Optical characteristics of biological molecules in the terahertz gap

Abstract

Terahertz Spectroscopy has been recently introduced as a promising technique for the collection of signature data in transmission spectra of biological materials including warfare agent simulants. To characterize material rather than sample, it is always desirable to obtain the material's optical properties as functions of frequency. In this work, we present results from parallel measurements of reflection and transmission spectra of biological molecules to enable detailed and direct calculation of refractive index and absorption coefficient spectra in the terahertz gap. DNA samples from herring and salmon as well as samples of Ovalbumin and Bacillus Subtillus spores have been characterized. The technique for simulation is described. Reflection spectra reveal resonance features similar to those demonstrated earlier for transmission, thereby affirming molecular vibrational modes in biological materials. The dispersion of refractive index and absorption coefficient is demonstrated within the Terahertz gap of 10 cm -1 to 25 cm -1 .

Influence of Base-Pair Interaction on Vibrational Spectrum of a Poly-dG Molecule Bonded to Si Substrates

“…Second, there are natural factors (e.g., 1%-5% absorption-signature variations) that limit one's ability to accurately acquire the spectral information that is available from the target bio-system. Specifically, current research efforts are forced to extract spectral information by averaging over molecules in large aperture samples and this leads to experimental results that are strongly related to the number of DNA molecules in a sample [12], the thickness of the samples [13], and the resulting conformations of DNA molecules when bound on the surfaces of differing substrates [14]. More importantly, the statistical effects associated with interacting molecules tend to obscure all sequence information of the individual DNA/RNA targets.…”

Dynamically tunable Fano resonance with high Q factor based on asymmetric Dirac semimetal split-ring structure

“…The results are shown in figures 9(a) and (b), as the refractive index of the analyte increases, both the frequencies of the Fano resonance and the quadrupole resonance show red shift. The following refractive indexes represent important technical indicators for the THz sensing technology; Chemicals-PTFE (n=1.43), Hexogen (RDX (n=1.66)), and TNT (n=1.76); biological materials-air-dried Herring DNA (n≈1.65) and Ovalbumin (n≈1.15) [34].…”

Submillimeter-wave Resonators for Investigation of the Dynamical Properties of Biological Molecules

“…hybridized vs. denatured DNA). Work has been done to transform transmission and reflection measurements into a refractive index and absorption coefficient, but the measurements are heavily subject to an intricate process of preparing the samples [1]. It is the absolute values of these measurements that provide values of the complex dielectric constant and therefore the precision is limited by the sample preparation.…”