Characterization of triplex RNA poly[rU]· poly[rA]· poly[rU] adsorbed on silver colloids by Fourier transform surface enhanced Raman scattering and scanning tunneling microscopy

Fourier transform surface enhanced Raman scattering (SERS) spectroscopy has been used to characterize triplex RNA poly[rU] · poly[rA] · poly[rU] adsorbed on silver colloid using an Nd:YAG laser as an excitation source. In this case, SERS spectra of high quality are recordable in a relatively short time. Compared to the FT-Raman spectrum of the triplex in solid, two distinct SERS bands centered at 835 and 819 cm−1 indicate that the helical structure of the triplex RNA in the proximity of the colloidal silver surfaces is well preserved. From UV-vis spectroscopy, the aggregation state of original silver colloids might not be distinctly altered after the triplex RNA was added up to 1 × 10−5 M. Moreover, scanning tunneling microscopy (STM) observations of the triplex-silver colloid complex also clearly reveal that the aggregation state of the silver colloids is changed from original dispersed particles to predominantly ordered adsorption along the phosphate backbone of the triplex with some aggregation, indicating that the microstructural changes of the silver surfaces play an important role in the SERS effect.