Molecular dynamics simulation of DNA-functionalized gold nanoparticles

Molecular dynamics methods have been used to study a 2 nm gold nanoparticle that is functionalized with four single stranded DNAs at the atomistic level. The DNA strands, which are attached to the [111] faces of a 201 atom truncated octahedral gold particle with a -S(CH ₂) ₆- linker, are found to be perpendicular to the surface of the particle, with the alkane chain lying on the surface. There are no significant hydrogen bonding interactions between the adsorbed ss-DNAs during the simulation. Even though the expected radius would be 49 Å (3.4 Å per base) for a Watson-Crick DNA structure, the simulation with 0.5 M salt shows a radius of about 29 Å (2.2 Å per base), which is a result that is consistent with recent experimental reports. It is alsofound that the sodium concentration within 30 Å of the gold particle is about 20% higher than the bulk concentration. This is consistent with an observed increase in the melting temperature of DNA when many functionalized gold particles are hybridized together.