Time-domain THz spectroscopy reveals coupled protein-hydration dielectric response in solutions of native and fibrils of human lyso-zyme

TL;DR

This study uses terahertz spectroscopy to investigate how human lysozyme proteins and their hydration shells interact, revealing insights into protein-protein interactions and fibril formation mechanisms.

Contribution

It introduces a dielectric model to analyze THz responses, uncovering hydration-mediated protein interactions and their role in fibril formation.

Findings

Amplitude of dipolar response decreases with concentration initially

Phase shifts occur beyond hydration shell interaction threshold

Hydration layers mediate protein-protein interactions

Abstract

Here we reveal details of the interaction between human lysozyme proteins, both native and fibrils, and their water environment by intense terahertz time domain spectroscopy. With the aid of a rigorous dielectric model, we determine the amplitude and phase of the oscillating dipole induced by the THz field in the volume containing the protein and its hydration water. At low concentrations, the amplitude of this induced dipolar response decreases with increasing concentration. Beyond a certain threshold, marking the onset of the interactions between the extended hydration shells, the amplitude remains fixed but the phase of the induced dipolar response, which is initially in phase with the applied THz field, begins to change. The changes observed in the THz response reveal protein-protein interactions me-diated by extended hydration layers, which may control fibril formation and may have an important role in chemical recognition phenomena.