Biomedical subjects

Yukui Zhang

Publications and source records attributed to Yukui Zhang.

41 records · Page 3Linked to original sources

PubMed2003

On-line hyphenation of capillary isoelectric focusing and capillary gel electrophoresis by a dialysis interface.

An on-line two-dimensional (2D) capillary electrophoresis (CE) system consisting of capillary isoelectric focusing (CIEF) and capillary gel electrophoresis (CGE) was introduced. To validate this 2D system, a dialysis interface was developed by mounting a hollow fiber on a methacrylate resin plate to hyphenate the two CE modes. The two dimensions of capillary shared a cathode fixated into a reservoir in the methacrylate plate; thus, with three electrodes and only one high-voltage source, a 2D CE framework was successfully established. A practical 2D CIEF-CGE experiment was carried out to deal with a target protein, hemoglobin (Hb). After the Hb variants with different isoelectric points (pIs) were focused in various bands in the first-dimension capillary, they were chemically mobilized one after another and fed to the second-dimension capillary for further separation in polyacrylamide gel. During this procedure, a single CIEF band was separated into several peaks due to different molecular weights. The resulting electrophoregram is quite different from that of either CIEF or CGE; therefore, more information about the studied Hb sample can be obtained.

Animals↗

PubMed2003

Separation of selected humic degradation compounds by capillary electrochromatography with monolithic and packed columns.

The separation of selected lignin/humic substance (HS) degradation compounds by capillary electrochromatography (CEC) with a methacrylate-based monolithic column and a conventional column packed with 5 microm octadecyl silica (ODS) particles is presented. The effects of organic modifier concentration, pH of the mobile phase, ionic strength, applied voltage, and temperature on the separation were investigated to determine the optimal separation conditions. With the increase of pH in the mobile phase, some of analytes start to ionize and both chromatographic partition and electrophoresis can play roles in separation simultaneously. Accordingly, different selectivity from high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) could be achieved. The performances of both kinds of columns were compared. The results showed that the peaks of compounds obtained on the former column were much wider than those on the latter one, although good separation efficiency of alkylbenzenes could be readily achieved; the most probable reasons for this behavior and method to solve this problem were briefly discussed. The CEC of a soil fulvic acid with a monolithic column produced partly resolved broad bands; by means of nuclear magnetic resonance (NMR) analysis a wide range of oxygen derived aromatic substitution patterns was found with prominent contributions from phenolic and carboxylic groups.

Benzopyrans↗

PubMed2002

Study on the multiple sites binding of human serum albumin and porphyrin by affinity capillary electrophoresis.

Equations to describe the two sites binding between proteins and ligands were deduced. According to these equations, not only the binding constants, but also the mole fraction of proteins in different forms could be obtained. Using the published data on the interaction between human serum albumin (HSA) and three kinds of porphyrin (coproporphyrin (CP), uroporphyrin I (UP) and protoporphyrin (PP)), a further study on their binding was carried out. It was concluded that there may exist two binding sites with the binding constants at the first site, proved to be the preferential one, being 6.50 x l0(5), 1.94 x 10(6) and 8.94 x 10(5), respectively. In addition, it was also demonstrated that the two binding sites of HSA with CP and UP might be of different kinds, though those of HSA and PP were of the same kind but at different positions.

Binding Sites↗

PubMed2002

Development of a precolumn derivatization method for the determination of free amines in wastewater by high-performance liquid chromatography via fluorescent detection with 9-(2-hydroxyethyl)acridone.

A simple, sensitive, and mild method for the determination of amino compounds based on a condensation reaction with fluorescence detection has been developed. 9-(2-Hydroxyethyl)acridone reacts with coupling agent N,N'-carbonyldiimidazole at ambient temperature to form activated amide intermediate 9-(2-acridone)oxyethylcarbonylimidazole (AOCD). The amide intermediate (AOCD) preferably reacts with amino compounds under mild reactions in the presence of 4-(dimethylamino)pyridine (base catalyst) in acetonitrile to give the corresponding sensitively fluorescent derivatives with an excitation maximum at lambda(ex) 404 nm and an emission maximum at lambda(em) 440 nm. The labeled derivatives exhibit high stability under reversed-phase conditions. The fluorescence intensities of derivatives in various solvents or at different temperatures were investigated. The method, in conjunction with a gradient elution, offers a baseline resolution of the common amine derivatives on a reversed-phase C18 column. The LC separation for the derivatized amines shows good reproducibility with acetonitrile-water including 2.5% DMF as mobile phase. The relative standard deviations (n = 6) for each amine derivative are <4.5%. The detection limits (at a signal-to-noise ratio of 3) per injection were 0.16-12.8 ng/mL. Further research for the field of application, based on the AOCD amide intermediate as derivatization reagent, for the determination of free amines in real water samples is achieved.

Acridines↗

PubMed2002

Characteristics of electroosmotic flow and migration of neutral solutes under stepwise gradient elution of capillary electrochromatography.

A theoretical study on the velocity of electroosmotic flow (EOF) and the retention times of neutral solutes under multiple-step gradient of capillary electrochromatography (CEC) was carried out, focusing on that with three kinds of mobile phases. Through the model computations, the detaining time of the second kind of mobile phase in the column was proved to play an important role in affecting EOF. The variation speed of EOF was shown to be determined by the differences among dead times in different steps. In addition, the prediction of the retention times of 13 aromatic compounds under gradient mode was performed with the deduced equations. A relative error below 3.3% between the calculated and experimental values was obtained, which demonstrated the rationality of the theoretical deduction. Our study could not only improve the comprehension of stepwise gradient elution, but also be of significance for the further optimization of separation conditions in the analysis of complex samples.

Chromatography, High Pressure Liquid↗