Far-infrared torsional modes of DNA components studied using highly sensitive broad-band terahertz Fourier transform spectroscopy

We demonstrate the use of broad-band low-intensity terahertz Fourier transform spectroscopy (THz-FTS) for recording the far-infrared (0.1 to 20 THz) absorption characteristics of the four nucleobases forming the building blocks of deoxyribonucleic acid (DNA) as well as presenting spectra for various DNA forms. Numerous and distinct spectral features are observed with large differences between the molecules in both frequency dependent absorption coefficient and index of refraction. These absorptions are highly conformationally dependent as a result of the differences in hydrogen bonding and their study should prove vital in the understanding of the effect of THz radiation on tissue and pave the way for quantifying biological damage thresholds resulting from THz illumination. To this end we also present initial spectroscopic results into the effects of high-intensity THz irradiation on the characteristic absorption spectra of nucleobases and DNA.