Global study of myoglobin-surfactant interactions

Area of Science:

• Biochemistry
• Physical Chemistry
• Protein Science

Background:

• Surfactants interact with proteins in complex ways dependent on concentration and structure.
• Understanding these interactions is crucial for various biological and industrial processes.

Purpose of the Study:

• To globally analyze the interaction of horse myoglobin with anionic (SDS) and cationic (CTAC) surfactants.
• To characterize the binding and conformational changes across different surfactant concentrations, including below and above the critical micelle concentration (cmc).

Main Methods:

• Equilibrium titration techniques.
• Stopped-flow kinetics.
• Thermal stability analysis.

Main Results:

• Identified five distinct interaction stages below the cmc and one above, with unique features for both SDS and CTAC.
• Observed protein denaturation and biphasic unfolding kinetics during aggregate formation (hemimicelles) on the protein surface.
• Noted significant changes in unfolding kinetics, including inhibition with CTAC and altered amplitudes with SDS.
• Characterized further surfactant adsorption and the formation of quasi-micellar structures, leading to varied unfolding rates above the cmc.

Conclusions:

• Protein-surfactant interactions are more nuanced than classical biphasic models suggest, involving multiple distinct stages.
• Surfactant structure and concentration critically influence protein conformational changes and stability.
• The study highlights the rich conformational plasticity of proteins when interacting with self-assembling molecules.