2.5.1.21 | -80°C, 25 mM sodium phosphate (pH 7.4, containing 20 mM NaCl, 2 mM dithiothreitol, 1 mM EDTA, 40% glycerol, 10% methanol, 1 mM phenylmethylsulfonyl fluoride, 0.01 mM leupeptin, 0.001 mM pepstatin), extended periods of time, no loss of activity |