X-ray photon correlation spectroscopy of hydrated lysozyme at elevated pressures

TL;DR

This study uses X-ray photon correlation spectroscopy to explore how increasing pressure affects the structural dynamics of hydrated lysozyme proteins, revealing a non-monotonic relaxation behavior and pressure-induced structural transitions.

Contribution

It introduces a novel application of XPCS with a diamond anvil cell to investigate pressure effects on protein dynamics, uncovering a crossover in relaxation behavior at high pressures.

Findings

Slowing down of protein dynamics up to 0.2 GPa

Re-acceleration of dynamics at 0.4 GPa

Identification of a structural crossover between 0.2 and 0.4 GPa

Abstract

Pressure provides a powerful parameter to control the protein conformation state, which at sufficiently high values can lead to unfolding. Here, we investigate the effects of increasing pressure up to $0.4$ GPa on hydrated lysozyme proteins, by measuring the nanoscale stress relaxation induced and probed by X-rays. Structural and dynamical information at elevated pressures was obtained using X-ray photon correlation spectroscopy (XPCS) in combination with a diamond anvil cell (DAC). The dynamical analysis revealed a slowing down of the system up to $0.2$ GPa, followed by a re-acceleration at $0.4$ GPa. A similar non-monotonic behavior was observed both in the Porod and Kohlrausch-Williams-Watts (KWW) exponents, consistently indicating a crossover between $0.2$ and $0.4$ GPa. These findings suggest the presence of pressure-induced structural changes that impact protein collective stress-relaxation as the system transitions from a jammed state to an elastically driven regime. These results may be relevant for a deeper understanding of protein stability under compression as well as for practical high-pressure technologies, including food processing and pharmaceutical applications.