Experimental studies provide strong support for these computational findings on THz-induced modulation of protein conformations and ligand-binding dynamics. For example, electron paramagnetic resonance (EPR) measurements have revealed that THz irradiation alters nitric oxide affinity and paramagnetic site mobility in serum albumin, reflecting conformational changes in protein functional groups [
105]. Another study has shown that strong coupling between THz cavity modes and vibrational modes in α-lactose resulted in 68-GHz Rabi splitting, suggesting the feasibility of polaritonic control over protein dynamics (Fig.
6G) [
47]. Functional protein complexes such as the
N-methyl-
d-aspartate receptor (NMDAR)–ligand system have also shown high structural sensitivity to THz perturbations; THz-TDS and quantum simulations revealed that water-mediated low-frequency vibrations play a key role in regulating receptor stability (Fig.
6H) [
106]. Moreover, THz spectroscopy has been applied to detect structural alterations in kidney proteins post-x-ray exposure, demonstrating its sensitivity to changes in hydrogen bonding and secondary structure content [
107]. Beyond static structure, protein folding dynamics have been probed by kinetic THz absorption (KITA) spectroscopy, capturing submicrosecond hydration-coupled transitions during early folding events [
108]. Additionally, environmental factors such as hydrogen-rich water have been shown to modulate enzyme structure and activity via localized hydrophobic interface remodeling, as evidenced by altered THz signatures in pepsin [
109]. This arises because molecular vibrations in the THz regime correspond to the timescale of water reorientation and hydrogen-bond rearrangements, whereby hydrogen molecules induce collective domain motions and structural changes in the enzyme. Similarly, THz radiation has also been found to influence both the activity and conformation of alkaline phosphatase nonthermally [
110]. Importantly, in the context of pathological aggregation, high-frequency THz radiation (e.g., 34.88 THz) has been experimentally shown to delay amyloid-β (Aβ) fibril formation by approximately 80% without causing cytotoxicity in normal cells [
111], and further computational work indicates that 42.55-THz stimulation enhances β-sheet formation in Aβ
42 monomers and dimers while mildly stabilizing protofibrillar assemblies, offering molecular-level insight into the potential of THz radiation as a modulator of neurodegenerative processes [
112]. Interestingly, Schroer et al. [
113] found no large-scale structural changes in proteins under THz irradiation, which suggests that THz effects may need to match frequencies and sufficient strength, and any observable changes could be transient, local, or outside the studied spectral and power range. In other words, radiation intensity plays a role comparable to frequency resonance in determining molecular responses. The intensity determines the amount of energy delivered to the molecules. At low intensities, the energy absorbed by the molecules may be insufficient to disrupt the weak interactions that maintain the stability of the molecular system, and thus will not significantly affect molecular structure or dynamics [
16,
17,
43]. This further highlights the importance of carefully controlling both the frequency and intensity of THz radiation in practical applications.