Practice question

Electrospray ionization is a soft ionization method that transfers large, nonvolatile biomolecules from solution into the gas phase without extensive fragmentation. Proteins in mildly acidic spray acquire protons at multiple basic residues such as lysine, arginine and histidine, generating a characteristic envelope of multiply charged ions [M+nH]n+ . This charge multiplication reduces mass-to-charge ratio into the accessible range of quadrupole or time-of-flight analyzers, allowing accurate deconvolution. Electron ionization and fast atom bombardment mainly produce singly charged species, while MALDI predominantly yields singly charged ions, making ESI uniquely suited for intact protein analysis.