tokens: Dynamic light scattering experiments were performed at 24 degrees C , with the protein ( at 2 mg ml - 1 concentration ) dissolved in a buffer consisting of 50 mM Tris - HCl ( pH 7 . 4 ) , 1 mM dithiothreitol , 1 mM EDTA and 200 mM sodium chloride on a Model DynaPro - 801 instrument ( Wyatt , Santa Barbara , CA , USA ) .