Lipid Bilayer Curvature and Pore Formation Induced by Charged Linear Polymers and Dendrimers: The Effect of Molecular Shape

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Abstract
We performed molecular dynamics (MD) simulations of multiple copies of poly-l-lysine (PLL) and charged polyamidoamine (PAMAM) dendrimers in dimyristoylphosphatidylcholine (DMPC) bilayers with explicit water using the coarse-grained model developed by Marrink et al. ( J. Chem. Theory Comput. 2008, 4, 819). Membrane disruption is enhanced at higher concentrations and charge densities of both spheroidally shaped dendrimers and linear PLL polymers, in qualitatively agreement with experimental studies by Hong et al. ( Bioconjugate Chem. 2006, 17, 728). However, larger molecular size enhances membrane disruption and pore formation only for dendrimers and not for the linear PLL. Despite more intimate electrostatic interactions of linear molecules than are possible for spheroidal dendrimers, only the dendrimers were found to perforate membranes, apparently because they cannot spread onto a single leaflet, and so must penetrate the bilayer to get favorable electrostatic interactions with head groups on the opposite leaflet. These results indicate that a relatively rigid spheroidal shape is more efficient than a flexible linear shape in increasing membrane permeability. These results compare favorably with experimental findings.