platelet granules marker protein

[soenke behrends]

Dear netters, 

we do biochemical fractionation of human platelets
to seperate plasma membrane from intracellular 
granules. We would need a good antibody for a protein
that is expressed in platelet granules to characterize
our fractions that we get over a sucrose gradient. 
So far we have found CD63 and a polyclonal and a mono-
clonal antibody is available from Santa Cruz. But there
are as yet no publications with Western blots and we 
do not know whether CD63 expression in human platelets
granules is high enough to be detected by these antibodies. 
I imagine that there should be other proteins in the 
membrane of human platelet granules that are better 
characterized and where antibodies are procurable for 
Western blot. 

Thanks for any tip or hint and thanks for your time and help
Soenke