A simple approach to study the conformational switching of i-motif DNA by fluorescence anisotropy

Fluorescence anisotropy, dictated by the rotational diffusion of the fluorophore associated entity, is sensitive to the volume and structural changes, and the measurements can be performed in a homogeneous manner. In this work, a simple approach based on fluorescence anisotropy was proposed for the study of conformational switching of the i-motif structure. Factors influencing the stability of the i-motif structure, including the composition of buffer, the number of i-motif tetrads and coexistence of the complementary DNA, were investigated in detail. This study elucidated the superiority of the fluorescence anisotropy measurement as a simple, cost-effective and sensitive method for the detection of DNA structural switching, opening a new avenue for the research of DNA structures and functions.