Determination of the pH difference across a cell membrane using a methylammonium-selective membrane electrode

Area of Science:

• Electrochemistry
• Biophysical Chemistry
• Cell Biology

Background:

• Accurate measurement of transmembrane pH gradients is crucial for understanding cellular processes.
• Existing methods for determining pH differences across membranes can be complex or invasive.

Purpose of the Study:

• To develop a novel methylammonium-selective electrode for quantifying pH differences across cell membranes.
• To validate the electrode's performance using liposomes and bacterial cells.

Main Methods:

• Construction of a methylammonium-selective electrode using a poly(vinyl chloride) membrane matrix with a calix[6]arene-hexaacetic acid hexaethyl ester neutral carrier.
• Characterization of the electrode's response to methylammonium in a buffer solution.
• Application of the electrode to measure methylammonium uptake in liposomes and determine transmembrane pH differences in Escherichia coli cells.

Main Results:

• The developed electrode demonstrated a near-Nernstian response to methylammonium (58 mV/decade) within the 2 x 10(-5)-1 x 10(-2) M range.
• A limit of detection of 5 x 10(-6) M was achieved.
• Quantitative correlation was established between methylammonium uptake and transmembrane pH differences in liposomes.
• The method was successfully applied to determine transmembrane pH differences in Escherichia coli cells.

Conclusions:

• A sensitive and reliable methylammonium-selective electrode was successfully developed for determining pH differences across biological membranes.
• The method provides a valuable tool for in situ monitoring of pH gradients in liposomes and bacterial cells.
• This technique offers a new approach for studying cellular physiology and membrane transport phenomena.