Journal of capillary electrophoresis and microchip technology最新文献

The effect of the addition of nonaqueous modifiers in capillary electrophoresis at varying concentrations was determined using synthetic peptides as model compounds. The electroosmotic flow is compared in each of the binary solvent systems and, in all cases, an increase in the concentration of organic solvent resulted in a decrease in the electroosmotic flow. The electrophoretic mobilities of each peptide were calculated and, in the case of acetonitrile, little or no change was observed in the peptide mobilities. In general, a decrease in the electrophoretic mobilities of the peptides was observed for increasing concentrations of methanol and N-methylformamide. The compatibility of each modifier at 25% (vol/vol) for use with mass spectrometric detection was evaluated. From our data, the addition of acetonitrile to the CE buffer appears to be the most compatible with mass spectrometry due to shorter analysis times and increased sensitivities in comparison to methanol and N-methylformamide.

Creatine kinase (ATP: creatine N-phosphotransferase; EC 2.7.3.2) plays a key role in the energy transport, muscle contraction, and reproduction of adenosine triphosphate (ATP). The activity of the enzyme is dependent on the correct folding of the peptide. We observed the unfolding and refolding processes of the creatine kinase of rabbit muscle, and concluded that traditional electrophoresis technology is unsuitable for the transient folding intermediates formed during protein unfolding and refolding. Capillary zone electrophoresis with diode array detection was used to monitor the unfolding and refolding of rabbit creatine kinase under different pretreatments and experimental conditions. This technique provides a simple, sensitive, and rapid approach to protein unfolding and refolding.

A straightforward method for stacking an extremely large volume of a sample solution containing weakly acidic organic compounds was developed. By using alcohols such as methanol, ethanol, and 1-propanol as run buffer solvents, the electroosmotic flow was suppressed, so that analyte anions could proceed to the outlet vial against the electroosmotic flow under a reverse voltage. This effect made large-volume sample stacking possible for large anions using a bare, fused-silica capillary without intermediate polarity switching. The detection limits were in the low nanomolar range with conventional UV absorbance detection. The applicability of the technique to other organic solvents was also tested.

The separation of paraquat, diquat, and difenzoquat bipyridilium herbicides and ethyl viologen as internal standard is shown. The separation has been carried out using a fused silica capillary with a high-sensitivity detection cell for a capillary electrophoresis system and with a diode array detector. The experiments have been performed using phosphate buffer 50 mM at pH = 4 and pH = 7. The effect of methanol has also been studied when used as an organic modifier. Different voltages and electrokinetic conditions have been used to optimize the separation. Twenty Kv voltage and 10 Kv for 3 sec for injection have been found to be reliable conditions of separation at pH 4 without organic modifier.

Acyl-CoA hydrolases catalyze the hydrolysis of fatty acyl CoA thioesters to free fatty acids and coenzyme A. These enzymes play an important role in the maintenance of cellular acyl-CoA and free CoASH pools and in the detoxification of nonphysiological metabolites. The assays most commonly used for acyl-CoA hydrolase quantitation are spectrophotometric and radioisotopic methods, both of which have limitations. In this study, capillary electrophoresis was used as an effective analytical technique to characterize rat liver peroxisomal acyl-CoA hydrolase reactivity using octanoyl-CoA as a substrate at different reaction conditions. The substrate and product of acyl-CoA hydrolase were identified by their migration times and quantitated using the peak areas. The enzyme activity exhibited a typical Michaelis-Menten pattern with increasing octanoyl-CoA concentration. The apparent Km and Vmax of octanoyl-CoA hydrolysis were determined using the enzyme activity at varying substrate concentrations. The rate of hydrolysis of octanoyl-CoA with increasing enzyme concentration appeared as a hyperbolic plot. The enzyme activity became elevated with increasing incubation time, showing the highest activity at 20 min, after which it started to decrease as the incubation time increased. Thus, capillary electrophoresis has been shown to be an effective, rapid, and reproducible method for the characterization of acyl-CoA hydrolase.

Glucosamine nonenzymatically forms autocondensation glycation products under physiological conditions. Many studies have reported the effectiveness of oral doses of glucosamine alone or in combination with the galactosamine containing chondroitin in treating osteoarthritis. However, none of these studies has considered whether it is the glucosamine itself and/or one or more of its autocondensation products that exert this effect. A capillary electrophoresis method was developed to monitor the nonenzymatic formation of autocondensation glycation products of glucosamine, galactosamine, and mannosamine under physiological conditions. Major components were detected and separated by CE with a UV detector. The effects of concentration and incubation time on product species were determined. The method described is simple, rapid, and effective.

A combination of the anti-HIV drugs lamivudine (3TC), didanosine (ddI), and nevirapine were separated and quantitated in human serum with capillary zone electrophoresis (CZE). The effects of various factors such as run buffer concentration and pH on the separation were investigated. The optimized resolution was achieved with a run buffer containing 100 nM N,N-dimethyloctylamine in 80 mM phosphate buffer (pH 2.5). Diltiazem was chosen as the internal standard. All analytes were separated within 10 min at 30 degrees C with a voltage of +20 kV and UV detection at 210 nm.

The molecular radii (r) of a series of peptides have been determined by molecular modeling. With these data, it is shown that electrophoretic mobility (mu(ep)) is proportional to 1/r2, and that the dependence presented in textbooks (mu(ep) infinity 1/r) is wrong. Use of the approximately equivalent, mass-based Offord equation is discussed, and other relevant considerations are presented.

Physostigmine (PHY) and pyridostigmine (PYR) are two important anticholinesterase compounds with several clinical uses. Recently, PHY has been investigated for the treatment of senile dementia in Alzheimer's disease. However, both PHY and PYR have gained importance as antidotes for anticholinergic drugs. In military medicine, PYR is used as a prophylactic against nerve gas poisoning and was used in Saudi Arabia during the Gulf War in 1991. A new capillary zone electrophoresis (CZE) method for the rapid determination of PHY and PYR in pharmaceutical preparations has been developed. An untreated fused-silica capillary tube (75 microm i.d., 44 cm total length, 36.5 cm length to the detector) was employed with detection at 200 and 270 nm for PHY and PYR, respectively. The optimal separation conditions for PHY were: 50 mM boric acid-HCl buffer (pH 3.25) with 30 mM NaClO4, electrokinetic injection for 5 sec at -5 kV, temperature 25 degrees C, and separation voltage 15 kV. The optimal separation conditions for PYR were: 20 mM phosphate buffer (pH 7), electrokinetic injection for 20 sec at -10 kV, temperature 25 degrees C, and separation voltage 15 kV. The limits of detection (LOD, S/N = 3) were 70 and 60 ppb for PHY and PYR, respectively. The method can be used for the monitoring of possible main degradation products in tablets of military antidote formulations.