Duchenne muscular dystrophy involving translocation of the dmd gene next to ribosomal RNA genes

Duchenne muscular dystrophy (DMD) is a severe X-linked disorder leading to early death of affected males. Females with the disease are rare, but seven are known to be affected because of a chromosomal rearrangement involving a site at or near the dmd gene on the X chromosome. One of the seven has a translocation between the X and chromosome 21. The translocation-derived chromosomes from this patient have been isolated, and the translocation is shown to have split the block of genes encoding ribosomal RNA on the short arm of chromosome 21. Thus ribosomal RNA gene probes may be used to identify a junction fragment from the translocation site, allowing access to cloned segments of the X at or near the dmd gene and presenting a new approach to the study of this disease.     

Catalysis by small metal clusters

Experimental and theoretical studies of small clusters of metal atoms are aimed at revealing how properties change in the ultrafinely divided state. Thermodynamic, electronic, and structural features can be size-dependent and may be involved in determining the activity of small-particle catalysts. Correlations between these properties give indications of the features important in catalysis.     

交联酶聚集体的生物催化

对一种崭新的无载体酶固定化技术——聚集体(Cross-linked Enzyme Aggregates,CLEAs)技术进行了文献综述。CLEAs技术是一种将蛋白质先沉淀后交联形成不溶性的、稳定的固定化酶。交联酶聚集体技术现已用于大量的合成反应。在沉淀和交联所需但具有潜在致变性化学品缺失的情况下,融合蛋白会将目的酶的相对选择性聚集体或其自组系统转为不溶性微粒,因而具有强劲的发展动力。在选定的生物转化中,用于多轮间歇式反应不溶蛋白颗粒的回收已经得到论证。然而,对于全连续生物催化过程应用来说,低耐机械应力和高压缩性依然是无载体酶颗粒所需要考虑的问题。     

头孢三嗪聚乙二醇催化合成研究

研究了聚乙二醇催化合成头孢三嗪的工艺,探讨了聚乙二醇分子量,用量,反应温度及反应时间等对缩合产物收率的影响。当用聚乙二醇－８００作为相转移催化剂,在二氯甲烷－水溶剂中于０℃反应４￣６ｈ收率９４％。     

化学催化制备鱼油三甘酯

[目的]用化学催化方法制备鱼油三甘酯。[方法]采用酯交换反应,以鱼油乙酯和醋酸三甘酯为原料,制备三甘酯型鱼油,同时研究催化剂种类及用量(基于醋酸三甘酯的质量)、反应温度、物料比(油乙酯和醋酸三甘酯的摩尔比)、反应时间对鱼油三甘酯制备的影响,并通过液相色谱对鱼油三甘酯产物的成分进行定量分析。[结果]制备鱼油三甘酯的最佳条件为:催化剂为甲醇钠,用量为三甘酯质量的3.0%,反应温度为100℃,物料比为鱼油乙酯过量5%(相对于醋酸三甘酯),反应时间为2 h。在此最佳条件下制备产物三甘酯含量大于80%。[结论]通过此方法可实现鱼油乙酯向鱼油三甘酯的转化,成本较低,扩大了鱼油类产品在医药和保健品中的应用。     

Sequence-directed DNA translocation by purified FtsK

DNA translocases are molecular motors that move rapidly along DNA using adenosine triphosphate as the source of energy. We directly observed the movement of purified FtsK, an Escherichia coli translocase, on single DNA molecules. The protein moves at 5 kilobases per second and against forces up to 60 piconewtons, and locally reverses direction without dissociation. On three natural substrates, independent of its initial binding position, FtsK efficiently translocates over long distances to the terminal region of the E. coli chromosome, as it does in vivo. Our results imply that FtsK is a bidirectional motor that changes direction in response to short, asymmetric directing DNA sequences.     

脂肪酶法制备生物柴油进展

脂肪酶催化法制备生物柴油具有反应条件温和,操作简单,环境友好等优点。综述了脂肪酶的选择,比较了游离酶与固定化酶的特点,分析了影响酶催化效率的因素。尤其对离子液体体系以及纳米粒子技术在生物柴油制备中的最新进展进行了相应介绍。     

Catalysis of ester hydrolysis by mixed micelles containing N-alpha-myristoyl-L-histidine

Model compounds are described for the study of the properties of amino acid side chains in the surface of micelles. Mixed micelles of N-(alpha)- mnyristoyl-L- histidine and cetyltrimethylammonium bromide catalyze the hydrolyses of p-nitrophenyl acetate and p-nitrophenyl caprylate at much higher rates than imidazole or histidinie do. The reaction shows a kinetic behavior similar to that of surface-catalyzed reactions.     

固体碱法制备生物柴油组分生成动力学

[目的]探讨固体碱法制备生物柴油中组分油酸甲酯的生成动力学。[方法]以精制菜籽油和甲醇为原料,固体碱CaO/MgO作催化剂,菜籽油与甲醇在固体碱催化下进行酯交换反应制备生物柴油,用气相色谱法跟踪分析生物柴油(脂肪酸甲酯)的含量,考察生物柴油中组分油酸甲酯的生成动力学。[结果]动力学研究表明,固体碱CaO/MgO催化菜籽油和甲醇的酯交换反应速率方程为rA=dCp/dt=k1CA2。反应速率动力学方程分3个阶段,反应开始为引发阶段,逐步转变为增长阶段的2级反应,最终反应达到平衡阶段。油酸甲酯增长阶段反应活化能为58.48 kJ/mol,频率因子为9.18×105 L/(mol.min)。[结论]该研究为固体碱催化菜籽油与甲醇酯交换反应的动力学提供了理论基础。     

Catalysis of the olivine to spinel transformation by high clinoenstatite

Although enstatite is a major constituent of the Earth's upper mantle and subducting lithosphere, most kinetic studies of olivine phase transformations have typically involved single-phase polycrystalline aggregates. Transmission electron microscopy investigations of olivine to spinel and modified spinel (beta phase) reactions in the (Mg, Fe)(2)SiO(4)-(Mg,Fe)SiO(3) system show that transformation of olivine in the stability field of spinel plus phase begins with coherent nucleation of spinel on high-clinoenstatite grains. These observations demonstrate that high clinoenstatite can catalyze the transformation by enhancing nucleation kinetics and therefore imply that secondary phases can influence reaction kinetics during high-pressure mineral transformations.     

Analysis of hydrothermal vent-associated symbionts by ribosomal RNA sequences

Ribosomal RNA (rRNA) sequences were used to establish the phylogenetic affiliations of symbioses in which prokaryotes appear to confer sulfur-based chemoautotrophy on their invertebrate hosts. Two submarine hydrothermal vent animals, the vestimentiferan tube worm Riftia pachyptila and the clam Calyptogena magnifica, and a tidal-flat bivalve, Solemya velum, were inspected. 5S rRNA's were extracted from symbiont-bearing tissues, separated into unique forms, and their nucleotide sequences determined and related to other 5S rRNA's in a phylogenetic tree analysis. The prokaryotic symbionts are related to one another and affiliated with the same narrow phylogenetic grouping as Escherichia coli and Pseudomonas aeruginosa. The sequence comparisons suggest that Riftia is more closely related to the bivalves than their current taxonomic status would suggest.     

Chromosomal translocation in domestic fowl induced by x-rays

The effect of x-rays at various voltages and intensities, with monochromatic and polychromatic beams, on Ektachrome daylight and artificial-light film was investigated. The colors were rated according to the Munsell color system and ranged over all the spectrum except red. The color in terms of hue, value, saturation, and chroma was a function of wavelength as well as intensity, and thus the method may be useful in dosimetry as well as in radiography. Microradiographs of metals and wood were remarkable in showing detail not obtainable with conventional black-and-white photographic emulsions.     

Catalysis by transition metals: metal-carbon double and triple bonds

Several well-characterized transition metal catalysts contain a metal-carbon double bond or a metal-carbon triple bond. In other homogeneous (or heterogeneous) catalyst systems in which the metal is likely to be in a relatively high oxidation state, such as molybdenum(VI) or tungsten(VI), metal-carbon multiple bonds may play an important role. Some recent results suggest that even supposedly well understood reactions such as ethylene polymerization may actually involve catalysts that behave as if they contained a metal-carbon double bond instead of a metal-carbon single bond. The chemistry of metal-carbon double and triple bonds should eventually complement and perhaps. overlap the known chemistry of complexes containing metal-oxygen double bonds or metal-nitrogen triple bonds, respectively; unique catalytic reactions involving carbon, nitrogen, and oxygen ligands multiply bonded to transition metals are therefore possible.     

土壤呼吸的酶促作用研究

在介绍土壤酶的来源与环境因子对土壤酶影响的基础上,探讨了土壤呼吸的酶促作用,旨在为相关研究提供参考。     

酶法催化蓖麻油生产生物柴油的研究

[目的]优化酶法催化蓖麻油生产生物柴油的条件。[方法]从种植蓖麻试验地土壤中分离出1株脂肪酶产生菌(Pseudomonassp.)H-4,以其发酵液制备的固定化酶为催化剂,催化蓖麻油与甲醇转酯化生产生物柴油,研究该酶的转酯能力。[结果]薄层检测和气相色谱检测表明,该脂肪酶具有催化蓖麻油与甲醇发生酯交换反应制备蓖麻油酸甲酯的功能。随着反应时间的延长,酯交换率不断升高。甲醇分3次加入,酯交换率最高(78%)。反应温度40℃,酯交换率最高(81%)。酶添加量0.6 g,酯交换率最高(85%)。[结论]在醇油摩尔比3∶1,甲醇分3次加入,固定化酶添加量0.6 g,反应温度40℃,150 r/min条件下反应10 h,油脂的酯交换率达85%。     

Recognition of cognate transfer RNA by the 30S ribosomal subunit

Crystal structures of the 30S ribosomal subunit in complex with messenger RNA and cognate transfer RNA in the A site, both in the presence and absence of the antibiotic paromomycin, have been solved at between 3.1 and 3.3 angstroms resolution. Cognate transfer RNA (tRNA) binding induces global domain movements of the 30S subunit and changes in the conformation of the universally conserved and essential bases A1492, A1493, and G530 of 16S RNA. These bases interact intimately with the minor groove of the first two base pairs between the codon and anticodon, thus sensing Watson-Crick base-pairing geometry and discriminating against near-cognate tRNA. The third, or "wobble," position of the codon is free to accommodate certain noncanonical base pairs. By partially inducing these structural changes, paromomycin facilitates binding of near-cognate tRNAs.     

Mammalian ribosomal protein: analysis by electrophoresis on polyacrylamide gel

Ribosomal protein from five mammalian tissues when analyzed by discontinuous electrophoresis on polyacrylamide gel at pH 4.5 yielded 24 bands. Densitometric tracings indicated that the patterns of the basic ribosomal proteins from the several tissues were qualitatively similar. Protein from Escherichia coli ribosomes analyzed at pH 4.5 gave 29 bands, and the pattern was different from that of mammalian ribosomal protein. No distinct band was found when mammalian ribosomal protein was analyzed at pH 8.3 (acidic proteins). Ribosomal protein from Escherichia coli gave eight bands at pH 8.3. Thus, the structure of the genes responsible for synthesis of ribosomal protein in several mammalian tissues is the same, and different genes direct synthesis of ribosomal protein in bacteria.     

废食用油碱与酶催化法制备生物柴油

以废食用油为原料,分别用碱催化和酶催化酯化法制取生物柴油,比较两种方法的优缺点.碱催化法实验周期短、成本低,且生物柴油转化率高,但存在废液污染,所得生物柴油质量较差;而酶法催化环保无毒,制得的生物柴油质量好,但用时长、成本高.生产中可以通过酶的预处理、重复利用提高反应效率,降低生产成本.