부산대학교 도서관

1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine(POPC), a lipid comprising a saturated and an unsaturated acyl chain,belongs to the class of glycerophosphatidylcholines, major lipidsin eukaryotic cell membranes. To get insight into the structural propertiesof this lipid within monolayers as membrane models, we performed moleculardynamics (MD) simulations of POPC monolayers under compression atthe air/water interface. MD simulations were carried out at 300 Kand at different surface pressures using the all-atom general Amberforce field (GAFF). A good agreement was found between the simulateddata and experimental isotherms. At surface pressures greater than15 mN/m, two orientations of the head groups clearly appear: one nearlyparallel to the monolayer interface and another one pointing towardthe water. On the basis of the analysis of headgroup dihedral angles,we propose that the conformational variations around the bonds connectingthe phosphorus atom to the adjacent oxygens are involved in thesetwo orientations of the headgroup. The glycerol group orientationis characterized by a large distribution centered around 50°with respect to the monolayer normal. The acyl chains are predominantlyin trans configuration from 7.5 to 43 mN/m surface pressures. Moreover,the calculated order parameter profiles of both chains suggest anindependent behavior of the saturated and unsaturated chains thatcould be correlated with the formation of chain-type clusters observedalong the simulated trajectories. [ABSTRACT FROM AUTHOR]