Protocol for protamin sulphate treatment

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

Measure volume of the crude extract.
Calculate an amount of protamin sulphate taking 2mg for each ml of the crude extract, weigh this amount into an eppendorf tube and suspend it in 1 ml of water. It will take a long time for protamin sulphate to dissolve, do not wait and use the suspensia instead.
Place a beaker with the crude extract into an ice bath (crude extract should be at 4°C) place on a stirrer and set to a reasonable speed. The vortex should appear in the middle of the beaker.
Add protamin sulphate suspensia drop by drop. Stir for about 10 minutes.
Spin down precipitate at 19000 rpm (40000g) for 15 minutes.
Recover supernatant fraction, check volume and protein concentration.