Influence of micelles on protein's denaturation.

International journal of biological macromolecules (2019-12-25)
Rachana Srivastava, Md Sayem Alam
ABSTRACT

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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Acetic acid, glacial, ACS reagent, ≥99.7%
Sigma-Aldrich
Albumin from human serum, lyophilized powder, ≥96% (agarose gel electrophoresis)
Sigma-Aldrich
Sodium phosphate dibasic, anhydrous, free-flowing, Redi-Dri, ACS reagent, ≥99%
Sigma-Aldrich
Sodium phosphate monobasic, anhydrous, free-flowing, Redi-Dri, ≥99.0%
Sigma-Aldrich
Pyrene, puriss. p.a., for fluorescence, ≥99.0% (GC)