Joule heating involving ion currents through channel proteins

Area of Science:

• Biophysics
• Cellular Physiology
• Thermodynamics

Background:

• Ion currents through channel proteins are fundamental to cellular function.
• Joule heating, a consequence of electrical resistance, is expected but often overlooked in biological ion transport.
• Understanding heat generation/absorption in biological systems is crucial for cellular energetics.

Purpose of the Study:

• To theoretically investigate Joule heating associated with ion transport proteins.
• To explore the role of Joule heating in biological processes like nerve action potentials and thermogenesis.

Main Methods:

• Derived Joule's law for ion transport proteins using electrochemical potential.
• Simulated temperature distribution around single and ensembles of channel proteins.
• Combined Joule heating theory with the Hodgkin-Huxley model for squid giant axon simulations.
• Applied Joule heating theory to uncoupling protein 1 (UCP1) in brown adipose tissue mitochondria.

Main Results:

• Joule heating and absorption can occur during ion transport through channel proteins.
• Single channel protein simulations showed minimal temperature changes (<10⁻³ K).
• Ensembles of channel proteins can exhibit noticeable temperature changes.
• Simulations accurately reproduced the heat production and absorption during nerve action potentials.
• Calculated Joule heat for UCP1 was comparable to experimental calorimetry data.

Conclusions:

• Joule heating is a significant, yet overlooked, phenomenon in biological ion transport.
• Joule heating contributes to cellular thermogenesis, particularly involving proteins like UCP1.
• This theoretical framework provides insights into cellular energy dynamics and thermal regulation.