**1.2 History of serum peptidomics platform**

Such are three major technical approaches for proteomics study as two-dimensional gel electrophoresis (2-DE), mass spectrometry (MS) and bioinformatics. Similar to the proteomics technology, serum peptidomics technology also involves in technical advancement and upgrade in sample preparation, detection and result analysis, which jointly constitute a platform in serum peptidomics research. Most of studies rely on matrixassisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). The working principle of MALDI-TOF-MS is: the pulse laser is utilized to force the matrix to absorb energy from laser so that the solid-phase polypeptide samples are ionized; the ionized peptides are put into the TOF mass analyzer and separated due to difference in the mass-to-charge ratio (m/z); the peptide mass fingerprint (PMF), peptide sequence tag (PST) or the amino acid sequences can be obtained through measuring peptide ions; qualitative identification or quantitative analysis of peptides can be accomplished through searching in the proteome database with corresponding software. On this basis, three serum peptidomics research platforms have been developed successfully.
