Inactivation by ionizing radiation of ion channels formed by polyene antibiotics amphotericin B and nystatin in lipid membranes: an inverse dose-rate behavior.
The phenomena reported are part of a study about the effects of ionizing radiation on membrane transport. We found that the conductance of lipid membranes in the presence of the polyene-antibiotics nystatin or amphotericin B is reduced to virtually zero following irradiation. Ion channels formed by these substances seem to represent extremely sensitive structures being inactivated by radiation doses in the range of a few Centigray (1 cGy = 1 rad) at sufficiently small dose rates. Inactivation shows a so-called inverse dose-rate behavior, i.e., at constant radiation dose the effect increases with decreasing dose rate. Similar to radiation-induced lipid peroxidation the phenomenon may be understood on the basis of a radical chain mechanism initiated by free radicals of water radiolysis. The process--via peroxidation of the polyene part of the molecules--is suggested to modify the hydrophobic exterior and to destabilize the barrel-like structure of the ion channels.
Barth
C
C
Bereich Strahlenchemie, Hahn-Meitner-Institut für Kernforschung, Berlin.
Stark
G
G
Wilhelm
M
M
D000666:Amphotericin B; D055592:Biophysical Phenomena; D001703:Biophysics; D004307:Dose-Response Relationship, Radiation; D004553:Electric Conductivity; D007473:Ion Channels / Q000737:chemistry / Q000528:radiation effects*; D008563:Membrane Lipids / Q000737:chemistry / Q000528:radiation effects; D008567:Membranes, Artificial; D008956:Models, Chemical; D009761:Nystatin
D007473:Ion Channels; D008563:Membrane Lipids; D008567:Membranes, Artificial; D009761:Nystatin; D000666:Amphotericin B