Plasma species of ¹²⁵I-Xa and α₂M:¹²⁵I-Xa after injection to mice. As described in the text, plasma samples (3 μL) obtained 30 seconds after the injection of ¹²⁵I-Xa or α₂M:¹²⁵I-Xa were subjected to 7.5% SDS-PAGE and autoradiography. Standards containing α₂M:¹²⁵I-Xa, AT-III:¹²⁵I-Xa,¹²⁵I-Xa, and ¹²⁵I-X were also analyzed as indicated. Molecular weight markers in kilodaltons are indicated on the left.