J. Iran. Chem. Soc., Vol. 2, No. 3 September 2005, pp.189~196.

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Thermodynamics of Protein Denaturation by Sodium Dodecyl Sulfate

A.A. Moosavi-Movahedi

Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran

The anionic surfactant sodium n-dodecyl sulfate (SDS) plays a variety of roles with regard to protein conformation,depending on its concentration. SDS at low concentrations mostly induces the compaction of protein (folding). Examples of this include: the molten globule state of acid-unfolded cytochrome c, associated with enhancement of the exothermic enthalpy values of isothermal titration calorimetry and a reversible profile by differential scanning calorimetry; the enzyme activation and compaction of Aspergillus niger catalase, and relationship of calorimetric enthalpy (ΔHcal) to van't Hoff enthalpy (ΔHVH), which proves the existence of intermolecular and intramolecular interaction during enzyme activation by SDS; the production of a new energetic domain for human apotransferrin and folded state for histone H1 by SDS. SDS at moderate concentrations below the critical micelle concentration (cmc) is a potent denaturant for protein in solution. Protein denaturation is a key method in thermodynamics and binding site analysis and can be used to enhance our understanding of the protein structure-function relationship. The interaction between protein and surfactant, such as SDS, at the cmc level is a complicated interaction, thermodynamically, that should bring about enthalpy correction through micellar dissociation and micelle dilution.

Keywords: SDS, Proteins, Enthalpy, Molten globule, Folding, Unfolding

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