A simple theory for molecular chemotaxis driven by specific binding interactions.

Area of Science:

• Biophysics
• Physical Chemistry
• Molecular Biology

Background:

• Recent experiments suggest enzymes and small molecules exhibit chemotaxis toward their substrates.
• The precise physical forces governing this molecular chemotaxis remain under debate.

Purpose of the Study:

• To develop a thermodynamic theory for molecular chemotaxis.
• To investigate the role of binding free energy in driving chemotaxis.

Main Methods:

• Utilized McMillan-Mayer theory for dilute solutions and Schellman's theory for macromolecular binding.
• Developed a thermodynamic model incorporating chemical binding equilibrium.
• Performed numerical simulations to validate the theoretical predictions.

Main Results:

• The chemical binding equilibrium introduces a coupling term in free energy, reducing the chemical potential of enzymes and substrates.
• This binding contribution generates an effective thermodynamic force promoting chemotaxis.
• Numerical simulations showed this force, though small, aligns with experimental observations.

Conclusions:

• A thermodynamic binding force can drive molecular chemotaxis even without direct interactions.
• The study provides a theoretical framework for understanding chemotaxis driven by binding free energy.
• This work offers insights into the physical mechanisms underlying molecular self-organization and transport.