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At least 235 records · Page 13Linked to original sources
PubMed1995

Electrophoresis between sieving and reptation: an investigation of the role of shape fluctuations in electrophoresis.

We present numerical simulation results of electrophoretic mobilities of flexible polyelectrolytes over a wide molecular size range moving through gels with various pore sizes. The data are compared to existing models for different molecular size regimes and to experimental results. We observe rather pronounced shape fluctuations of the polyelectrolytes which, especially for larger gel pores or small molecules, have a strong impact on the dynamics of the molecules. Electrophoretic separation, as is used e.g. for DNA sequencing, is best achieved for polyelectrolytes with a radius of gyration of the order of the average pore radius of the gel, i.e. in a molecular size regime where the polyelectrolyte interacts with only a few gel fibers at a given time. A decrease of the gel pore size leads to a systematic decrease of the electrophoretic mobility, but does not lead to a qualitative change in the molecular size dependence, as long as the pore size is larger than the persistence length of the polyelectrolyte.

Electrolytes↗
PubMed2005

Pre-equilibrium capillary zone electrophoresis or frontal analysis: advantages of plateau peak conditions in affinity capillary electrophoresis.

The feasibility of using the affinity CE methodologies pre-equilibrium CZE and CE frontal analysis was tested on interaction systems exhibiting rapid on-and-off kinetics. Experimentally, the methodologies differ only with respect to the volume of sample introduced into the capillary. Pre-equilibrium CZE has been considered amendable to interactions with slow on-and-off kinetics only; however, it has recently been applied in studies of interactions with fast on-and-off kinetics. The effect of varying the sample volume introduced hydrodynamically into the capillary on the apparent degree of complexation was studied. For two different binding systems, the fraction of free analyte was found to be overestimated using pre-equilibrium CZE as compared to volumes providing plateau peak conditions as used with frontal analysis. Results indicate that frontal analysis conditions lead to more robust binding assays and thus more reliable data. The validity of data obtained by pre-equilibrium CZE may be low, thus the use of an experimental setup providing plateau peaks is highly recommended. It is suggested that the effect of altering the sample volume on the degree of binding should be investigated as part of method development and validation.

Benzoic Acid↗
PubMed2006

Determination of tobacco-specific N-nitrosamines in rabbit serum by capillary zone electrophoresis and capillary electrophoresis-electrospray ionization-mass spectrometry with solid-phase extraction.

In this paper, we propose a new strategy for separation and determination of tobacco-specific N-nitrosamines (TSNAs), a group of strong carcinogens found only in tobacco products, by using CZE and CE-MS associated with SPE. Six TSNAs: N'-nitrosonornicotine, N'-nitrosoanatabine, N'-nitrosoanabasine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, and 4-(methylnitrosamino)-4-(3-pyridyl)-1-butanol were simultaneously separated by either of two CZE methods, one of which worked with ammonium formate buffer (pH 2.5) and another with citrate buffer (pH 2.4), as well as a CE-MS method. The CZE conditions including pH and concentration of running buffer, capillary length, applied voltage, and capillary temperature were systematically optimized. For CE-MS method, an optimized sheath liquid consisted of methanol-water was used at a flow rate of 10 muL/min. With SPE procedure, our proposed CE-MS method was successfully applied to determine TSNAs after 15 min metabolism in rabbits. A comparison study between CZE and CE-MS methods for quantitative purposes was carried out, showing that both methods provided similar separation efficiency, selectivity, repeatability, linearity, and recovery. However, CE-MS method was better suited for the analysis of TSNAs in complicated biological samples for its sensitivity and extra information on molecular structure. Having good accordance with our previous work by using LC-MS, the new CE-MS method is expected to be an alternative to the LC-MS method and applied to study the metabolism of TSNAs.

Animals↗