Top-down characterization of biopharmaceuticals

•Top-down analysis allows the characterization of intact (glyco)proteins.•Top-down analysis ensures coverage of the whole protein sequence in characterization.•Using different instruments, top-down analysis is more accessible to laboratories.

Applied mass spectrometric techniques can fundamentally be divided into those starting from intact proteins (top down) and those starting from peptides derived by chemical or, more commonly, enzymatic digestion (bottom up). This article primarily covers top-down analysis and the information that it can obtain. It therefore covers electrospray ionization and matrix-assisted laser desorption/ionization techniques and top-down fragmentation techniques.