Biomedical subjects

P Gebauer

Publications and source records attributed to P Gebauer.

26 records · Page 2Linked to original sources

PubMed1991

Innovative developments in isotachophoresis (displacement electrophoresis).

This Mini Review is aimed at characterizing the innovative developments in isotachophoresis (ITP) during the past few years, discussing in turn new theoretical, analytical, preparative and applicative aspects of this unique separation method. Examples given from our laboratory include the study of the detailed dynamics of the ITP separation of four components by computer simulation and experimental validation in a capillary-type instrument with multiple sensors along the separation trough; the anionic ITP analysis in presence of a strong cathodic electroosmotic flow using an open-tubular fused-silica capillary with on-column multiwavelength detection, and the fractionation of proteins in a screen-segmented, rotating column as well as by recycling ITP.

Electrophoresis↗

PubMed1990

Mathematical description of electrophoretic separation of weak acids by means of an H+ pulse.

The paper gives a detailed theoretical description of the recently published principle of separation by a dynamic pulse in zone electrophoresis. The theory is illustrated by using a system in which weak acids are separated by migrating against an H+ pulse. The mathematical description pertains to (i) the evolution and migration of the concentration profile of the H+ pulse, and (ii) the migration of a sample substance (here a weak acid) against and through the pulse. As a result the migration (detection) times of the separated sample components are obtained. Based on the theory, a graphical treatment was developed which allows fast optimization of the separation conditions by observing (on the PC monitor) how the trajectories of the substances (drawn in a time vs. distance coordinate system) change with a change in the parameters of the pulse. Some of the results illustrate the possible advantages of using the dynamic pulse method in analytical practice.

Acids↗

PubMed1985

Recent developments in isotachophoresis.

This paper is summarizing the contributions to the analytical capillary isotachophoresis published during the period 1981-1984. It characterizes the present state of the method and covers theory, fundamental analytical aspects, instrumentation and applications. Special attention was payed to the fundamental analytical aspects, and a detailed discussion is given of the selection of electrolyte systems, stability of zones and separability of substances. The present commercial instrumentation is also briefly described.

Animals↗

PubMed1985

Determination of heavy metals by isotachophoresis.

The suitability of isotachophoresis for the analysis of metals in, e.g., environmental samples was studied. In a cationic operational system the heavy metals Fe, Cu, Ni, Cd, Co, Zn, Pb and Mn were simultaneously determined. The separation was achieved through complex formation with one of the counter ions, hydroxyisobutyric acid. The other counter ion was acetic acid, the leading ion was 0.02 M potassium or sodium (pH 4.1) and the terminator was H+. The analysis time was 15 min at 60 microA in a 0.2 mm I.D. capillary. Aqueous samples containing ppm and ppb amounts were enriched on a cation exchanger with an extremely low affinity for sodium (Chelex 100). Good recovery, linearity, precision and accuracy were obtained even down to the ppb range. Although the sensitivity of the method is not greater than that of some of the more established methods for the individual metals, a great advantage of isotachophoresis is the simultaneous determination of the metals, with equal response factors. An example is given of the determination of metals, including aluminium, in serum.

Cation Exchange Resins↗

PubMed1983

Chloroperoxidase generation of singlet Delta molecular oxygen observed directly by spectroscopy in the 1- to 1.6-mum region.

The (0,0) (1)Delta(g) --> (3)Sigma(-) (g) singlet molecular oxygen chemiluminescence emission from a biological reaction system, chloroperoxidase (EC 1.11.1.10) acting on hydrogen peroxide at low pH (phosphate buffer, pH 2.85) with Cl(-) as a cosubstrate, was recorded with an ultrasensitive IR spectrometer. The strong chemiluminescence emission peak observed at 1.30 mum provides clear evidence of the enzymatic generation of (excited) singlet oxygen from peroxide in this system.

Journal Article↗

PubMed1981

Histamine content in human kidneys with hypernephroid carcinoma. Is there a pathophysiological mechanism?

The hypernephroid carcinoma is the most common tumour of the kidney in adults. Haematuria can occur, even in the early developmental stages. In investigations of 30 patients with-haematuria, radiological examinations were made and the plasma histamine levels were determined in both from the renal artery and vein, the vena cava and the aorta. After nephrectomy, the histamine content of various tissues in different regions of the kidney were investigated. Significant increases of plasma and tissue histamine levels were found in the veins of the tumour-riddled kidney and in the tissue surrounding the tumour. an experimental study on dogs investigated whether or not an injection of histamine into the renal artery would provoke haematuria. Dose-dependent haematuria occurred, which was most pronounced following intra-arterial injection of 25 micrograms/kg of histamine.

Adenocarcinoma↗

PubMedDate not supplied

Identification of peaks in capillary zone electrophoresis based on actual mobilities.

A procedure is proposed for the calculation of the actual effective mobility of a zone from its migration time. It is based on the use of internal standards with known mobilities; the use of two internal standards provides reliable mobility data even if the magnitudes of the effects of sample composition, capillary temperature, capillary length, migration distance, used voltage, as well as the tube length occupied by the injected sample are unknown. Formulas have been derived for the calculation of the actual mobilities, and their experimental verification has been carried out by using a model set of anionic solutes with mobilities ranging from -56 to -20 x 10(-9) m2V-1s-1 and chloride as the ion modelling the effect of the sample matrix.

Electrolytes↗

PubMedDate not supplied

Fractionation of human serum proteins by capillary and recycling isotachophoresis.

The fractionation of human serum proteins using capillary isotachophoresis (CITP) and recycling isotachophoresis (RITP) in presence of low molecular mass spacer compounds is reported. Anionic CITP was performed in an instrument equipped with a Teflon capillary of 0.5 mm ID as well as in an apparatus which features an open-tubular fused-silica capillary of 75 microns ID. RITP was performed in a recycling fast flow focusing apparatus in which fluid flows rapidly through a narrow, rectangular cell and the effluent from each outlet port is reinjected into the electrophoresis chamber through the corresponding input port. Typically, 1 mL serum was processed batchwise within about 2.5 h prior to collection of 30 fractions of about 4 mL each. The fractions were analyzed separately for conductivity, pH and UV absorbance and selected fractions were characterized by an immunoassay for transferrin, as well as by gel isoelectric focusing, two-dimensional gel electrophoresis, CITP and capillary zone electrophoresis. The search for suitable electrolyte systems and spacers was executed by CITP and by computer simulation. For simple configurations, separations predicted by simulation are shown to qualitatively agree with fractionation performed by CITP and RITP. Configurations producing three protein subgroups, the first containing mainly albumin, the second transferrin and the third the globulins, are discussed.

Blood Proteins↗