PubMed Health⌕ Search

Biomedical subjects

K J van der Merwe

Publications and source records attributed to K J van der Merwe.

At least 37 records · Page 2Linked to original sources
PubMed1985

Coated glass beads in enzyme linked immunosorbent assays.

Successful enzyme linked immuno-sorbent assays (ELISA) were conducted with frosted glass beads coated directly with an immune reactant (antigen or antibody) using glutaraldehyde as cross linking agent. Equally effective ELISA experiments were made by attaching the antigen to a thin layer of gelatin which had been cross-linked over the entire surfaces of the frosted glass beads. The enzyme and substrate used were alkaline phosphatase and p-nitro-phenyl phosphate.

Alkaline Phosphatase↗
PubMed1984

Metabolic activation and deactivation of fusarin C, a mutagen produced by Fusarium moniliforme.

The metabolic activation and deactivation of fusarin C, a mutagen produced by Fusarium moniliforme strain MRC 826, was studied by the Salmonella typhimurium mutagenicity assay using tester strain TA 100. A microsomal monooxygenase, preferably induced by phenobarbitone (PB) activities the mutagen to its active mutagenic form. Deactivation of the mutagenic metabolite seems to occur through chemical binding to thiol groups and by enzymatic conjugation mediated by a cytosolic glutathione -S-transferase.

Animals↗
PubMed1984

Agarose: a possible universal gel exclusion agent.

Granulated agarose gels suitable for gel exclusion chromatography of proteins of any molecular weight may now be prepared. This was made possible by the observation that agarose solutions of 16% polysaccharide may be prepared by displacing 8% agarose from solution with 8% polyethylene glycol Mr 6000. The displaced polysaccharide concentrates in a viscous mass occupying half the volume of the original carbohydrate solution. By diluting the displaced polysaccharide with hot watery solutions of electrolyte and allowing the solutions to congeal, gels of any desired concentration, ranging from low to the maximum of 16%, may be prepared.

Animals↗
PubMed1984

Bead centrifuge tube inserts--a semi-quantitative theory.

A semi-quantitative theory is proposed for the sedimentation of particles in centrifuge tubes filled with polymer beads acting as sedimentation aids. The theory concerns the attainment of approximate sedimentation-diffusion equilibrium in minimum time of centrifugation. It is shown empirically that the time to reach this state is approximately proportional to the diameter of the polymer beads as predicted by the theory.

Diffusion↗
PubMed1983

A mutagen produced by Fusarium moniliforme.

A mutagenic compound produced by Fusarium moniliforme on maize was isolated by CHCl3--iso-PrOH extraction, solvent partitioning and liquid chromatography on silica gel and Sephadex LH-20. HPLC studies showed that different mutagenic and non-mutagenic forms can be derived from the mutagen (P3) and that prolonged exposure to longwave u.v. light and to high temperatures causes a total loss of its u.v. absorption and mutagenic characteristics. Spectral data presented for P3 include u.v., i.r., mass spectra as well as 1H NMR and 13C NMR. Mass spectral data indicated a molecular formula of C23H29NO7.

Chromatography, High Pressure Liquid↗
PubMed1983

Novel application of H tube electrophoresis to separation technology.

The H tube electrophoresis technique was used for isolating human IgG by the net effect of electrophoresis and electro-endosmosis in agarose gel containing human serum. In a similar experiment human serum albumin was purified by extracting the agarose gel slice containing the albumin following zone electrophoresis of serum in agarose. By taking advantage of the relatively high reverse electro-endosmotic flow compared to the migration of IgG in agarose gel, sheep anti chicken immunoglobulin was fractionated into active and inactive portions. It was estimated that 90% of the nonspecific IgG could be eliminated in this manner. The specific immunoglobulin fraction showed a higher mobility to the positive electrode than the bulk of the non specific IgG. The H tube proved to be ideal for zone electrophoresis in concentration gradients of inert substances. For this purpose sugar gradients were used for electrophoretic separation of proteins and viruses which are not affected by high osmotic pressures but, for separating animal cells it was necessary to use Ficoll gradients. A mixture of yellow Atypical Tomato Mosaic Virus and the haemocyanin of Burnupena cincta were separated into discrete zones and chicken IgY anti haemocyanin was subfractionated. The specific fraction showed a lower migration rate to the positive pole than the bulk of the non specific material.

Animals↗
PubMed1982

Determination of the number of Fab1 pieces which react with high molecular weight antigens.

The sedimenting-droplet technique was used for the determination of the masses of immune Fab1 pieces which may bind to antigenic sites on three haemocyanins. Similar experiments were conducted on three viruses which belong to the Tobamo group. It was calculated that 384 homologous Fab1 pieces could bind to a molecule of the haemocyanin of Burnupena cincta and 950 homologous Fab1 pieces to a virion of tobacco mosaic virus. By taking special precautions the number of undegraded antibody molecules which can bind to a Tobacco mosaic virus particle may be determined with the same technique.

Animals↗
PubMed1981

Electro-extraction of viruses from infected plant tissue.

An apparatus is described which was used for rapid extraction of viruses from frozen and thawed infected plant tissues. The novel principle is the establishment of a potential gradient of 15 to 20 volts/cm at approximately 90 degrees across the leaves of the infected plant while the leaves are surrounded by buffer of low molarity and of the appropriate hydrogen ion concentration. To keep the leaves in the correct orientation they were placed as single layers between coarse rigid plastic gauze. The method, termed electro-extraction, was used as the initial step in the purification of turnip yellow mosaic, tobacco mosaic and maize streak viruses. An electron micrograph of the purified maize streak virus is presented.

Freezing↗
PubMed1978

The chemical composition and stability of bacillomycin S.

Bacillomycin S, an antifungal antibiotic from culture filtrates of Bacillus subtilis, was shown to consist of proteinaceous matter (83.6 g/100 g) and lipid material (16 g/100 g). The amino acid and fatty acid components were determined qualitatively and quantitatively. It was shown that bacillomycin S is stable at physiological pH and it is suggested that its antifungal activity resides in the intact molecule.

Antifungal Agents↗
PubMedDate not supplied

Binding and elution of serum glycoproteins from agarose.

Evidence in support of previous observations by different authors that agarose is not an entirely inert support in affinity chromatography is presented. In the present communication it is shown that 8% granulated agarose adsorb serum glycoproteins in 10mM phosphate buffer, pH 7.2 and desorb these in 200mM NaCl in 10mM phosphate buffer, pH 7.2. The desorbed glycoproteins retained their abilities to react with antibodies elicited in sheep to normal human serum glycoproteins, despite the loss of mannose and galactose following the agarose treatment.

Adsorption↗