Self-Assembly Of Single Stranded DNA and Gold Nanoparticles

The unique properties of gold nanoparticles are utilized in a range of applications such as sensors, catalysis

and drug delivery. Gold nanoparticles are often functionalized with ligands to prevent aggregation and control

nanoparticle binding. Previous work in our group has shown that nanoparticles with positively charged ligands

have the ability to wrap double stranded DNA (dsDNA) above a critical charge density. The interaction of

dsDNA with AuNPs is dependent on parameters such as charge and polarity of attached ligands. Positively

charged ligands are able to wrap DNA, while polar ligands cause less distortion in the DNA helix. Herein, we

describe the use of molecular dynamics simulations to study the interactions of a random sequence of single

stranded DNA (ssDNA) with varying ligands.We vary charge and polarity of ligand end groups by studying

methyl (CH3), amine (NH2) and ammonia (NH3)modified ligands. Because ssDNA is much more flexible than

dsDNA, we find a greater degree of wrapping for all particles. However, ssDNA is more compactly wrapped

around gold nanoparticles with positively charged ligands (NH3) than with the CH3 and the NH2 end groups.