Howard H. Weetall

Enzymes immobilized on inorganic supports

Abstract Enzymes immobilized on inorganic supports by covalent attachment show unique pH optimums, thermal profiles and kinetics. Organic functional groups are covalently attached to the support using a silane coupling agent. The enzyme may then be covalently coupled to the organic functional groups now on the support. Immobilized enzymes have been characterized and used for several applications.

Antibodies immobilized on inorganic supports

Antibodies and antigens can be covalently coupled to a variety of carriers, both organic and inorganic. The methods for coupling these proteins may be found scattered throughout the technical literature. This report, although it concentrates on inorganic supports, describes several of the more successful methods used in laboratories today. Each of these methods is described in enough detail for the reader to carry out the coupling method of interest in his or her own laboratory. The coupling methods have been divided into two groups, direct and silane. Under each of these general headings are described the specific methodologies.

Antibodies in water immiscible solvents immobilized antibodies in hexane

Anti-progesterone antibodies covalently coupled to paramagnetic particles (PMPs) retain their immunologic activity to progesterone in hexane as solvent. Although reaction rates appear slowed, activity is not lost. The antibodies still bind similar quantities of antigen to those bound in aqueous solution. It is most likely that the increased reaction time is the result of a phase transfer. The immobilized antibodies are present in an aqueous phase, while the antigen is present in the more soluble organic solvent phase.

Studies on the nutritional requirements of the oil-producing algaBotryococcus braunii

Studies were carried out on the ability of the algaeBotryococcus braunii to grow in the presence of possible carbon sources. Sources examined included compounds for C1-C6, as well as the disaccha rides sucrose and lactose. Dividing times were decreased from an av erage of over 1 wk to less than 3 d by addition of the appropriate car bon sources.Examination of the oils produced in the presence and absence of exogenous carbon indicated no differences. However, the total bio mass produced in the presence of a usable carbon source exceeded that produced in the carbon’s absence.

Scaling Up an Immobilized Enzyme System

The development of an immobilized enzyme system for commercial application involves a series of decisions and compromises beginning with the choice of enzyme support and ending with the decision on operational mode. Each step is dependent on the other steps, and all the steps influence the overall economics of the final process. Compromises need to be made about the support, method of enzyme attachment, reactor type, kinetic behavior, and operating strategy. Selection of the enzyme carrier and its composition will have a major effect on the pH optimum, metal requirements, and overall performance of the immobilized enzyme system. The reactor type and its behavior will also affect performance. For commercial applications the fixed-bed reactor is generally the reactor type of choice. Knowledge of the appropriate kinetics is necessary to achieve the desired product quality and to reduce cost. One important kinetic parameter is reaction velocity under real world conditions. Rate expressions must take into consideration back-mixing and mass transfer limitations, both internal and external to the immobilized enzyme particles. In addition to understanding kinetic behavior, one must devise a proper operating strategy for producing the greatest amount of product at the least cost, while maintaining constant productivity over time. The success of any scale-up will be determined by the final processing cost as compared to that of the alternatives.

A Simple, Inexpensive, Disposable Electrochemical Sensor for Clinical and Immuno-assay

An inexpensive, rapid, disposable electrochemical system has been developed for both clinical and immunochemical assays. The three-electrode planar configuration is produced by silk screening graphite paint on to cardboard. Assays are carried out amperometrically using constant voltage and monitoring current produced by the oxidation of an electron mediator. In the case of immuno-assay the system described uses the enzyme glucose oxidase with 1,4-benzoquinone as the mediator. The assay is carried out by effecting a separation of the bound and free fractions of the immunoreactants via immobilizing the antibodies on to magnetic particles which are magnetically concentrated on the electrode surface for analysis. This concentration of the bound antigen-antibody complex with the glucose oxidase label effectively increases the concentration of the reduced mediator in the electrode vicinity, thus increasing the amperometric response to the bound fraction of the label.