Polymorphism of lactate dehydrogenase in gelada baboons

In a group of 21 gelada baboons, three different lactate dehydrogenase patterns were observed after starch-gel electrophoresis of tissue extracts. The patterns indicate that a mutation has occurred in this population in the gene responsible for the A-subunit. The normal and variant homozygotes each contain five isozymes, those containing the A subunit having characteristically different electrophoretic mobilities. The heterozygote contains the expected 15 isozymes.     

Efficient activation of aromatic C-H bonds for addition to C-C multiple bonds

Efficient electrophilic metalation of aromatic C-H bonds leading to new C-C bond formation through regio- and stereoselective addition to alkynes and alkenes has been realized by a catalytic amount (0.02 to 5 mole percent) of palladium(II) or platinum(II) compounds in a mixed solvent containing trifluoroacetic acid at room temperature. Various arenes undergo unexpected selective trans hydroarylation to terminal or internal C&cjs0812;C bonds inter- and intramolecularly with high efficiency (up to a turnover number of 4500 for palladium), especially for electron-rich arenes, giving thermodynamically unfavorable cis-alkenes, and the oxygen- and nitrogen-containing heterocycles. The simplicity, generality, and efficiency of this process should be very attractive to the possible industrial application for the functionalization of arenes.     

Photolytic cleavage of sulfonamide bonds

It has been found that the sulfonamide bond is relatively susceptible to photolytic cleavage. The breakdown was effected either by irradiation with a source having a continuous emission above the wavelengths of 1800 angstroms or by another source emitting principally at 2537 angstroms. Less destruction of the amino acids was seen with the latter relative to the sulfonamide bond cleavage. The cleavage was not effected by irradiation at wavelengths greater than about 3000 angstroms. Side reactions were noted involving decarboxylation, demination, and destruction of certain susceptible amino acids such as tryptophan. In only one case was a product found that arose from cleavage of a carboxamide bond; glycyltyrosine gave glycine and tyrosine upon irradiation. A yield of 75 percent of the corresponding amino acid has been obtained by irradiation of tosylhistidine; yields of 75 to 100 percent have been obtained from sulfamic acid (NH(2)SO(3)H). A qualitative method for identifying sulfonylated amino acids is described.     

Symmetries of hydrogen bonds in solution

The nuclear magnetic resonance method of isotopic perturbation can distinguish between single- and double-well potentials in intramolecularly hydrogen-bonded monoanions of dicarboxylic acids. These are classic cases of a "strong," symmetric hydrogen bond in the crystal. The observed carbon-13 isotope shifts induced by the substitution of oxygen-18 demonstrate that these monoanions exist as a single symmetric structure in a nonpolar solvent but as two equilibrating tautomers in aqueous solution. The change is attributed to the disorder of the aqueous environment. These are simple counterexamples to the hope that the crystal structure reveals the actual molecular structure in aqueous solution.     

Probing and controlling the bonds of an artificial molecule

We demonstrate how molecular quantum states of coupled semiconductor quantum dots are coherently probed and manipulated in transport experiments. The applied method probes quantum states by the virtual cotunneling of two electrons and hence resolves the sequences of molecular states simultaneously. This result is achieved by weakly probing the quantum system through parallel contacts to its constituting quantum dots. The overlap of the dots' wave functions and, in turn, the splitting of molecular states are adjusted by the direct influence of coupling electrodes.     

The use of hypnosis to enhance recall

The forensic use of hypnosis is increasing. A hypermnesic procedure was used in an experiment that calls this practice into question. Subjects tried for a week to recall 60 previously presented pictures. They were then either hypnotized or not and encouraged to recall even more pictures. Most of the newly recalled material was incorrect, especially for highly hypnotizable subjects in the hypnosis condition. Such errors in recall can have profound implications for forensic investigations.     

An engineered pathway for the formation of protein disulfide bonds

We have engineered a pathway for the formation of disulfide bonds. By imposing evolutionary pressure, we isolated mutations that changed thioredoxin, which is a monomeric disulfide reductase, into a [2Fe-2S] bridged dimer capable of catalyzing O2-dependent sulfhydryl oxidation in vitro. Expression of the mutant protein in Escherichia coli with oxidizing cytoplasm and secretion via the Tat pathway restored disulfide bond formation in strains that lacked the complete periplasmic oxidative machinery (DsbA and DsbB). The evolution of [2Fe-2S] thioredoxin illustrates how mutations within an existing scaffold can add a cofactor and markedly change protein function.     

Isolation of a benzene valence isomer with one-electron phosphorus-phosphorus bonds

A tetraphosphabenzene analog of the postulated anti-tricyclohexylene, a singlet biradical valence isomer of benzene, has been isolated. The tricyclic derivative features one-electron phosphorus-phosphorus bonds, which result from the pi*-pi* interaction between two diphosphirenyl radicals. Such one-electron bonds may play a wider role in phosphorus chemistry.     

外语教师专业发展的途径

在调查问卷、座谈和课堂观察基础上,指出我国英语教师专业发展中存在的突出问题,提出英语教师专业发展的途径：充实英语学科知识;加强敬业精神;建立教师学习共同体;开发和运用教学策略。     

提高漏磁检测器通过能力的方法

介绍了17”(φ426)高清晰度管道漏磁检测器的机械结构和性能指标,指出通过能力是其机械性能的重要指标.以该检测器在陕西某天然气管网内检测工程和东北某天然气管网内检测工程的实际应用为例,总结了其存在的问题:支撑力不足,皮碗磨损严重,检测器易停球等.据此,提出了改进措施:使用刚度更大的压簧增加第1排支撑轮的支撑力,但使用效果不佳;采用环形钢刷或类似支撑作为电池驱动节的支撑系统,可使检测器的运行状态远远优于采用支撑轮作为支撑的情况;改变皮碗形状,使用支撑力更强的皮碗结构,或通过增加直皮碗的方式增强支撑力,是最简便而直接的方法,取得了较好的应用效果.     

Catalytic activation of carbon-fluorine bonds by a soluble transition metal complex

Homogeneous catalytic activation of the strong carbon-fluorine bonds under mild conditions was achieved with the use of rhodium complexes as catalysts. The catalytic reactions between polyfluorobenzenes and hydrosilanes result in substitution of fluorine atoms by hydrogen atoms and are chemo- and regioselective. With individual stoichiometric steps observed and combined, and with intermediates isolated and fully characterized (including crystal structures), these systems demonstrate the effectiveness of a rational approach to catalytic design.     

Revealing the angular symmetry of chemical bonds by atomic force microscopy

We have measured the angular dependence of chemical bonding forces between a carbon monoxide molecule that is adsorbed to a copper surface and the terminal atom of the metallic tip of a combined scanning tunneling microscope and atomic force microscope. We provide tomographic maps of force and current as a function of distance that revealed the emergence of strongly directional chemical bonds as tip and sample approach. The force maps show pronounced single, dual, or triple minima depending on the orientation of the tip atom, whereas tunneling current maps showed a single minimum for all three tip conditions. We introduce an angular dependent model for the bonding energy that maps the observed experimental data for all observed orientations and distances.     

Adrenal medulla grafts enhance recovery of striatal dopaminergic fibers

The drug, 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP), depletes striatal dopamine levels in primates and certain rodents, including mice, and produces parkinsonian-like symptoms in humans and nonhuman primates. To investigate the consequences of grafting adrenal medullary tissue into the brain of a rodent model of Parkinson's disease, a piece of adult mouse adrenal medulla was grafted unilaterally into mouse striatum 1 week after MPTP treatment. This MPTP treatment resulted in the virtual disappearance of tyrosine hydroxylase-immunoreactive fibers and severely depleted striatal dopamine levels. At 2, 4, and 6 weeks after grafting, dense tyrosine hydroxylase-immunoreactive fibers were observed in the grafted striatum, while only sparse fibers were seen in the contralateral striatum. In all cases, tyrosine hydroxylase-immunoreactive fibers appeared to be from the host rather than from the grafts, which survived poorly. These observations suggest that, in mice, adrenal medullary grafts exert a neurotrophic action in the host brain to enhance recovery of dopaminergic neurons. This effect may be relevant to the symptomatic recovery in Parkinson's disease patients who have received adrenal medullary grafts.     

Copulatory vocalizations of chacma baboons (Papio ursinus), gibbons (Hylobates hoolock), and humans

The copulatory vocalizations of female baboons (Papio ursinus) are more complex than those of female gibbons (Hylobates hoolock) or human females. Adult males of all these species begin calling later than the female, but subordinate baboon males do not call. Copulatory vocalizations may serve to mutually stimulate the mating partners or to incite male competition.     

提高党的执政能力的若干思考

社会转型期,党的执政环境、执政基础和执政条件发生了深刻变化,迫切需要加强党的执政能力建设。加强党的执政能力建设,必须增强执政效益意识:注重体制创新,实现发展效益;强化规则意识,实现法治效益;扩大群众参与,实现民主效益;激活人才机制,实现用人效益。     

The retina of the newborn human infant

We have examined a pair of eyes from a normal, full-term infant who died at 8 days as a result of accidental injury. Eyes were obtained immediately after death, fixed, and sectioned for light microscopy. Results from both eyes were substantially the same. The macular region was still drastically immature at 1 week. Even though a foveal depression existed, all cell layers were still present across it. Furthermore, the inner nuclear layer was divided into two separate layers. The receptor layer was reduced to one or two cells thick; receptors had both inner and outer segments, but they were very short and stumpy. The region of immaturity covered about 5 degrees of the retina. These findings suggest that the central region of a human infant's retina is probably not fully functional at birth.