Ultrastructural immunonanogold localization of SNAP-23 in unstimulated human platelets.

(A) Most silver-enhanced gold particles are bound to the plasma membrane (arrows). Some are also observed on membranes of the OCS (open arrows) and on α-granule membranes (arrowheads). Mitochondria (M) are not labeled. (B) Two labeled α-granule membranes are shown at higher magnification. (C) Labeled OCS membrane. (D) Negative control in which the specific primary antibody was replaced by an irrelevant rabbit IgG. Original magnifications: A, × 42 000; B, × 86 000; C, × 70 000; D, × 38 000.