Expression of talin1(W359A) causes decelerated αIIbβ3 activation in platelets. The kinetics of αIIbβ3 activation were assessed in real time by flow cytometry. Jon/A-PE and Par4-AP were added simultaneously (arrow) to platelets of the indicated genotype. Jon/A-PE binding (integrin activation) was monitored continuously for 10 minutes. Tln1^W359A/flCre⁺ (Tln1^WA/flCre⁺) platelets were compared with (A) Tln1^wt/wtCre⁺(WT), Tln1^wt/flCre⁺, Tln1^fl/flCre⁺, and Tln1^L325R/flCre⁺ (Tln1^LR/flCre⁺) platelets, and CalDAG-GEFI^−/− (CDGI^−/−) platelets. Traces are representative of 3 independent experiments. (B) Real-time Jon/A-PE binding data are shown normalized for maximum binding within each group. Maximum values for the indicated groups were calculated as the average MFI over the final 10 seconds of the 10-minute assay. (C) Maximum velocity of αIIbβ3 activation, determined as the maximal rate of change of MFI over time (ΔMFI/minute). *P < .05, **P < .01, ***P < .001.