Mobility of spin probes having a primary,secondary, tertiary,or quaternary amino group in drawn and undrawn nylon 6 film

The mobility of spin probes having a secondary, tertiary, or quaternary amino group in dried nylon films was investigated by means of electron spin resonance (ESR) measurements and compared with the behavior of previously investigated spin probes having a primary amino group, a carboxylate group, or a sulfate group. The spin probes having a primary or secondary amino group showed effects of drawing on the mobility, while the other probe molecules did not. This result could be interpreted by considering the interactions between the spin probes and the nylon chains. In the undrawn nylon film, the mobilities of the nonionic spin probes were almost the same, and smaller than those of the charged spin probes, suggesting that the location in the nylon film is different for the uncharged and charged spin probes. These results are discussed in detail using separation of extrema of the ESR spectra, rotational correlation times, and anisotropy parameters.     

Gemini surfactants: new synthetic vectors for gene transfection

The superior surfactant properties of cationic gemini surfactants are applied to the complex problem of introducing genes into cells. Of almost 250 new compounds tested, of some 20 different structural types, a majority showed very good transfection activity in vitro. The surfactant is shown to bind and compact DNA efficiently, and structural studies and calculations provide a working picture of the "lipoplex" formed. The lipoplex can penetrate the outer membranes of many cell types, to appear in the cytoplasm encapsulated within endosomes. Escape from the endosome--a key step for transfection--may be controlled by changes in the aggregation behavior of the lipoplex as the pH falls. The evidence suggests that DNA may be released from the lipoplex before entry into the nucleus, where the new gene can be expressed with high efficiency.     

Direct observation of a rho decay of the D13(1520) baryon resonance

The reaction gammap-->pi(+)pi(0)n has been measured at MAMI for photon energies up to 820 MeV. Invariant mass spectra of the particles in the final state (pi(+)n), (pi(0)n), (pi(+)pi(0)) have been determined for several bins of incident photon energy. Differences in pi(+)pi(0) and simultaneously measured pi(0)pi(0) invariant mass distributions are assigned to a rho branch of the D13(1520) nucleon resonance.