Microdetermination of ether lipids by the isotopic derivative technique

Summary Complex mixtures of ether lipids and ester lipids are subjected to reduction with lithium aluminiumhydride to yield 1-alkylglycerols, 1-alk-1'-enylglycerols, and alcohols. Acetylation of these reduction products with radioactively labelled acetic anhydride leads to mixtures of alkyldiacetylglycerols, alk-1-enyldiacetylglycerols, and alkyl acetates. These derivatives are resolved by thin-layer chromatography and then estimated by scanning of the chromatogram or by liquid-scintillation counting of the eluted fractions.

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Mikroanalyse von Ätherlipiden mit Hilfe der Radioreagens-Methode

Zusammenfassung Komplexe Gemische von Ether- und Esterlipiden werden mit Lithiumaluminiumhydrid zu 1-Alkylglycerolen, 1-Alk-1'-enylglycerolen und Alkoholen umgesetzt. Diese Reaktionsprodukte werden mit radioaktivem Essigsäureanhydrid acetyliert. Die markierten Derivate, Alkyldiacetylglycerole, Alk-1-enyldiacetylglycerole and Alkylacetate, werden dünnschichtchromatographisch getrennt. Das Verhältnis dieser drei Fraktionen wird durch Scanning der Chromatogramme oder durch Flüssigkeitszintillationszählen der eluierten Fraktionen bestimmt.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Preparation of lipids from plant and animal tissues: Pure compounds and reference mixtures

Summary The systematic analysis of complex lipid mixtures is based on the consecutive application of complementary principles of chromatography. Pure compounds, synthetic standard mixtures, and biological lipid extracts are required as reference materials. Procedures for the preparation of individual compounds and standard mixtures are outlined, and recommendations are offered regarding the choice of biological reference materials and their certification.

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Gewinnung von Lipiden aus pflanzlichen und tierischen Geweben: reine Verbindungen und Referenzgemische

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In this article, lipids have been named according to the Recommendations of the IUPAC-IUB Commission on Biochemical Nomenclature (see Eur J Biochem (1977) 79:11–21)     

Reference electrodes based on conducting polymers

Several attempts to produce conducting polymer based all-solid-state reference electrodes are presented. Open circuit potential of conducting polymers is redox sensitive and Donan equilibrium dependent. Therefore, more sophisticated constructions are necessary. Most promising were bilayers composed of conducting polymers with different ion-exchanger properties.     

Preparation and Properties of Composite Polypyrrole/Pt Catalyst Systems

Three different methods for the preparation and modification of conducting polymer/noble metal catalyst systems consisting of polypyrrole (PPy) and platinum (Pt) are described for the anodic oxidation of methanol. The first method consists of the electrochemical deposition of a thin PPy film on glassy carbon substrate, which is modified with Pt either by electroreduction of hexachloroplatinate, codeposition from a nanodispersed Pt solution, or incorporation of tetrachloroplatinate as counterion followed by cathodic reduction. A second method is based on the preparation of nanoscale PPy(PSS) particles by chemical polymerization with polystyrenesulfonate PSS^– as the counterion. This material is a favorable catalyst support for nanodispersed Pt due to its mixed electronic and cationic conductivity. To study the electrochemical properties, the particulate system PPy(PSS)/Pt is fixed in a carbon fiber electrode. A third method was developed which brings the polypyrrole in close contact to a proton exchanger membrane (Nafion) using a special chemical deposition procedure. This method is useful for preparing a membrane electrode assembly (MEA) consisting of Nafion/PPy/Pt. The structural, morphological, and electrocatalytic properties for methanol oxidation were studied depending on the preparation method applied using surface analytical techniques (TEM, SEM, and EDX) and electrochemical measurements (cyclic voltammetry and transient techniques).     

Vorrichtung zum Abw?gen von Oelen

Ohne Zusammenfassung     

Immobilization of histidine-tagged proteins on electrodes

The development of new enzyme immobilization techniques that do not affect catalytic activity or conformation of a protein is an important research task in biotechnology including biosensor applications and heterogeneous reaction systems. One of the most promising approaches for controlled protein immobilization is based on the immobilized metal ion affinity chromatography (IMAC) principle originally developed for protein purification. Here we describe the current status and future perspectives of immobilization of His-tagged proteins on electrode surfaces. Recombinant proteins comprising histidine-tags or histidine rich native proteins have a strong affinity to transition metal ions. For metal ion immobilization at the electrode surface different matrices can be used such as self-assembled monolayers or conductive polymers. This specific technique allows a reversible immobilization of histidine-tagged proteins at electrodes in a defined orientation which is an important prerequisite for efficient electron transfer between the electrode and the biomolecule. Any application requiring immobilized biocatalysts on electrodes can make use of this immobilization approach, making future biosensors and biocatalytic technologies more sensitive, simpler, reusable and less expensive while only requiring mild enzyme modifications.     

The calculation of electron density and temperature in Ar spectroscopic plasmas from continuum and line spectra

The measurement of electron temperature and electron density from line and continuum radiation in Ar plasmas used for spectroscopic purposes is discussed. The correct equations for the calculation of these parameters from experimentally observable quantities are identified. Such expressions yield the theoretical spectral irradiance expected from line and continuum radiation. To aid calculations, grouped constants from these equations are calculated using SI units of measure. The sources of accurate values for the parameters and correction factors appearing in the irradiance equations are listed. In addition the approximations made in order to simplify electron temperature and electron density determinations are reviewed. Practical aspects of making accurate measurements of these parameters in Ar plasmas are considered. Theoretical plots of line to continuum emission ratio vs electron temperature and of continuum irradiance vs electron density are presented as an illustration using parameters appropriate for Ar emission at 430 nm and the spectrally adjacent continuum.