Purified ADAMTS13 were correctly folded and functional. (a) AFM images of purified WT-ADAMTS13 (left) and commercial WT-ADAMTS13 (right). The horizontal scale bar is 200 nm. The vertical scale bar indicates the height. The volume (b) and aspect ratio (c) of purified WT-ADAMTS13 (n = 229) and commercial WT-ADAMTS13 (n = 369) at pH 7.5. (d) WT- and GOF-ADAMTS13 specifically bound to VWF-A2. The experiments of bared or functionalized AFM tips contacting to BSA coated surfaces served as controls (Hollow bars). The left two black bars were the adhesion frequencies of bared tips contacting to the WT- or GOF-ADAMTS13 coated surfaces. The right two black bars were the adhesion frequencies of VWF-A2 functionalized AFM tips contacting to the WT- or GOF-ADAMTS13 coated surfaces. Data were presented as mean ± SD.