Surface‐Enhanced Raman Scattering (SERS) Spectroscopy of Nucleic Acids

Synthesis of Nucleic Acid Analogues by Alternating Cyclocopolymerization

“…Formation of the double helical structure of 4U with poly(dA) was confirmed by surface-enhanced Raman spectroscopy (SERS). As well documented in the previous studies, we observed the variation of the band intensities associated with the polymer backbone (sugar−dicarboxyalkylene and sugar−phosphate) and nucleic acid base moieties during the conformational change from two separated single strands to a double helical structure. As shown in Figure , strong bands for the polymer backbone at 2950 cm -1 and for adenine moieties at 730 and 1330 cm -1 were initially observed in the SERS spectrum of the mixed solution of 4U and poly(dA).…”

“…This is indicative of the close proximity of the backbone on the Ag film substrate and further out in the case of adenine moieties as a result of the formation of a double helix by base-pairing. Spectrum b in Figure resembles that of the double helix of the natural poly(dU) and poly(dA) 16b 4 SERS spectra of the mixed solution of 4U and poly(dA).…”

The Controversial Orientation of Adenine on Gold and Silver

“…Among the initial SERS investigations of adenine, adenosine, and DNA adsorption, there was uncertainty whether adenine adsorbs on a silver electrode in a planar or perpendicular orientation . Subsequent studies of adenine on various silver surfaces proposed perpendicular adsorption through its N7 atom, planar adsorption, planar at low concentrations and perpendicular through N1 at higher concentrations, perpendicular through the amino group, planar again, planar at positive electrode potentials and by N7 at negative potentials, perpendicular through the amino group based on comparison with adenine analogues, and again via the amino group .…”

Raman spectroscopy

“…Low-frequency lines observed in the Raman spectra of living cells have been interpreted and comparisons made between malignant and normal cells (131). Surface-enhanced Raman spectroscopy has proved useful in studies of biological molecules in general (132) and nucleic acids in particular (133). Techniques have been described for studying isolated cell populations (134) and the examination of microsamples (135).…”