Terahertz Time-Domain Spectroscopic (THz-TDS) Insights into Protein Deformation

Abstract

In this study, we utilized terahertz time-domain spectroscopy (THz-TDS) to study the radiation-induced protein deformation. The absorption coefficient spectra obtained from THz-TDS measurements in the frequency range (0.06–2 THz) was fitted using the Lorentzian model. The absorption coefficient fitting data was used to identify the α-helix and β-structure relative contributions in the protein secondary structure of the kidney tissue of rats irradiated with 10-cGy and 2-Gy X-ray separately or in combination. Our data show that 2-Gy X-irradiation leads to an increase in the β-structure contribution associated with a decrease in the α-helix contribution as indicated by the fitting parameters extracted from fitting the absorption coefficient α(ω) spectra with the Lorentzian function. The results point out that there is a strong correlation between the strength of the hydrogen bonds located between or inside the polypeptide chains of the extended β-sheet and α-helix, respectively, and the absolute value of the absorption coefficient α(ω), the refractive index, and the dielectric constant. The lowest refractive index and dielectric constant are recorded in the 2-Gy-irradiated group followed by the 10-cGy–2 Gy-irradiated group while the least effect was recorded in the 10-cGy-irradiated group. These data provide evidence of the adaptive effect of the 10-cGy X-irradiation delivered 24 h prior to the 2-Gy x-irradiation.