Protocol for precipitation of proteins using ammonium sulphate

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Protocols and tips in protein purification or How to purify protein in one day.

Measure the volume of the protein solution, pour it in to a beaker with a magnet bar and place it in an ice bath or at 4°C on a stirrer.
Calculate the required amount of ammonium sulphate, taking 0.6 grams of salt per millilitre of the protein solution and weigh the amount out.
Start stirring the solution and add salt to it in small portions, allow salt to dissolve before adding the next portion.
When all the salt has been added take beaker off stirrer and leave it at 4°C for some time, ideally overnight.
As a rule, you can store protein this way for a very long time. This is true for the majority of proteins, but not for all of them.