Mass spectrometry of biomolecules (proteins, oligosaccharides, peptides,...)
The actual mass of a protein, can differ significantly from the calculated value due to a variety of post translational modifications. ESI Q-TOF MS (mostly in combination with LC-purification) enables the determination of the true molecular mass and the isoform distribution even of large biomolecules such as entire proteins.
Protein identification by mass spectrometry (Proteomics, LC-ESI, MALDI)
The standard procedure for the identification of proteins involves LC-ESI Q-TOF and/or MALDI-TOF analysis of (usually) tryptic peptides. A valuable side product of this approach is the site-specific determination of post translational modifications such as glycosylation.
de novo sequencing of proteins by tandem mass spectrometry (LC-ESI)
When the proteins of interest cannot be "identified" by mass spectrometry because no sequence data is available, de novo sequencing by tandem MS can generate partial sequences which often allow the design of degenerated primers for cloning or the BLAST search for homologous proteins in other organisms. Usually, low microgram amounts or less are sufficient for these experiments.
Amino acid analysis
Well established protocols guarante the accurate quantitative analysis of amino acids by HPLC.