Prevention of unwanted proteolysis.

Inescapably, all cells contain proteases, introducing the possibility that disruption of the tissue can bring together a protease and a protein, with the result that the latter suffers hydrolytic damage. To quote Pringle (1,2), "Proteolytic artifacts are pervasive, perplexing, persistent and pernicious but with proper precautions, preventable." Autolysis has long been recognized as a problem during protein purification, but methods for its control are still far from perfect. Moreover, there are many circumstances other than during protein purification in which endo- or exopeptidase attack upon a protein can be at best a frustrating nuisance and at worst an undetected artifact that leads to erroneous conclusions.