Nanostructures via DNA scaffold metallization

The critical role of polymers in process of noble metals nanostructures formation is well known, however, the use of DNA chain template in this process is yet largely unknown. In this study we demonstrate different ways of silver deposition on DNA template and report the influence of silver nanostructures formation on DNA conformational state. Metallization of DNA chain proceeds by two different scenarios depending on DNA conformation. If DNA chain is unfolded (elongated) chain, silver reduction leads to the nucleation of silver nanoparticles and their growth on DNA scaffold. Silver nanoparticles assemble on negatively charged DNA template due to electrostatic interactions. During formation of silver nanoparticles, DNA chain, similarly to other polyelectrolytes, plays a role of stabilizing agent, and silver nanoparticles formed in DNA solutions are smaller and have narrower size distributions as compared to the particles formed in DNA-free solutions. Since positive change of thus formed silver nanoparticles is rather low, DNA chain remains in unfolded conformation no matter how high is a concentration of silver nanoparticles. On the other hand, when DNA molecule has been compacted into tight condensate, naturally of a toroid shape, deposition of silver on compacted DNA chain proceeds in a different manner without discretion into nanoparticles. As a result of such silver metal deposition, DNA-templated silver nanorings are formed. By comparison of UV-Vis spectra changes, the detection of transition point between unfolded and compact DNA conformations becomes possible. Metallization of unfolded DNA chain brings nanoparticles of about 30-50 nm size, while deposition of silver metal on a compact DNA condensate gives 100-150 nm metal rings that are distinguished by optical properties. The approach of different scenario of metallization can be used for detection of conformational changes in biopolymers.