Polarization of the fluorescence of macromolecules. II. Fluorescent conjugates of ovalbumin and bovine serum albumin

The importance of life-time changes in fluorescence depolarization

The rotational relaxation time, rho, calculated from measurements of fluorescence depolarization, is clearly dependent on the assumed mean life-time, tau, of the excited state. However, variations in tau with experimental conditions (temperature and solvent composition) occur and the effect of such alterations in tau is demonstrated. In particular it should be noted that, unless life-time changes can be excluded, the occurrence of linear plots of reciprocal degree of polarization against the temperature/viscosity ratio does not necessarily indicate the absence of intramolecular freedoms. An attempt to correct for such life-time changes by measurement of the fluorescence intensity is made for the bovine serum albumin-1-dimethyl-aminonaphthalene-5-sulphonyl chloride system. The value of rho/3tau thus obtained for this system at 20 degrees is approx. 4.7, as against approx. 3.4 obtained by several workers in the absence of life-time corrections.

Carbonic anhydrase isoenzymes in the erythrocytes and dorsolateral prostate of the rat

1. Three forms of the zinc-containing enzyme carbonic anhydrase (EC 4.2.1.1) were isolated from the erythrocytes of the rat and two forms from the dorsolateral prostate of the rat. Several additional minor components were observed but not isolated. Separation of the isoenzymes was achieved by ion-exchange chromatography, polyacrylamide-gel electrophoresis and isoelectric focusing. 2. The general properties of the isolated isoenzymes, their molecular weights and their contents of zinc were closely similar. As catalysts of the hydration of carbon dioxide, however, they were distinctly different. The two most abundant isoenzymes of the erythrocytes, which were found in equal proportions, differed 70-fold in specific activity, whereas the isoenzymes of the dorsolateral prostate were similar to one another and resembled the high-activity component of the erythrocytes. The inhibition of the latter by acetazolamide (5-acetamido-1-thia-3,4-diazole-2-sulphonamide) was mainly competitive, whereas in identical conditions the low-activity erythrocyte component and the dorsolateral prostate isoenzymes were non-competitively inhibited. 3. The use of chloroform-ethanol to remove haemoglobin from the rat haemolysate was found (a) to bring about changes in the kinetic properties of the soluble isoenzymes and (b) to cause the appearance of an additional isoenzyme. 4. The actions were compared of the inhibitors acetazolamide, 1,1-dimethylaminonaphthalene-5-sulphonamide and ethoxzolamide (6-ethoxybenzothiazole-2-sulphonamide) on the hydrolysis of p-nitrophenyl acetate catalysed by the isoenzymes. 5. The low-activity erythrocyte isoenzyme was an efficient catalyst of the hydrolysis of beta-naphthyl acetate whereas the high-activity forms were much less active towards this ester. Neither of the isoenzymes present in the dorsolateral prostate catalysed this reaction. 6. Carbonic anhydrase in the rat dorsolateral prostate accounts for no more than 5% of the unusually high content of zinc in this organ.

Fluorescein-labeled beta-glucosidase as a bacterial stain

Fluorescein isothiocyanate-labeled beta-glucosidase was used as a simple staining reagent with selected gram-positive and gram-negative organisms. Staining in situ appeared to be dependent on the presence of accessible glycosidic-type linkages in the bacterial cell wall. Extensive wall damage or lysis did not occur when stained cells were suspended in washing and mounting solutions. The apparent specificity of labeled enzyme for wall substance was tested by blocking reactions, staining of isolated cell walls, and failure to stain substances lacking appropriate glycosidic linkages. Severe cell wall lesions were produced after prolonged contact with labeled enzyme, and this phenomenon may also be related to staining specificity. Gram-negative organisms and spores were poorly stained unless protected glycopeptide substrate was previously exposed by treatment of cells with thioglycolic acid or dilute alkaline sodium hypochlorite solution. A potential for staining tissues and cell lines may also exist. Some possible applications of labeled enzymes are briefly discussed.

Immunocytochemical localization of the immunoglobulin factors Gm(a), Gm(b) and Inv(a) in human lymphoid tissue

Fluorescent antibodies to the human immunoglobulin allelic characters Gm(a) and Gm(b) were found to be localized in different plasma cells in the red pulp of the spleen and the medullary cords of the lymph nodes of heterozygous Gm(a⁺ b⁺) individuals. Approximately 45 per cent of the cells, which were subsequently shown to contain immunoglobulin after bleaching the section and restaining with fluorescent anti-whole human immunoglobulin, reacted with the fluorescent anti-Gm(a), 25 per cent with the fluorescent anti-Gm(b) and 30 per cent did not react at all. Sections already labelled with the fluorescein anti-Gm(a) and rhodamine anti-Gm(b) upon staining with fluorescein anti-Inv(a) showed approximately 60 per cent of all cells with mixed fluorescence and 25 per cent previously unlabelled cells fluorescing with the Inv(a) label only. In Gm(a⁺ b⁺ x⁺) individuals Gm(a) and Gm(x) seemed to be localized in the same plasma cells. However, in the germinal centres of the lymph nodes and the white pulp of the spleen Gm(a), Gm(b) and Inv(a) appeared to be contained in the same cells.