Characterization of Parallel-Stranded DNA Duplexes by Surface-Enhanced Raman Spectroscopy and Bromide-Modified Gold Nanoparticles.

The parallel double-stranded DNA (dsDNA) demonstrates potential utility in molecular biology, diagnosis, therapy, and molecular assembly. However, techniques for the characterization of parallel dsDNA are limited. Here, we demonstrate that a series of intensive characteristic Raman bands of three parallel dsDNAs, which are stabilized by reverse Hoogsteen A + ·A + base pairs or hemiprotonated C + ·C, G·G minor groove edge, Hoogsteen A·A base pairs, or Hoogsteen T·A, C + ·G base pairs, have been observed by surface-enhanced Raman spectroscopy (SERS) when the gold nanoparticles modified by bromine and magnesium ions (Au BMNPs) were used as substrates. The featured bands can not only accurately discriminate parallel dsDNA from antiparallel one but also identify the strand orientation within dsDNA. The proposed approach will have a significant impact on DNA analysis, especially in the detection and differentiation of various DNA conformations.