An extraction chromatography method for Hf separation prior to isotopic analysis using multiple collection ICP-mass spectrometry.

A novel method for the single-step separation of Zr + Hf from all matrix elements of geological samples has been developed for Hf isotopic measurements using multiple collector-ICP-mass spectrometry. The method combines an effective sample decomposition by LiBO2 fusion with a selective separation of Hf + Zr by a solid-phase extraction material based on dipentyl pentyl phosphonate, commercially available as U-TEVA.Spec.

A simple spectrophotometric assay of plasminogen activator: comparison with the fibrinolytic method.

We describe a simple assay of plasminogen activator in which the enzyme reacts with a mixture of plasminogen and H-D-valyl-L-leucyl-L-lysine-p-nitroanilide for 1 h at 37 degrees C after which the absorbance is measured at 405 nm. The method detects as little as 2 CTA milliunits of activator and is linear over a 100-fold range of enzyme concentration. The new procedure has been used successfully for the assay of activator in breast tumor cytosols, cell culture supernatants, and pleural or ascitic fluids.

Activated steroid-receptor complex. Comparison of assays using DNA-cellulose or homologous nuclei.

When soluble steroid-receptor complexes are exposed to DNA-cellulose only activated complexes bind. The specificity of the binding was shown by its dependence on the presence of hormone during activation. However, prolonged incubation of non-activated steroid-receptor complexes with DNA-cellulose led to a progressive activation of these complexes.