It is well known that lipids form bilayer membranes, similarly certain peptide sequences with hydrophilic residues at one end and hydrophobic residues at other end can also form bilayer membranes. These peptides resembling surfactants are commonly referred as surfactant like peptides (SLPs). One such short SLP, A<sub>3</sub>K, comprising three contiguous alanine residues with a lysine residue at C-terminal has been experimentally determined to form a bilayer membrane. The molecular features that lead to stable membrane formation is not completely understood. Earlier, a molecular dynamics study has identified a few favorable peptide arrangements constituting stable membranes through random trials. We intended to systematically identify the key molecular interactions and packing geometry affecting the stability and integrity of the membrane. We have investigated the various possible ways of packing peptides into a small bundle that could minimize the inter-peptide distance and the interaction energy through a series of implicit solvent calculations. The identified favorable peptide bundle is used as the repeating unit to construct the bilayer membrane and its stability is analyzed through long explicit solvent simulation. We find sufficient peptide-peptide hydrogen bonding is required to retain the membrane intact by counteracting the favorable peptide-water interactions. In this talk, we will present our results of how peptide conformation, peptide orientation (parallel vs antiparallel stacking), packing (cubic vs. hexagonal packing) strictly affect the stability and flexibility of the peptide membrane. We will also discuss how the change in hydrophilic residue (lysine to aspartate) and the alteration of the location of the hydrophilic residue (C-terminal to N-terminal) influence the membrane structure.

Pertinence of packing geometry on peptide bilayer integrity

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