INTERACTION OF HEMATOPORPHYRIN DIMETHYL ETHER WITH MODEL MEMBRANE SYSTEMS - DOUBLE-BONDS OF HYDROCARBON CHAINS AS A TARGET FOR PHOTODYNAMIC DAMAGE OF LIPID-MEMBRANES

We compared the interaction of hematoporphyrin dimethyl ether (HpDME) with model membrane systems composed of saturated and unsaturated lipids. HpDME was shown to bo incorporated into phosphatidylcholie monolayers independing on the presence of double bonds in the hydrocarbon chains. At an addition of 15muM HpDME under a monolayer compressed to a surface pressure of 29 dyn/cm the change in its area was about 10% for all phosphatidylcholines. For monolayers formed from fatty acids the increase of the monolayer area measured under the same conditions was less than 0.1%. This suggested that HpDME is incorporated into bilayers from different phosphatidylcholines to the same extent, independing on the presence of unsaturated bonds in their hydrocarbon chains. In bilayer lipid membranes (BLMs) from unsaturated lipids, exposure to visible light led to an increase in membrane conductance and capacitance and ultimate rupture of the membrane. In BLMs from saturated lipids, these parameters were not affected. The results suggest that the double bonds of hydrocarbon chains are a target for photodynamic damage of lipid membranes.