Cooperativity between two selected RNA Pdases in the synthesis of Pdnanoparticles

Abstract

We have made the surprising discovery that the crystallinity of nanoparticles formed from solutions containing RNA depends upon the presence of sequence mixtures. That is, a single sequence selected from the original random RNA sequence library produced mostly amorphous hexagonal nanoparticles, while a combination of sequences that emerged from the selection yields crystalline material as determined by SAED. To our knowledge this is the first example in which two biomolecules (RNA, DNA, or peptides) selected in vitro work together to provide a unique chemical outcome. In addition, this article provides a rigorous examination of the chemistry of Pd nanoparticle formation using RNA and the organometallic precursor complex Pd₂(DBA)₃ (DBA is dibenzylideneacetone). These studies have identified the specific conditions required for the successful RNA-mediated synthesis of Pd nanoparticles from aqueous solutions (10% THF : 90% H₂O) containing Pd₂(DBA)₃, as well as conditions that led to anomalous results. A variety of techniques were employed to characterize materials formed under different solution conditions including SEM, AFM, TEM, selected area electron diffraction (SAED), and a chemical reactivity test. These analysis methods support the formation of Pd particles by RNA mediation when accounting for and controlling the important variables in the execution of the experiments. It is now clear that nanoparticles formed from RNA sequences isolated viain vitro selection can be dependent on many factors and it is understood that the specific sequence or sequence mixtures must be taken into account to fully understand RNA mediation of nanoparticle formation.