ISSN:
1432-1424
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Chemie und Pharmazie
Notizen:
Summary Oxidized cholesterol lipid films were studied under voltage clamp conditions. Certain kinds of conductance phenomena closely resembling effects described in the literature and atributed to various additives were observed with unmodified lipid films. These include spontaneous conductance changes, multilevel conductance states and negative resistance phenomena in films formed from aged oxidized cholesterol-inhydrocarbon solutions. The multilevel conductance state manifests itself in the form of step changes in current under voltage clamp, the magnitudes of which correspond to conductance intervals of 5±2×10−10 mho and its multiples in 0.1n sodium chloride. These steps are attributed to channels that form in the film. Under certain conditions it has been observed that the action of the electric field was to close channels that were open at lower voltages. Under these conditions the current-voltage plot shows a distinct region of “negative differential” resistance. Films generated from freshly prepared oxidized cholesterol solutions did not exhibit multistable phenomena but under a prolonged voltage clamp the membrane conductance went into a transition from a stable, relatively noise-free-current state to a gradually increasing current with a large noise component. This sequence generally signalled imminent breakdown but the membrane could spontaneously revert to the original high-resistance, low-noise state. These kinds of intrinsic behavior sufficiently resemble certain effects produced by additives to merit special consideration during membrane reconstitution experiments.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01870182
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