During the centrifugation process, detergents are normally used to lyse the cells, that is, to release the soluble proteins in the cells.
Detergents are used during cell fractionation because their properties allow for manipulation of the hydrophobic hydrophilic interactions which exist among molecules in the cell samples. Generally, detergents are used to lyse cells, solubilize membrane proteins and lipids, prevent non specific binding in purification procedures and to control protein crystallization.