SEC of VWF/fVIII complexes. Heparin-Sepharose purified VWF/fVIII underwent Sephacryl S-1000 SEC as described in Experimental procedures. Closed circles, A280; open circles, fVIII activity. Fractions corresponding to the elution volumes shown in the figure, designated Samples A, B, C, D, and E, respectively, were pooled, exchanged into HBS/Ca Buffer, and concentrated by repeated ultrafiltration.