Analysis of vWF binding in Chinese hamster ovary (CHO) βIX cells expressing GPIbα, and the GPIbαC⁶⁵ → R and GPIbαTrp⁴⁹⁸ → stop constructs. The binding of vWF in the presence of botrocetin was assessed in CHO βIX cells that were mock-transfected (A), in CHO βIX cells transiently transfected with the wild-type (WT) GPIbα (B), and in CHO βIX cells transfected with the constructs GPIbαCys⁶⁵ → Arg (C) and GPIbαTrp⁴⁹⁸ → stop (D). The x-axis is fluorescence detected with an anti-GPIbα MoAb. The y-axis is fluorescence detected with a polyclonal anti-vWF antibody. A: Neither GPIbα expression or binding of vWF is detected in the mock-transfected cells. B: In cells transfected with the WT GPIbα, GPIbα is readily detectable on the cell surface (9.77% of cells) and binds vWF (2.94% of cells). C: Whereas the GPIbαCys⁶⁵ → Arg construct results in a significant increase in fluorescence when detected with the anti-GPIbα antibody (6.66%) of cells, there is no binding of vWF. D: In the cells transiently transfected with the GPIbαTrp⁴⁹⁸→ stop construct, there is no significant increase in surface fluorescence when detected with the anti-GPIbα antibody, and there is no binding of vWF.