The dialysate was acidified by addition of acetic acid to 10% (vol/vol) and fractionated on a 10 mm6250 mm Vydac C18 reversed phase high performance liquid chromatography (RP-HPLC) column equilibrated in aqueous 0.1% trifluoroacetic acid (TFA). Proteins were eluted using a water-acetonitrile (ACN) gradient containing 0.1% TFA. As discussed in Results, His 6 - 