DNA stabilized silver nanoclusters as the fluorescent probe for studying the structural fluctuations and the solvation dynamics of human telomeric DNA

We have prepared fluorescent silver nanoclusters (AgNCs) in the human telomeric sequence (d[AG(3)(T(2)AG(3))(3)], Hum 22). There are two types of AgNCs that can be formed in Hum 22. The red emissive AgNCs (lambda(em) = 620 nm) are originated from the AgNCs attached onto the guanine bases, while the green emissive AgNCs (lambda(em) = 520 nm) are due to the AgNCs located between the adenine and guanine bases. We found that the fluorescence of the AgNCs is significantly quenched when Hum 22 forms a G-quadruplex structure. The fluorescence anisotropy decay dynamics and the time-resolved emission spectra of the AgNCs reveal the structural fluctuation and the solvation dynamics of Hum 22. The results indicate that the silver nanoclusters are an ideal fluorescent probe for human telomeric DNA and might be used as an important tool for studying the G-quadruplex structure.