Light-induced pH changes inside bacteriorhodopsin vesicles as measured by 31 P NMR

Area of Science:

• Biochemistry
• Biophysics
• Spectroscopy

Background:

• Bacteriorhodopsin is a light-driven proton pump.
• Understanding pH gradient formation in vesicles is crucial for bioenergetics research.
• Sodium glucose-6-phosphate is a substrate used in metabolic studies.

Purpose of the Study:

• To measure light-induced pH changes within bacteriorhodopsin vesicles.
• To investigate the homogeneity of pH gradient generation in vesicle preparations.

Main Methods:

• Utilized Phosphorus-31 Nuclear Magnetic Resonance (31P NMR) spectroscopy.
• Employed bacteriorhodopsin-containing vesicles with entrapped sodium glucose-6-phosphate.
• Performed measurements at various external pH values.

Main Results:

• Observed reversible light-induced pH changes inside the vesicles.
• Demonstrated that pH gradient generation varied across vesicle preparations.
• Indicated a lack of homogeneity in the studied vesicle system.

Conclusions:

• 31P NMR is effective for monitoring intravesicular pH dynamics.
• The heterogeneity in pH gradient formation impacts the interpretation of vesicle-based experiments.
• Further refinement of vesicle preparation methods is warranted for consistent results.