High-Resolution THz Spectroscopy to Measure Strong THz Absorption Signatures of si-RNA in Solution

摘要

Molecular spectroscopy of aqueous solutions has been more challenging in the THz region than at near-infrared wavelengths for several reasons, such as the strong absorption by liquid water. We have measured high-absorbance and high-Q (≈90) resonant signatures around 1.0 THz from linear small-interfering double-stranded RNA molecules suspended in buffer solution in nanofluidic chan-nels. The measurement instrument is a coherent photomixing transceiver. A physical model is developed to explain the measurements based on high-order flexural reso-nances of the entire double-strand with polar coupling to the THz radiation via the ionized phosphate groups. The predicted resonant frequencies are within 2% of ex-periment for the three double-strands studied (15, 19. and 23 base pairs), supporting the conclusion that each si-RNA molecule has a unique THz resonant frequency.