Question

What is the purpose of the 10 minute incubation on ice prior to centrifuging when we are doing ammonium sulfate precipitations? What exactly is happening during that 10 minutes?

Answer 1

The latex extract was centrifuged for 15 minutes at 2500 x g, at room temperature. The supernatant obtained was
centrifuged at 5000 x g for 15 minutes at room temperature to obtain clean liquids. Proteins were sequentially
precipitated from 50 mL of this crude extract by stepwise addition of solid ammonium sulphate with stirring at a
certain degree of saturation, followed by incubation on ice for at least 2 h and centrifugation at 10,000 x g at 4°C for
15 minutes. The pellet obtained after each centrifugation was resuspended in max. 10 mL of buffer containing 10
mM phosphate, pH 7. Those steps above were done for 50, 60, 70 and 80% of ammonium sulphate saturation,