RESONANT TERAHERTZ SPECTROSCOPY OF BACTERIAL THIOREDOXIN IN WATER: SIMULATION AND EXPERIMENT

The experimental and computational study of bacterial thioredoxin, an E. coli protein, at THz frequencies is presented. The absorption spectrum of the entire protein in water was studied numerically in the terahertz range (0.1 – 2 THz). In our work, the initial X-ray molecular structure of thioredoxin was optimized using the molecular dynamical (MD) simulations at room temperature and atmospheric pressure. The effect of a liquid content of a bacterial cell was taken into account explicitly via the simulation of water molecules using the TIP3P water model. Using atomic trajectories from the room-temperature MD simulations, thioredoxin's THz vibrational spectrum and the absorption coefficient were calculated in a quasi harmonic approximation.

For our terahertz transmission measurements, we used solutions of thioredoxin in distilled water obtained from Sigma. The experimental and simulated signatures are correlated and dominant peaks are close in frequencies. The results of this study demonstrate that terahertz spectroscopy is a promising tool in generating spectral data for cellular components of bio agents such as bacterial cells and spores.