Non-coherent visible and infrared radiation increase survival to UV (254 nm) in Escherichia coli K12

Interactions between visible or infrared (IR) and ultraviolet (UV, 254 nm) radiation have been studied in E. coli. Pre-illumination with non-coherent monochromatic 446, 466, 570 and 685 nm radiation, as well as with polychromatic red and IR radiation at room temperature, leads to increased cell survival after a subsequent irradiation with UV light. In the thermic range of the spectrum (red and IR), IR but not red light pre-treatment is able to increase cell survival to a subsequent lethal heat (51 degrees C) challenge, suggesting that increased UV survival may be due to IR-induced heat-shock response. On the other hand, visible-light-induced resistance may be due to a different mechanism, possibly involved with unknown bacterial light receptors.     

用C60键合硅胶固定相液相色谱分离杯芳烃及杯芳冠醚类化合物

以自合成的C60 键合硅胶液相色谱固定相 ,分别选用3种不同选择性的流动相体系 :异丙醇 -环己烷 ,氯仿 -环己烷和二氯甲烷 -环己烷 ,考察了流动相组成对杯芳烃及杯芳冠醚化合物保留行为和分离选择性的影响。在一定的流动相条件下溶质能得到较好分离。     

Spectrophotometric determination of samarium(III) with chrome azurol S in the presence of cetylpyridinium chloride

A sensitive, simple method for the determination of trace amounts of samarium by spectrophotometry is described based on the formation of the samarium-chrome azurol S (CAS) complex in micellar medium. The molar absorptivities of the complexes at pH 7.5 at 505 nm were 3.6x10(4) and 1.4x10(5) l mol(-1) cm(-1) for water media and cetylpyridinium chloride (CPC), respectively. Beer's law is obeyed from 0.05-2 mg l(-1) of samarium at 505 nm as Sm-CAS-CPC complex. Optimal conditions such as reagent amounts, and pH for the samarium determination were reported. The effects of foreign ions were also investigated. The proposed method was successfully applied to the determination of samarium contents in synthetic samples.     

Synthesis, structural, spectroscopic characterization, and structural comparison of 3-hydroxybenzoate and nicotinamide/N,N-diethylnicotinamide mixed ligand complexes with Zn(II)

The mixed-ligand 3-hydroxybenzoic acid complex of Zn(II) with nicotinamide and N,N-diethylnicotinamide were synthesized and characterized (colorless single crystals, [Zn(3-hba)₂(H₂O)₂(na)₂] and [Zn(3-hba)₂(H₂O)₂(dena)₂]). The chemical, FT-IR, thermal, mass spectral analyses, and X-ray data results revealed that both of the compounds contain two water molecules, two 3-hydroxybenzoate (3-hba) and two nicotinamide (na) or two N,N-diethylnicotinamide (dena) ligands per formula unit. 3-hba and na or dena ligands bind to the Zn(II) ion monodentately through their acidic oxygen and pyridinic nitrogen atoms, respectively. The coordination of metal atoms are completed by two molecules of aqua ligands. The charge balance of complexes is accommodated by two molecules of 3-hba ions. The unit cell has two molecules coordination molecules and each of them was as settled to four surfaces of unit cell cage in na complex. There is one mole molecule that was occupied to center of unit cell cage in dena complex. The two dimensional network structure of the complex is like a hexagonal for na and square plane for dena complexes. The thermal decomposition takes place in three steps; first, dehydration of the two aqua ligands, second, elimination of the two nicotinamide ligands, finally, burning of the two benzoate ion ligands.     

Identification of isomeric spin adducts of Leu-Tyr and Tyr-Leu free radicals using liquid chromatography-tandem mass spectrometry

Free radical species are generally short-lived due to their high reactivity and thus direct measurement and identification are often impossible. In this study we used a spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), to trap radical intermediates formed during the oxidation of isomeric dipeptides tyrosine-leucine (Tyr-Leu) and leucine-tyrosine (Leu-Tyr), induced by the hydroxyl radical. To investigate the influence of the amino acid position in the peptide chain on the oxidation and free radical generation, the spin adducts were characterized using LC-MS and MS(n) . We detected carbon and oxygen DMPO adducts and adducts bearing two DMPO, which were analyzed by MS(n) . Both alkoxyl and peroxyl radicals were identified. Radical intermediates were localized in Tyr during oxidation of Tyr-Leu, while radicals were identified in Leu and Tyr during oxidation of Leu-Tyr. DMPO adducts of acyl radical species formed from cleavage of the peptide backbone, promoted by the alkoxyl radical in α carbon of the N-terminal amino acid were observed. The results show that the amino acid position has an influence in the oxidation process, at least on small peptides, and that the α carbon of the N-terminal amino acid is more vulnerable to the attack of the electrophilic hydroxyl radical.     

Interpretation of the Metabolic Enthalpy Change, ΔHmet,Calculated for Microbial Growth Reactions in Soils

The microcalorimetric method was used to calculate the metabolic enthalpy change per mol of glucose degraded by soil microorganisms, ΔH _met. This parameter has been calculated by microcalorimetry for many organic, inorganic and biochemical reactions, but there is only some information about its quantification for microbial growth reactions in soils. Values of ΔH _met were calculated for different soil samples collected in Galicia (Spain) and Campinas (Săo Paolo, Brazil). Exponential microbial growth was stimulated in all soil samples by the addition of glucose and power-time curves were recorded. Results showed changes in the values of ΔH _met calculated for all the soil samples, suggesting a dependence of this value with the microbial growth rate constant, with the percentage of growth, with the initial number of microorganisms of soil samples, with the quantity of glucose added and with the strain of bacteria growing in soil. The interpretation of variations of ΔH _met provides important qualitative and quantitative information. It reports data that allow to interpret from a qualitative point of view, the increase in biomass as a consequence of the degradation of the organic matter in soil, to understand changes in the percentages of soil organic matter and to know if the microbial population growing in differential soil samples is homogeneous. Therefore, to report that value would be very important in ecological studies, but beforehand, it is necessary to solve some problems that can appear in the experiments done to make the quantification . This revised version was published online in August 2006 with corrections to the Cover Date.     

氧化态Co/γ-Al_2O_3催化剂的结构与反应性能研Ⅰ.活性及体相、表相结构表征

采用等量浸渍法 ,制得 5 0 0、 6 0 0、 75 0和 95 0℃焙烧的 Co/ γ- Al2 O3催化剂 ;考察了它们对 CO氧化和乙烯选择还原 NO的反应性能 ;用 XRD和 XPS方法表征了催化剂的体相与表相结构 .活性测试结果表明 ,随焙烧温度升高 ,样品对 CO的氧化活性呈下降趋势 ;对乙烯选择还原 NO反应 ,活性先上升 ,而后又有所下降 (当焙烧温度高于 75 0℃时 ) .从硝酸钴制得的样品 ,其氧化活性要高于从醋酸钴制得的样品 ,但对乙烯选择还原 NO,后者的活性更好 .结构表征结果表明 ,催化剂中钴物种的存在形式与原料盐类及焙烧温度密切相关 .在 Co/ γ- Al2 O3催化剂中主要存在两种钴相 ,即 Co3O4和非化学计量的 Cox Al( 8/ 3- 2 x/ 3) O4尖晶石相 ,前者为完全氧化活性中心 ,后者是 NO选择还原的活性中心 .在相同焙烧温度下 ,以醋酸钴为原料时 ,更容易形成 Cox Al( 8/ 3- 2 x/ 3) O4尖晶石相 .随着焙烧温度提高 ,活性组分与载体的相互作用加强 ,Co3O4相逐步向 Cox Al( 8/ 3- 2 x / 3) O4尖晶石相转化 ,这可能是样品氧化活性下降和选择还原活性升高的主要原因 .在更高焙烧温度下 ,随着 Cox Al( 8/ 3- 2 x / 3) O4尖晶石相颗粒度的增加和晶形改变 ,以及钴离子由表相向体相的迁移 ,使样品比表面积下降 ,表面氧空位及活性位减少 ,     

Alloy formation in mechanically activated mixtures

The physical mixtures of hydroxocarbonates of Cu and Ni with aluminium were activated using a laboratory planetary mill. The chemical reactions and alloy formations as the effects of grinding were followed by the phase analysis of solid products based on the thermogravimetry and X-ray diffractometry. Experimental evidence indicates that the nature of reactions and products of mechanical activation was dependent on the amount of aluminium and time of grinding. This revised version was published online in July 2006 with corrections to the Cover Date.     

Production of recombinant bleaching enzymes from thermophilic microorganisms in fungal hosts

Cost-effective production of enzymes for industrial processes makes the appropriate selection of the host-vector expression system critical. We have developed two systems for the bulk production of bleaching enzymes from thermophiles. Kluyveromyces lactis has been developed as a secretion host employing expression vectors based on the 2μ-like plasmid pKD1 of Kluyveromyces drosophilarium. Our second system involves the filamentous fungus Trichoderma reesei. Fusion and nonfusion vectors have been constructed using the strong cellobiohydrolase 1 (cbh1) promoter. The KEX2 protease cleavage site and a 6 × HIS-tag have been incorporated to facilitate both cleavage and purification of the mature foreign proteins.