The presence or absence of a phosphate can be the difference between an active protein and an inactive one. After you’ve gone to all the trouble to treat your cells, you don’t want the phosphorylation states of their proteins to change before you’ve completed your experiments. Unfortunately, there are a broad range of phosphatases which can foil your attempts to purify phosphorylated proteins. Keep those proteins phosphorylated with the products listed below. These reagents will stop acid, alkaline, serine/threonine, and/or tyrosine phosphatases. Choose an inhibitor targeted to a specific class of phosphatase or a cocktail that will act against them all. Your results will reflect the effects of your treatment, not your purification scheme.