The Experimental Research Of Silver Ion-induced DNA Conformational Change

The silver ion—DNA interaction play an important role in medical use of silver ions and related technologies such as DNA sensors.However,the mechanism of the interaction between silver ions and DNA is not fully understood.In this research,the dynamics of Ag⁺—DNA interaction at a single-molecule level was studied using magnetic tweezers.AgNO₃ solutions with concentrations ranging from 1?M to 20?M led to a 1.4–1.8?m decrease in length of a single?-DNA molecule,indicating that Ag⁺has a strong binding with DNA,causing the DNA conformational change.The compaction process comprises one linear declining stage and another sigmoid-shaped stage,which should be attributed to the interaction mechanism.Considering cooperative effect,the sigmoid trend was well explained using a phenomenological model.In contrast,addition of silver nanoparticle solution induced no detectable transition of DNA.In contrast,the DNA conformation did not change after the silver nanoparticle solution was added.Atomic Force Microscope?AFM?was used to characterize the morphology of DNA and dynamic light scattering?DLS?was used to study the effects of silver ion concentration and DNA concentration on Ag⁺—DNA interaction.The size of the Ag⁺—DNA complex decreased with an increase in Ag ionic strength ranging from 1?M to 1 mM.Morphology characterization confirmed that silver ions induced DNA to adopt a compacted globular conformation.At a fixed[AgNO₃]:[DNA base pairs]ratio,increasing DNA concentration led to increased sizes of the complexes.Intermolecular interaction is believed to affect the Ag⁺—DNA complex formation to a large extent.