Cross-linking mass spectrometry (XL-MS) can reveal protein interactions, binding interfaces, and structural information in a single experiment. Our cutting-edge XL-MS workflows allow characterizing samples of any complexity, ranging from purified protein complexes to whole cells. When applied to cells or cellular compartments, XL-MS works in endogenous settings and does not require protein engineering or cell lysis. XL-MS applications include mapping of interactomes under different physiopathological conditions, identifying binding partners of clinically relevant proteins, and discovering protein interactions that may serve as biomarkers or drug targets. In addition, we offer mass spectrometry services associated with our protein and antibody products, including characterization of their interactors by affinity purification-mass spectrometry.