Effect of sodium dodecyl sulfate on the heat denaturation and aggregation of arachin at pH 3.6

Abstract

The effect of an anionic detergent, sodium dodecyl sulfate, on the heat‐induced denaturation and protein‐protein interactions of arachin at pH 3.6 was studied by melting temperature, turbidity, electrophoresis and fluorescence spectral measurements. Sodium dodecyl sulfate induced aggregation in arachin at room temperature, in the concentration range 1 times 10‐5 to 1 times 10‐2 M, as shown by turbidity, electrophoresis and fluorescence spectral measurements. However, higher detergent concentrations (> 1 times 10‐2 M SDS) decreased the aggregation. Electrophoretic experiments at pH 3.6 showed that sodium dodecyl sulfate at a concentration of 5 times 10‐2 M changes the protein charge from positive to negative. Fluroescence spectral measurements suggested that the detergent at 5 times 10‐2 M level unfolds arachin. Heating and cooling arachin at pH 3.6 in the presence of sodium dodecyl sulfate increased the protein‐protein interactions as compared to those at room temperature, in the detergent concentration range 1 times 10‐5 to 1 times 10‐2 M; at higher detergent concentrations there was a sharp decrease. The observed effects of sodium dodecyl sulfate on the structure and conformation and heat‐induced protein‐protein interactions of arachin at the experimental pH may arise out of the detergent binding to the protein involving both ionic and hydrophobic interactions.