Agarose gel electrophoresis of platelet RT-PCR and cDNA library PCR fragments. Lane M, molecular-weight markers (1-kb ladder; GIBCO-BRL, Life Technologies Ltd, Paisley, UK); lanes 1 through 5 show a single 521-bp product amplified from the following sources. Lane 1, platelet cDNA; lane 2, HEL cell cDNA library; lane 3, K562 cDNA library; lane 4, U937 cDNA library; lane 5, HL60 cDNA library.