The objectives of my research are: (1) developing integrative structural mass spectrometry (MS) technique (including native top-down MS, hydrogen deuterium exchange MS, crosslinking MS, surface labelling MS) to analyze structures of large protein complexes and to probe mechanism of drug action. (2) developing middle-down and top-down proteomics mass spectrometry approaches to characterize posttranslational modifications (PTMs) and to probe their roles in biological or disease processes.