Force-Triggered Thermodynamically Uphill Disulfide Reduction through Sulfur Oxidation State Control.

Area of Science:

• Mechanochemistry
• Biophysics
• Protein Science

Background:

• Mechanical forces, alongside thermal energy, current, and light, can activate chemical reactions and alter reaction pathways.
• Single-molecule mechanochemistry has shown that force accelerates bond scission and ring-opening in polymers.
• The S_N2 thiol-disulfide reaction is a model for studying force-dependent nucleophilic substitution, but the reactivity of inorganic sulfur-oxyanions is less understood.

Purpose of the Study:

• To investigate whether mechanical forces can activate the rupture of protein disulfide bonds by inorganic sulfur-oxyanions.
• To explore the force-dependent reactivity of thermodynamically nonfavored reactions involving protein disulfide bonds.

Main Methods:

• Single-molecule force-clamp spectroscopy to measure force-dependent reaction rates.
• Density functional theory (DFT) calculations to model reaction mechanisms.
• Colorimetric assay measurements to quantify reaction outcomes.

Main Results:

• Demonstrated that mechanical force can activate the thermodynamically nonfavored reduction of disulfide bonds by inorganic oxyanions.
• Showed that this force-activated reactivity occurs within the protein core, impacting proteins with physiological mechanical roles.
• Quantified the direct impact of force-unlocked disulfide bond rupture on protein elasticity.

Conclusions:

• Mechanical force can overcome thermodynamic barriers to activate disulfide bond reduction by less reactive inorganic oxyanions.
• This mechanochemical activation has significant implications for understanding protein mechanics and function under force.
• The findings reveal a novel pathway for modulating protein elasticity through force-induced chemical transformations.