Three binding sets analysis of alpha-lactalbumin by interaction of tetradecyl trimethyl ammonium bromide

The interaction between tetradecyl trimethyl ammonium bromide (TTAB) with b ovine alpha -lactalbumin has been investigated at pH = 9 and at 37 degreesC by isothermal titration calorimetry, equilibrium dialysis and UV-Vis spect rophotometry methods. The binding data from unusual Scatchard plot have bee n analyzed in terms of the Hill equation for three sets of binding sites. T he calorimetric data show that TTAB interacts endothermically with alpha -l actalbumin and causes protein unfolding below 2 mM concentration of TTAB, w hich is confirmed by spectrophotometric data. The unfolding of the protein would be mainly due to occupation of the second set of binding sites.