The incorporation of amphiphilic derivates of L -ascorbic acid induce stiffness of phospholipid bilayers

FRANCESCA GIUDICE; MILAGRO MOTTOLA; MARIA LAURA FANANI

Sierra de la Ventana

Congreso; XLIII Reunión Anual Sociedad Argentina de Biofísica; 2014

Sociedad Argentina de Biofísica

We investigated the interaction of three amphiphilic derivatives of L-ascorbic acid (ASCn), ascorbyl palmitate (ASC16), ascorbyl myristate (ASC14) and ascorbyl laurate (ASC12) with model membranes. The membrane system chosen was phospholipid bilayers organized in nanoscale vesicles. Since ASCn have an acidic group with a pKa of 4.2, the insertion of these drugs to originally neutral phospholipid vesicles, was monitored by measurements of changes in zeta potential. Our results show a large change in the hydration of the polar head group of phospholipids by measuring changes in the Generalized Polarization of laurdan, consistent with a rigidifying effect for all the ASCn studied in a magnitude ASC14 > ASC12 > ASC16. Similar effect was observed by measurement of the anisotropy of DPH (diphenylhexatriene), which reported an increase in the microviscosity of the hydrophobic core of the membranes. Those rheological changes in the membrane occur with the maintaining of the structural integrity of the membrane: the low amount of soluble phosphorus in ASCn-treated vesicles along with a negligent release of vesicles fluorescent content leads to the conclusion that none of the three drugs have a detergent effect. These studies show that the ASCn interact strongly with model lipid membranes and alter their rheological properties, likely by increasing the stiffness of the membranes. This work is a first attempt to characterize the biophysical properties of ASCn-phospholipids systems, which is aimed to get a better understanding of their pharmacological and immunological effects.