“…Rheological measurements were made with a cone and plate Rheometrics rheometer (Rheometrics Inc., Piscataway, NJ) in the small amplitude(strain Յ 2%), forced oscillation mode (Sato et al, 1984). Arp2/3 complex in KME buffer (50 mM KCl, 10 mM imidazole, pH 7.0, 1 mM EGTA, and 1 mM MgCl 2 ) was mixed with actin in Buffer G [2 mM Tris-HCl (pH 8.0), 0.2 mM CaCl 2 , 0.2 mM ATP, 0.5 mM DTT, and 1 mM NaN 3 ], polymerized by adding one-tenth volume of 10 ϫ KME and immediately placed between the metal plates of the rheometer to polymerize at 25°C.…”