Rigid DNA chains near nanoparticles

Two-photon excitation time-resolved fluorescence anisotropy and lifetime measurements were used to study the conformation of DNA near oppositely charged nanoparticles. Negatively-charged rhodamine-labeled DNA was allowed to adsorb onto positively-charged nanoparticles in deionized water and surface-induced fluorescence quenching was observed by measuring the fluorescence lifetime. Fluorescence quenching decreased with the addition of NaCl to the DNA-nanoparticle complex, which implies that the separation of DNA from the nanoparticles increased. However, comparison of fluorescence lifetime decays between free labeled-DNA and the DNA-nanoparticle complex shows that the adsorbed DNA remained less flexible than free labeled-DNA.