Transition metal speciation in the cell: insights from the chemistry of metal ion receptors

The essential transition metal ions are avidly accumulated by cells, yet they have two faces: They are put to use as required cofactors, but they also can catalyze cytotoxic reactions. Several families of proteins are emerging that control the activity of intracellular metal ions and help confine them to vital roles. These include integral transmembrane transporters, metalloregulatory sensors, and diffusible cytoplasmic metallochaperone proteins that protect and guide metal ions to targets. It is becoming clear that many of these proteins use atypical coordination chemistry to accomplish their unique goals. The different coordination numbers, types of coordinating residues, and solvent accessibilities of these sites are providing insight into the inorganic chemistry of the cytoplasm.     

ON THE BASIS FOR THE PHYSIOLOGICAL ACTIVITY OF CERTAIN ONIUM COMPOUNDS

(1) An outline is given of an extended, cooperative investigation now being made on the basis for the physiological activity of onium compounds on the nervous system. (2) Evidence has been obtained which shows that the process is much less simple than is indicated by a number of theories that have been advanced to explain drug action. (3) It would appear that the action of these substances is not due either to their chemical decomposition, their activity as bases or to their distribution coefficients. The mobility of their ions is not, at least, of primary significance. To be physiologically active, these substances must exist in the body fluids as cations. (4) Indirect evidence is given of the necessity of taking into account the probable differences of structure of the mechanism of the nervous system on which these substances act, or (and) the environment at the seat of action. (5) The probability that the first determining factor in the action of these compounds is something in the nature of a selective adsorption depending on the spacial configuration of the groups involved in the ion structure is suggested. The author wishes to express his appreciation to the directors of the Bache Fund of the National Academy of Science for grants made to aid the experimental work of this investigation.     

PHYSIOLOGY OF THE AMINO ACIDS

We have followed the amino acids from their entrance into the alimentary tract in the form of food proteins through the successive steps of digestion, absorption into the blood stream and passage from the blood stream into the tissues, where they are concentrated by some unknown mechanism to many times their concentration in the blood plasma. We have seen something of the way in which certain of the amino acids can be transformed into one another in the body or synthesized from ammonia and keto acids. However, we have had to admit that our bodies can form in such ways only about half of the different amino acids that are required, and that the other half must be made for us by plants, bacteria or other organisms which have greater synthetic powers than we. And finally we have seen something of the manifold fates of the amino acids after they have entered our tissues; how they may be destroyed and their nitrogenous parts turned into urea in the liver before it is possible to put them to their more specialized uses, how their carbon fractions can be used to form glucose, how they may sacrifice themselves to protect us from toxic products, how they can serve as source material for certain vitamins, hormones and other compounds with physiological functions still to be identified, and how finally those amino acids which are not deflected to these various fates may enter into the proteins of the tissues and become for a time parts of our living structures.     

食品动物组织中兽药结合残留的毒性

动物性食品中兽药残留对人类健康的影响日益被人们所重视。动物用药后,其体内可能存在两类残留:第一类是以游离或结合形式存在的原药及其主要代谢物;除高亲脂性化合物外,因代谢和排泄迅速,这些代谢物出现得早,且不在动物体内蓄积。但这些物质具有毒性,且在人体内可生成高度活化的中间产物（亲电子基团、自由基等）,导致核酸、蛋白质烷基化、膜脂质过氧化等,从而对消费者具有潜在的危害性;第二类包括出现较晚的共价结合代谢物（结合残留）,其排出相对较慢。它们的存在对于靶动物预示着潜在的毒性作用,而对于消费者,由于结合残留在人体内不可能再活化,以及其生物利用度和含量均低,因而可能只显示很低的毒性。     

Liquid chromatography in 1982

Classical liquid chromatography gave rise 15 years ago to new ideas about high-speed separations. Today, difficult separations can be made almost routinely by use of liquid chromatography instruments with automated controls and sensitive detectors. Sorptive effects are often best achieved with small, porous, "bonded phase" particles. The trend is to control the chemical selectivity by means of the liquid phase. These techniques are easily learned, and they have been widely accepted throughout chemistry and its allied disciplines. As a result, liquid chromatography has become the most rapidly expanding branch of the chemical instrumentation field.     

THE METAL CARBONYLS

When the metal carbonyls were first discovered, their properties were startling because they seemed to violate nearly all the previously recognized generalizations of chemistry. Even to-day the existence of the carbonyls is not particularly emphasized in elementary courses of chemistry because it is rather hard to reconcile them with the first presentations of the generalizations of chemistry. Nevertheless, as the student progresses deeper into the knowledge of chemistry it becomes desirable to include the knowledge of the carbonyls both because they become more comprehensible when viewed in the light of Werner's system of coordination and because they themselves contribute to the comprehension of the Werner theory. As long ago as 1931, Reiff in his discussion of cobalt nitrosyl carbonyl recognized the correlation between the effective atomic number and the volatility of carbonyls. A more recent study of charged Werner coordination complexes, that is, of complex ions, has shown a similar role of the effective atomic number. We are standing on fairly firm ground when we point out the correlation between E.A.N. and the volatility of the carbonyl complexes and the existence of complex ions. Be it noted that we have made no postulates as to the arrangement of the electrons in quantum levels. In the inert gases the outer principal quantum group is supposed always to contain eight electrons. In the carbonyls and other Werner complexes there is no compelling reason to suppose that the electrons in the coordinating layer, be this layer of eight, ten, twelve or sixteen electrons, are not all at the same energy level. Although we have confined our discussion almost exclusively to the property of volatility, the carbonyls are very interesting from the standpoint of several other properties, for example, magnetic susceptibility and dielectric constant. Enthusiasts in the interpretation of such properties try to draw conclusions as to the condition of the electrons, sometimes they become so dogmatic as to seem really.to believe in the actual existence of the condition they postulate. As Professor Smith said, "Theories come and theories go, but facts live on forever." The facts of chemistry are so multitudinous that we would be utterly helpless to use them had we not means of correlating them. Any postulates which reach beneath the surface of the directly observable to give a mechanism to correlate the facts are helpful. But a scientist without a sense of humor is pretty hopeless. Who in his right mind can regard as other than absurd the idea that an electron pair can simultaneously occupy positions in two atom shells to make up the supposedly necessary number in each atom? In fact, is not the electron itself a pretty ridiculous figment of the imagination? To be sure, we recognize the electron as a discrete entity with certain very definite properties, but in the light of comparison with any mechanism within our comprehension is not the electron perfectly impossible? By all means let us use a postulate which allows us to make a useful classification of facts, but never let us lose the sense to see how utterly ridiculous the postulate will look to one who has not like ourselves grown attached to it. We do not expect ever to discover the ultimate reason for things, but we do expect ever to make progress in correlating and classifying the facts which we have already discovered and shall continue to discover. Dogmatic belief in ridiculous postulates retards this progress.     

7种菜用豆中凝集素活性的比较

菜用豆中的豆科凝集素主要存在于豆粒中,加工不当易引起食用者中毒。通过血凝试验对7种菜用豆中凝集素的活性进行了测定和比较,确定了凝集素提取液中的凝集素最适检测浓度。结果表明,7种菜用豆中凝集素的活性各不相同,刀豆样品中凝集素活性最强,凝集效价为27,蚕豆样品最弱,为23。     

微生物技术在烟草种植中的应用探究

由于我国科学技术的快速发展,在生物技术领域的研究也取得了很大的进步,微生物技术也 逐渐被广泛应用在农业生产之中。由于微生物可以在土壤中分解一些有害的物质,有效改变土壤环 境,从而促进农作物的生产量以及提供农作物的综合质量,所以也开始在烟草种植中逐步实施。对 此,本文对微生物技术在烟草种植中的应用进行探究,希望能为利用微生物技术进行烟草种植提供参 考作用。     

Use of Trichoderma spp. in remediation of polluted soils and waters

Trichoderma spp. probably have a role in remediation of polluted soils and waters. Highly rhizosphere competent strains persist on roots for an extended period of time (at least months) and continuously interact with the plants. They can increase general plant and root growth and increase uptake of a variety of materials. This makes the Trichoderma-plant interaction highly attractive for use in phytoextraction technologies. Moreover, Trichoderma spp. are resistant to a wide range of toxic…     

Silica-like malleable materials from permanent organic networks

Permanently cross-linked materials have outstanding mechanical properties and solvent resistance, but they cannot be processed and reshaped once synthesized. Non-cross-linked polymers and those with reversible cross-links are processable, but they are soluble. We designed epoxy networks that can rearrange their topology by exchange reactions without depolymerization and showed that they are insoluble and processable. Unlike organic compounds and polymers whose viscosity varies abruptly near the glass transition, these networks show Arrhenius-like gradual viscosity variations like those of vitreous silica. Like silica, the materials can be wrought and welded to make complex objects by local heating without the use of molds. The concept of a glass made by reversible topology freezing in epoxy networks can be readily scaled up for applications and generalized to other chemistries.     

Research Status Quo and Future of Low Temperature Wheat Genotypes

Low temperature wheat genotypes are a group of wheat with a slightly low canopy （plant） temperature, and the research on their biological characters and utilization in wheat breeding has been done at home and abroad for more than 20 years, and has made great progress. The research contents and advances include the following respects： Wheat genotypes with slightly low canopy temperature have been verified to exist in nature; these wheat genotypes, which present cold temperature, are superior to conventional wheat materials in some important biological characters and particularly prominently in metabolic function and cellular structure; when they suffer stresses such as drought, high temperature and overcast and rainy weather, they still retain their superiority in some of their important biological characters and therefore have a wide range of ecological adaptability; slightly low canopy temperatures of these genotypes are closely correlated with low temperatures of their second heat sources and their vigorous plants; since their low canopy temperatures can be inherited, they can exert favorable influence on the temperatures of their offspring while crossing with other wheat materials, and in particular, the discovery of cold-source wheat as a contributor to low temperature, has further formed good conditions for breeding high and stable quality low temperature wheat varieties with a high and stable yield. Thus, low temperature wheat genotypes are of great research importance and have great prospects.     

担子菌中甲羟戊酸途径影响萜类物质合成的研究

担子菌中具有多种萜类活性物质,这些活性物质对人类的营养和健康有着很重要的影响。甲羟戊酸途径是担子菌合成萜类物质的一条主要途径,萜类物质的含量水平受到甲羟戊酸途径的控制,但是生物细胞内萜类物质的产量很低,并且目前活性萜类物质的化学以及生物合成方法效率低、成本高,因此为了能够更好的增加萜类物质在担子菌细胞内的产量,介绍了担子菌甲羟戊酸途径中乙酰辅酶A、HMG\|CoA、甲羟戊酸激酶影响萜类物质的合成作用,旨在通过调控这些物质来增加目标萜类物质的产量。     

Male Esterase 6 Catalyzes the Synthesis of a Sex Pheromone in Drosophila melanogaster Females

Esterase 6, a component of the seminal fluid of Drosophila melanogaster males, hydrolyzes cis-vaccenyl acetate, a lipid made only by males, to cis-vaccenyl alcohol. This reaction occurs in the female reproductive tract and is virtually complete within 6 hours after copulation. Both the alcohol and the acetate decrease the number of matings among pairs of virgin flies in which the female is treated topically with these substances. Although females tested 10 minutes after copulation elicit less courtship than virgin females, females tested 6 hours after copulation stimulate even less courtship if they received active esterase 6 in the seminal fluid of their respective mates. Either the alcohol or a derivative appears to be an antiaphrodisiac that decreases courtship elicited by inseminated females and thus reduces the probability of further mating. Thus the activity of the pheromone depends on a final reaction which occurs in the female, using both substrate and enzyme provided by the male.     

Hydroxamic acids in nature

The hydroxamic acid bond occurs in products from fungi, yeast, bacteria, and plants. The -CON(OH)-bond arises by oxidation of a free or bound amino group in a unit structure which is often closely related to conventional amino acids. Products are known with one, two, or three hydroxamic acid groups per molecule. The chemistry of the ferrichrome type compounds, which are ferric trihydroxamate-containing peptides, has been worked out in detail and includes a complete crystallographic analysis of the ferrichrome A molecule. The trihydroxamates form potent complexes with ferric ion, called siderochromes, and these are believed to play a role in the metabolism of the metal ion in microorganisms. The actual physiological activity observed ranges from that of growth factor, antibiotic, antibiotic antagonist, tumor inhibitor or cell-division factor. The precise molecular mechanism whereby these substances exert their potent beological activity remains to be elucidated.     

Cancer therapy: a possible new approach

Two substances, one promoting growth (promine) of ascites tumors in mice and the other inhibiting it (retine) have both been found in several tissues, namely, thymus, aorta, muscle, and tendon. In spite of similar solubilities in the solvents used for their extraction, the substances could be roughly separated. The value of the ratio between these substances in the same tissue may be significant.     

浅述利用植物对受污染土壤中重金属的修复

对于土壤中积累的大量有毒有害物质,尤其是重金属污染物,由于其对人类具有潜在的威胁,已经越来越多地引起了人们的关注。目前,处理重金属污染主要是一些物理化学方法,它们虽各有优点,但不同程度地存在投资费用高、操作运行难、易产生2次污染等缺点。近年来出现的植物修复则可以满足这一需要,尽管植物修复会受到植物种类、植物根系分布、污染物种类等影响,但已有研究表明,与传统的处理技术相比,该技术在环境保护中具有重要的理论价值和广阔的实用前景。     

生物质居里点热裂解研究

[目的]为生物质裂解的机理分析提供理论基础。[方法]利用JHP-5型居里点裂解仪,在不同的居里点温度下研究杨木屑及其磨木木质素的裂解。同时,在试验的裂解温度范围内研究温度对主要裂解液相产物的影响。[结果]通过GC-MS在线分析裂解的液相产物显示2,种原料的液相产物都为酚类物质,产物基本相同,只是杨木屑的酚类物质种类较多,并且有糠醛产生。液相产物的相对含量随温度的升高都表现为先增加后减少的变化规律,温度为445～590℃时液相主要产物的相对含量较大。[结论]居里点热裂解与气质联用分析技术已成为木质化学研究领域一个固定的技术。     

Drugs in the brain

In our studies on the entry of drugs into the central nervous system we have found the technique of autoradiography combined with radioassay to be a valuable research tool. It has disclosed such unsuspected phenomena as the dual routes of entry into the brain of acetazolamide. Although many factors controlling drug entry remain to be studied, we propose certain general conclusions. 1) The anatomical boundaries of brain are clearly reflected by the penetration and accumulation of all compounds we have studied-a finding that confirms the original proposition that whole-brain homogenates are inadequate for the study of drug and brain relationships. 2) Circulation, expressed as egional blood flow or volume of capillary blood, was seldom decisive in nfluencing entry or accumulation of exogenous substances in the brain. To date, the only compounds demonstrated to be circulation-dependent are trifluoroiodomethane and thiopental. Both are extremely fat-soluble. Tissue binding appears to be an additional factor in the case of thiopental. 3) Penetration is retarded by myelin. All substances we have studied have shown a relatively slower rate of entry into this tissue. In immature brain, before myelinization has taken lace, the primordial white matter is readily penetrated. We have suggested that entry into mature white matter is retarded by the lamellated membranes of the myelin sheath, which should be regarded, therefore, as a component of the blood-brain barrier. The small interstitial space indicated by the limited entry of sulfate ion is an additional hindrance to dispersal of exogenous substances into brain parenchyma. The blood-brain barrier is a complex anatomical, physiological, and biochemical phenomenon, and no unitary hypothesis is adequate to embrace all the observed events. 4) Accumulation of a drug in the brain implies some form of binding or interaction between drug and tissue. Findings on injection of phenobarbital, thiopental, or diphenylhydantoin illustrate such an accumulation. These binding interactions may be nonspecific, as is probable in the case of drugs bound to plasma protein. However, a more fundamental significance is suggested when a drug is found to bind, react with, or accumulate in, a specific anatomical structure of the brain. We have made reference to this possibility in connection with the localization of isonicotinic acid hydrazide or its metabolites in the hippocampus (46), and we have also reported the striking accumulation of acetazolamide in hippocampus, caudate nucleus, and hypothalamus. Although the binding process is poorly understood, further investigation of these phenomena should lead to a clearer understanding of regional variations in brain chemistry. While one should not assume that the demonstration of a focal concentration of a drug implies site of action, correlation between pharmacological action, electrophysiological events, biochemical changes, and temporal and regional drug concentrations may indeed exist (47).     

五元氮杂环的芳香性和稳定性

自然界中许多含有五元环的有机物都具有芳香性,其中这些五元环大部分是由（CH）单元和N原子组成的.（CH）单元和N原子是等电子体,笔者对一些五元杂环及其正负离子的稳定性和芳香性的规律进行了详细的研究.选用从头算和密度泛函理论方法,用cc-pVDZ基组对五元氮杂环及其正负离子的几何结构进行了优化,同时对它们的能量和频率进行了计算,得到了一些具有稳定平面结构的氮杂环和其正负离子.并在相同的计算水平下,对这些稳定结构的核独立化学位移（NICS）和谐振子模型的芳香性（HOMA）进行了计算,利用这两个判断标准对这些结构的芳香性进行了讨论,并得到了有关这些结构的稳定性和芳香性的一些规律.     

Intermetallic compounds for high-temperature structural use

The next generation of efficient turbines and engines will require materials that can withstand operating temperatures approaching 2000 degrees C. Intermetallic compounds with high melting temperatures are candidates for this application, but the obstacle of their limited ductility must first be overcome. Because the available data on these materials is limited, a survey of the effects of chemistry and crystal structure must be performed. With the use of melting temperature and density as figures of merit, the most likely candidates have been identified for preliminary screening.