The effects of temperature, shear rate, shear time, and concentration on the rheological properties of 11S globulin in ionic strength 0.5, pH 7.6 phosphate buffer were studied by a cone and plate viscometer at shear rates up to 384 sec-1. The secondary structure changes caused by elevated temperature and shearing were also monitored by Fourier transform infrared spectroscopy (FTIR). The effects of concentration on apparent viscosity were pronounced. A 3-percent solution behaved as a Newtonian solution. The solutions become pseudoplastic when the concentrations were higher than 5 %. The effects of shearing time up-to 30min on apparent viscosity also depended on the concentration. Shear thinning first become nearly time-independent, later was observed in 5 or 10% solution, while 3 % and 20 % solutions behaved as time independent. Increasing temperature at 1.4°C/min with shearing time up to 40min result in the 3, 5, and 10% solutions behaving with shear thinning earlier and with shear thickening later. The reason that elevation temperature and longer shear time caused shear thickening in the solution was a change of secondary structure seen in the FTIR spectrum. The amount of a-helix of 11S globulin increased from 7.8% to 19.6 or 28.1 % as the temperature increased from 25°C to 80 or 90°C, respectively.
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Chen et al. (1990) studied this question.