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.

     

Dispersive viscosity coefficient of nuclear matter

By application of Landau's kinetic theory of a Fermi liquid in non-equilibrium, we have deduced a dispersive, momentum and frequency dependent shear viscosity coefficient η(q, ω) for symmetric nuclear matter. The resulting formula for η is found to be complicated for arbitrary q, ω; however, simple interpretation is possible in the limit of small momentum q → 0. In the static limit, ω → 0, η reduces to the well known kinetic formula for the hydrodynamic viscosity coefficient η_o, while in the high frequency (zero sound) limit, ωτ ? 1, η(ω) is found proportional to (?iω)^? indicating elastic behaviour of nuclear matter. As is discussed shortly, application of these results to finite nuclei unfortunately does not seem justified.     

Phosphorus-containing dendrimers bearing galactosylceramide analogs: self-assembly properties

We report the synthesis and the supramolecular auto-assembly of catanionic phosphorus-containing dendrimers mimicking multisite analogs of galactosylceramide.     

Investigation of the Interactions of Polyvinylpyrrolidone with Mixtures of Anionic and Nonionic Surfactants or Anionic and Zwitterionic Surfactants by Pulsed Field Gradient NMR

The interaction of polyvinylpyrrolidone (PVP) with an anionic surfactant (sodium dodecyl sulfate, SDS), a nonionic surfactant (pentaethylene glycol monodecyl ether, C(10)E(5)), and a zwitterionic surfactant (lauryl amido propyl betaine, LAPB) has been investigated by means of pulsed gradient spin-echo NMR (FT-PGSE NMR), allowing self-diffusion coefficients to be determined. The results confirm the strong interaction prevailing in the PVP/SDS system, whereas no association has been observed in the PVP/C(10)E(5) and PVP/LAPB systems. Mixing PVP with two surfactants, namely SDS and C(10)E(5) or SDS and LAPB, results in the formation of ternary aggregates between the polymer and the mixed micelles. Copyright 2001 Academic Press.     

Comprehensive on-line HPLC-GC for screening potential migrants from polypropylene into food: The effect of pulsed light decontamination as an example

High performance liquid chromatography (HPLC) was used for the fractionation of extracts from polypropylene (PP) films and coupled on-line to gas chromatography (GC) with automated transfer of the complete HPLC fractions (comprehensive on-line HPLC-GC, i.e. HPLCxGC). Flame ionization detection (FID) was used for the estimation of concentrations, mass spectrometry (MS) for identification work. This method was applied to investigate whether pulsed light (PL) treatment for the microbiological decontamination of polypropylene packaging materials produces reaction products requiring an evaluation to meet regulatory requirements. To demonstrate the safety of PL treatments with regard to the formation of reaction products, i.e. that no component is formed that could endanger human health, basically comprehensive analysis of components potentially migrating into food is required, but comprehensiveness cannot be proven and remains an approximation. The threshold concentration in the film was estimated either from the conventional European non-detection limit of 0.01 mg/kg food or the concept of the threshold of toxicological concern (TTC) for an unknown substance, i.e. an exposure to 0.15 μg per person and day. PL treatment of the films containing Irgafos 168 produced several new components exceeding these limits, i.e. a toxicological safety assessment would probably be required. No such peaks were detected for Tinuvin 326, Irganox 1076 and Chimassorb 81. No degradation of the polymer was detected.     

Enhanced structure determination of beta-pyrrole and N-substituted porphyrins by desorption chemical ionization mass spectrometry.

The extensive macrocycle—but minimal substituent—fragmentation occurring in the chemical ionization mass spectra of porphyrins when ammonia, rather than hydrogen, is the reagent gas leads to more detailed structure determinations.     

Experiments on the total synthesis of Lysolipin I. Part II. Michael addition of 1,3-cyclohexanedione to quinone acetals

Base-catalyzed reaction of 1,3-cyclohexanedione ( 3 ) with the quinone monoacetals 4 and 7 leads to the polycyclic products 5 and 8 , respectively, and in the case of 4 to variable amounts of dibenzofuranone 6 . The 2-arylcyclohexanedione 9 , on the other hand, is isolated from the reaction of 3 and bisacetal 11 catalyzed by ZnCl₂ (Scheme 2). Treatment of the adduct 8 with (CH₃O)₂SO₂/K₂CO₃ results in cleavage of teh heterocyclic ring by a retro-Michael reaction affording teh liable enone 23 which was further transformed to 24 by selective hydrogenation. The 8-acetoxydibenzofuranone 22 is obtainable from 8 by acid treatment and acetylation (Scheme 4). The reactions of the silylenol ethers 27 and 35 with quinone monoacetals were very complex (Scheme 6). The desired arylcyclohexanone derivatives 28 and 36 were formed in very low yields. Under certain conditions (elevated temperature or strong Lewis acids as catalysts), single-electron transfer or addition to the ene-acetal rather than to the enone function of the quinone monoacetals became predominant. In connection with this study, the sensitive 2-methoxy-p-benzoquinone monoacetals 15 (Scheme 3) and 29 (Scheme 6) have been prepared and characterized.     

Coordination of methanol clusters to benzene: a computational study

Benzene-methanol cluster structures were investigated with theoretical chemistry methods to describe the microsolvation of benzene and the benzene-methanol azeotrope. Benzene-methanol (MeOH) clusters containing up to six methanol molecules have been calculated by ab initio [MP2/6-311++G(d,p)//MP2/6-31+G(d,p) + BSSE correction] method. The BSSE was found quite large with this basis set, hence, different extrapolation schemes in combination with the aug-cc-pVxZ basis sets have been used to estimate the complete basis set limit of the MP2 interaction energy [ΔE(MP2/CBS)]. For smaller clusters, n ≤ 3, DFT procedures (DFTB+, MPWB1K, M06-2X) have also been applied. Geometries obtained for these clusters by M06-2X and MP2 calculations are quite similar. Based on the MP2/CBS results, the most stable C(6)H(6)(MeOH)(3) cluster is characterized by a hydrogen bonded MeOH trimer chain interacting with benzene via π···H-O and O···H-C(benzene) hydrogen bonds. Larger benzene-MeOH clusters with n ≥ 4 consist of cyclic (MeOH)(n) subclusters interacting with benzene by dispersive forces, to be denoted by C(6)H(6) + (MeOH)(n). Interaction energies and cooperativity effects are discussed in comparison with methanol clusters. Besides MP2/CBS calculations, for selected larger clusters the M06-2X/6-311++G(d,p)//M06-2X/6-31+G(d,p) procedure including the BSSE correction was also used. Interaction energies obtained thereby are usually close to the MP2/CBS limit. To model the benzene-MeOH azeotrope, several structures for (C(6)H(6))(2)(MeOH)(3) clusters have been calculated. The most stable structures contain a tilted T-shaped benzene dimer interacting by π···H-O and O···H-C (benzene) hydrogen bonds with a (MeOH)(3) chain. A slightly less negative interaction energy results for a parallel displaced benzene sandwich dimer with a (MeOH)(3) chain atop of one of the benzene molecules.     

Antibody capture by mixed-mode chromatography: a comprehensive study from determination of optimal purification conditions to identification of contaminating host cell proteins

We evaluated mixed mode chromatography for the capture of recombinant antibodies from CHO cell culture supernatants. We studied PPA HyperCel, HEA HyperCel, MEP HyperCel and Capto adhere resins, which all contain hydrophobic and cationic groups. A microplate approach combined with DoE modeling allowed the exploration of the complex behaviors of these mixed mode resins. Optimal conditions for antibody purification and host cell proteins (HCPs) elimination were determined and then directly up-scaled to laboratory columns. Then we used mass spectrometry to identify the major HCPs potentially coeluted with the antibody. Differences between the four resins in terms of amount, complexity and identity of the HCPs present in the elution fractions were investigated.     

Magnetic dipolar interactions in solid gold nanosphere dimers

We report the first observation of a magnetic dipolar contribution to the nonlinear optical (NLO) response of colloidal metal nanostructures. Second-order NLO responses from several individual solid gold nanosphere (SGN) dimers, which we prepared by a bottom-up approach, were examined using polarization-resolved second harmonic generation (SHG) spectroscopy at the single-particle level. Unambiguous circular dichroism in the SH signal was observed for most of the dimeric colloids, indicating that the plasmon field located within the interparticle gap was chiral. Detailed analysis of the polarization line shapes of the SH intensities obtained by continuous polarization variation suggested that the effect resulted from strong magnetic-dipole contributions to the nanostructure's optical properties.