Density Gradient Centrifugation and Electron Microscopic Characterization of Subcellular Fractions from Human Blood Platelets

Isolation of platelet granules

Functional analysis of platelet intracellular structures requires isolation and purification of these cellular compartments. With regard to the function of platelets, both, dense (delta) and alpha granules are relevant target structures. However, the availability of sufficient purification protocols for these structures is rather limited. This unit describes two protocols for isolation and purification of platelet granule structures. The Basic Protocol describes a new technique based on immunolabeling with target-specific antibodies followed by magnetic sorting, whereas the Alternate Protocol describes the more traditional procedure based on differential centrifugation and density-based sedimentation. For both methods, the degree of granule purification can be most easily determined by immunoblotting using various antibodies that recognize structure-specific proteins. The immunomagnetic sorting method is especially good for studies requiring highly purified material (e.g., for the identification of specific transporters and receptors).