Incubation of Endothelial cells with 14C labeled Monocrotaline Pyrrole yields radioactive proteins targeted by MCT. These are separated by two dimensional gel electrophoresis and targeted proteins localized by autoradiography. These labeled proteins are then cut from the gel and their identity determined Mass spectrometry (MALDI-TOF).  Spectral analysis is compared with databases to determine identity.  MCT targets proteins involved with post-translational processing in Golgi and ER.  These include a family of protein disulfide isomerases (PDI)