Bruker Daltonik GmbH 1 article published in JoVE Chemistry Analysis of Complex Molecules and Their Reactions on Surfaces by Means of Cluster-Induced Desorption/Ionization Mass Spectrometry Karolin Bomhardt*1, Pascal Schneider*1, André Portz1, Christoph R. Gebhardt2, Michael Dürr1 1Institute of Applied Physics and Center for Materials Research (LaMa), Justus Liebig University Giessen, 2Bruker Daltonik GmbH Neutral SO2 clusters of low kinetic energy (< 0.8 eV/constituent) are used to desorb complex surface molecules such as peptides or lipids for further analysis by means of mass spectrometry using an ion trap mass spectrometer. No special sample preparation is required, and real-time observation of reactions is possible.