University of Konstanz

About: University of Konstanz is a education organization based out in Konstanz, Baden-Württemberg, Germany. It is known for research contribution in the topics: Population & Membrane. The organization has 12115 authors who have published 27401 publications receiving 951162 citations. The organization is also known as: University of Constance & Universität Konstanz.

Statistical analysis of alamethicin channels in black lipid membranes.

Abstract: Pore formation of alamethicin has been studied by the analysis of steadystate fluctuations of single-pore conductances. An aggregation model is proposed where transitions to the next higher or lower pore state occur by uptake or release of one monomer. It is assumed that alamethicin forms an elongated loop in the bilayer. The main voltage-dependent step is the insertion of this monomer into the membrane after complexation with a cation. This mechanism is equivalent to dipole orientation in an electric field. Pore formation is restricted by the energy required to enlarge the channel in the membrane.

Reversible electrical breakdown of lipid bilayer membranes: a charge-pulse relaxation study.

Abstract: Charge-pulse experiments were performed with lipid bilayer membranes from oxidized cholesterol/n-decane at relatively high voltages (several hundred mV). The membranes show an irreversible mechanical rupture if the membrane is charged to voltages on the order of 300 mV. In the case of the mechanical rupture, the voltage across the membrane needs about 50–200 μsec to decay completely to zero. At much higher voltages, applied to the membrane by charge pulses of about 500 nsec duration, a decrease of the specific resistance of the membranes by nine orders of magnitude is observed (from 108 to 0.1 Ω cm2), which is correlated with the reversible electrical breakdown of the lipid bilayer membrane. Due to the high conductance increase (breakdown) of the bilayer it is not possible to charge the membrane to a larger value than the critical potential differenceV c. For 1m alkali ion chloridesV c was about 1 V. The temperature dependence of the electrical breakdown voltageV c is comparable to that being observed with cell membranes.V c decreases between 2 and 48°C from 1.5 to 0.6 V in the presence of 1m KCl. Breakdown experiments were also performed with lipid bilayer membranes composed of other lipids. The fast decay of the voltage (current) in the 100-nsec range after application of a charge pulse was very similar in these experiments compared with experiments with membranes made from oxidized cholesterol. However, the membranes made from other lipids show a mechanical breakdown after the electrical breakdown, whereas with one single membrane from oxidized cholesterol more than twenty reproducible breakdown experiments could be repeated without a visible disturbance of the membrane stability. The reversible electrical breakdown of the membrane is discussed in terms of both compression of the membrane (electromechanical model) and ion movement through the membrane induced by high electric field strength (Born energy).