Protein binding of palmitate measured by transmembrane diffusion through polyethylene

Area of Science:

• Biochemistry
• Physical Chemistry

Background:

• Long-chain fatty acids are crucial in biological systems.
• Accurate measurement of free fatty acid fractions and binding constants is vital for understanding their biological roles.
• Polyethylene membranes offer unique permeability properties for studying these molecules.

Purpose of the Study:

• To develop a method for measuring the free fraction of protonated long-chain fatty acids.
• To estimate the ionization constant (pKa) of long-chain fatty acids.
• To determine the binding constants of fatty acids to proteins like albumin.

Main Methods:

• Utilizing thin polyethylene membranes for selective diffusion of protonated fatty acids.
• Employing tracer palmitate to study binding to bovine albumin and beta-lactoglobulin.
• Measuring unidirectional flux to confirm membrane impermeability to protein and ions.

Main Results:

• Polyethylene membranes effectively separate protonated fatty acids from proteins and ions.
• The binding constant for palmitate on albumin was determined and validated against existing data.
• An estimated pKa of 4.9 for palmitic acid was obtained, aligning with theoretical predictions.

Conclusions:

• Polyethylene membranes provide a simple and reliable method for studying fatty acid-protein interactions.
• The pKa of long-chain fatty acids can be accurately estimated using this membrane-based approach.
• This technique offers an alternative to traditional methods, avoiding potential alterations to protein binding characteristics.