Use BLOTTO whenever procedures call for immunoanalytical grade non-fat dry milk. Alternative blocking agents such as BLOTTO A (solution of TBS, 5% non-fat dry milk and 0.05% Tween-20) and BLOTTO B (solution of TBS, 1% non-fat dry milk, 1% BSA and 0.05% Tween-20) are also available. BLOTTO A is a convenient general purpose blocking agent. BLOTTO B is recommended for blocking when phospho-specific antibodies are used. BLOTTO A and BLOTTO B provide Tween-20 in a separate vial in liquid form. Users should consider the addition of protease inhibitors and phosphatase inhibitors when required. Typically 50 mM NaF can be added to BLOTTO solutions to inhibit phosphatase activity.