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Biomedical subjects

B Mattiasson

Publications and source records attributed to B Mattiasson.

At least 19 recordsLinked to original sources
PubMed1992

Process monitoring by flow-injection immunoassay. Evaluation of a sequential competitive binding assay.

A new variation on the theme of flow-injection binding assays is presented, namely the sequential competitive binding assay, in which the sample containing the native antigen is first introduced into the flow system followed by a pulse of labelled antigen. The flow-injection binding assay was used in monitoring the effluent from column chromatographic separations of proteins. By applying a computer-based evaluation system, concentrations are automatically read and compensation is made for denaturation in the affinity sorbent.

Binding, Competitive↗
PubMed1992

Maximizing the expression of a recombinant gene in Escherichia coli by manipulation of induction time using lactose as inducer.

The use of isopropyl-beta-D-thiogalactoside (IPTG) for induction of the lac-promoter in small-scale cultivations is well established. However, for large-scale microbiological processes the cost of this inducer is a severe limitation. Here is described a method by which lactose is used as inducer of the lac promoter with the same efficiency as that of IPTG. It was found that after growth on glucose the time of the addition of lactose is important for the quality of induction. The resulting yield of the recombinant protein increased when lactose was added to the culture if the glucose concentration was rather low. By careful monitoring of the glucose level in the fermentation, using a biosensor, it was possible to add the inducer when the carbon source was nearly depleted. Using Escherichia coli BL21 (pET3), in which was cloned the main antigen coat protein of the foot and mouth disease virus, induction of the gene led to expression of the target protein at a level exceeding 20% of the total cell protein.

Aphthovirus↗
PubMed1992

Immunochemically based assays for process control.

Immunoanalysis for process control is reviewed. The development of non-equilibrium immunoassays from a manually operated flow injection system to a completely computerized system for sample analysis as well as calibration and data evaluation is discussed. Several other approaches in using immunochemistry in biosensors for process control are discussed. The fact that reuse of antibodies raises specific demands on their properties is discussed. Even if the area is young, much progress has been achieved and one can foresee an interesting future development of the area.

Biomedical Engineering↗
PubMed1991

Tailoring the microenvironment of enzymes in water-poor systems.

Biocatalytic systems using enzymes in organic solvents open up the possibility of performing a whole range of reactions which would not normally occur under physiological conditions. The ability to perform reverse hydrolysis, or to convert substances relatively insoluble in aqueous environments on a scale of practical value in commercial applications are among those reactions for which water-poor systems are appropriate.

Emulsions↗
PubMed1990

Interesterification of phosphatidylcholine with lipases in organic media.

Lipases were investigated with respect to their ability to catalyse the incorporation of fatty acids into phosphatidylcholine (PC) by interesterification reactions. The enzymes were dried onto solid support materials and the conversions were carried out in water-saturated toluene. Three lipases (two fungal and one plant enzyme) had the desired activity; immobilized lipase from Mucor miehei (Lipozyme) was the most active enzyme. The Lipozyme-catalysed interesterification was selective for the sn-1 position of PC and during 48 h of reaction around 50% of the fatty acids in this position were replaced with heptadecanoic acid, a fatty acid which was practically absent in the original phospholipid. Due to adsorption on the support material and the competing hydrolysis reaction the total amount of PC in the reaction solution decreased to about 40% of the original amount. Higher interesterification rates were obtained with free fatty acids as acyl donors than with fatty acid esters.

Chromatography, Gas↗
PubMed1990

Enzymatic peptide synthesis in organic media: a comparative study of water-miscible and water-immiscible solvent systems.

Peptide synthesis was carried out in a variety of organic solvents with low contents of water. The enzyme was deposited on the support material, celite, from an aqueous buffer solution. After evaporation of the water the biocatalyst was suspended in the reaction mixtures. The chymotrypsin-catalyzed reaction between Z-Phe-OMe and Leu-NH2 was used as a model reaction. Under the conditions used ([Z-Phe-OMe]0 less than or equal to 40 mM, [Leu-NH2]0/([Z-Phe-OMe]0 = 1.5) the reaction was first order with respect to Z-Phe-OMe. Tris buffer, pH 7.8, was the best buffer to use in the preparation of the biocatalyst. In water-miscible solvents the reaction rate increased with increasing water content, but the final yield of peptide decreased due to the competing hydrolysis of Z-Phe-OMe. Among the water-miscible solvents, acetonitrile was the most suitable, giving 91% yield with 4% (by vol.) water. In water-immiscible solvents the reaction rate and the product distribution were little affected by water additions in the range between 0% and 2% (vol. %) in excess of water saturation. The reaction rates correlated well with the log P values of the solvent. The highest yield (93%) was obtained in ethyl acetate; in this solvent the reaction was also fast. Under most reaction conditions used the reaction product was stable; secondary hydrolysis of the peptide formed was normally negligible. The method presented is a combination of kinetically controlled peptide synthesis (giving high reaction rates) and thermodynamically controlled peptide synthesis (giving stable reaction products).

Chromatography, High Pressure Liquid↗
PubMed1979

Use of an enzyme thermistor in continuous measurements and enzyme reactor control.

The enzyme thermistor measures the heat produced by the action of an immobilized enzyme on a substrate present in the sample. Its application in analysis of discrete samples, e.g., in clinical chemistry, is well documented, but it has not been used so far for continuous measurements. We decribe here the application of the enzyme thermistor for continuous monitoring and control of enzyme reactors. An enzyme thermistor filled with coimmobilized glucose oxidase and catalase was used to measure the amount of glucose in the outflow from a column reactor containing immobilized lactase acting on a lactose solution pumped through the reactor. The lactose conversion was kept on a constant level, irrespective of the actual enzymatic activity in the reactor, by regulating the flow through the reactor. The experiments were carried out with aqueous solutions of lactose as well as with whey from cow's milk.

Calorimetry↗
PubMed1979

Uptake and efflux of noradrenaline from platelets; a model system for neurogenic mechanisms in essential hypertension.

1. The rate (k) of initial efflux of noradrenaline from platelets was determined in 63 individuals. A highly significant correlation was found between diastolic blood pressure and efflux rate. 2. When platelets are incubated in buffers with various Na+ concentrations in the range 110-170 mmol/l a higher Na+ concentration will give a faster efflux of noradrenaline for each concentration tested. 3. The value for k was determined in 41 normotensive first-degree relatives of hypertensive individuals and 21 persons with no family history of hypertension. Efflux rate of noradrenaline was significantly higher in the relatives and within this group was a subgroup with very high k values.

Adult↗
PubMed1978

Thermometric enzyme linked immunosorbent assay in continuous flow system: optimization and evaluation using human serum albumin as a model system.

Thermometric enzyme-linked immunosorbent assay (TELISA) is described. After the procedure of optimization, human serum albumin was assayed using anti-human serum albumin bound to Sepharose CL 4-B in the enzyme thermistor unit and catalase as label on the free antigen. The model system was used for assays down to 10(-13)M and the preparation of immobilized antibodies was used repeatedly up to 100 times. Comparative studies of the TELISA technique with bromocresol green, immunoturbidimetric and rocket immunoelectrophoretic methods were carried out and showed that TELISA could be used as an alternative method.

Catalase↗