Direct Base-to-Base Transitions in ssDNA Revealed by Tip-Enhanced Raman   Scattering
  In the present contribution, specifically designed single-stranded DNA (ssDNA) sequences composed of adenine and cytosine were used as nanometric rulers to target the maximum achievable spatial resolution of tip-enhanced Raman spectroscopy (TERS) under ambient conditions. By stepping along a strand with a TERS tip, the obtained spectra allowed for a clear spectral discrimination including conformational information of the nucleobases, and even sharp adenine-cytosine transitions were detected repeatedly with a spatial resolution below 1 nm. 
Xiu-Mei Lin, Tanja Deckert-Gaudig, Prabha Singh, Michael Siegmann,   Stephan Kupfer, Zhenglong Zhang, Stefanie Gr\"afe, Volk...
physics.chem-ph cond-mat.mes-hall