Collective vibrational modes in biological molecules investigated by terahertz time‐domain spectroscopy

TLDR

The study presents well‑resolved far‑IR absorption spectra of biological molecules obtained by terahertz time‑domain spectroscopy (THz‑TDS). The authors illustrate the method by measuring the spectra of benzoic acid, its monosubstituted derivatives (salicylic acid, 3‑ and 4‑hydroxybenzoic acid), and aspirin in the 18–150 cm⁻¹ range. The spectra display distinct low‑frequency vibrational modes arising from collective intra‑ and intermolecular motion and lattice dynamics, making them highly sensitive to molecular structure, configuration, and environment, and enabling THz‑TDS to serve as a direct fingerprint of a compound’s conformation. © 2002 Wiley Periodicals, Inc.

Abstract

Abstract We present well‐resolved absorption spectra of biological molecules in the far‐IR (FIR) spectral region recorded by terahertz time‐domain spectroscopy (THz‐TDS). As an illustrative example we discuss the absorption spectra of benzoic acid, its monosubstitutes salicylic acid (2‐hydroxy‐benzoic acid), 3‐ and 4‐hydroxybenzoic acid, and aspirin (acetylsalicylic acid) in the spectral region between 18 and 150 cm −1 . The spectra exhibit distinct features originating from low‐frequency vibrational modes caused by intra‐ or intermolecular collective motion and lattice modes. Due to the collective origin of the observed modes the absorption spectra are highly sensitive to the overall structure and configuration of the molecules, as well as their environment. The THz‐TDS procedure can provide a direct fingerprint of the molecular structure or conformational state of a compound. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 310–313, 2002