Copyright @ IFAC Computer Applications in Biotechnology, Quebec City, Canada, 2001 MOLECULAR MODELLING OF DIFFUSIONAL MOTION AND TRANSFER OF PYRE NE IN LIPID MEMBRANES Michael Herrenbauer, D. Peter Tieleman, Clemens Posten Universitiit Karlsruhe (TH) -Institutfor Mechanische Verfahrenstechnik und Mechanik (MVM) - KaiserstrajJe 12 - 76128 Karlsruhe University ofCalgary, Department of Biological Sciences, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1 N4 email: clemens.posten@ciw.uni-karlsruhe.de Abstract: Molecular dynamics simulations of the motion of pyrene molecules in a lipid membrane are shown. Additionally the transfer of such molecules into the lipid membrane is investigated by a molecular simulation technique. The results indicate that pyrene molecules move relatively fast to a position located about 1 to 1.2 nm away from the phospholipid head groups and show only lateral diffusion in z-plane. Sorption experiments suggests that there is a transport resistance for the solute transfer over the water - lipid interface. Simulations where pyrene molecules were pulled into the membrane support the theory of the existence of a barrier. Copyright © 2001 IFAC Keywords: Dynamic Modelling, Modelling, Environmental Engineering, Motion I. INTRODUCTION The interactions between organic hydrophobic compounds and lipid membranes are of great importance for the estimation of the environmental impact of such compounds. Furthermore it plays an important role in pharmacy, especially in drug delivery by Iiposomes. Experimental techniques which give insight into the behaviour of aromatic compounds are mostly NMR or other spectrometric techniques. It is difficult and expensive to get detailed information out of the experiments. Molecular dynamic simulations, based on empirical force fields, are a powerful tool to get insight into the time-resolved motion of a probe within a lipid membrane. Numerous simulations have been done 311 on lipid-protein interaction in lipid membranes with molecular modelling (a recent review is given in Forrest and Sansom, 2000) but only a few publications are known about motion of small organic molecules in lipid bilayers. Bassolino- Klimas et al. (1995) have investigated the diffusion of benzene in lipid membranes. In this study, simulations of diffusion of pyrene within lipid bilayers and transfer of this molecules into the membranes were examined by molecular dynamic simulations. 2. METHODS: MOLECULAR DYNAMIC SIMULATIONS