节的累积含量和瞬时含量都随着共聚物相对链长的增加而增加,即随着聚合物相对链长的增加共聚物的微观组成从St链节占主导地位逐渐变化为以MMA链节占主导地位,表明确实形成了St和MMA的梯度或渐变共聚物.     

Synthesis and autoconversions of furanthiols and -selenols

Furanthiols and selenols have been synthesized by a modified procedure via organolithium derivatives, with the formation of trimethylsilyl ethers as intermediate products. It has been shown that the thiols as well as the selonols undergo autoconversions when standing in air and in the presence of triethylamine with the formation of furylthio-(seleno)-substituted thio-(seleno)-butyrolactones.Institute of Organic Chemistry, Irkutsk 664033. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 891–895, July, 1994. Original article submitted June 2, 1994.     

3D-ASL灌注成像和血清Hcy、NPY水平与癫痫患者病情及认知功能的相关性探究

选取我院108例癫痫发作患者作为研究组,同期82例健康体检者设为对照组,均接受3D-ASL灌注成像检查和血清同型半胱氨酸(Hcy)、神经肽(NPY)水平检测。结果发现,研究组患者平均脑血流量(CBF)和简易智能精神状态检查量表(MMSE)评分低于对照组,血清Hcy、NPY水平高于对照组(P<0.05);癫痫发作患者CBF、Hcy、NPY与发作类型、脑电图特征存在一定相关性(P<0.05);患者病程、发作频率、发作类型、痫性放电、发作持续时间、用药种类、癫痫持续状态史、受教育程度、Hcy、NPY、CBF均是癫痫认知障碍的重要影响因素(P<0.05)。可见,早期共同检测3D-ASL灌注成像、血清Hcy、NPY,可为癫痫的临床诊治、病情程度评估、预后改善提供循证指导。     

柔红霉素和阿霉素自旋标记衍生物的合成与抗肿瘤活性

合成了5个新的柔红霉素及阿霉素的氮氧自由基自旋标记衍生物(5_9),经元素分析,IR,MS和ESR分析确证了其组成和结构,并对它们进行了抑制小鼠白血病P388、小鼠黑色素癌B16、人胃腺癌MGC和人肝癌SMMC7721细胞的体外筛选.初步药理试验表明,化合物5_9对4种瘤株均有一定的抑制活性,其中化合物9的活性与阿霉素相当.     

Comparison of PBDE congener profiles and concentration levels in human specimens from China and the US and identification of human exposure sources

In an effort to investigate the status of human exposure to PBDEs in China,available monitoring data in human specimens(including breast milk,serums,and blood) was collected from the general population as well as specific groups that are occupationally exposed.PBDEs exposure profiles and concentration levels were compared with their counterparts in the United States of America.It was found that PBDE burdens in general Chinese population are one order lower and have different congener profiles from that in t...