Gene Literature Dashboard

A comparison was made between the use of ammonium sulfate (AS) and Dextran coated charcoal (DCC) to separate free and antibody-bound estrogens in the RIA of estrone and estradiol in serum. Under the conditions tested, AS yielded values which were approximately twice those obtained using DCC. This difference was found for both estrogens, using male and female serum and regardless of whether the estrogens were separated from one another by means of the Girard reagent or TLC. There was no significant difference in the sensitivity, accuracy or usable range of the standard curve or in the water-blank for the two procedures.

Thrombin partially purified from bovine plasma can be inactivated at 60 degress C. In the presence of 10 units of heparin the extent of inactivation decreases. When thrombin and heparin are mixed and incubated for 5 min at 0 degrees C before gel filtration on Sephadex G-200, thrombin with heparin is eluted prior to either thrombin or heparin laone. These data suggest a complex formation between thrombin and heparin. Immobilized heparin binds thrombin. The enzyme can be eluted with 0.05 M Tris-HCl buffer, pH 7.3, containing an ion mixture of Na+, K+ and Ca2+ at 73, 3 and 11 mM, respectively, at 0 degrees C and with 0.05 M Tris-HCl buffer, pH 7.3, containing 0.5 M NaCl at 20 degrees C. During the same chromatographic procedure, antithrombin-III (heparin cofactor) partially purified from human plasma is eluted with 0.05 M Tris-HCl buffer, pH 7.3, at 0 degrees C as well as 20 degrees C. Although, as described in the literature, heparin binds to antithrombin, our findings suggest another possibility, i.e. that the binding of heparin to thrombin induces a conformational change in the enzyme facilitating a complex formation between thrombin and antithrombin-III.