Study Of Capture Reactions Research Articles

A new dynamic model system for the study of capture reactions for diffusable compounds in cytochemistry. III. Influence of the matrix composition on the lead phosphate precipitation process in acid phosphatase cytochemistry.

A model system for the study of the dynamics of precipitation processes, described elsewhere and consisting of polyacrylamide films, was used to investigate the influence of the composition of the matrix, in which precipitation occurs, on the lead phosphate precipitation process in acid phosphatase cytochemistry. The situation at an enzymatic site can be simulated by pumping a phosphate-containing solution and the Gomori medium for acid phosphatase (lead containing medium) along opposite sides of a polyacrylamide film. The procipitation of lead phosphate was found to start at a lower phosphate concentration of the solution flowing along films into which histone, casein, RNA or polygalacturonate had been incorporated, than in control films. DNA, chondroitin sulphate and bovine serum albumin (unfixed) did not give this effect. Fixed bovine serum albumin incorporated into the film slightly decreased the phosphate concentration at which a precipitate appeared. Nuclear staining occurring under suboptimal conditions for phosphate trapping is probably due to a local matrix effect. The model studies suggested DNA-associated phosphorylated histones and phosphoproteins as likely candidates for such an effect, and RNA as a less likely one. Artefactual precipitates at the plasma membrane might be due to carboxyl groups of sialic acid.

A new dynamic model system for the study of capture reactions for diffusable compounds in cytochemistry. II. Effect of the composition of the incubation medium on the trapping of phosphate ions in acid phosphatase cytochemistry.

A model system developed for the study of the dynamics of capture reactions for diffusable compounds in cytochemistry served as a basis for the experiments reported in the present paper. The model was used to study the effect of the composition of the cytochemical medium on the trapping of phosphate ions by lead (II) ions in acid phosphatase cytochemistry. In this system a phosphate-containing solution and a lead-containing solution (cytochemical medium) are pumped along opposite sides of a polyacrylamide film. The phosphate concentration at which measurable precipitation starts in the film (critical phosphate concentration) was taken as a measure of the trapping efficiency of the cytochemical medium. The addition of beta-glycerophosphate and cytidine-5'-monophosphate to a buffered lead-containing solution resulted in a higher critical phosphate. The addition of chloride ions and acetone, as well as decreasing the molarity of the acetate buffer of the cytochemical medium, were found to lower the critical phosphate concentration, whereas the addition of fluoride ions, glucose, and sucrose had no effect. From the effect of variations in the composition of the cytochemical medium on the trapping efficiency and the turnover number of acid phosphatase in the medium, it was possible to predict which cytochemical medium would be the most suitable for the demonstration of acid phosphatase activity in guinea-pig peritoneal exudate cells. The results were in accordance with the localization of acid phosphatase activity: the higher the trapping efficiency and the turnover number, the higher the amount of precipitate and the number of positive enzymatic sites. In this way an improved cytochemical medium for acid phosphatase was developed.

Enzyme layers on glass as a new model for the quantitative study of capture reactions in cytochemistry, with special attention to acid phosphatase.

A model system is described for the study of capture reactions for diffusable compounds in enzyme cytochemistry. The model, which allows the investigation of the influence of the composition of the cytochemical medium, the enzymatic activity, and the dimensions of the enzymatic site on the capture reaction, consists of very thin homogeneous layers of enzyme (0.01-0.1 micrometer thick) on glass, which are incubated in the cytochemical medium. The fraction of the total amount of liberated product precipitated in the enzyme layer is dependent not only on the trapping efficiency of the cytochemical medium but also on the concentration of the primary reaction product that can be built up in the enzyme layer. Calculations were performed to determine the steady-state concentration of the primary reaction product that can be built up in the enzyme layer. Acid phosphatase was used as enzyme. The problems associated with the model and its applicability to other types of cytochemical reactions are discussed.

A target chamber for the measurement of capture reactions

Abstract A high vacuum target chamber for the study of capture reactions is described. It can be employed with solid or gaseous targets and allows the measurement of gamma ray angular distributions over a wide range of angles with a small, uniform absorption.