Glycosylation site-specific, analysis

As mentioned earlier, ECD is ideally suited for the analysis of the glycosylated sites in peptides this mild activation process does not require the removal of the carbohydrate chains. In the mass spectrum of intact glycopeptides, the carbohydrate chains remain attached to the sequence-specific ions, thereby providing direct evidence of the glycosylation sites.76... 

A top-down sequence analysis approach has been developed in which sequence information on intact glycoproteins is obtained.121 First, the charge state of the ES-ionized protein is optimized through ion-ion reactions with [M - F and [M - CF3] anions. The CID spectrum of that precursor ion is well endowed with abundant sequence-specific ions, which are used to identify glycosylation sites. The top-down approach has the advantage that additional time- and sample-consuming purification and proteolytic cleavage experiments can be avoided. 

Samyn-Petit B, Wajda Dubos JP, Chirat E, et al. Gomparative analysis of the site-specific N-glycosylation of human lactoferrin produced in maize and tobacco plants. Eur. J. Biochem., 2003 270(15) 3235-3242. 

This information, however, defines only the primary translation product. The post-translational processing events crucial to the biological activity of many proteins can only be determined by direct structural analysis of the protein itself, such as determining the site of proteolytic processing and side-chain modification, including glycosylation and phosphorylation. In a similar fashion, site-specific sequencing also defines amino acid side-chains labeled by active site or other chemical modifications. 

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