Interaction of a homologous series of n-alkyl trimethyl ammonium bromides with egg white lysozyme -: Microcalorimetric and spectroscopic study

The interaction of a series of n-alkyl trimethyl ammonium bromides (C-12, C-14 and C-16) with egg white lysozyme have been studied using fluorescence and UV-Vis spectroscopies and isothermal titration calorimetry (ITC). The trend of variation of molar absorptivity at 281 nm, quantum yields (lambda(ex)=281 nm) and heat of interaction with respect to surfactant concentration, were measured. The spectrophotometric results show that the hydrophobic interactions have a major role in denaturation mechanism and it would be increased with increasing in hydrocarbon tail length of surfactant. The ITC results indicated the two-step mechanism for unfolding of lysozyme due to its interaction with surfactants.