STUDY OF THE INTERACTION OF POLYGODIAL WITH POPC LIPOSOMES

ANDREA C. CUTRÓ; ANDREA C. CUTRÓ

Buzios,

Congreso; ? VII Iberoamerican Congress of Biophysics; 2009

SAB; LaFBES

Polygodial is a natural sesquiterpene that has shown to be a potent uncoupler of mitochondrial ATP synthesis, which exerts its effect without increasing the proton permeability of the inner mitochondrial membrane (Biochem. Pharmacol. 70:82-89, 2005). It has also been reported that polygodial interacts with interfaces and penetrates phospholipid monolayers changing the surface potential (Biocell 28:33, 2004). In order to study its interaction with bilayers, the effect of polygodial on the fluorescence enhancement of ANS upon binding to liposomes was determined. The study was carried out at 25ºC using POPC liposomes prepared by the extruder technique. The fluorescence enhancement could be resolved into two kinetic phases: the fast one was inhibited up to 41.5±2.4% (I0.5=154.2± 21.7 µM polygodial). When the fluorescence enhancement was determined at different [ANS], a hyperbolic dependence with [ANS] was observed. The maximal fluorescence enhancement estimated for the fast phase was 90.1±2.5 and 73.3±0.6 a.u. in the absence and in the presence of 110 µM polygodial, respectively. The apparent Kd (ANS) was 16.8±2.6 µM in the absence and 26.8±0.7 µM in the presence of polygodial. These results let us conclude that polygodial decreases the number of sites and/or the fluorescence efficiency of the ANS bound and decreases the apparent affinity of ANS for the bilayer. On the other hand, polygodial up to 440 µM did not induce carboxyfluorescein leakage from liposomes of POPC. Hence it has no lytic properties, contrarily to what has been previously suggested by others.