Chemists use biological compounds to assemble nanoparticles.

Chemists use biological compounds to assemble nanoparticles.

When looking to synthesise novel nanoparticles, chemists have traditionally used synthetic polymers as catalysts and templates. Increasingly, however, they are trying to mimic nature by using biological compounds as the basis for nanoparticle assembly.

Now, a team of chemists from North Carolina State University, Raleigh, US, has used RNA in nanoparticle assembly by creating strands that can control the formation of hexagonal palladium nanoparticles. Not only have such particles proved difficult to create by other means, but their RNA-mediated production could also shed light on the role that RNA may have played in the origin of life.

The team thought that RNA could be an efficient catalyst for inorganic particle formation because ’it is a highly structured biopolymer that can reproducibly fold into intricate 3D structures’. To test this theory, the chemists created a library of RNA strands. They chemically altered the strands with 5-(4-pyridylmethyl)-UTP to provide additional metal coordination sites and then incubated the strands with the metal complex dibenzylideneacetone palladium.

The team was looking for strands that could mediate the formation of palladium particles from the precursor complex or bind to particles that had already formed. They performed eight selection cycles, choosing those strands that performed best in each cycle to go on to the next. This eventually resulted in 25 strands that could efficiently catalyse the production of palladium nanoclusters and which the researchers were able to group into five different families, based on their base sequences.

Testing strands from each of the families, the researchers found that individual strand types could produce relatively large and uniform hexagonal particles (1.2-1.3?m) in only one minute.

RNA has been postulated as the basis for the origins of life on earth, because it can act as both an enzyme and a store of genetic material. Based on their findings, the chemists speculate that there could have been an important inorganic component to the early RNA world and that this may have resulted in a variety of as-yet-unknown RNA activities.

Jon Evans