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Science 6 October 2006:
Vol. 314. no. 5796, p. 13
DOI: 10.1126/science.314.5796.13d
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Mass spectrometry is a rapid method for proteomic analysis and for identifying posttranslational modifications. Identification is less ambiguous for "top-down" approaches, where the entire protein is introduced into the gas phase (as opposed to bottom-up approaches that analyze proteolytic fragments). However, fragmentation of the protein becomes more difficult for larger proteins, and top-down approaches are usually limited to proteins with masses below 50 kilodaltons (kD). Han et al. (p. 109; see the Perspective by Chait) extend this approach to proteins with masses in excess of 200 kD by adding small molecules to the electrospray solution that inhibits folding and by activating the ions through heating and collisions induced by voltage acceleration. This process creates hundreds of interresidue cleavages at the C- and N-terminal ends of the chain that allow for identification of larger proteins and provides sufficient mass resolution to assign features such as disulfide linkages.




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