Coarse-grained molecular dynamics simulations within the framework of MARTINI force field were employed to study the G4 poly(amidoamine) (PAMAM) dendrimer interacting with the lysine-flanked (KALP) peptide.The influence of KALP peptide on the structure of the dendrimer under the neutral and acidic pH conditions was considered.The radius of gyration

shape factor and radial distribution function of the dendrimer were analysed.Meanwhile

the free energy between molecules was calculated.It was found that the peptide provided a slight effect on the size and density profile of the dendrimer under the two pH conditions

which implied that there existed enough space in the interior of the dendrimer for the KALP peptide penetration.The dendrimer keeps its sphere-like shape as the peptide approaches from the center-of-mass distance of 5.0 nm to 1.0 nm.The results of potential of mean force between two molecules imply that the dendrimer repels the peptide at low pH possibly due to the steric interaction and electrostatic repulsion.At neutral pH

a stable complex of two molecules is also hard to form under the influence of thermal fluctuation.The finding suggests PAMAM dendrimer is unfavourable to adsorb the KALP-like trans-membrane proteins.