Studies of aggregation of proteins is essential in various fields such its preparation, storage, delivery. It is well known[1] that condition medium such temperature, pH, salt concentration etc. affect the aggregation. Recently, researchers[2,3] have started exploring the effect of shear on the aggregation behaviour. This is relatively less explored than the other mentioned factors. Here we have explored the effect of shear, combination of shear and stagnant condition and temperature on the aggregation behaviour of BSA.

We have used DV-III Ultra rheometer to control the shear and observed the change in viscosity of mixture at different shear rate (80 rpm to 250 rpm) and at different temperatures (40, 50 and 60⁰C). We also observed the FTIR spectra in the amide-I band region to see the secondary structures of proteins at all conditions of our studies.

We found that the viscosity of mixture at a fixed concentration depends on both temperature and shear rate. The interesting observations are follows (i) At 40⁰C the viscosity of solution is independent on continuous shearing time at shear rate 80 rpm but dependent (increases) on continuous shearing time at shear rate 200 rpm and above. (ii) At 50⁰C the viscosity of solution increases with continuous shearing time at all shears rates of our studies. (iii) At 60⁰C the viscosity of solution increases with continuous shearing time at all shears rates of our studies. But the rate of increase is more pronounced for shear rate 80 rpm. (iv) regular intermediate stoppage of constant shearing at 40⁰C affect the above dependence. (v) At 40 and 50⁰C temperature, initial stagnant condition affect the viscosity of solution   but at 65⁰C it does not affect the viscosity. This observation indicates the relaxation of the aggregated proteins can control its final structure. All these behaviours are explained in terms of the secondary structure of aggregated proteins.