The interaction between ribonuclease A and surfactants.

Area of Science:

• Biochemistry
• Protein Chemistry
• Surfactant-Protein Interactions

Background:

• Ribonuclease A is a well-characterized enzyme.
• Surfactants are known to interact with proteins and can alter their conformation and activity.

Purpose of the Study:

• To investigate the differential effects of anionic (sodium n-dodecyl sulphate) and cationic (n-dodecyltrimethylammonium bromide) surfactants on ribonuclease A conformation and activity.
• To elucidate the binding interactions between these surfactants and ribonuclease A.

Main Methods:

• UV difference spectroscopy to monitor conformational changes.
• Equilibrium dialysis to assess surfactant binding.
• Enzyme activity assays.
• Ultracentrifugation to study interactions.
• Microcalorimetry to determine thermodynamic parameters.

Main Results:

• Sodium n-dodecyl sulphate unfolds ribonuclease A at pH 7.3 and 10.3, indicating significant interaction and binding.
• N-dodecyltrimethylammonium bromide does not affect ribonuclease A conformation, activity, or show detectable binding.
• Microcalorimetry reveals an exothermic binding enthalpy coupled with an endothermic unfolding enthalpy for sodium n-dodecyl sulphate binding.

Conclusions:

• Anionic surfactants like sodium n-dodecyl sulphate can induce unfolding in ribonuclease A through direct binding.
• Cationic surfactants like n-dodecyltrimethylammonium bromide exhibit minimal interaction with ribonuclease A under the tested conditions.
• The thermodynamic profile of sodium n-dodecyl sulphate binding suggests a complex process involving both binding and unfolding.