Effect of Phloretin on the Binding of 1-Anilino-8-naphtalene sulfonate (ANS) to 1,2-Dimyristoyl-sn-glycero-3-phosphocoline (DMPC) Vesicles in the Gel and Liquid-Crystalline State

ANDREA C. CUTRO; MONTICH GUILLERMO; OSCAR A. ROVERI

JOURNAL OF MEMBRANE BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2014

0022-2631

Phloretin is a known modifier of the internaldipole potential of lipid membranes. We studied theinteraction of phloretin with model lipid membranes andhow it influences the membrane dipole organization usingANS as fluorescent probe. The fluorescence increaseobserved when ANS binds to DMPC liposomes in gelphase (13 C) was 2.5 times larger in the presence ofphloretin. This effect was due to an increase in ANSaffinity, which can be related to the known capability ofphloretin in decreasing the dipole potential. Conversely,when the experiments were carried out at 33 C (liquidcrystalline phase), phloretin completely inhibited theincrease in ANS fluorescence. In addition, phloretin onlyaffected the electrical properties of the membrane in the gelphase, whereas it modifies structural ones in the liquidcrystallinestate. We postulate that phloretin was boundonly to the DMPC interface in the gel phase decreasing thesurface negative charge density without modifying thestructural properties of the ANS binding sites. In the liquidcrystallinephase instead, it increased the accessibility ofwater to the ANS binding sites decreasing the intrinsicaffinity and the fluorescence quantum yield of ANS.