RESUMEN
Transformation of Brassica napus mesophyll protoplasts was performed with the ß-glucuronidase gene fusion system. After electroporation, transient expression in protoplasts transformed directly after isolation was about 1 to 2 per million. By the use of 2,6-dichloro-benzonitrile, a non-toxic inhibitor of cell wall synthesis, and in the presence of 5% polyethyleneglycol, transformation of the cell material was performed three days after isolation. At that time, about 25-30% of the protoplasts had reached the first S-phase of the mitotic cycle. A 1000 fold increase of protoplasts expressing the ß-glucoronisidase gene transiently was obtained, in the partly synchronized protoplasts, compared to those transformed directly after isolation.
RESUMEN
Opening of the terminal hemi-acetal in dihydronigericin drastically reduces the ionophoric properties of nigericin and dehydroxymethylnigericin with 6 intact heterocycles. This is shown by 2 complementary methods, first with a liquid membrane electrode system, secondly by testing their ionophoric activities in rat liver mitochondria.
Asunto(s)
Antibacterianos/farmacología , Mitocondrias Hepáticas/metabolismo , Nigericina/farmacología , Animales , Transporte Biológico/efectos de los fármacos , Glutamatos/metabolismo , Cinética , Mitocondrias Hepáticas/efectos de los fármacos , Potasio/metabolismo , Ratas , Relación Estructura-Actividad , Valinomicina/farmacologíaRESUMEN
The alkali cations discrimination on a liquid membrane electrodes system, was determined for the carboxylic ionophores grisorixin, alborixin and two derivatives, dihydrogrisorixin and hexahydroalborixin. The two antibiotics exhibited a great perference for K+. Dihydrogrisorixin again showed the selectivity curve of a carboxylic ionophore, but with a discrimination power lowered compared with grisorixin. Hexahydroalborixin had lost all the complexing properties of the natural molecule. The selectivity scales measured for cations, were directly correlated with the K+ and glutamate effluxes measured in rat liver mitochondria. The chemical modifications of the natural structures of grisorixin and alborixin resulted in a drastic reduction of their ionophoric properties. The loss of K+-glutamate might occur in two steps, the efflux of K+ catalysed by the ionophores then causing a loss of negative charges in the form of glutamate.