αIIbβ3 integrin with a missing αIIb C490-C545 disulfide bond is predetermined and selectively partitions into focal adhesions on the activated platelet surface. The result for C545 for the total integrin pool is shown as it represents the fraction of the C490-C545 disulfide bond that is unformed (as discussed in Figure 1). (A) Redox state of the αIIb C490-C545 disulfide bond in healthy human donor resting platelets (6 male subjects, 7 female subjects; 21-48 years old), thrombin/collagen–activated platelets (5 male subjects, 4 female subjects; 23-48 years old), αIIbβ3 naturally produced by human megakaryoblastic MEG-01 cells (4 different preparations), and recombinantly expressed in mammalian BHK cells (3 independent experiments). The bars and errors are mean ± standard deviation. (B) Redox state of the αIIb C490-C545 disulfide bond in the total integrin pool or bound to talin in focal adhesions in resting or thrombin-activated donor platelets (2 male subjects, 1 female subject; 29-42 years old). The bars and errors are mean ± standard deviation. *P < .05.