Chromatographie d'élution des aminoacides et de leurs dérivés sur colonne d'échangeurs d'ions à trame hydrophile

Sommaire Le comportement chromatographique des dansylaminoacides hydrosolubles (acide dansylcysteique, -monodansylarginine, -monodansylhistidine, -monodansyllysine, -monodansyllysine), des aminoacides correspondants, et du dansylacide sur colonne d'échangeur de cation à trame hydrophile (Phospho-cellulose, Sulfoéthyl-dextrane réticulé) est rappelé. Les monodansyldérivés de l'arginine, de l'histidine, de la lysine peuvent être isolés à l'état pur de leur milieu de formation par un procédé chromatographique employant ces échangeurs de cations. L'acide dansylcysteique, non retenu (comme le dansylacide) par ces échangeurs de cations, peut être séparé du dansyl-acide et de l'acide cysteique, par chromatographie sur colonne de Diéthylaminoéthyldextrane réticulé. Un procédé chromatographique similaire permet de séparer les deux dérivés monodansylés de la lysine.

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Elution chromatography of aminoacids and their derivatives on an ion exchange column with hydrophilic cross-linkagePart 2: Behaviour of water-soluble dansylamino acids on an ion exchange column of cross-linked DEAE dextrane

Summary The chromatographic behaviour of water soluble dansylamino acids (dansylcysteic acid, -monodansyl arginine, -monodansyl histidine, -monodansyl lysine, -monodansyl lysine), of the corresponding amino-acids, and of dansyl acid on a cation exchange column with hydrophilc crosslinks (Phosphocellulose, cross-linked Sulfoethyl dextrane) is reported. The monodansyl derivatives of arginine, histidine, and lysine can be isolated in pure form from the medium in which they have been formed, by means of a chromatographic procedure using these cation exchangers. Dansylcysteic acid. Which is not retained (like dansyl acid) by these cation exchachangers, can be separated from dansyl acid and from cysteic acid by chromatography on a column of cross-linked diethyl aminoethyl dextrane. A similar chromatographic process permits the separation of the two monodansyl derivatives of lysine.

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Elutions-Chromatographie von Aminosäuren und ihren Derivaten auf einer Ionenaustauscher-Säule mit hydrophiler Füllung2. Teil: Verhalten der hydro-säurelöslichen Dansylaminosäuren auf einer Ionenaustauscher-Säule mit vernetztem DEAE-Dextran

Zusammenfassung Es wird an das chromatographische Verhalten der hydrolöslichen Dansylaminosäuren (Dansyl-Cysteinsäure, -Monodansyl-arginin, -Monodansyl-histidin, -Monodansyl-lysin, -Monodansyl-lysin) sowie der entsprechenden Aminosäuren und von Dansylsäure auf einer Kationenaustauscher-Säule mit hydrophiler Füllung (Phospho-cellulose, vernetztes Sulfoäthyldextran) erinnert. Durch ein chromatographisches Verfahren mit derartigen Kationen-Austauschern lassen sich die Monodansylderivate von Arginin, Histidin und Lysin im Reinzustand aus ihrem Entstehungs-Medium isolieren. Die nicht (wie die Dansylsäure) von diesen Kationenaustauschern zurückgehaltene Dansylcysteinsäure kann durch Chromatographie auf einer Säule mit vernetztem Diäthylaminoäthyldextran von der Dansylsäure und der Cysteinsäure getrennt werden. Durch ein ähnliches chromatographisches Verfahren lassen sich die beiden Monodansylderivate von Lysin trennen.

     

Influence of mixing conditions on rheological behavior and electrical conductivity of polyamides filled with carbon black

The introduction of carbon black in a polyamide matrix allows one to obtain conductive materials because of the formation of a filler network. Resulting electrical properties depend, among others, on the processing conditions. In a first part, we investigate the influence of mixing conditions (rotor speed, temperature, mixing time) on electrical conductivity. Then, in a second part, we try to characterize the conducting network by rheological measurements and to establish relationships between rheological parameters and electrical properties. For that purpose, we propose to perform successive strain sweep experiments at constant frequency, from 0.5 to 100%, then from 100 to 0.5%, and finally, again, from 0.5 to 100%. Between two successive strain sweeps, we observe a drop in the moduli values that can be attributed to the breakdown of the carbon black network. A clear relationship is established between rheological and electrical properties of the compounds. Moreover, we propose a presentation of the rheological data that permits to rank the samples according to the strength of the carbon black network.     

Hemoglobin as a major binding protein for methylmercury in white-sided dolphin liver

As methylmercury (MeHg) can be bioaccumulated and biomagnified in the trophic web, its toxicity for marine mammals is of major concern. Mercury speciation in marine biota has been widely studied, mainly focused on the discrimination and quantification of inorganic Hg and MeHg. Less attention has been paid to the interactions of Hg with biomolecules and the characterization of its specific binding, which play a key role in metabolic pathways controlling its uptake, transformation, and toxicity. In the studied white-sided dolphin (Lagenorhynchus acutus) liver homogenate (QC04LH4) sample, approximately 60 % of the total MeHg was found in the water soluble fraction, specifically associated with high molecular weight biomolecules. The identity of the involved proteins was investigated (after tryptic digestion of the fraction) by μRPLC with parallel detection by ICP-MS and ESI-MS/MS. Molecular mass spectrometry experiments were carried out at high resolution (100000) to ensure accurate protein identification and determination of the MeHg binding sites. Cysteine residue on the dolphin hemoglobin β chain was found to be the main MeHg binding site, suggesting that hemoglobin is a major MeHg binding protein in this marine mammal and could be a potential carrier of this MeHg from blood to liver prior to its degradation in this organ. In parallel, a significant proportion of selenium was found to be present as selenoneine and a potential role for this compound in Hg detoxification is discussed.