Fluorescence Quenching in Self-Assembled 2-Aminopurine-Ag+ Nanofibers

Thumbnail Image



Journal Title

Journal ISSN

Volume Title


The Ohio State University

Research Projects

Organizational Units

Journal Issue


The binding of Ag+ ion to DNA nucleobases is of interest because of the unique ability of silver ions to direct the formation of novel base pairs. These Ag+-mediated non-canonical base pairing motifs provide the structural elements for DNA-templated silver clusters, which have highly tunable absorption and emission wavelengths from blue to near infrared and thus are strong candidates for the development of novel detection and labeling methods. Atomic force microscopy (AFM) reveals that nanofibers with diameter of tens of nanometers and length of microns are formed when Ag+ is added to monomeric bases such as adenine and guanosine monophosphate (GMP). However, the molecular-level detail of these self-assembled nanostructures, such as metal binding sites and interaction between bases, that leads to global structure and properties is still unclear. Thiazole orange is a weakly emissive molecule in water but becomes much more fluorescent when intercalated into π stacks. In this project, we used thiazole orange to probe the structure of the supramolecular assemblies formed from mix-ing Ag+ and 2-aminopurine, the fluorescent analog of adenine. We show that the π- π stacking between 2-aminopurine molecules is present in the nanofibers, as evident from the enhanced fluorescence of thiazole orange when it is intercalated into the stacks. We further confirmed this result by adding methanol as a denaturant, which significantly reduces the fluorescence from thiazole orange but enhances the fluorescence from 2-aminopurine – both are hallmarks of dis-rupted π- π stacking. The fluorescent enhancement of thiazole orange in a nucleobase system lacking a covalent backbone is of particular significance as there are to date few examples of such enhancement.



DNA templated silver clusters