A spectroscopic study of the interaction catalase–cationic surfactant (n-decyltrimethylammonium bromide) in aqueous solutions at different pH and temperatures

Abstract

A surfactant-induced and temperature conformational transition of catalase has been examined by difference spectroscopy for n-decyltrimethylammonium bromide (C₁₀TAB) in different media (pHs 3.2, 6.4 and 10.0). The conformational transition of catalase by C₁₀TAB was followed as a function of denaturant concentration using absorbance measurements at 280 nm and the data were analysed to obtain the Gibbs energy of the transition in water (ΔG⁰_w) and in a hydrophobic environment (ΔG⁰_hc) for saturated protein–surfactant complexes. Changes in absorbance at 280 nm of catalase with temperature were used to determine the parameters characterising the thermodynamics of unfolding, melting temperature (T_m), enthalpy (ΔH_m), entropy (ΔS_m) and heat capacity (ΔC_p). The results suggest that catalase interacts with C₁₀TAB in the media of pHs 6.4 and 10.0 inducing a conformational transition. However, an interaction in acid medium of pH 3.2 was not present. Finally, we compared the interaction of catalase with other cationic surfactants studied by other authors.