Cross-linked poly(vinyl alcohol) as permanent hydrophilic column coating for capillary electrophoresis.

A fast method for the generation of permanent hydrophilic capillary coatings for capillary electrophoresis (CE) is presented. Such interior coating is effected by treating the surface to be coated with a solution of glutaraldehyde as cross-linking agent followed by a solution of poly(vinyl alcohol) (PVA), which results in an immobilization of the polymer on the capillary surface. Applied for capillary zone electrophoresis (CZE) such capillaries coated with cross-linked PVA exhibit excellent separation performance of adsorptive analytes like basic proteins due to the reduction of analyte-wall interactions. The long-term stability of cross-linked PVA coatings could be proved in very long series of CZE separations. More than 1000 repetitive CE separations of basic proteins were performed with stable absolute migration times relative standard deviation (RSD > 1.2%) and without loss of separation efficiency. Cross-linked PVA coatings exhibit a suppressed electroosmotic flow and excellent stability over a wide pH range.

Directed control of electroosmotic flow in nonaqueous electrolytes using poly(ethylene glycol) coated capillaries.

Poly(ethylene glycol) (PEG)-coated capillaries exhibit unique properties in nonaqueous electrolytes. Immobilized PEG interacts significantly with different cations present in nonaqueous electrolytes. This can induce a positive surface charge on PEG-coated capillaries and results in an adjustable anodic electroosmotic flow (EOF) in nonaqueous electrolytes whereas a reduced cathodic EOF is observed in aqueous electrolytes. The EOF can reversibly be adjusted by the variation of the electrolyte constitution, namely the type of the solvent used and the nature and concentration of background cations. In methanol and especially in acetonitrile electrolytes the magnitude and also the direction of EOF is strongly dependent on the water content. Using different alkali metal cations, the EOF can be increased, reduced, or even reversed depending on the nature of the cation. The directed manipulation of EOF in methanolic electrolytes using PEG-coated capillaries was applied for optimization of nonaqueous capillary electrophoretic separations of acidic compounds with regard to reproducibility, resolution, and analysis time.

Influence of pH*-value of methanolic electrolytes on electroosmotic flow in hydrophilic coated capillaries.

The dependency of EOF on the H+-concentration and the related so called pH* value of methanolic electrolytes has been examined with poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA) and uncoated capillaries. These results were compared with the pH dependency of EOF of these capillaries using aqueous buffers. In uncoated capillaries the dependency of EOF on the pH(*)-value is very similar for aqueous and methanolic electrolytes. The EOF increases with increasing H+-concentration and pH-hysteresis is observed. In PVA coated capillaries the EOF is strongly reduced over wide pH* or pH ranges for both methanolic electrolytes and aqueous buffers. The EOF in PEG coated capillaries is surprisingly directed to the anode with methanolic electrolytes whereas a reduced cathodic EOF is observed in aqueous electrolytes. The anodic EOF of PEG-coated capillaries in methanolic electrolytes is independent of the pH*-value. The usefulness of PEG- and PVA-coated capillaries for adjusting the EOF in non-aqueous electrolytes for the analysis of isomeric organic acids was demonstrated.

[Enflurane blocks ion current through the nicotinic acetylcholine receptor]. / Enfluran blockiert den Ionenstrom durch den nikotinischen Acetylcholinrezeptor.

AIM: The study investigates the influence of enflurane (EN) on macroscopic currents of the nicotinic acetylcholinergic receptor channel (nAChR). This ion channel is a representative member of the superfamily of ligand-gated receptor channels and is better characterized than all the other receptors in respect of structure and function. METHODS: For the experiments the patch-clamp technique was used to study the embryonic type of the nAChR expressed by cultured mouse-myotubes. Patch-clamp recordings were performed in the outside-out-mode from these preparations. To match the rapid desensitization kinetics of ligand-activated ion channels, a liquid filament switch technique was used for the application of agonists to the excised patches. This technique allows for change of solution within 300 microseconds. We used a saturating concentration of 10(-4) M acetylcholine (ACh), activating almost all available ion channels on a patch. Pulses of 10(-4) M ACh together with EN in different concentrations were applied repetitively. RESULTS: The current elicited by 10(-4) M ACh is reduced reversibly in a concentration-dependent manner by EN in clinically relevant concentrations: 1,44 x 10(-5) M EN inhibit about 10%, 1.44 x 10(-4) M 25%, 1.44 x 10(-3) M 35%, and 1.44 x 10(-2) M 75% of the ion flux (averaged results from 48 patches). EN decreases the time constant of the current decay. This acceleration of desensitisation kinetics is partly reversible if followed by application of 10(-4) M ACh. CONCLUSION: In this study we were able to show that EN reduces the currents of the ligand-gated embryonic-like nAChR in clinically relevant concentrations. Volatile anaesthetics are known to influence GABAA-, glutamate-, and glycine- activated receptors, which are members of the same family of ligand-gated receptor-channel units. Thus, the action of volatile anaesthetics on ligand-gated receptors may play a role in the mechanism of general anaesthesia. The interaction of volatile anaesthetics with nondepolarising neuromuscular blockers may also be based on this effect at the neuromuscular junction.

De novo synthesis and desaturation of fatty acids at the mitochondrial acyl-carrier protein, a subunit of NADH:ubiquinone oxidoreductase in Neurospora crassa.

We have cultivated the cel mutant of Neurospora crassa defective in cytosolic fatty acid synthesis with [2-14C]malonate and found radioactivity covalently attached to the mitochondrial acyl-carrier protein (ACP), a subunit of the respiratory chain NADH:ubiquinone oxidoreductase. We purified the ACP by reverse-phase HPLC: the bound acyl groups were trans-esterified to methylesters and analyzed by gas chromatography. The saturated C6 to C18 fatty acids and oleic acid were detected. De novo synthesis and desaturation of fatty acids at the ACP subunit of NADH:ubiquinone oxidoreductase and use of the products of this mitochondrial synthetic pathway for cardiolipin synthesis is discussed.

A new and rapid method for the assay of bacterial fatty acids using high resolution capillary gas chromatography and trimethylsulfonium hydroxide.

Gas-liquid chromatography of cellular fatty acids is a useful tool for the identification of bacteria. Derivatization of bacterial fatty acids to methyl esters by conventional techniques is usually time-consuming and complicated. A new one-step technique using trimethyl-sulfonium hydroxide allows the direct formation of fatty acid methyl esters within 1-2 min. Some random examples of profiles demonstrate that straight, branched, saturated, unsaturated, hydroxy and cyclopropyl fatty acids match conventional preparations well. The method is a very sensitive one, since only a few colonies are sufficient for preparation of fatty acid methyl esters.