Proteome comes from the combination of protein and genome, which means "a complete set of proteins expressed by a genome", that is, all proteins expressed by a cell or even a organism.            

There are many similarities between proteome and transcriptome, and they also have space-time specificity, which will change with the change of environment, tissue or individual.            

Peptidomics analysis is defined as a systematic, comprehensive, qualitative and quantitative study of endogenous peptide segments (up to 20 kDa) in biological samples obtained from specific time and location. Polypeptidomics is a complement to proteomics and a bridge between proteomics and metabonomics. Valuable information can be obtained by studying a large number of soluble peptide segments, including signal molecules such as cytokines, growth factors and peptide hormones, as well as other small protein fragments and peptide segments with undetermined functions or from disease-specific enzymatic digestion.            

Peptidomics can provide a great deal of information about disease status, drug efficacy or toxicity. At present, most of the ultra-high abundance proteins need to be removed before analysis in the sample preparation of peptide histology, which has unparalleled sensitivity in the detection of biomarkers. Because of their diverse functions, endogenous peptides have great potential as drug targets or biomarkers.            

Amino Acid Analysis is a physicochemical method used to determine the composition or content of amino acids in proteins, peptides and other pharmaceutical preparations.            

According to amino acid composition analysis, proteins and peptides can be identified. Amino acid analysis can be used to determine the contents of proteins, peptides and amino acids, and to determine atypical amino acids that may exist in proteins and peptides. Before amino acid analysis, proteins and peptides must be hydrolyzed into a single amino acid. Specific hydrolysis methods are stipulated under various varieties. After hydrolysis of protein and peptide, the amino acid analysis process is the same as that of free amino acid used in other pharmaceutical preparations.            

This method includes four pre-column derivatization methods, namely, phenyl isothiocyanate (PITC), 6-aminoquinoline-N-hydroxysuccinimide carbamate (AQC), o-phenylenedialdehyde (OPA) and 9-fluorene methyl chloroformate (FMOC), 2,4-dinitrofluorobenzene (FDNB) and a post-column derivatization of ninhydrin. Different varieties should select suitable amino acid analysis methods according to the kinds of amino acids contained in them and the content of each amino acid, and do the corresponding methodological verification.            Proteomics essentially refers to studying the characteristics of proteins on a large scale, including protein expression level, post-translational modification, protein-protein interaction and so on, so as to obtain a comprehensive understanding of disease occurrence, cell metabolism, growth and development, and various stress responses at the protein level.            

Proteomics and transcriptome are mature and effective tools for systematically studying biological laws and mechanisms. Since life is a multi-level and multi-functional complex structure, a single omics technology can not reveal the essential law of life activities in a panoramic way. Using proteomics and transcriptome technology to simultaneously detect the overall status of proteins and RNA, and integrating the data of these two histories for analysis, not only can we perspective the law and essence of life activities at two different levels of protein level and transcription level, but also reveal the interaction or correlation between them.            

Protein Quantification can be divided into "total quantitative method" of whole protein and "individual quantitative method" of specific protein according to its purpose. Protein quantification is an indispensable part of biological experiments. In order to verify the success of cell lysis, or to compare or standardize the preservation of multiple samples in parallel experiments, protein quantification of cell lysate is necessary; in order to determine the yield of protein, the purified protein needs to be quantified; in order to label the purified protein with biotin or reporter enzyme, it is also necessary to quantify the protein sample first to ensure the labeling anti-labeling. It should be carried out at an appropriate chemical concentration.            

ITRAQ and TMT are the most widely used differential proteomics techniques in recent years. Both of them use in vitro labeling method to label polypeptides produced by enzymatic hydrolysis of proteins with isotope reagents, and carry out relative quantitative analysis on two or more samples at the whole proteomic level.            

At this point, many people may think that iTRAQ and TMT are two different quantitative technologies. In fact, they are produced by different manufacturers (iTRAQ is AB SCIEX R&D, TMT is Thermo Fisher R&D), and there are some differences in label specifications (iTRAQ is 4 and 8; TMT is 2, 6 and 10), label molecular structure, and other principles are basically the same.