Conformational Ensembles from Experimental Data and Computer Simulations

Conformational Ensembles from Experimental Data and Computer Simulations

Poster Abstracts

96-POS Board 16 Coarse Grained Monte Carlo Simulations of Polyelectrolyte-nanoparticle Complexation Morten Stornes , Binamra Shrestha, Rita S. Dias. NTNU - Norwegian University of Science and Technology, Trondheim, Norway. The formation of complexes between polyelectrolytes (PEs), and other charged macroions have received much attention in recent years. Studying these systems are important to understand e.g. DNA condensation and protein-membrane interactions, and PE-nanoparticle complexes have potential applications in gene and drug delivery systems. Of special interest are weak (annealed) PEs which, contrary to strong (quenched) polyeletrolytes, have a pH dependent ionization. In addition, annealed PEs exhibit charge mobility, where protons are mobile along the chain, giving rise to non-uniform charge profiles and charge patches. This charge mobility has previously been shown to increase the binding between oppositely charged species, such as DNA or protein adsorbing on membranes. We have studied the complexation of one and two charged nanoparticles with multiple PE chains of opposite charge, to better understand the influence of chain concentration and length on the PE ionization with increasing pH, the effect chain ionization has on bridging between nanoparticles and the effect of charge mobility on the PE-nanoparticle adsorption. This has been done using Monte Carlo simulations. Rather than using more detailed all-atomic models or molecular dynamics simulations, the simpler coarse grained Monte Carlo approach allows us to focus on the importance of the electrostatic interaction between constituents without large computational costs. It is found that the PE ionization decreases with increasing concentration relative to the nanoparticle, and the combination of chain length and concentration can significantly influence the ionization. Contrary to previous studies, we also find that quenched PEs adsorb better than annealed PEs on the nanoparticle at similar degrees of ionization. It is suggested that this is due to the difference in PE stiffness compared to other studies, and the formation of PE loops.

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