Proton transport across charged membrane and pH oscillations

Area of Science:

• Biophysics
• Physical Chemistry
• Biochemistry

Background:

• Proton diffusion is crucial for biological processes.
• Understanding ion transport in protein membranes is complex.
• Eyring's multibarrier activation process provides a framework for diffusion studies.

Purpose of the Study:

• To develop a mathematical model for proton diffusion through immobilized protein and enzyme membranes.
• To investigate the influence of electrolytes, substrates, and buffers on proton diffusion.
• To explain observed phenomena like pH oscillations and ion oscillations in membranes.

Main Methods:

• Developed a mathematical model based on Eyring's multibarrier activation process.
• Applied the model to membranes of papain and bovine serum albumin.
• Simulated the effect of salt and buffer on proton diffusion.

Main Results:

• The model rapidly approaches the continuum case in the presence of a buffer.
• The theory accurately simulates experimental observations on salt and buffer effects.
• pH oscillations in enzymatic reactions may stem from dissolved CO2 at high pH.
• Buffer penetration depth oscillates near papain membrane boundaries under specific conditions.
• Small ions and buffers oscillate in highly charged membranes at low ionic strength.

Conclusions:

• The developed model effectively describes proton diffusion in protein membranes.
• The model provides insights into the mechanisms behind pH and ion oscillations.
• Findings have implications for understanding enzyme kinetics and membrane transport phenomena.