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Biomedical subjects

G Marko-Varga

Publications and source records attributed to G Marko-Varga.

41 records · Page 3Linked to original sources
PubMed1990

Bioselective detection in liquid chromatography by the use of immobilized enzymes.

The combination of liquid chromatography and immobilized enzyme reactors (LC/IMER) is a rapidly developing field of research. The enzymes are used to catalyse chemical reactions and thereby facilitate selective detection. In this instance the chemical derivatizations are performed in the post-column mode. The selectivity is demonstrated with respect to interfering compounds present in complex samples.

Amino Acids↗
PubMed1990

Liquid chromatographic separation and stereoselective detection of L- and D-amino acids with catalytic reaction detection using immobilized enzymes.

A post-column LC detection system is described for the stereoselective detection of L- and D-amino acids. The effluent of the LC column passes an immobilized enzyme reactor (IMER) containing either L- or D-amino acid oxidase. The hydrogen peroxide formed in this reactor by the oxidation of the amino acids is then transported to a second IMER containing horse-radish peroxidase. With the addition of 4-aminophenazone and dichlorophenosulphonyl chloride to the carrier, the hydrogen peroxide is reacted to form a red-coloured complex which is detected in a flow-through photometric cell at 514 nm. Applications to the analysis of amino acids in bovine and human sera are described.

Amino Acid Oxidoreductases↗
PubMed1987

High-performance liquid chromatographic separation of some mono- and disaccharides with detection by a post-column enzyme reactor and a chemically modified electrode.

The effluent from a chromatographic column was mixed with nicotinamide adenine dinucleotide coenzyme (NAD+) buffer and passed through a packed-bed reactor containing immobilized glucose dehydrogenase. Oxidation of the carbohydrates emerging from the column produced an equivalent amount of reduced coenzyme (NADH), which was detected electrochemically using an electrode modified with 7-dimethylamino-1,2-benzophenoxazine (Meldola Blue). Separation was effected in three different chromatographic systems containing a protonated ion exchanger, a calcium(II)-saturated or a lead(II)-saturated ligand exchange column. Separation, detection and k' values are reported for glucose, 2-deoxyglucose, xylose, mannose, cellobiose, lactose, ribose and glucosamine. The detection limit was 2 ng for a 20-microliter injection of glucose and the response was linear up to 6300 ng. Samples from fermentation of penicillin were analysed for lactose and glucose with the described detector. A comparison with the recordings from a refractive index detector showed that the selectivity of the enzymes and the modified electrodes are necessary for the determination of glucose and lactose.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Integrated protein microchip assay with dual fluorescent- and MALDI read-out.

A pore chip protein array (PCPA) concept based on a dual readout configuration, fluorescence imaging, and MALDI-TOF MS has been developed. Highly packed, (>4000 spots/cm2), antibody arrays were dispensed on the porous chip by using a piezo-electric microdispenser. Sandwich assay was made after blocking by addition of a secondary antibody either IgG-FITC-labeled or anti-Ang II. The antigen in the first system was a large protein (IgG), and in the other system, a FITC marked peptide Angiotensin II (Ang II) was used. Ang II antibodies showed specificity for Ang II, while the Ang I antibodies showed binding properties for Ang I, II, and Renin. Fluorescence and MALDI TOF MS read-out was made for IgG and Ang II. A major advantage of the dual read-out PCPA approach is that both affinity binding and mass identity are derived. Detection limits for Ang II on the chip is as low as 500 zmol (Ang II).

Angiotensin I↗