RUI: Nanoscale DNA-Silver Cluster Catalysts

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Jeffrey Petty of Furman University is developing hierarchal nanoparticles that catalyze chemical reactions. Nanometer-sized gold particles will be platforms for assembling and organizing a dense array of DNA. In turn, these appended strands of DNA will encapsulate and shield silver nanoclusters to yield nanoscale conjugates that survive in harsh aqueous and biological environments. While DNA-cluster conjugates are distinguished by their strong fluorescence, the proposed studies will investigate their catalytic activity. Alkyne-azide cycloadditions are widely used in nanoscience because they are efficient and rapid, and these reactions have been shown to be catalyzed by DNA bound silver clusters. In this project, DNA-silver cluster conjugates will be assembled using gold nanoparticles to form hierarchal constructs that will be potent catalysts for alkyne-azide click cycloadditions. The proposed studies will comprehensively educate young scientists through interdisciplinary chemistry research coupled with community outreach. Undergraduate students will study a multifaceted scientific problem that bridges nanoscience, physical chemistry, and biochemistry. Undergraduate students will develop the needed expertise for nanomaterial characterization by using a diverse suite of spectroscopic, chromatographic, and mass spectrometry tools, while furthering their education through external collaborations. Thus, this research will develop young scientists to perform independent research early in their careers and to contribute their knowledge to their broader community. With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Jeffrey Petty of Furman University is exploiting multifunctional DNA ligands to synthesize a multivalent nanoparticle catalyst. Three specific aims will be pursued. First, polydentate DNA ligands will secure an atomically-precise, fluorescent silver cluster, and the DNA host will be site-specifically modified by enzymatically excising DNA nucleobases and by substituting noncanonical nucleobases. Underlying these studies is a fundamental feature of silver clusters – they communicate changes in their DNA environment through their steady-state and time-resolved spectra. Second, a dense array of these cluster-tagged DNA strands will be assembled around a gold nanoparticle. The resulting spherical nucleic acids will tangentially direct a dense layer of oligonucleotides to the surrounding solution, thereby facilitating catalysis. Third, the activity of these immobilized catalysts will be assessed via kinetic measurements using electrospray ionization mass spectrometry. These results will be compared with the spectra of the silver cluster catalysts to understand how changes in the DNA binding site correlate with catalytic activity. These hierarchical nanoscale catalysts will offer new ways to modulate catalysis by an embedded silver cluster through targeted changes in their DNA host. The projected outcome is to develop a new class of atomically-precise cluster catalysts whose activity can be specifically tuned by targeted changes in the DNA hosts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.