Pellets were vacuum-dried and then resuspended
in lysis buffer [9 mol L-1 urea, 4% (w/v) 3-[(3-
Cholamidopropyl) dimethylammonio] propanesulfonic
acid (CHAPS), 65 mmol L-1 dithiothreitol (DTT), and
0.5% (v/v) carrier ampholytes pH 3.5-10] and sonicated
in ice bath for 20 min.