Interaction of unprotonated and protonated polyethylenimine with phoshpholipid bilayer: A molecular dynamics study

Abstract

The Interaction of Polyethylenimine with lipid bilayer has several applications in biophysical research such as transfer of DNA to the target cell. The physical process of interaction at atomistic level has not been fully understood. Here, we have studied the interaction of completely protonated PEI (at very low pH) and unprotonated PEI (at very high pH) with 1,2 dioleyl -sn-glycero-3-phosphocholine (DOPC) bilayer using molecular dynamics method. Both protonated and unprotonated PEI associates with the hydrophilic head group of the lipid molecule. Pore formation is observed in the bilayer when protonated PEI is inserted in to the bilayer. A single chain of unprotonated PEI doesn’t significantly change the density profile and area per lipid of the bilayer. Coiled PEI makes hydrogen bonds with itself when in coiled conformation and number of hydrogen bonds with water of the lipid bilayer is lesser compared to the situation in which PEI has relatively open conformation. Protonated PEI also when associated with the one leaflet of bilayer doesn’t cause to change density profile and area per lipid significantly. But when protonated PEI is inserted in the bilayer, area per lipid increase and decrease in bilayer thickness is observed