Peptide mass fingerprinting identification

The peptide mass fingerprinting identification method is a very accurate and quick approach, particularly using MALDI MS as an analytical tool. This method is optimal for the identification of proteins that are annotated in sequence databases. There are, however, a number of limitations to this technology. A number of small proteins are not producing a reasonable number of peptide ions to allow for unambiguous identification only by their masses. Very basic, very small (< 15 kDa) and highly hydrophobic... 

The purpose of the molecular scanner is for the identification of proteins that were separated with a 2-DE gel. Therefore, for each scan point, the lists of peptide masses are submitted to the peptide mass fingerprint identification program Smartldent [51], which searches the protein sequence database SWISS-PROT and returns a list of matching proteins and their score. 

Proteomics ultimately hinges upon protein identification to reveal the meaning behind the masses, spots, or peaks detected by other means. Because fraction collection is a natural component of HPLC separations, intact proteins can be readily collected either for direct analysis or for proteolytic digestion and identification using peptide mass fingerprinting (PMF) in conjunction with matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). 

PAPPIN, D.J.C., HOJRUP, P., BLEASBY, A.J., Rapid identification of proteins by peptide-mass fingerprinting, Curr. Biol., 1993,3, 327-332. 

Protein Identification Strategies 15.2.8.1 Peptide Mass Fingerprinting (PMF)... 

Mass spectrometry provides a more direct and precise technique to study histone modifications. As with the other methods discussed above, mass spectrometry also has several pitfalls that should be taken into account when analyzing histone modifications. First of all histones and especially the core histones H3 and H4 are rich in lysine residues. Consequently, trypsin as an enzyme that is routinely used for the identification of proteins via peptide mass fingerprints cannot be used for regular in gel digestion of histones. Other enzymes that have a different specificity (such as Asp-N or Arg-C) are more frequently used in the analysis of histones [25]. A drawback... 

MULTIIDENT (Proteins Identification Using pi, MW, Amino Acid Composition, Sequence Tag and Peptide Mass Fingerprinting Data)... 

Different authors used RP-HPLC and UV detection to monitor peptide formation during cheese ripening [174-178], providing valuable information about proteolysis. When large hydrophobic peptide need to be separated an lEC represents the best choice [179]. Nevertheless, the identification of these peptides is essential for the complete understanding of the proteolytic process. The peptides eluted from the LC column can be subjected to ESl-MS for molecular weight determination and MS/MS for amino acid sequence determination, which allow rapid peptide identification [172]. HPLC-ESl-MS and MS/MS techniques have been successfully used for peptide mass fingerprint purposes for sequence analysis of purified albumin from Theobroma cacao seeds [180,181]. 

Zabet-Moghaddam, M. et al., Pyridinium-based ionic liquid matrices can improve the identification of proteins by peptide mass-fingerprint analysis with matrix-assisted laser desorption/ionization mass spectrometry. Anal. Bioanal. Chem., 384, 215, 2006. 

Matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (TOF)-mass spectrometry (MS) is now routinely used in many laboratories for the rapid and sensitive identification of proteins by peptide mass fingerprinting (PMF). We describe a simple protocol that can be performed in a standard biochemistry laboratory, whereby proteins separated by one- or two-dimensional gel electrophoresis can be identified at femtomole levels. The procedure involves excision of the spot or band from the gel, washing and de-stain-ing, reduction and alkylation, in-gel trypsin digestion, MALDI-TOF MS of the tryptic peptides, and database searching of the PMF data. Up to 96 protein samples can easily be manually processed at one time by this method. 

Keywords Proteomics MALDI-TOF mass spectrometry SDS-PAGE 2D-gel in-gel digestion peptide mass fingerprint protein identification database searching. 

Arnott, D. P Henzel, W. J. Stults, J. T. 1995. Identification of proteins from two-dimensional electrophoresis gels by peptide mass fingerprinting. In Biochemical and Biotechnological Applications of Electrospray Ionization Mass Spectrometry, Snyder, A. E, ed., Washington, D.C. American Chemical Society, 619,226-243. 

Cottrell JS. Protein identification by peptide mass fingerprinting. Pept Res 1994 7 115-124. 

The QMS platform combines the identification of proteins with their quantitative detection in one procedure. While protein identification can be deduced from peptide mass fingerprinting (PMF) or MS/MS spectra (see section Mass Spectrometry (MS)), protein quantitation is based on analysing either peak areas or signal intensities, or a combination of both. Several computer programs, in most cases reagent specific ones, are available. For each peak, quantitation values are calculated before differentially expressed proteins are identified by the comparison of control and treated samples. 

Figure 4.2 Schematic overview of two protein identification strategies commonly followed in proteomics. Protein samples are separated by either two-dimensional (2-D) or one-dimensional (1 -D) polyacrylamide gel electrophoresis (PAGE). In both strategic tracks, proteins are converted into a set of peptides by enzymatic digestion (e.g., with trypsin) prior to MS analysis. Peptide mass fingerprinting (PMF) by MALDl MS is predomi-...

The methods for each study are divided into the initial protein separation step, a second separation step if applicable, the type of mass analysis, and the software used for peptide identification. ID = one dimensional polyacrylamide gel electrophoresis, 2D = two dimensional polyacrylamide gel electrophoresis, MS = mass spectrometry (peptide mass fingerprinting), MS/MS = tandem mass spectrometry, MALDI-TOF = matrix assisted laser desorption/ionization-time of flight, MS FIT = software from Protein Prospector, http //prospector.ucsf edu/, ESI = electrospray ionization, Q-TOF = quadrupole-time of flight, PPSS2 =Protana s Proteomic Software Suite (ProtanaEngineering, Odense, Denmark), Mascot = Matiix Science, http //www.matrixscience.com/, TOF-TOF = MALDI plus TOF tandem mass spectrometry, RP-HPLC = reverse phase high performance liquid chromatography, Q-IT = quadrupole ion trap, LIT = linear ion trap. Bioworks = Thermo Electron Corporation. 

An important development in high-throughput protein identifieation is the introduction of protein database searching [111]. After separation on ID- or 2D-GE, the proteins were blotted onto a membrane and enzymatically digested after reduction and alkylation. The tryptic peptide mixture is analysed by MALDl-MS to achieve a peptide map or peptide mass fingerprint (PMF). The m/z information of the peptides is used to search the protein database, e.g., the Protein Identification Resource (PIR) database [112-114]. If the mass of just 4-6 tryptic peptides is accurately measured (between 0.1 and 0.01%), a useful database search can be performed. 

---