Surface enhanced raman spectroscopy on nucleic acids and related compounds adsorbed on colloidal silver particles

Abstract

Various nucleic acids and related compounds have been investigated by surface enhanced Raman spectroscopy (SERS) on silver sol. The time delay between the addition of the various nucleic acids to the silver sol and the appearance of their SER spectra, i.e. the time needed by the various molecules to adsorb on an active site of the silver surface with an adsorption geometry which allows a SERS enhancement, shows strong differences. For instance, an immediate appearance of SER spectra has been found for DNA, whereas ribonucleic acids (RNAs) demonstrated a strong time delay (up to days) of the appearance of their SER spectra. This delay can be tentatively explained by the higher rigidity of RNA molecules compared with DNA. The more flexible DNA molecules are better adaptable to adsorption on silver than RNAs. The SER spectra of RNAs and DNAs showed strong changes within their relative line intensities as a function of time before they achieved stationary conditions, which indicates a protracted re-arrangement of the large molecules on the silver surface.