Ultrastructural immunonanogold localization of syntaxin-2 in resting and activated human platelets. (A) Resting platelets demonstrate syntaxin-2 staining on the plasma membrane, α-granule membranes, and on membranes of the open canalicular system. Occasional staining is observed on the extracellular surface of the plasma membrane (arrows). (B) SFLLRN-stimulated and (C) PMA-stimulated platelets demonstrate more intense staining generally and increased staining of syntaxin-2 on the extracellular surface (arrows). Bars, 0.5 μm. See “Materials and methods, Immunofluorescence microscopy” for image acquisition information.