Vibrational fingerprints of N6-methyladenine and N6,N6-dimethyladenine in Raman spectra

Abstract

Vibrational fingerprints of N6-methyladenine (NMA) and N6,N6-dimethyladenine (NDMA) on gold nanoparticles (AuNPs) were investigated by means of Raman spectroscopy. NMA and NDMA have one methyl group and two methyl groups, respectively, at the amino moiety of the adenine purine unit. Surface-enhanced Raman scattering (SERS) spectra were analyzed to explain the difference in the spectral features among adenine, NMA, and NDMA based on density functional theory (DFT) calculations on gold clusters. NMA has unique bands at 717 and 1101cm−1 in their SERS spectra on AuNPs, which can be differentiated from those of adenine. After observing these unique spectra features, the SERS spectra of NMA and NDMA on AuNPs were dissimilar, suggesting that the methyl group at the amino groups of the adenine may be significantly affecting the binding on AuNPs, as supported by DFT calculations of NMA and NDMA on gold clusters. Our Raman study indicates that the methylation at the amino group in adenine may play a significant role in providing vibrational finger prints in the SERS spectra on metal surfaces.