The inherent complexity associated with therapeutic monoclonal antibodies and other modalities poses a great challenge to their in-depth analytical characterization by LC-MS approaches.Analytical workflow that incorporates various sample preparation methodologies is usually undertaken to overcome the barrier.Indeed,quantitative and qualitative information can be enhanced by simplifying the structures of molecular entities.The removal of heterogeneity sources(e.g.N-glycans) and/or the reduction of the molecular size of the protein under analysis by enzymatic or chemical means makes the samples more amenable for chromatographic and mass spectrometric analysis.Therefore,in-depth structural elucidation and quality control(QC) analysis of biopharmaceutics are usually performed at intact,subunit and peptide levels.In this presentation,workflows that employ LC/MS techniques and combines enzymatic dissection using a set of proteases and glycosidases to rapidly achieve in-depth characterization are described.General sample preparation approaches used to generate peptide,subunit and glycan level analysis are provided,and application examples highlighting the use of proteolysis,IdeS and papain digestion,deglycosylation by PNGase F as well as EndoS2 enzymes are shown to demonstrate how structural information and drug product understanding can be obtained and transferred from AA residue,to peptide,to subunit and to whole protein level.