Biomedical subjects

Akos Végvári

Publications and source records attributed to Akos Végvári.

8 recordsLinked to original sources

PubMed2006

Theoretical and nomenclatural considerations of capillary electrochromatography with monolithic stationary phases.

During the past decade, CEC has been one of the few novel achievements in the field of separation science attracting a wide interest. The technology progress permitted the realization of the long-sought idea to employ an electroosmotically driven flow through the columns improving the separations in terms of both resolution and efficiency. The early practical obstacles related to the use of conventional bead-packed columns have been solved by the introduction of continuous beds, also known as monoliths. Hitherto, various synthesis approaches have been successfully developed producing monolithic beds in situ in capillary columns, sharing similar physical structure built up of tiny particles (in the sub-microm range) that are covalently linked together and to the capillary wall. Parallel with the practical column technology studies, the theory of electrochromatography has been continuously developed, focusing on such basic issues as EOF characterization, separation efficiency, and peak dispersion effects. This review provides a short introduction to the theory of CEC with special attention to monolithic separation beds. The paper also summarizes the latest achievements in CEC and discusses the nomenclature, EOF characteristics, and some specific advantages of monolithic column technology.

Chromatography, High Pressure Liquid↗

PubMed2006

Universal method for synthesis of artificial gel antibodies by the imprinting approach combined with a unique electrophoresis technique for detection of minute structural differences of proteins, viruses, and cells (bacteria). III: gel antibodies against cells (bacteria).

Artificial antibodies in the form of gel granules were synthesized from the monomers acrylamide and N,N'-methylenebisacrylamide by the imprinting method in the presence of Echerichia coli bacteria as template. The electrophoretic migration velocities of the gel antibodies (i) saturated with the antigen (Escherichia coli MRE-600), (ii) freed of the antigen, and (iii) resaturated with bacteria, were determinated by electrophoresis in a rotating narrow-bore tube of 245 mm length and the 2.5 and 9.6 mm inner and outer diameters, respectively. Removal of bacteria from the gel antibodies was made by treatment with enzymes, followed by washing with SDS and buffer. Gel granules becoming charged by adsorption of bacteria move in an electrical field. We obtained a significant selectivity of gel antibodies for E. coli MRE-600, since the granules did not interact with Lactococcus lactis; and when E. coli BL21 bacteria were added to the gels selective for E. coli MRE-600, a significant difference in the migration rate of the complexes formed with the two strains was observed indicating the ability of differentiation between the two strains. The gel antibodies can be used repeatedly. The new imprinting method for the synthesis of artificial gel antibodies against bioparticles described herein, and the classical electrophoretic analysis technique employed, thus represent - when combined - a new approach to distinguish between different types and strains of bacteria. The application area can certainly be extended to cover other classes of cells.

Acrylamide↗

PubMed2005

Homogeneous gels for capillary electrochromatography.

Homogeneous gels represent a new type of (electro)chromatographic media possessing unique separation properties unmatched with any other chromatographic beds. It is important to emphasize that they principally differ from continuous beds, polymer rods (better known as monoliths), which are particulate separation media with pores permitting hydrodynamic flow through the columns. Monoliths, thus, are more similar to beds conventionally packed with beads, although the particles building up monolithic columns are usually smaller in size (few submicometers) and covalently linked together. Consequently, homogeneous gels deserve better the term "monoliths" having a non-particulate structure formed by crosslinked free polymer chains (according to a dictionary a monolith is a non-modularized column). The goals of this minireview are to clarify the position of homogeneous gels among the separation media (including polymer solutions), to explain and to exemplify their outstanding (electro)chromatographic properties. This review gives hopefully a complete list of references to homogeneous gels developed for capillary electrochromatography.

Electrophoresis, Capillary↗

PubMed2003

Hybrid microdevice electrophoresis of peptides, proteins, DNA, viruses, and bacteria in various separation media, using UV-detection.

Recently we described the design of a hybrid microdevice for micro(nano)electrophoresis and electrochromatography, discussed its advantages and disadvantages compared to conventional microdevices and presented a few applications with low-molecular-weight samples. In this paper, we demonstrate the broad application range of this device using UV-based analyses of (i) peptides by free-zone electrophoresis and electrophoresis in a recently introduced gel (polyacrylamide cross-linked with allyl-beta-cyclodextrin), (ii) proteins by electrophoretic molecular-sieving in a polymer solution supplemented with SDS, (iii) DNA fragments by electrophoresis in the above gel, (iv) virus particles in this gel, as well as in free buffer and (v) bacteria in free buffer. To illustrate the advantages of the hybrid microdevice we can mention that electrophoresis of proteins in a polymer-containing buffer, supplemented with sodium dodecyl sulfate (SDS), in a 4.30 (2.75) cm long channel gave a resolution similar to that in conventional capillary electrophoresis in a 23.5 (18.6) cm long capillary and analysis times which were 15-fold shorter.

Bacteria↗

PubMed2002

High-resolution capillary zone and gel electrophoresis of structurally similar amphipathic glutathione conjugates based on interaction with beta-cyclodextrins.

The tripeptide glutathione is a prominent intracellular constituent that provides protection against genotoxic and carcinogenic electrophiles and is also a component of several biological signal substances. Glutathione conjugates, free glutathione, and glutathione disulfide contain charged amino acid residues, which contribute to solubility in aqueous media. However, the amphipathic nature of glutathione conjugates and the small differences that may distinguish the S substituents, pose analytical problems in their resolution. The present study demonstrates how homologous S-alkyl and S-benzyl conjugates of high structural similarity can be efficiently resolved by capillary electrophoresis. Inclusion of beta-cyclodextrins in the buffer or in a polyacrylamide gel affords baseline separation of the analytes. The separation methods described are applicable to enzyme assays in vitro and to the identification and quantification of glutathione conjugates of importance in toxicology and physiology. The contribution of beta-cyclodextrin to the separation is primarily based on interactions between its hydrophobic cavity and the S-alkyl and S-benzyl groups of the analytes.

Alkylation↗

PubMed2002

Stable homogeneous gel for molecular-sieving of DNA fragments in capillary electrophoresis.

A polyacrylamide gel crosslinked with allyl-beta-cyclodextrin can be used repeatedly for several weeks for the separation of DNA fragments, since bubbles are not generated during a run. Allyl-beta-cyclodextrin can easily be synthesized in one step from allylglycidylether and beta-cyclodextrin. The plate numbers for DNA fragments, up to about 1500 bp, are high: for the separation of pBR322/HaeIII fragments they were in the range 450,000-1,600,000 m(-1). The resolution was almost independent of the concentration of the crosslinker (allyl-beta-cyclodextrin)--in sharp contrast to gels crosslinked with N,N'-methylenebisacrylamide.

Base Pairing↗

PubMed2002

A hybrid microdevice for electrophoresis and electrochromatography using UV detection.

We have designed a new class of microdevices composed of a supporting plastic (polyvinyl chloride, PVC) plate integrated with a groove for a piece of fused silica capillary (the separation channel), a slit for on-tube detection, an "islet" for the application of sample, electrode vessels and platinum electrodes. The design permits electrophoretic, electrochromatographic and chromatographic separations with on-tube UV detection. The efficient heat dissipation allows relatively high field strengths. This article is the first one dealing with microdevices where polymer solutions are replaced by homogeneous gels. A new type of gels synthesized from acrylamide and 2-hydroxy-3-allyloxy-propyl-beta-cyclodextrin (allyl-beta-CD) as a cross-linker was employed for electrophoresis and electrochromatography. 2-Acrylamido-2-methylpropanesulfonic acid was added to the monomer solution to create a high electroendosmotic flow in electrochromatographic runs. These gels have excellent electrochromatographic and electrophoretic properties for low-molecular-weight compounds and DNA, as shown previously, namely high resolution combined with high stability. The unique cross-linker can be used for specific interaction with the alkyl and phenyl groups. The tripeptide glutathione (gamma-L-glutamyl-L-cysteinyl-glycine) and its benzyl conjugates were selected as model compounds to study the resolving power of the gel because they are difficult to separate by free zone electrophoresis. The limit of detection (LOD) for S-benzyl-glutathione was determined (ca. 7 microM). Run-by-run reproducibility was high (the separation factor of glutathione in the gel was 0.3 with 2.5% coefficient of variation, CV). Neutral compounds (acetone, acetophenone, propiophenone and butyrophenone) were separated electrochromatographically in the gel. The influence of organic solvent (acetonitrile) on the electroendosmotic mobility was similar to that in reversed-phase separations, although the separation mechanism is different. ATP, ADP and AMP were separated in less than 10 s by free-zone electrophoresis.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2002

Tripeptide interference with human immunodeficiency virus type 1 morphogenesis.

Capsid assembly during virus replication is a potential target for antiviral therapy. The Gag polyprotein is the main structural component of retroviral particles, and in human immunodeficiency virus type 1 (HIV-1), it contains the sequences for the matrix, capsid, nucleocapsid, and several small polypeptides. Here, we report that at a concentration of 100 micro M, 7 of 83 tripeptide amides from the carboxyl-terminal sequence of the HIV-1 capsid protein p24 suppressed HIV-1 replication (>80%). The three most potent tripeptides, glycyl-prolyl-glycine-amide (GPG-NH(2)), alanyl-leucyl-glycine-amide (ALG-NH(2)), and arginyl-glutaminyl-glycine-amide (RQG-NH(2)), were found to interact with p24. With electron microscopy, disarranged core structures of HIV-1 progeny were extensively observed when the cells were treated with GPG-NH(2) and ALG-NH(2). Furthermore, nodular structures of approximately the same size as the broad end of HIV-1 conical capsids were observed at the plasma membranes of treated cells only, possibly indicating an arrest of the budding process. Corresponding tripeptides with nonamidated carboxyl termini were not biologically active and did not interact with p24.

Capsid Proteins↗