Practice question

Electrospray ionization revolutionized biological mass spectrometry because it gently converts nonvolatile, thermally labile biomolecules from liquid phase to gas-phase ions without pyrolysis. High voltage applied to capillary produces charged droplets that desolvate, leaving intact proteins, oligonucleotides and glycans ionized. Electron ionization demands vaporization and hard ionization causing extensive fragmentation, unsuitable for large polymers. Ultraviolet absorption and nuclear magnetic resonance are spectroscopic, not ionization methods. Soft nature of ESI preserves covalent structure, post-translational modifications and noncovalent complexes, making it method of choice for liquid chromatography mass spectrometry of proteomes.