The changes in capacitance and conductance of lipid bilayer membranes have been studied with adsorbed membrane fragments containing Na + ,K + ATPase. These changes have been initiated by fast release of protons from a bound form ("caged H + ") induced by an UV flash. The changes of the capacitance in the presence of Na + ,K + ATPase were affected by the frequency of the applied voltage, pH and the concentration of sodium ions. Addition of sodium ions altered the changes of capacitance caused by a pH jump in the medium due to caged H + photolysis, and the magnitude and sign of this effect depended on the initial pH. These results are explained by competitive binding of sodium ions and protons to the ion binding sites of the Na + ,K + ATPase at its cytoplasmic side. The pH at which the sign of the sodium ion effect changed allows the evaluation of the pK of the proton binding site, which is about 7.6.
The esters of hydroxycinnamic acids in more than 300 species out of 55 genera of Labiatae are investigated. The following compounds have been proved: the caffeic-, 1-caffeyl-, chlorogenic-, cryptochlorogenic-, neochlorogenic-, rosmarinicisochlorogenic-acid as well as the 1-caffeyl-, 6-caff eyl-and 1,6-dicaffeyl-glucose esters. The distribution of the derivatives of the hydroxycirznamic acids and especially of the rosmarinic-acid and the depsides of the caffeic-and quinic-acid may be of taxonomic importance. Zusammenfassttng Es wird ein kurzer Oberblick iiber den derzeitigen Stand der Erforschtrng der ,,GerbstoffeM und der Abkommlinge der Oxyzimtsauren in Labiaten gegeben. Die Ester der Oxyzimtsauren in mehr als 300 Arten aus 55 Gattungen wurden untersucht. Es wurden Kaffee-, 1-Kaffeyl-, Chlorogen-, Kryptochlorogen-, Neochlorogen-, Rosmarin-und lsochlorogensauren, die Ester der Kaffeesaure mit Glukose (die I-Kaffeyl-, 6-Kaffeyl-und 1,6-Dikaffeylglucose) sowie die Abkommlinge der p-Oxyzirnt-und Ferulasauren entdeckt. Auf Grund der Verteilung der Derivate der Oxyzimtsaztren and, besonde.rs, d e~ Rosmarinsaure und der Depside der Kaffee-und Chinasaure wird deren chemotaxonomische Bedeutung fur die Labiaten diskutiert.
The electric properties of the bilayer lecithin membranes have been studied in the presence of the antibiotic nigericin. When the antibiotic concentration is about 10(-7) ohm-1 cm-2. The potassium ion concentration gradient gives rise to a transmembrane potential of the order of 40 mV per 10-fold concentration gradient with the side of the higher potassium concentration negative. The transmembrane potential produced by the hydrogen ion concentration gradient is a function of the potassium ion concentration which is equal on both sides of the membrane. For low potassium ion concentrations the hydrogen potential has the expected polarity with the solution having higher concentration of protons negative. For potassium ion concentrations exceeding 0.03 M the hydrogen potential has the reverse polarity. This unexpected result cannot be accounted for in terms of the available simple hypotheses about the charge transport mechanism for nigericin in BLM. In order to account for the experimental results obtained, a theoretical approach has been developed based on the assumption that charge is transported across the membrane by nigericin dimers. The theoretical predicitons are in satisfactory agreement with the experimental results. The model also yields some predictions which may be verified in future experiments.
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