Effect of the sugar and polyol additives on the aggregation kinetics of BSA in the presence of N-cetyl-N,N,N-trimethyl ammonium bromide

Abstract

The kinetics of the aggregation of bovine serum albumin (BSA) in the presence of N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB) was studied by monitoring turbidity as a function of time. BSA–CTAB aggregation exhibits an exponential growth, with a pronounced lag phase and a subsequent rapid growth of the aggregates. On the addition of sugars and polyols to BSA–CTAB solution, there is an increase in the lag time and decrease in the rate constant of growth phase indicating that the inhibitors affect both the pre- and post-nucleation processes. The concentration dependence studies of lag time of BSA–CTAB aggregation in the presence of additives points towards the involvement of more number of monomers in the nucleus/start aggregate. The increase in the stability of BSA in the presence of these additives indicates probable role of activation energy in the aggregation. However, the temperature dependence of lag time of BSA–CTAB aggregation shows that the hindrance to molecular collisions, as indicated by decrease in the pre-exponential factor, due to increased viscosity in the presence of additives is the main factor responsible for their inhibitory action. Similarly, higher viscosity of sucrose makes it a much better inhibitor of the heat and surfactant induced aggregation of BSA–CTAB than mannitol.