FAB and tandem mass spectrometry for endorphin‐ and ACTH peptides of molecular weight to 2000

Four β‐endorphins (β‐endorphin 6–17, 2–17, 1–16, and 1–17) and two adrenocorticotropic hormone (ACTH) peptides (ACTH 1–10 and (1–16)‐NH₂) were studied by using fast atom bombardment coupled with tandem mass spectrometry. The capability to reproduce metastable ion and collisionally activated decomposition spectra on two different commercial sector mass spectrometers in two different laboratories was found to be acceptable (deviations in relative abundance are less than ± 50%). The endorphin peptides fragment metastably or upon collisional activation to give abundant B‐series ions as well as Y‐series ions, whereas Y‐series ions are the principal ionic species produced upon the desorption by fast atom bombardment. The ACTH peptides also fragment to give Y‐series ions, but of relatively low abundance compared to those from the endorphins. For both sets of peptides, high‐energy collisionally activated decomposition and metastable ion decomposition daughter ion spectra are precise, structurally informative—even for peptides up to m/z 2000—and complementary to spectra of daughter ions produced by desorption ionization alone.