MS Analysis Expert

Target S ample D eposition Classic Dry Liquid Droplet Method Step I: Preparation of semi-saturated cyano-4-hydroxycinnamic acid (approximately 5 mg / ml): Dissolve α-cyano-4-hydroxybenzoic acid in 300 μl of 1: 1 acetonitrile / TFA solution (ultrasonication for 10 min) .   C entrifuge  the liquid  for several seconds to obtain t he supernatant.  Add 200 μl of the supernatant to a microcentrifuge tube, and add the same volume (200 μl) of a 1: 1 acetonitrile / TFA solution t o prepare a semi-saturated α-cyano-4-hydroxycinnamic acid. Step II: Take 0.8 μl of digestion solution and 0.8 μl of matrix into a microcentrifuge tube and mix them quickly (avoid crystallization at the tip of the pipette) . Take 0.8 μl of the mixed solution onto the MALDI base . The remaining 0.8 μl of the mixed solution can be dropped on another position of the MALDI base , and the tip of the pipette should not touch the standard. Step III: Let the mixture dry naturally   and ...

SILAC  quantification is suitable for the analysis of living cultured cells and can be used for the identification and quantification of whole protein and membrane proteins. SILAC is mainly quantified by MS1, and iTRAQ / TMT  is mainly quantified by MS2. There is not much difference in quantitative accuracy and protein resolution between the two, but due to the complicated operation, long time span and high cost required by SILAC technology implementation, it has not been widely commercialized. Label-free , as its name implies, is a method for the identification and quantification of protein enzymatic peptides by non-labeled quantification. It is not necessary to use a reagent containing a stable isotope label. It is only necessary to compare the intensity of MS1 signal between the two groups of samples in a specific peptide to obtain a change in the amount of protein expression between the samples, which is usually used for the analysis of mass spectral data produce...

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 fragmen...