title: Top-down mass spectrometry of integral membrane proteins.
abstract: 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.
authors.affiliation: University of California, Pasarow Mass Spectrometry Laboratory, Jane and Terry Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, Los Angeles, CA 90024, USA. jpw@chem.ucla.edu
authors.forename: Julian
authors.initials: J
authors.lastname: Whitelegge
authors.forename: Frederic
authors.initials: F
authors.lastname: Halgand
authors.forename: Puneet
authors.initials: P
authors.lastname: Souda
authors.forename: Vlad
authors.initials: V
authors.lastname: Zabrouskov
mesh_terms: D000818:Animals; D001436:Bacteriorhodopsins / Q000737:chemistry; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D008565:Membrane Proteins / Q000737:chemistry*; D040901:Proteomics
chemical_list: D008565:Membrane Proteins; D001436:Bacteriorhodopsins