Measurement of storage time, estimation of ion number and study of absorption line profile in a Paul trap

Europium (Eu⁺) ions were confined in a Paul trap and detected by non-destructive method. Storage time of Eu⁺ ions achieved in vacuum was improved by orders of magnitude employing buffer gas cooling. The experimentally detected signal was fitted to the ion response signal and the total number of ions trapped was estimated. It is found that the peak signal amplitude as well as the product of FWHM and the peak signal amplitude is proportional to the total number of trapped ions. The trapped ion secular frequency was swept at different rates and its effect on the absorption line profile was studied both experimentally and theoretically.     

Microanalysis of catecholamines in human plasma by high-performance liquid chromatography with amperometric detection as compared with a radioenzymatic method

A high-performance liquid chromatographic procedure is described for the quantitative determination of epinephrine, norepinephrine, and dopamine in human plasma. The method, which is based on adsorption of the catecholamines to alumina and, after liberation, separation on a microparticulate bonded strong cation-exchange resin and amperometric detection, has been optimized to give complete baseline separation of the substances of interest. Dihydroxybenzylamine, a nonendogenous catecholamine, is used as the internal standard. The detection limit is about 0.1 pmol for dopamine. Analysis of data obtained for norepinephrine and epinephrine from a total of 59 plasma samples showed a good correlation to the corresponding values obtained with a radioenzymatic method. Some results from normal and pathological conditions are compared.     

Correction: Dermatan sulfate in tunicate phylogeny: Order-specific sulfation pattern and the effect of [→4IdoA(2-Sulfate)β-1→3GalNAc(4-Sulfate)β-1→] motifs in dermatan sulfate on heparin cofactor II activity

After the publication of the work entitled "Dermatan sulfate in tunicate phylogeny: Order-specific sulfation pattern and the effect of [→4IdoA(2-Sulfate)β-1→3GalNAc(4-Sulfate)β-1→] motifs in dermatan sulfate on heparin cofactor II activity", by Kozlowski et al., BMC Biochemistry 2011, 12:29, we found that the legends to Figures 2 to 5 contain serious mistakes that compromise the comprehension of the work. This correction article contains the correct text of the legends to Figures 2 to 5.     

Liquid chromatographic monitoring of pseudocholinesterase activity: comparison of methods.

In order to study the activity of pseudocholinesterase in vitro, two liquid chromatographic techniques have been developed. One is based on phase transfer-catalyzed (PTC) esterification of the carboxylic acid formed during hydrolysis of the substrate, and the other on the use of a radioisotopically labeled substrate. In both cases, the substrate used was a long-chain choline ester. The PTC method, utilizing (N-9-acridinyl)bromoacetamide as a fluorogenic labeling reagent in an aqueous-organic two-phase system, gives esters with very high fluorescence intensity. The radiochromatographic method makes use of on-line radioactivity monitoring of the substrate and product in order to follow the hydrolysis reaction. In both methods reversed-phase liquid chromatography is used. A method for the synthesis of 3H-labeled choline esters is also described. Both techniques are compared with regard to sensitivity, reproducibility and practical considerations.     

Precolumn fluorogenic labelling of carboxylic acids with the use of N-(1-pyrenyl)-bromoacetamide and phase-transfer catalysis

Summary N-(1-Pyrenyl)-bromoacetamide, which is readily synthesized from 1-aminopyrene and bromoacetyl bromide, has proved to be an excellent derivatization reagent for carboxylic acids. A technique has been developed, based upon a reaction with the carboxylate as an ion pair in ethylene dichloride at 90 °C, which gives highly fluorescent ester derivatives, permitting quantitative determination by liquid chromatography of less than one pmol using conventional fluorimetric detection. Further, the method is highly reproducible and of general utility.