Synthesis and stable isotope dilution assay of ethanethiol and diethyl disulfide in wine using solid phase microextraction. Effect of aging on their levels in wine     

Belancic Majcenovic A  Schneider R  Lepoutre JP  Lempereur V  Baumes R 《Journal of agricultural and food chemistry》2002,50(23):6653-6658

Ethanethiol and diethyl disulfide (DEDS) most often occurred at levels above their olfactive threshold in wines with nauseous sulfur-linked smells. As ethanethiol is very oxidizable and chemically reactive, a stable isotopic dilution analysis of both ethanethiol and its disulfide in wines using solid phase microextraction and GC-MS was developed. The latter involved the determination of the proportion of DEDS formed by oxidation of the thiol during the analysis conditions, which was obtained by the use of two differently labeled disulfide standards. An original synthesis of labeled ethanethiol standards in conditions minimizing oxidation was developed, and the corresponding labeled diethyl disulfides were obtained from these thiols. This analytical method was used to follow the levels of these sulfur compounds during aging in a young red wine spiked with ethanethiol and added with enological tannins, with or without oxygen addition. The total levels of these two sulfur compounds were shown to decrease steadily after 60 days of aging, up to 83%. The effect of oxygen sped this decrease, but the effect of enological tannins was very slight. Residual ethanethiol was detected in its disulfide form from approximately 36% in the nonoxygenated wines to 69% in the oxygenated samples.  相似文献   

Heavy Metal Contamination in Sediments of Lake Nahuel Huapi,Nahuel Huapi National Park,Northern Patagonia,Argentina     

Ribeiro Guevara  Sergio  Massaferro  Julieta  Villarosa  Gustavo  Arribére  María  Rizzo  Andrea 《Water, air, and soil pollution》2002,137(1-4):21-44

Trace metals (Sb, As, Br, Cs, Co, Cr, Ag and Hg), rare earth elements (Ce, Eu, La, Lu, Sm, Tb and Yb), and Sc. were analysed in suspended load and in two sediment cores from Lake Nahuel Huapi, Nahuel Huapi National Park, Patagonia, Argentina, by using Instrumental Neutron Activation Analysis. The core activity profiles of ²¹⁰Pb and ¹³⁷Cs were measured to estimate the age of the sediments. Silver was enriched in the upper layers of both cores, and correlated with the strong growthof the population of Bariloche City in the last 50 yr. Concentrations are higher in the core sampled near Bariloche, andindicate some transport in the water body. Silver concentrationsmeasured in the suspended load were 4.58±0.36 and 3.46±0.40 μg g^-1 in the southern margin of the lake, near San Carlos de Bariloche City, whereas in the northern margin the concentrations were 1.68±0.18 and 1.88±0.23 μg g^-1. Concentration ratio for silver in suspended load and upper core layers were equal in both sampling points. These facts suggest that Ag contents correspond to inputs associated with human activities. Bromine concentrations show a strong increase abovebase line values, similar to silver. In contrast, caesium, chromium, and cobalt concentrations do not differ from base linevalues. The metalloids antimony and arsenic show little variationwith regard to base line concentration. Noticeable, the mercurycontents found in the suspended load.  相似文献   

Ein neues Verfahren zur Extraktion von organischen Stoffen aus Böden mit überkritischen Gasen 2. Mitteilung     

Michael Spiteller  Andrea Ashauer 《植物养料与土壤学杂志》1982,145(6):567-575

A new procedure for the extraction of organic matter from soils by supercritical gases Extracting soil samples with supercritical gases high amounts of nearly ash-free organic preparations can be obtained. A direct fractionation in classes of compounds with different chemical constitution is achieved by using solvents of variable polarity. Fats and dicarboxylic acids can be solved in pentan, phenols and hemicelluloses in ethanol, lignin and cellulose in ethanol/water. The substances obtained from the pentan extract were identified by GC/MS analysis. The non volatile compounds of the ethanol/water extract were decomposed by permanganate and the products compared with those of the oxidized humic acids. Though there is a high number of different compounds the podzol profile investigated shows typical patterns of distribution for certain components.  相似文献   

Deciphering the reaction dynamics underlying optimal control laser fields     

Daniel C  Full J  González L  Lupulescu C  Manz J  Merli A  Vajda S  Wöste L 《Science (New York, N.Y.)》2003,299(5606):536-539

Femtosecond high-resolution pump-probe experiments have been used together with theoretical ab initio quantum calculations and wave packet dynamics simulations to decode an optimal femtosecond pulse that is generated from adaptive learning algorithms. This pulse is designed to maximize the yield of the organometallic ion CpMn(CO)3 while hindering the competing fragmentation. The sequential excitation and ionization of the target ion are accomplished by an optimized field consisting of two dominant subpulses with optimal frequencies and time delays.  相似文献   

A predator unmasked: life cycle of Bdellovibrio bacteriovorus from a genomic perspective     

Rendulic S  Jagtap P  Rosinus A  Eppinger M  Baar C  Lanz C  Keller H  Lambert C  Evans KJ  Goesmann A  Meyer F  Sockett RE  Schuster SC 《Science (New York, N.Y.)》2004,303(5658):689-692

Predatory bacteria remain molecularly enigmatic, despite their presence in many microbial communities. Here we report the complete genome of Bdellovibrio bacteriovorus HD100, a predatory Gram-negative bacterium that invades and consumes other Gram-negative bacteria. Its surprisingly large genome shows no evidence of recent gene transfer from its prey. A plethora of paralogous gene families coding for enzymes, such as hydrolases and transporters, are used throughout the life cycle of B. bacteriovorus for prey entry, prey killing, and the uptake of complex molecules.  相似文献   

Crystal structure of the eukaryotic 40S ribosomal subunit in complex with initiation factor 1     

Rabl J  Leibundgut M  Ataide SF  Haag A  Ban N 《Science (New York, N.Y.)》2011,331(6018):730-736

Eukaryotic ribosomes are substantially larger and more complex than their bacterial counterparts. Although their core function is conserved, bacterial and eukaryotic protein synthesis differ considerably at the level of initiation. The eukaryotic small ribosomal subunit (40S) plays a central role in this process; it binds initiation factors that facilitate scanning of messenger RNAs and initiation of protein synthesis. We have determined the crystal structure of the Tetrahymena thermophila 40S ribosomal subunit in complex with eukaryotic initiation factor 1 (eIF1) at a resolution of 3.9 angstroms. The structure reveals the fold of the entire 18S ribosomal RNA and of all ribosomal proteins of the 40S subunit, and defines the interactions with eIF1. It provides insights into the eukaryotic-specific aspects of protein synthesis, including the function of eIF1 as well as signaling and regulation mediated by the ribosomal proteins RACK1 and rpS6e.  相似文献   

The ultrasmoothness of diamond-like carbon surfaces     

Moseler M  Gumbsch P  Casiraghi C  Ferrari AC  Robertson J 《Science (New York, N.Y.)》2005,309(5740):1545-1548

The ultrasmoothness of diamond-like carbon coatings is explained by an atomistic/continuum multiscale model. At the atomic scale, carbon ion impacts induce downhill currents in the top layer of a growing film. At the continuum scale, these currents cause a rapid smoothing of initially rough substrates by erosion of hills into neighboring hollows. The predicted surface evolution is in excellent agreement with atomic force microscopy measurements. This mechanism is general, as shown by similar simulations for amorphous silicon. It explains the recently reported smoothing of multilayers and amorphous transition metal oxide films and underlines the general importance of impact-induced downhill currents for ion deposition, polishing, and nanopattering.  相似文献   

Radar soundings of the subsurface of Mars   总被引：2，自引：0，他引：2  

Picardi G  Plaut JJ  Biccari D  Bombaci O  Calabrese D  Cartacci M  Cicchetti A  Clifford SM  Edenhofer P  Farrell WM  Federico C  Frigeri A  Gurnett DA  Hagfors T  Heggy E  Herique A  Huff RL  Ivanov AB  Johnson WT  Jordan RL  Kirchner DL  Kofman W  Leuschen CJ  Nielsen E  Orosei R  Pettinelli E  Phillips RJ  Plettemeier D  Safaeinili A  Seu R  Stofan ER  Vannaroni G  Watters TR  Zampolini E 《Science (New York, N.Y.)》2005,310(5756):1925-1928

The martian subsurface has been probed to kilometer depths by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument aboard the Mars Express orbiter. Signals penetrate the polar layered deposits, probably imaging the base of the deposits. Data from the northern lowlands of Chryse Planitia have revealed a shallowly buried quasi-circular structure about 250 kilometers in diameter that is interpreted to be an impact basin. In addition, a planar reflector associated with the basin structure may indicate the presence of a low-loss deposit that is more than 1 kilometer thick.  相似文献   

A neutralizing antibody selected from plasma cells that binds to group 1 and group 2 influenza A hemagglutinins   总被引：2，自引：0，他引：2  

Corti D  Voss J  Gamblin SJ  Codoni G  Macagno A  Jarrossay D  Vachieri SG  Pinna D  Minola A  Vanzetta F  Silacci C  Fernandez-Rodriguez BM  Agatic G  Bianchi S  Giacchetto-Sasselli I  Calder L  Sallusto F  Collins P  Haire LF  Temperton N  Langedijk JP  Skehel JJ  Lanzavecchia A 《Science (New York, N.Y.)》2011,333(6044):850-856

The isolation of broadly neutralizing antibodies against influenza A viruses has been a long-sought goal for therapeutic approaches and vaccine design. Using a single-cell culture method for screening large numbers of human plasma cells, we isolated a neutralizing monoclonal antibody that recognized the hemagglutinin (HA) glycoprotein of all 16 subtypes and neutralized both group 1 and group 2 influenza A viruses. Passive transfer of this antibody conferred protection to mice and ferrets. Complexes with HAs from the group 1 H1 and the group 2 H3 subtypes analyzed by x-ray crystallography showed that the antibody bound to a conserved epitope in the F subdomain. This antibody may be used for passive protection and to inform vaccine design because of its broad specificity and neutralization potency.  相似文献   

Impact of genetic manipulation on the fitness of Anopheles stephensi mosquitoes     

Catteruccia F  Godfray HC  Crisanti A 《Science (New York, N.Y.)》2003,299(5610):1225-1227

Genetic modification of mosquitoes offers exciting possibilities for controlling malaria, but success will depend on how transformation affects the fitness of modified insects. The expression of an exogenous gene, the mutations caused by its insertion, and inbreeding while transformed lines are established can all lead to reductions in fitness. Factors influencing fitness were investigated in cage experiments with four lines of transgenic Anopheles stephensi, a vector species of human malaria. The results indicate direct costs of the introduced transgene in at least three out of the four lines, as well as an apparent cost of the inbreeding involved in making transgenic homozygotes.  相似文献