MS Analysis Expert

With the development and maturity of mass spectrometry, the technical advantages of high throughput, high sensitivity and wider dynamic range have been emerged, which provides a reliable research method for proteomics research. In recent years, quantitative proteomics has become one of the research hotspots in omics field. Quantitative proteomics  is an emerging technology used for accurate quantification and identification of proteins expression in biological samples. It can not only identify the proteins expressed in different states, but also accurately quantify their abundance. According to different quantitative purposes, quantitative proteomics can be divided into two categories relative quantitative proteomics and absolute quantitative proteomics. Relative quantitative proteomics, also known as comparative proteomics, is a comparative analysis of protein expression level in cells, tissues or organism in different physiological or pathological conditions. Absolute quantitati

I ’ ve  mentioned in   The Principle of Protein De Novo Sequencing   that the theoretical basis for de novo  sequencing  analysis of proteins is based on the fact that the peptides are regularly broken when fragmentation is induced by MS/MS. According to the position of the peptide fragment, different types of ions can be generated. The ions produced near the N-terminus are a, b, and c types of ions, and the ions generated near the C-terminus are x, y, and z. Take the N terminal  cleavage ion as an example, the a-type ion is the N-terminal ion   generated by the cleavage of the C - C bond in front of the first amino acid  C=O, t he b-type ion is the N-terminal iongenerated by the cleavage of the C-N bond between the first amino acid and the second amino acid ,  and the c-type ion is formed by the cleavage of the N - C bond of the second amino acid (as shown in Figure 1 ).   For N-terminally cleaved ions, the different positions of the fractures produce different types of a, b, and

P rinciple  of PTH- A mino A cid  A nalys ing by Edman S equencing In general, in each sequencing cycle, the PTH-amino acid is first separated by an Edman sequencer, and then determine the PTH-amino acid chromatogram with HPLC , which is followed by comparison with the standard HPLC chromatograms of 20 amino acids . Finally, the corresponding amino acids information  is  obtain ed . The standard HPLC profile of 20 amino acids is shown in the lower panel. HPLC chromatograms of 20 amino acids Protein N-terminal  B locking  C ase Edman degradation  met hod has been widely used as the gold standard for the N   terminal sequence analysis  of existing protein samples. However, in practica l applications, the Edman degradation method also has certain limitations. For example, one of our customers sent a sample  to our library to sequence the N-terminus  of a recombinant protein expressed in Bacillus. However, after we transferred the sample to the PVDF membrane, it was

It is inevitable that beginners may encounter various troubles while doing protein sequencing experiments in the lab.   For U nknown P roteins, H ow to   A ccurately A nalyze P rotein S equences I f the N-terminus of the P rotein is C yclized or   the N-terminus H as U nknown M odifications? For proteins of unknown sequence, especially engineered recombinant proteins, in vitro synthesized proteins, and engineered antibodies, or proteins whose gene sequences have not been studied, their information is often not included in protein databases.To achieve accurate analysis of such protein sequences ,   de novo  protein sequencing   must be used .   D e novo  protein sequencing is an analytical method based on mass spectrometry. Similar to the traditional method of mass spectrometry, t he de novo  sequencing  me thod also   cuts the protein into small polypeptide fragments   first, and  separates the polypeptide fragments through high performance liquid chromatography, then determin