Insights from Void Volumes and Hydration Dynamics on Protein Spontaneous Rupture via Dynamic Internal Impact Forces: Protein Compressibility Changes Under External Piconewton Compressive Force

Mechanical forces play a critical role in modulating the conformational landscape of protein-like biomolecules. Thermal force fluctuation and molecular interaction force fluctuation, under both ambient and physiological conditions, provide a fundamental background for the fluctuation of force vectors in the energy landscape of biomolecules within living cells. The nonlinear compressibility of proteins, a key biophysical property influenced by internal cavities and hydration dynamics, plays a critical role in determining their structural responses to mechanical stress. In this study, we employed all-atom steered molecular dynamics (SMD) simulations to investigate how the internal void volumes and hydration dynamics of the epidermal growth factor receptor (EGFR) change during compressive force-induced tertiary structural rupture, considering EGFR as a model system. Our SMD simulations revealed that the tertiary structure-ruptured state of EGFR exhibits reduced internal cavity volumes, increased surface hydrophobicity, and a more ordered hydration shell while retaining overall surface hydrophilicity, along with shifts in surface electrostatic potential compared to the native structure. Together, these changes suggest enhanced hydration and reduced structural flexibility, indicating that EGFR adopts a mechanically less compressible conformation upon rupture. The identified void volumes and hydration dynamics can contribute to the internal force time-dependent redistribution and internal dynamic impact force that can result in a much smaller static and external compressive force to rupture a protein from the inside-out. The mechanistic understanding obtained from studying EGFR is likely generally applicable to other proteins and protein complexes for their responses and spontaneous ruptures under the external pN compressive force. It is the dynamic and internal structural and force fluctuations under dynamic stress, stiffness, damping, nonlinearity of group displacements, and group velocity and acceleration that result in stochastic and spontaneous ruptures from the inside-out. These results shed light on the mechanical stability and structural responsiveness of proteins under compressive force, providing valuable insights into the development of biomaterials with tunable mechanical properties.