VWF multimers from VWF:IbCo ELISA. Serial VWF:IbCo ELISA measurements were performed and the supernatants analyzed for multimer distribution. A control plasma sample is shown in the first lane, followed by the supernatant from the initial ELISA well for the tGPIbα^235Y;239V construct (mutant A sup) and the supernatant after 5 serial incubations with tGPIbα^235Y;239V (mutant E sup) in the absence of ristocetin. The last wells show the supernatant from the initial ELISA well for the wild-type GPIbα construct (WT A sup) and the supernatant after 5 serial incubations with wild-type GPIbα (WT E sup) in the presence of 1 mg/mL ristocetin.