Top-down mass spectrometry of integral membrane proteins.
Whitelegge, Julian +1; Halgand, Frederic 2; Souda, Puneet 3; Zabrouskov, Vlad 4
[Review] Expert Review of Proteomics. 3(6):585-596, December 2006.

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: Top-down mass spectrometry focuses on intact proteins, thereby avoiding loss of information accompanying 'shotgun' protocols that reduce the proteome to a collection of peptides. A suite of liquid-chromatography technologies has been developed for purification of intact integral membrane proteins in aqueous/organic solvent mixtures compatible with biological 'soft-ionization' mass spectrometry, preserving covalent structure into the gas phase. Multiply charged protein ions are fragmented in the gas phase, using either collision-activated or electron-capture dissociation, thus yielding complex spectra of sequence-dependent product ions that collectively define the original native covalent state of an intact protein. Top down offers a more detail-orientated approach to post-transcriptional and post-translational diversity allowing an enhanced insight beyond genomic translation, which has now extended into the bilayer proteome.

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