Decoupling of Protein and Water Dynamics at 200 K

Core Concepts

The author explores the decoupling of anharmonicity onset between protein and water dynamics around 200 K, revealing intrinsic transitions in both components.

Abstract

The content discusses the decoupling of anharmonicity onset between protein and hydration water dynamics at approximately 200 K. Contrary to previous beliefs, the study reveals that the transition in protein is independent of hydration water dynamics. Elastic neutron scattering experiments on various proteins show that the onset temperature for protein anharmonicity varies with structure and hydration level but remains consistent across different instrumental resolutions. In contrast, the onset temperature for hydration water is solely determined by instrumental resolution, indicating a resolution effect rather than a physical transition. The findings suggest that the dynamical transition in proteins is intrinsic and related to freezing structural relaxation beyond equilibrium time, akin to glass transitions in polymers. Differential scanning calorimetry measurements support this by showing step-like changes in heat flow corresponding to protein transitions. The study sheds light on the complex interplay between protein and hydration water dynamics at cryogenic temperatures.

Stats

Neutrons are highly sensitive to hydrogen atoms as their incoherent scattering cross section is an order of magnitude higher than other elements.
Three neutron backscattering spectrometers were chosen with varying resolutions from 1 μeV to 100 μeV.
Four globular proteins were studied: myoglobin (MYO), cytochrome P450 (CYP), lysozyme (LYS), and green fluorescent protein (GFP).
Ton values for different proteins varied: LYS (213 K), MYO (198 K), CYP (228 K).
TDSC values approximated Ton values probed by neutrons.
Relaxation time τ of hydration water varied continuously with temperature, crossing instrument resolution at Ton.

Quotes

"The dynamical transition in proteins is an intrinsic property dependent on structure and hydration levels."
"The onset temperature for hydration water dynamics is solely determined by instrumental resolution."
"Protein transitions resemble glass transitions in polymers involving freezing of structural relaxation."

Key Insights Distilled From

Decoupling of the Onset of Anharmonicity between a Protein and Its Surface Water around 200 K

by Zheng,L., Li... at www.biorxiv.org 10-20-2023

https://www.biorxiv.org/content/10.1101/2023.10.18.562890v4

Deeper Inquiries

How does the decoupling of protein-water dynamics impact our understanding of biomolecular interactions

The decoupling of protein-water dynamics revealed in this study challenges the prevailing notion that the dynamical transition in proteins is slaved to the motion of surrounding hydration water. This finding suggests that the onset of anharmonicity in proteins and water around 200 K are independent phenomena, with different origins and characteristics. By demonstrating that the protein's dynamical transition is intrinsic and related to freezing structural relaxation beyond equilibrium time, while the water's transition is merely a resolution effect, our understanding of biomolecular interactions undergoes a significant shift.
This decoupling implies that protein functionality may not be solely dependent on hydration dynamics as previously thought. Instead, it highlights the complexity of biomolecular systems and emphasizes the need to consider multiple factors influencing protein behavior. Understanding these independent transitions can lead to more nuanced insights into how proteins function and interact with their environment, paving the way for targeted research on specific aspects of biomolecular activity.

Could there be alternative explanations for the observed intrinsic transitions in proteins beyond freezing structural relaxation

While this study attributes intrinsic transitions in proteins to freezing structural relaxation beyond equilibrium time, there could be alternative explanations worth exploring. One possibility is that these transitions are linked to conformational changes within proteins rather than solely being a result of frozen structural dynamics. Proteins exhibit various functional states based on their conformational flexibility, suggesting that dynamic transitions could arise from shifts between these states rather than freezing motions.
Additionally, other factors such as solvent effects or intermolecular interactions within protein structures might contribute to observed intrinsic transitions. Investigating these alternative explanations through further experimentation or computational modeling could provide deeper insights into the mechanisms underlying protein dynamics at cryogenic temperatures.

How might insights from this study influence advancements in cryogenic temperature research

Insights from this study have significant implications for advancements in cryogenic temperature research by shedding light on fundamental processes governing biomolecular interactions at low temperatures. Understanding how proteins undergo intrinsic dynamical transitions independent of hydration dynamics opens up new avenues for studying complex biological systems under extreme conditions.
These findings can inform future studies focusing on cryopreservation techniques for biological samples or enhancing stability during cold storage processes. By elucidating the role of freezing structural relaxation in protein functionality at cryogenic temperatures, researchers can develop strategies to optimize preservation methods or design novel materials tailored for applications requiring stability at low temperatures.
Moreover, this research paves the way for investigating how different environmental conditions impact biomolecular behavior at subzero temperatures, offering valuable insights into biophysical processes relevant to fields such as biophysics, biochemistry, and pharmaceuticals where cryogenic conditions play a crucial role in preserving biological materials or studying molecular interactions under extreme environments.