An ion-exchange separation of metal cations on a C-18 column coated with dodecylsulphate

The retention mechanism was studied for the cations of the alkaline earth metals and Zn(2+) Ni(2+), Co(2+), Cd(2+) and Bi(3+) on a C(18) column permanently coated with sodium dodecylsulphate, with aqueous mobile phases containing cupric chloride or sulphate, or cerous nitrate. The dependencies of the logarithm or the capacity ratio on the logarithm of the eluent concentration were linear, demonstrating that ion-exchange was the predominating separation mode; the slopes of these dependencies were in good agreement with the values predicted from the ion-exchange theory. Indirect UV photometric detection yielded limits of detection (LOD) of 21, 44, 120 and 275 ng in the volume injected, 20 mul, for Mg(2+), Ca(2+), Sr(2+) and Ba(2+), respectively, with the 10(-2)M copper(II) chloride mobile phase; the respective LOD values decreased to 0.8, 1.6, 3.0 and 6.7 ng with the 5 x 10(-4)M cerium(III) nitrate eluent. The method was found to be primarily suitable for determination of the alkaline earths and was applied to analyses of surface and mineral waters.     

Carnitine Palmitoyltransferase-I and Regulation of Mitochondrial Fatty Acid Oxidation

Summary. Carnitine palmitoyltransferase-I catalyzes the regulated step in overall mitochondrial fatty acid oxidation. The enzyme is controlled by the steady state level of malonyl-CoA and the enzyme’s sensitivity to inhibition by malonyl-CoA. The former is established by the activities of acetyl-CoA carboxylase 2 and malonyl-CoA decarboxylase, while the latter is influenced by post-translational modification (phosphorylation) of CPT-I and/or by changes in the lipid environment of CPT-I.     

Umwandlung von 6-Methylen-tricyclo[3.2.1.02,7]oct-3-en-8-onen mit Ameisensäure in kernmethylierte Phenylessigsäuren

In a preceding communication [5] it was shown that 1, 5-dimethyl-6-methylene-tricyclo[3.2.1.0^2,7]oct-3-en-8-one ( 2 ) and related tricyclic ketones are converted by strong acids (CF₃COOH, FSO₃H) into polymethylated tropylium salts with loss of carbon monoxide, e.g. the 1, 2, 4-trimethyltropylium ion 4 from 2 (Scheme 1). Under the influence of neat formic acid at 20°, 2 gives rise to ring-methylated phenylacetic acids, i.e. 2, 4, 5-trimethylphenylacetic acid ( 5 , main product) as well as smaller amounts of 2, 4, 6-and 2, 3, 5-trimethylphenylacetic acids ( 6, 7 resp.; Scheme 2). –On rearrangement of 2 in HCOOD, ca. 2 D-atoms are incorporated (formula d₂-5) into the 2, 4, 5-trimethylphenylacetic acid. The tricyclic 15 , containing 3 methyl groups, gives 2, 3, 5, 6-tetramethylphenylacetic acid ( 11 ; Scheme 4) with formic acid; the isomeric tricyclic 16 , 2, 3, 4, 5-tetramethylphenylacetic acid ( 12 ; Scheme 5). From 1, 2, 4, 5-tetramethyl-6-methylene-tricyclo[3.2.1.0^2,7]oct-3-en-8-one ( 17 ) one obtains pentamethylphenylacetic acid ( 14 ; Scheme 6). Similarly from 18 , a phenylacetic acid derivative, most probably 4-ethyl-2, 5-dimethyl-phenylacetic acid ( 19 ; Scheme 17), has been obtained. –In no case was the formation of α-phenylpropionic acid derivatives observed, not even from the tricyclic 23 containing six methyl groups. From the tricyclic ketone 2 in 70% formic acid a trimethyl-cyclohepta-2, 4, 6-triene-1-carboxyclic acid with partial formula 24 , besides 2, 4, 5-trimethylphenylacetic acid ( 5 ), is formed. 24 remained practically unchanged on standing in neat formic acid and thus does not represent an intermediate product arising by the rearrangement of 2 in that solvent. On standing in methanolic sulfuric acid, tricyclic 2 furnishes the two stereioisomeric methanol-addition products Z- 26 and E- 26 (Scheme 10); these are converted into the phenylacetic acids 5 , 6 and 7 by neat formic acid. The conversion of 2 and related compounds into ring-polymethylated phenylacetic acids, represents a novel and rather complicated reaction. In our opinion the reaction paths represented in Schemes 12 and 18 are responsible for the conversion of 2 into the trimethylphenylacetic acids, compound 40 representing a key intermediate. Analogous reaction paths can be assumed for the other tricyclic ketone transformations. The use of shift reagents in the NMR. spectroscopy and the high-resolution gas-chromatography of the corresponding methyl esters proved particularly important for the analysis of the reaction mixtures. The majority of the polymethylated phenylacetic acids were independently synthesised by means of the Willgerodt-Kindler reaction (chap. 3.2.), whose course is strongly influenced by methyl groups in the ortho-positions of the acetophenone derivatives employed.     

A novel crossed microfluidic device for the precise positioning of proteins and vesicles

Herein we present a novel way to create arrays of different proteins or lipid vesicles using a crossed microfluidic device. The concept relies on the combination of I) a designated two-step surface chemistry, which allows activation for subsequent binding events, and II) crossing microfluidic channels for the local functionalization by separated laminar streams. Besides its simplicity and cost efficiency, this concept has the advantage that it keeps the proteins in a hydrated environment throughout the experiment. We have demonstrated the feasibility of such a device to create a chessboard pattern of different fluorescently labeled lipid vesicles, which offers the possibility to contain biomolecules, drugs or membrane proteins.     

A Convenient Preparation of β-Acetamido Substituted Tryptamine Derivatives

Summary. In view of finding new 5-HT₆ receptor ligands various -acetamido substituted tryptamine and N,N-dimethyltryptamine derivatives were synthesized from a common intermediate. A trimolecular condensation between indole, Meldrums acid and N-phthalimidoacetaldehyde followed by careful deprotection and functional group manipulations were proposed for this purpose.Present address: GEVSM, UMR 7565 CNRS-UHP, Faculté de Pharmacie, F-54001 Nancy Cedex, FrancePresent address: University of Global and National Economy, Studentski Grad Christo Botev, BG-1700 Sofia, Bulgaria     

Reversed-phase high-performance liquid chromatography of ionogenic compounds: comparison of retention models

Two kinds of retention models describing a behaviour of ionogenic substances in reversed-phase chromatographic systems were compared. Model A utilises a concept of limiting retention factors and is especially suitable for the prediction of retention of compounds co-existing in several forms in mobile phase. An effect of the concentration of organic modifier (e.g., methanol) on the magnitudes of the limiting retention factors and equilibrium constants (dissociation constants of the separated substances) can be expressed with the aid of various, more or less sophisticated, relationships. A stoichiometric displacement model (model B) in its original form simply relates the analyte retention to the content of organic modifier in the mobile phase. In this work, it was modified to also express an effect of the mobile phase pH introducing side equilibria (acid-base) into the model. Both models predict a sigmoidal dependence of the analyte retention factor on the mobile phase pH in accordance with experimental data, and allow, among others, to estimate dissociation constants from those data. Experimental dependencies between the analyte retention and the concentration of methanol in the mobile phase comply well with model A, whereas the stoichiometric displacement model could be used only in a limited range of the methanol concentrations.     

Synthesis,Opiate Receptor Binding and Analgesic Activity of Enkephalin Analogues

The synthesis and biological testing of analogues of Met-enkephalin, a recently discovered opioid peptide from mammalian brain, are described. Testing involved determination of affinity constants for an opiate receptor site and of analgesic potency in the tail-flick test in mouse. The effects on opioid activity of modifying various parts of the enkephalin molecule are discussed. Tyr-D -Ala-Gly-MePheMet (O)-ol

1 The ending -ol added to the symbol of an amino acid designates the aminoalcohol obtained by reduction of the α-carboxyl group of the amino acid.

(FK 33-824), which was highly active in these tests, was subsequently selected for clinical testing. The use of two complementary models - in vitro binding studies and in vivo test for analgesia - for the assessment of biological activity in the evaluation of analogues is explained.     

Thermische Umlagerung von Propargyloxy-cycloheptatrien-Derivaten

The thermal rearrangement of 7 -propargyloxy-cycloheptatriene in decane solution at 180°C gave bicyclo[3.3.2]deca-3,7,9-trien-2-one ( 13 ) and the unstable 2,7-dihydro-cyclohepta[ b ]-pyran ( 12 ) (Scheme 2). The structures of these compounds were determined mainly by NMR. spectroscopy. Derivatives of 13 were also identified by comparison with known compounds (Scheme 3). Possible mechanisms for the formation of 13 and 12 are outlined in Schemes 5 and 6 respectively. The thermal rearrangement of 2-propargyloxy-cycloheptatrienone ( 21 ) gave, in high yield, 2-methyl-8H-cyclohepta[b]furan-8-one ( 22 ) (Scheme 7).     

Low angle laser light scattering and photon correlation spectroscopy in surfactant vesicles

Using low angle laser light scattering, weight averaged molecular weights, M?_w, diffusion coefficients, and hydrodynamic radii, R_H, have been determined for completely synthetic surfactant vesicles, prepared by ultrasonic irradiation of dioctadecyldimethylammonium chloride. DODAC, and dihexadecylphosphate. DHP dispersion. Both the M?_w and R_H values were found to decrease exponentially as a function of sonication time. At the limit, M?_w and R_H for DODAC vesicles are 12.6 × 10⁶ dalton and 396 Å, and those for DHP vesicles are 23 × 10⁶ dalton and 595 Å. Calculations indicate both vesicles to be prolates.     

Synthesis of fragments of the glycocalyx glycan of the parasite Schistosoma mansoni

The chemical synthesis of alpha-L-Fucp-(1 --> 3)-beta-D-GalpNAc-(1 --> 4)-beta-D-GlcpNAc-(1 --> 3)-alpha-D-GalpO(CH2)5NH2, beta-D-GalpNAc-(1 --> 4)-[alpha-L-Fucp-(1 --> 3)-]beta-D-GlcpNAc-(1 --> 3)-alpha-D-GalpO(CH2)5NH2, and alpha-L-Fucp-(1 --> 3)-beta-D-GalpNAc-(1 --> 4)-[alpha-L-Fucp-(1 --> 3)-]beta-D-GlcpNAc-(1 --> 3)-alpha-D-GalpO(CH2)5NH2 is described. These structures represent fucosylated oligosaccharide fragments of the glycocalyx glycan of the cercarial stage of the parasite Schistosoma mansoni, and in protein-conjugated form they are potential diagnostics in the search for antibodies raised against the glycan in the serum of infected humans.