Analytisch-chemische Bestimmung nichtradioaktiver Stoffe mit einem Flüssig-Szintillationsspektrometer durch Radiolumineszenz und Absorptionsphotometrie im Čerenkov-Licht

Summary Three techniques are described which allow a quantitative chemical determination of non-radioactive substances by the means of a liquid scintillation counter. The first method is based on the chemical quenching of a radioluminescent solution through the substance that is to be determined. The second method may be described as absorption photometry in erenkov-light and the third one as absorption photometry in radiofluorescence light.     

Fehlende Wasserstoff-Übertragung von Östradiol auf Androstendion im Diäthylnitrosamin-induzierten Hepatom der Ratte

Summary In liver-tissue of female rats estradiol-17 -T is oxydized by NAD or NADP, yielding the tritiumlabelled coenzymes NAD-T or NADP-T which can transfer the tritium to androstendione. So tritium-labelled androstandiol is obtained. Of the added activity 10–30% is oxydized to water. In diethylnitrosamine-induced hepatomas estradiol-17 -T is oxydized to tritium-water in a comparatively small amount and no transport of the tritium to reduction-products of androstendions occurs. Testing the in-vivo-oxydation of estradiol in normal female rats and in females with hepatoma with the aid of the Stoffwechsel-labil labelling (measuring the specific activity of tritium in body-water after injecting estradiol-17 -T) a lower oxydation-rate was also found in rats with hepatoma than in normal rats.     

Stereospecificity of allantoin degradation inStreptococcus allantoicus

Zusammenfassung Die Stereospezifität der Enzyme des Allantoinabbaus inStreptococcus allantoicus und die optische Drehung der Reaktionsprodukte wurde bestimmt. Allantoinase war aspezifisch, während Allantoate-amidohydrolase ausschliesslich (-)-Ureidoglykolate bildete. Diese Substanz wurde durch (-)-Ureidoglykolase hydrolysiert.     

Structure of the actin-myosin interface

The topography of the rigor complex between F-actin and myosin heads (S1) has been investigated by carbodiimide zero-length cross-linking. The results demonstrate for the first time that the 95,000-molecular weight (95K) heavy chain of the myosin head enters into van der Waals contact with two neighbouring actin monomers; one is bound to the 50K domain and the other to the 20K domain of the myosin chain. The covalent F-actin-S1 complex can be isolated; it shows a vastly elevated Mg2+-ATPase. Each pair of actin subunits in the thin filament seems to act as a functional unit for specific binding of a myosin head and stimulation of its Mg2+-ATPase activity.