Characterization of purified rADAMTS13 and native HNPs. (A) Fifteen percent SDS-polyacrylamide gel electrophoresis demonstrates the purity of rADAMTS13 (2 µg per lane; lane 1) and purified native HNPs (2.0 µg per lane; lane 2) under denaturing but nonreducing conditions. (B) Mass spectrometric analysis demonstrates the relative abundance of HNP1 (m/z, 689.3113) and HNP2 (m/z, 675.3050) in the preparations. No peaks for HNP3 and HNP4 were seen. M, prestained molecular marker.