sentence: The remaining pellet was resuspended in 0.4 ml of SN3 buffer ( 20 mM HEPES-NaOH [ pH 7.5 ] , 200 mM NaCl , 4 mM EDTA , 0.1 % Igepal CA-630 , 0.04 % sodium deoxycholate , 4 mM imidazole , 0.1 mg / ml heparin , 1 mM dithiothreitol ( DTT ) , C ø mplete , 600 U / ml RNasin ) and incubated for 20 min at room temperature with moderate agitation .