Mass spectrometry proteolytic cleavage

HSP27 and Tau protein, respectively. 2D immunoblotting combined with mass spectrometry-based identification methods has been widely applied to the characterization of 2D electrophoretic cross-reactive isoforms of the same protein, e.g., resulting from alternative splicing, co- and/or posttranslational modifications and proteolytic cleavages (15-19). 

Figure 1.2 The classical continuous labeling (bottom-up) HX-MS experiment. HX of an equilibrated protein solution is initiated by dilution into a Dfl-containing buffer, and exchange is quenched at various time points. Global HX (protein level) can be measured directly by liquid chromatography (LC) and mass spectrometry (MS) analysis of the intact protein, or local HX (peptide level) can be measured by enzymatic cleavage and subsequent LC-MS analysis of the proteolytic peptides. (See insert for color representation of the figure.)...

Top-down proteomics. This strategy deals with intact protein molecules no proteolytic cleavage is performed [41], It involves the accurate molecular mass measurement of the intact protein nsing high-resolution mass spectrometry within 2 Da, followed by a molecular mass database search. The identity of... 

Arsene CG, Ohlendorf R, Burkitt W, Pritchard C, Henrion A, O Connor G, Bunk DM, Guttler B. Protein quantification by isotope dilution mass spectrometry of proteolytic fragments Cleavage rate and accuracy. Anal Chem 2008 80(11) 4154—4160. 

Although the most practiced method for MS-based protein sequencing combines proteolytic cleavage of the intact protein with subsequent sequencing of the resulting peptide fragments by tandem mass spectrometry, especially with LC-MS/MS and MAL-DI-MS/MS, there is value in the direct measurement and fragmentation of intact proteins. 

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