Electrical conduction through DNA molecules

The question of whether DNA is able to transport electrons has attracted much interest, particularly as this ability may play a role as a repair mechanism after radiation damage to the DNA helix. Experiments addressing DNA conductivity have involved a large number of DNA strands doped with intercalated donor and acceptor molecules, and the conductivity has been assessed from electron transfer rates as a function of the distance between the donor and acceptor sites. But the experimental results remain contradictory, as do theoretical predictions. Here we report direct measurements of electrical current as a function of the potential applied across a few DNA molecules associated into single ropes at least 600 nm long, which indicate efficient conduction through the ropes. We find that the resistivity values derived from these measurements are comparable to those of conducting polymers, and indicate that DNA transports electrical current as efficiently as a good semiconductor. This property, and the fact that DNA molecules of specific composition ranging in length from just a few nucleotides to chains several tens of micrometres long can be routinely prepared, makes DNA ideally suited for the construction of mesoscopic electronic devices.     

Preadult lethality in four populations ofDrosophila melanogaster treated with formaldehyde

Summary Samples from 4 populations ofD. melanogaster were treated with formaldehyde by the larval feeding method, and induced lethality was scored. The results showed relevant differences among the populations analyzed.     

Der Einfluss des Urin-pH auf die Aktivität von Urinenzymen

Summary The relationship between the pH of urine and the measured activity of ULDH, UAP and UAA was investigated in vivo and in vitro. The activity of ULDH and UAP is only half as much, or less, in acid urine (pH 4.8–5.1) as it is in alkaline urine (pH 7.0–8.1). The UAA activity, however, does not change in the pH range measured. The isoenzymes ULDH 2–4, present in alkaline urine of normal adults, does not appear in acid urine.     

Experimentelle Reversion von Tumorzellen in vivo

Summary European eels with fast growing epidermal papillomas (cauliflower disease) were treated with quinine-sulphate. At concentrations of 15 to 60 mg/l and after 8 weeks of treatment, there occurred newly formed mucous cells and club cells in the tumor tissue. Tight contact between all cells was reestablished. The nucleus-plasma-relation had evidently decreased. Electron microscopical studies showed a restauration of degenerated cell organelles, especially of the outer membrane. Growth rate of the tumors was reduced, and at a concentration of 60 mg/l the tumor tissue ceased growing from the beginning of treatment.     

Dosis-Wirkungs-Beziehungen zwischen Koronardurchfluss und Herzfrequenz für Adenosin

Summary In the isolated guinea-pig heart, it has been found that the amount of adenosine which slows the heart rate is about 100 times greater than the amount which increases coronary flow.     

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.     

Interaction of cocaine and bunaphtide on the3H-norepinephrine uptake mechanism on isolated left atrium of guinea-pig

Summary Bunaphtide induces a blockade in the³H-norepinephrine uptake and retention in the isolated guinea-pig left atrium. However, this blockade does not seems to be related with the cardiodepressant effect of the drug.