Silver Binding Dichotomy for 7-Deazaadenine/Thymine: Preference for Watson-Crick Pairing over Homobase Interactions...

DNA strands modified with 7-deazaadenine (X) and 7-deazaguanine (Y) have shown promise in forming silver-DNA assemblies while maintaining canonical Watson-Crick base pairing, highlighting the compatibility of silver binding with standard DNA structures. However, critical questions remain regarding the binding preferences of Ag^I ions to sequences containing 7-deazapurine bases, particularly the prevalence of silver-modified Watson-Crick base pairs versus alternative homobase pair arrangements. To address this, we examined the binding of Ag^I to complementary X-T sequences, demonstrating a strong preference for canonical X-Ag^I-T pairing over homoleptic X-Ag^I-X or T-Ag^I-T pairs. Additionally, we report the discovery of a novel metallized DNA duplex featuring continuous X-Ag^I-X homobase pairs, whose structural analysis at the monomeric level, using model base 9-propyl-7-deazaadenine (pX) and Ag^I salts, reveals a unique silver-binding pattern through the Watson-Crick face. These findings not only advance our understanding of silver-mediated DNA architectures using 7-deazapurines but also provide a foundation for the rational design of sophisticated metal-DNA nanostructures with tailored properties, opening new avenues for the development of functional DNA-based materials.