Influence of micelles on protein's denaturation

• Published in: International journal of biological macromolecules 2020-02, Vol.145, p.252-261
• Main Authors: Srivastava, Rachana, Alam, Md. Sayem
• Format: Article
• Language: English
• Subjects: Critical micelle concentration; Human serum albumin; Hydrophobic interaction; Protein-surfactant complex; Rabbit serum albumin; Sodium dodecyl sulfate
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2019.12.154

To evaluate the role of micelles for protein-surfactant interaction, we have studied the binding modes of serum albumin proteins (human (HSA) and rabbit (RSA)) with anionic-surfactant, sodium dodecyl sulfate (SDS) by using UV–visible, fluorescence, circular dichroism, fluorescence lifetime, atomic force microscopy (AFM) techniques. The study performed with three different pHs (below (4.0), at (4.7), and above (7.0) isoelectric point). Hydrocarbon chain of the surfactant, dominant role of hydrophobic forces and electrostatic interactions helped in polar interaction on protein on binding surfaces. The change above and below the critical micelle concentration (CMC) in fluorescence spectra was due to polarity of the microenvironment. The CD spectra different binding aspects as below CMC and above CMC, explain about folding and unfolding in secondary structure. Surfactant's binding induces fluctuations in the microenvironment of aromatic amino acid's residues of both proteins at different pHs. AFM images clarify the structural changes in both proteins (HSA & RSA). AFM images also indicate some different interesting conformational and structural changes in both proteins below/above the CMC of the surfactant. The molecular docking studies indicate the binding energy −4.8 kcal mol−1 and −4.7 kcal mol−1 for HSA-SDS and RSA-SDS, respectively. Structural changes can be seen above and below the CMC. [Display omitted] •This study demonstrates that proteins (HSA/RSA) interact with SDS at three pHs.•The denaturation ratio begins sequentially with the CMC.•Lifetime measurements also indicate greater denaturation after CMC.•AFM pictures indicate structural changes in above and below CMC.•Micelles play a vital role in controlling the denaturation of proteins.