Determination of _IIbβ₃protein expression in murine platelets using immunoblotting. This figure shows the analysis of platelets from 8 different radiation chimeras that were repopulated with liver cells of the indicated Syk genotype. One hundred microliters of PRP was washed with CGS and then solubilized in RIPA buffer. The proteins were separated by SDS-PAGE on a 7.5% gel and transferred to nitrocellulose. The resulting blot was cut in two at approximately the 80-kD point. The upper portion of the blot was immunoblotted with the anti-_IIbβ₃polyclonal #41. The lower portion of the blot was probed with the anti-Syk antiserum #2131. As little as 3% contamination of Syk null platelets with Syk-expressing platelets could be detected by this method.