MD Simulation Study of Complex Formation Between LysHisArg Dendrimer and Molecules of AlaGluAspGly Bioactive Peptide

In previous papers we studied behavior of lysine dendrimers of second generation with charged double lysine and arginine (KK, RR) spacers, hydrophobic double leucine, alanine and glycine (LL, AA, GG) spacers and pH dependent double histidine (HH) dipeptide spacers inserted between each pair of neighboring branching points of dendrimer. We also studied their complexes of these dendrimers with molecules of several bioactive peptides (including AEDG tetrapeptide) necessary for delivery of these peptides to different cells. It was shown that lysine dendrimers with charged internal insertions are good for delivery of oppositely charged oligopeptides and genetic material while dendrimers with hydrophobic internal insertions are good for delivery of bioactive hydrophobic molecules. In present work we study the complexes of molecules of AEDG peptide and dendrimer with repeating unit LysHisArg containing histidine-arginine (HisArg, HR) spacer. In our case aminoacid residues (H and R) in spacers of dendrimer are different and the charge of H residue depends on pH. We performed molecular dynamics simulations of the complexation of 16 AEDG molecules with a dendrimer at two different value of pH: a) pH>7 with fully uncharged histidines (H) and b) pH<5 with fully protonated (Hp) histidines in aqueous solution with explicit counterions. It was found that the dendrimer with protonated histidines could carry a larger number of AEDG tetrapeptide molecules.