Effect of shear on human insulin in zinc suspension

Human insulin in zinc suspension was used as a model protein to test the ef fect of shear on the settling rate of proteins, a possible inference for pr otein denaturation. The rats of settling was determined directly in a spect rophotometer. Sheer effects are important in retaining the activity of prot eins and are present in bubble, foam, and droplet protein fractionation pro cesses. A simple test, such as that conducted here, may even be useful for monitoring changes in protein structure caused by commercial shipping of th e protein. The settling rate for insulin was continuously monitored in the original bottle by spectrophotometric absorbance changes as a function of t ime. A settling curve was determined following each shear experiment, which included shaking the "worked" insulin solution in a vortex mixer for diffe rent lengths of time. It was determined, when comparing long shaking times with short ones, that the initial settling rate was less for the long-term shaking of the insulin samples and greater for the short-term shaking. The secondary effects of light and heat, along with shaking, apparently did not produce differences from shaking alone.