Surface-enhanced Fourier transform Raman scattering from a DNA triple helix poly[dA]center dot 2poly[dT] at a silver electrode: Beyond the short-range mechanism

Surface-enhanced Fourier transform Raman scattering (FT-SERS) spectroscopy was used to characterize the adsorption structure of a poly[dA]. 2poly[dT] DNA tripler at an ex-situ roughened silver electrode, We found that the tripler molecules have a favorable tendency to be adsorbed without any obvious destabilization at higher positive-charged surfaces via a phosphate-moiety-directed mechanism. However, the observed enhancement of intense Raman signals exhibits long-range rather than short-range character, as evidenced by the appearance of several strong SERS bands involving relevant vibrations of the ribose-phosphate backbone and the dT residues. Therefore, this phenomenon cannot be satisfactorily interpreted by the short-range enhancement mechanism that is usually believed to be the main contribution of the Raman enhancement of double-helical nucleic acids at a charged silver surface.