Interaction between sodium n-undecyl sulfate and insulin

Area of Science:

• Biochemistry
• Physical Chemistry
• Protein-Ligand Interactions

Background:

• Insulin, a vital hormone, interacts with various molecules, influencing its function.
• Anionic surfactants are known to bind to proteins, potentially altering their structure and activity.
• Understanding these interactions is crucial for drug development and biochemical studies.

Purpose of the Study:

• To investigate the binding of sodium n-undecyl sulfate (an anionic surfactant) with bovine insulin.
• To determine the thermodynamic parameters (Gibbs energy and enthalpy) of this interaction.
• To compare the binding behavior with other anionic surfactants and insulin.

Main Methods:

• Equilibrium dialysis at 25°C and pH 3.2 and 10.
• Determination of Gibbs energies of interaction using the Wyman binding potential model.
• Direct measurement of enthalpies of interaction using microcalorimetry.

Main Results:

• Binding data revealed limiting Gibbs energies of interaction around -14 kJ/mol at high ligand saturation.
• Enthalpies of interaction showed increased exothermicity at lower pH (pH 3.2) compared to higher pH (pH 10).
• The observed binding patterns were consistent with interactions of other anionic surfactants with insulin.

Conclusions:

• Sodium n-undecyl sulfate exhibits significant binding to bovine insulin, with thermodynamic parameters influenced by pH.
• The pH-dependent exothermicity suggests conformational changes in insulin upon surfactant binding.
• These findings contribute to the understanding of protein-surfactant interactions and their implications in biological systems.