Nouvelles techniques de separations chromatographiques a l'aide de couches minces sur support flexible: Eastman Chromagram

Résumé La chromatographie sur couche mince donne lieu chaque jour à des applications nouvelles. Sa mise au point sur support souple a par exemple, permis de réaliser des progrès dans plusieurs domaines.Grâce à la possibilité de courber la feuille, on a pu faire des séparations sur cône, en conservant la finesse de séparation de la couche mince, et en profitant des possibilités de concentration croissante avec la migration, caractéristique de la technique sur cône.En chromatographie quantitative, ou dans certains cas de séparation, on a pu sur des couches suffisamment épaisses isoler complètement les produits séparés en découpant les taches ou les zones avec des ciseaux. Cette technique peut être employée simultanément avec la chromatographie sur cône. Dans le cas de séparations sur couche de polyamide non insolubilisée, il a été possible, après séparation, de clarifier la couche par des vapeurs d'éthanol. Après découpage et pelliculage de la couche chromatographique, on a pu faire ensuite des spectrophotomètries par transmission dans le visible et l'ultra-violet jusqu'à 240 nm afin de caractériser les produits séparés. L'étude du déplacement des bandes d'absorption par rapport à une spectrophotométrie en solution a été faite dans quelques cas expérimentaux.D'autre part, en travaillant sur des couches très minces (silice, alumine, résine micro-coagulée de type polycarbonate) on a pu accroître le pouvoir résolvant de la couche, c'est à dire diminuer les prises d'essais à 0,2, µl et réduire la distance de séparation à moins de 4 cm.Des exemples de séparations notamment de colorants, de vitamines, de corps gras, de sucres, de pesticides sont cités dans ces divers domaines.

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Summary Thin-Layer chromatography finds new applications each day. Its use of a flexible support, for instance, made possible advancement in several fields.Thanks to the possibility of bending the sheet it was possible to make separations on a cone, while preserving the fineness of separations obtained on thin-layer and taking advantage of the possibilities of concentrations increasing with the migration, characteristic of the technique on cones.In quantitative chromatography, and in certain cases of separation, it was possible, on sufficiently thick layers, to completely isolate the separated products by cutting out the spots or zones with scissors. This technique can be used simultaneously with cone chromatography. In the case of separations on layers of unsolibilized polyamide, it was possible, after separation, to clarify the layer with ethanol vapours. After cutting out and turning the chromatographic layer into a film, it was possible to achieve spectrophotometries by transmission in the visible and the ultraviolet zone until 240 nm in view to characterize the isolated products. The study of the migration of absorption bands compared to a solution spectrophotometry has been done in a few experimental cases.On the other hand, by operating on very thin layers, (silica, alumina, micro-coagulated resin of polycarbonate type) it was possible to increase the resolving power of the layer, which means that it was possible to diminish the importance of the experimental sample to 0.2 µl, and reduce the distance of separation to less than 4 cm.Examples of separations, more particularly of dyes, vitamins, fats, sugars, pesticides, are given in these various fields.

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Zusammenfassung Die Dünnschichtchromatographie findet immer neue Anwendungsbereiche. Die Technik mittels flexiblen Trägern erlaubte auf verschiedenen Gebieten nennenswerte Fortschritte.Infolge der Möglichkeit, das Band zu biegen, konnte man Trennungen gemäß der Konustechnik durchführen, wobei die Trennfeinheit der dünnen Schicht gewahrt blieb und von der mit der Migration anwachsenden Konzentrierung, die charakteristisch ist für die Konustechnik, profitiert wurde.In der quantitativen Chromatographie, oder für bestimmte Trennungen, konnte man auf genügend dicken Schichten die getrennten Stoffe durch Abschneiden der Flecke oder der Zonen völlig isolieren. Diese Technik kann ebenfalls für die Konus-Chromatographie zur Anwendung kommen. Im Fall der Trennungen auf unlöslich gemachten Polyamid-Schichten war es nach der Trennung möglich, die Schicht mittels Ethanoldämpfen zu klären. Nach Schneiden und Zubereiten der chromatographischen Schicht konnte man anschließend Spektrophotometer-Aufnahmen durch Übertragung in den sichtbaren und Ultraviolettbereich bis 240 nm herstellen, die der Charakterisierung der getrennten Produkte dienten. Das Studium der Verschiebung der Absorptionsstreifen im Verhältnis zur Spektrophotometeraufnahme in Lösung wurde für einige Versuche durchgeführt.Man hat andererseits bei Versuchen mit sehr dünnen Schichten (Siliziumdioxyd, Aluminiumoxyd, mikrokoaguliertes Harz vom Polykarbonate-Typ) das Lösungsvermögen der Schicht vergrößern können, was zu einer Verringerung der Proben auf 0.2 µl und des Trennabstandes auf weniger als 4 cm führte.Beispiele von Analysen der Farbstoffe, der Vitamine, von Fetten, Zuckern und Pestiziden werden gegeben.

     

Relevance of isotopic and molecular biomarkers for the authentication of milk according to production zone and type of feeding of the cow

The first objective of the present paper was to assess the potential of both isotopic ( (18)O/ (16)O in milk water) and molecular biomarkers (terpenes, fatty acids, carotenoids, and vitamins) and milk color to discriminate the production zone (lowland or upland areas) from which 49 tanker bulk milks were collected over one year from a total of 204 farms. The milk water (18)O enrichment was higher in lowland (<500 m altitude) than in upland (>700 m altitude), but the delta (18)O values failed to discriminate systematically the production zone at the scale of the year because of its high variability related to the sampling period. In contrast with vitamins A and E, carotenoids, and milk color measurements, terpenes and fatty acids were confirmed to be relevant tracers of the production zone. The milk compounds with the strongest discriminative potential were fatty acids, which were determined by high-resolution gas chromatography. The calculation of fatty acid ratios, which permits the limitation of using fatty acid relative quantity expressed in percentage of total fatty acids to be overcome, was shown to be particularly relevant in discriminating upland from lowland milk ratios. The selection of two pairs of ratios, namely, iso-C17:0/C18:3 n-3 and iso-C15:0/iso-C14:0, enabled the authentication of 100% of the highland versus lowland milks whatever the season. The second objective was to evaluate the relevance of fatty acid composition to discriminate milks according to the proportion of corn silage in the diets of dairy cows. The selection of two fatty acids ratios, namely, trans11 cis15-C18:2/trans11-C18:1 and cis9-C16:1/iso-C16:0, enabled the correct classification of 100% of the milk samples according to the proportion of corn silage in the basic fodder rations (<25% vs >30%). The relationship between the milk production zone and the type of forage fed to the cows is discussed.     

Molecular Detection of Phytophthora ramorum by Real-Time Polymerase Chain Reaction Using TaqMan, SYBR Green, and Molecular Beacons

ABSTRACT Sudden oak death, caused by Phytophthora ramorum, is a severe disease that affects many species of trees and shrubs. This pathogen is spreading rapidly and quarantine measures are currently in place to prevent dissemination to areas that were previously free of the pathogen. Molecular assays that rapidly detect and identify P. ramorum frequently fail to reliably distinguish between P. ramorum and closely related species. To overcome this problem and to provide additional assays to increase confidence, internal transcribed spacer (ITS), beta-tubulin, and elicitin gene regions were sequenced and searched for polymorphisms in a collection of Phytophthora spp. Three different reporter technologies were compared: molecular beacons, TaqMan, and SYBR Green. The assays differentiated P. ramorum from the 65 species of Phytophthora tested. The assays developed were also used with DNA extracts from 48 infected and uninfected plant samples. All environmental samples from which P. ramorum was isolated by PARP-V8 were detected using all three real-time PCR assays. However, 24% of the samples yielded positive real-time PCR assays but no P. ramorum cultures, but sequence analysis of the coxI and II spacer region confirmed the presence of the pathogen in most samples. The assays based on detection of the ITS and elicitin regions using TaqMan tended to have lower cycle threshold values than those using beta-tubulin and seemed to be more sensitive.     

Preventing Acid Mine Drainage with an Elevated Water Table: Long-Term Column Experiments and Parameter Analysis

The elevated water table (EWT) technique for preventing acid mine drainage (AMD) was tested using instrumented laboratory columns containing reactive tailings from the Louvicourt and Sigma mines, Abitibi, Quebec. The tests were performed in short (0.4 m) and long (1.4–1.7 m) columns over 400–500 days and included periodic surface recharge and subsequent monitoring of the leached drainage water. In each column, the water table depth was adjusted relative to the air entry value (AEV or ψ_a) of the tailings. The influence of different water table elevations was evaluated by measuring the effluent pH, as well as the concentrations of major ions including sulphate, iron, zinc, copper and lead. Provided the water table depth below the tailings surface remained less than one half of the tailings’ AEV, the observed data showed that an EWT can be very effective in reducing acid mine drainage. The principal factors controlling drainage quality were the saturated hydraulic conductivity (k _sat) and the air entry value (ψ_a) of the tailings. A lower k _sat and a higher ψ_a in the tailings tend to increase the performance of an elevated water table by limiting drainage-induced desaturation. Mineralogical composition had relatively little effect on the hydrogeochemical evolution provided the tailings remained highly saturated (S _r?≥?90%). The results presented here indicate that an elevated water table can be an effective means for controlling the production of AMD when the design conditions are properly selected and applied.     

Assessment of three strategies practiced by fishery managers for restoring native brown trout (Salmo trutta) populations in Northern French Alpine Streams

Abstract – The efficiency of three strategies carried out by fisheries managers to restore native Mediterranean brown trout populations threatened by non‐native Atlantic populations were assessed. The strategies tested were (i) genetic refuge area where stocking is banned, (ii) stocking with Mediterranean fry and (iii) translocation of wild Mediterranean spawners. Using two discriminatory microsatellite loci between Atlantic and Mediterranean alleles, we compared the genetic composition of samples before and after the changes of practices. The three strategies had several detectable effects in the standing populations causing strong temporal changes in departures from Hardy–Weinberg equilibrium and linkage equilibrium between loci and the apparition of new Mediterranean alleles. The significant reductions in the proportions of Atlantic alleles observed over time can mostly be explained by the disappearing of the pure non‐native Atlantic trout after the stopping of hatchery releases. The results, however, also suggest that the active strategies carried out by managers led to intraspecific introgression between both non‐native Atlantic and native Mediterranean strains.     

Biological control at work: demonstrating the complementary effects of natural enemies on two contrasting pests and the damage they cause

Journal of Pest Science - Natural pest control is a significant service supporting agricultural production. However, the relative contribution of several functional groups of natural enemies to...     

Host cell invasion by apicomplexan parasites: insights from the co-structure of AMA1 with a RON2 peptide

Apicomplexan parasites such as Toxoplasma gondii and Plasmodium species actively invade host cells through a moving junction (MJ) complex assembled at the parasite-host cell interface. MJ assembly is initiated by injection of parasite rhoptry neck proteins (RONs) into the host cell, where RON2 spans the membrane and functions as a receptor for apical membrane antigen 1 (AMA1) on the parasite. We have determined the structure of TgAMA1 complexed with a RON2 peptide at 1.95 angstrom resolution. A stepwise assembly mechanism results in an extensive buried surface area, enabling the MJ complex to resist the mechanical forces encountered during host cell invasion. Besides providing insights into host cell invasion by apicomplexan parasites, the structure offers a basis for designing therapeutics targeting these global pathogens.     

有效微生物群(EM)对饲料pH值及营养价值的影响

研究了EM发酵饲料中pH值及饲料营养的变化.结果表明:EM对饲料具有明显的酸化作用,提高了饲料的适口性;饲料经EM发酵4 d后,营养价值有所提高.扣除"浓缩效应"后,粗蛋白、NDF含量无显著性变化(P＞0.05),ADF含量下降了10.06%(P ＜0.05),总氨基酸含量提高了8.87%,限制性赖氨酸提高了10.83%.