21 research outputs found
Spektroskopische Untersuchungen an Isomeren des Bacteriorhodopsins
Artificial BR isomers are formed in vitro with 7-cis and 7,13-dicis retinal as chromophores : In contrast to the native BR this artificial BR system allows us to measure physico-chemical parameters which help us to understand the native BR system - BR and BR, are clearly distinguishable by their absorption spectra; maxima are at 475 nm and 560 nm, respectively - For the regeneration of BR with 7-cis or 7,13-dicis retinal the rate constants are nearly the same (10 I mol s) - Between the two isomers, BR and BR the equilibrium is reached within seconds, possibly milliseconds - For the dissociation of BR or BR, the rate constant was measured (10s). This rate constant has not been measured yet for the rative BR system - The equilibrium constant K= c(BO).c(Ret)/c(BR) was determined for the BRsystem ( K = 10 mol 1) - A photo-induced, irreversible transformation of BR into BR was shown - The quantum yield for this photo-induced BR formation from BR, or BR was determined to be on the order of 10 - Because of the relative small quantum yield, photocycles are presumed for both artificial BR isomers, BR and BR - An irreversible, thermal transformation of BR to BR was observed - Flash-spectroscopically it was shown, that the photoproducts of both isomers, BR and BR, have absorption maxima shifted bathochromically with respect to the initial isomers. We showed that, besides the naturally occurring chromophores, 13-cis and trans retinal, only 7-cis and 7,13-dicis retinal can regenerate BR. BR shows a high binding selectivity, obviously the binding site is strongly specialized within the protein In the case a chromophore is incorporated into the protein,BR functions as an isomerase: only the C13-double bond of the chromophore is isomerized. The fast thermal isomerization presumed for the BR/BR -equilibrium might be important for the trans BR cycle, especially for the mechanism of the proton pump. BR shows an extreme selectivity for "its" naturallyoccurring chromophores, 13-cis and trans retinal
Isomeric composition of bacteriorhodopsin under different environmental light conditions
Vorschläge der Expertenkommission zur Neuregelung des Fahrerlaubnisrechts für motorisierte Zweiradfahrer
Es wird über die Arbeit einer Expertenkommission berichtet, die der Bundesminister für Verkehr mit der Erarbeitung eines neuen Konzepts für das Fahrerlaubnisrecht für alle motorisierten Zweiräder beauftragt hat. Schwerpunkte der Arbeit waren die Entwicklung aussagefähiger statistischer Unterlagen für eine Neueinteilung der Fahrerlaubnisklassen und die Erarbeitung von Vorschlägen zur Verbesserung der Ausbildung und Prüfung von Zweiradfahrern. Die Expertengruppe schlägt fünf Fahrerlaubnisklassen für motorisierte Zweiradfahrer vor (Mofa, Mokick, Leichtkraftrad, Anfängermotorrad und Motorrad unbeschränkt). Die einzelnen Klassen werden durch technische Kriterien definiert, die Vorschläge für die einzelnen Fahrerlaubnisklassen betreffen das jeweilige Mindestalter, Anforderungen an die Ausbildung sowie an die Prüfung