Biopolymer-surfactant interaction: 4. Kinetics of binding of cetyltrimethyl ammonium bromide with gelatin, hemoglobin, beta-lactoglobulin and lysozyme.
The binding of CTAB with the proteins, gelatin, hemoglobin, beta-lactoglobulin and lysozyme follow first order kinetics and occurs either in two or three distinct stages. The number of stages depends on the overall configuration of the biopolymers. The denatured protein, gelatin has shown three-stage kinetics under all conditions, whereas the native proteins, hemoglobin, beta-lactoglobulin and lysozyme have exhibited two stage kinetics. Heat treated lysozyme in 8 mol dm-3 urea medium has also shown a two-stage kinetics. On the basis of non interacting binding sites on the proteins and independent sequential binding, the rates of reaction have been observed to increase with temperature and follow the trend k1 >> k2 > k3. The interaction of CTA+ with the proteins is both electrostatic and hydrophobic. Hemoglobin has shown maximum reaction rate whereas, beta-lactoglobulin has shown a minimum. The activation parameters for the kinetic process have exhibited almost non-variant delta G++ and delta H++ < T delta S++. The formation of activation complex in the Eyring model is entropy controlled so also the overall kinetics. An isokinetic entropy-enthalpy compensation phenomenon has been observed for the respective kinetic stages.