RESUMO
We introduce a stable isotope labeling approach for glycopeptides that allows a specific glycosylation site in a protein to be quantitatively evaluated using mass spectrometry. Succinic anhydride is used to specifically label primary amino groups of the peptide portion of the glycopeptides. The heavy form (D4(13)C4) provides an 8 Da mass increment over the light natural form (H4(12)C4), allowing simultaneous analysis and direct comparison of two glycopeptide profiles in a single MS scan. We have optimized a protocol for an in-solution trypsin digestion, a one-pot labeling procedure, and a post-labeling solid-phase extraction to obtain purified and labeled glycopeptides. We provide the first demonstration of this approach by comparing IgG1 Fc glycopeptides from polyclonal IgG samples with respect to their galactosylation and sialylation patterns using MALDI MS and LC-ESI-MS.
Assuntos
Glicopeptídeos/química , Processamento de Proteína Pós-Traducional , Glicosilação , Humanos , Imunoglobulina G/química , Marcação por Isótopo , Proteômica/métodos , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Anidridos Succínicos/químicaRESUMO
A phosphine-mediated olefination of 2-alkynoates with aldehydes forming 1,3-dienes with high E-selectivity and up to 88% yield is described. Reaction conditions are optimized and reactions are demonstrated for various aryl, alkyl, and alkenyl aldehydes and for ethyl 2-alkynoates with different substituents in the δ-position. Proof of concept is shown for the generation of a ß,γ-unsaturated lactone by intramolecular olefination, and furthermore the use of the generated 1,3-dienes in the Diels-Alder reaction has been demonstrated.