Terahertz Fourier transform characterization of biological materials in a liquid phase

Abstract

Significant progress has been achieved during the last several years relating to experimental and theoretical aspects of terahertz (or submillimetre wave) Fourier transform spectroscopy of biological macromolecules. However, previous research in this spectral range has been focused on bio-materials in solid state since it was common opinion that high water absorption will obscure the spectral signatures of the bio-molecules in solutions. At the same time, the biological functions of DNA and proteins take place in water solutions. In this work, the spectra of DNA samples have been measured in liquid phase (gel) over the spectral range 10–25 cm−1 and compared with spectra obtained from solid films. The results demonstrate that there is very little interference between the spectral features of the material under test and the water background except for the band around 18.6 cm−1. Multiple resonances due to low frequency vibrational modes within biological macromolecules in solutions are unambiguously demonstrated. Higher level of sensitivity and higher sharpness of vibrational modes are observed in the liquid environment in comparison with the solid phase, with the width of spectral lines 0.3–0.5 cm−1. Gel sample spectra are found to be polarization-dependent. The ability of THz spectroscopy to characterize samples in liquid phase could be very important since it permits examination of DNA interactions in real (wet) samples. One demonstrated example of practical importance is the ability to discriminate between spectral patterns for native and denaturated DNA.

Sub-THz Vibrational Spectroscopy of Bacterial Cells and Molecular Components

“…Each data point is an average of 32 scans. The experimental technique is described in more details in earlier publications [13,18]. Spectral resolution for all experiments was 0.25 cm -1 , which is the smallest allo wable setting in the hardware.…”

“…Our previous results on characterization of bio-mo lecules using Fourier transform (FT) spectroscopy detected mult iple resonances in transmission/absorption spectra of bio-molecules in the sub-THz frequency region [12][13][14]. Simu lations can help us to interpret the experimental data by assigning spectral features to specific molecu lar motions, and simultaneously with experimental characterizat ion co mputational modeling techniques have been developed using the energy min imization, normal mode analysis and mo lecular dynamics (MD) approaches to predict low frequency vibrational absorption spectra of short artificial DNA, and RNA [12,[15][16][17][18], large macro molecules of DNA [19,20] and proteins [21,22].…”

High-Resolution Terahertz Spectrometer

“…In case of asymmetric split ring resonators, there is an extraordinary strong field enhancement in the gap region of the ring resonator [37]. Compared to classic free-space radiation analysis [38], [39], this field localization leads to a much higher sensitivity of THz-FSS-based sensing reducing the required amount of samp le material significantly. For diagnostic applications, however, up to 100 arrayed gene sensors need to be read out in a reasonably short time.…”

Terahertz optical measurements of correlated motions with possible allosteric function

“…Unfortunately these reports contained irreproducible and/or conflicting observations which likely resulted in false assignments because they did not address one chief artifact in this frequency range, namely, multiple reflection effects or Fabry-Perot etalon (Crowe et al 2004;Edwards et al 1984;Globus et al 2002Globus et al , 2006Parthasarathy et al 2005;Woolard et al 2002). Fabry-Perot etalon is an interference between copropagating light beams arising from reflections at the sample/ window surfaces.…”