Abstraet. Model DNA-membrane contacts were studied in the system containing polyadenylic acid(imlyA): polyuridilic acid (polyU) duplex and egg phosphatidylcholine (PC) vesicles without or in the presente of MgCI 2. PolyU containing O-(1-oxyl-2,2,5,5-teWamethylpyrmline-3-carbonyl) spin label at 2'-OH moiety was used for spin labeling study of nucleic acid-phospholipid interactions. For polyA labeled with the same nitmxyl radical EPR speclra from spin labels attached at terminal and at intemal nucleofide tmits conlribute into the EPR speetrum of d.s. polynucleolide without or in the presente of egg PC vesicles and Mg ions. Intemal spin labels are more sensifive to the interaction with PC-MLV than terminal ones. The complexation between s.s. polynucleofide and PC-MLV was shown. The values of spin labels' melling temperatta'e of polyA : SL-polyU duplex at 1 mM MgCI 2 reflect the changes in rotafional mobility of terminal spin labels connected with duplex --triplex Iransition. AnŸ plots of temperatta~ dependence of EPR spectm parameters prove that ribose moieties of sugarphosphate backbone are involved into the interaction between polynucleotide duplex and phospholipid bilayer. Egg PC vesicles demonsWate stabil~kg effect on polyA : polyU duplex at 1 mM of Mg :+ and destabilizing effect at 5mM Mg: § .