Molecular Structure and Dynamics in Wet Gecko β-Keratin

Area of Science:

• Biophysics
• Materials Science
• Computational Chemistry

Background:

• Gecko keratin's unique properties are partly due to its interaction with water.
• Understanding water sorption is crucial for explaining keratin's mechanical behavior.

Purpose of the Study:

• Investigate water sorption mechanisms in gecko keratin at the molecular level.
• Analyze the influence of relative humidity (RH) on water structure and dynamics within keratin.
• Correlate water dynamics with keratin's mechanical properties.

Main Methods:

• Molecular dynamics simulations were employed to model water-keratin interactions.
• Simulations were conducted across a range of relative humidity (RH) conditions.
• Analysis included hydrogen bonding, water cluster formation, and molecular dynamics.

Main Results:

• Water sorption occurs via hydrogen bonding, with multimolecular sorption and cluster formation at high RH (>80%).
• A percolating water network forms at high RH, correlating with increased water uptake and swelling.
• Water molecules exist in bound and free states, with dynamics transitioning from hopping to translation as RH increases.
• Two distinct regimes of dynamical property dependence on RH were identified, with a drastic acceleration above 80% RH.

Conclusions:

• Water sorption in gecko keratin is strongly dependent on relative humidity, driving structural and dynamic changes.
• The formation of a water network above 80% RH is linked to significant alterations in keratin's mechanical properties.
• A linear relationship exists between relaxation times and water content, providing insights into keratin's hydration dynamics.