Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) spectra of degradation products from exendin-4 incubated in rat kidney homogenate for (a) 5 min, (b) 15 min, and (c) 30 min, and in rat liver homogenate for (d) 6 h.

<p>Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) spectra of degradation products from exendin-4 incubated in rat kidney homogenate for (a) 5 min, (b) 15 min, and (c) 30 min, and in rat liver homogenate for (d) 6 h.</p>