AFM system successfully imaged proteins. (a) WT- and GOF-ADAMTS13 plasmids were double digested by restriction enzymes HindIII and XhoI, and verified in agarose gel electrophoresis. (b) Purified WT- and GOF-ADAMTS13 were analyzed by SDS-PAGE under reducing conditions on a 7.5% gel and Western blotting with anti-His antibody. (c) AFM images of VWF-A1 (30 kDa), BSA (67 kDa), anti-His tag antibody (150 kDa) and commercial ADAMTS13 (190 kDa). The horizontal scale bar is 200 nm. The vertical scale bar indicates the height. (d) The plot of volumes of these four proteins versus their molecular weights. The data was well fitted into a straight line. The goodness of fit is indicated by R2. According to the linear relationship y = 5.31817*x + 256.175, the volume of purified WT-ADAMTS13 (red square) corresponds to the molecular weight of 213 kDa. Data were presented as mean ± SD.