Accurate mass measurement Proteomics

The results for bacterial whole-cell analysis described here establish the utility of MALDI-FTMS for mass spectral analysis of whole-cell bacteria and (potentially) more complex single-celled organisms. The use of MALDI-measured accurate mass values combined with mass defect plots is rapid, accurate, and simpler in sample preparation then conventional liquid chromatographic methods for bacterial lipid analysis. Intact cell MALDI-FTMS bacterial lipid characterization complements the use of proteomics profiling by mass spectrometry because it relies on accurate mass measurements of chemical species that are not subject to posttranslational modification or proteolytic degradation. 

He, F., Emmett, M.R., Hakansson, K., Hendrickson, C.L., Marshall, A.G., Theoretical and experimental prospects for protein identification based solely on accurate mass measurement. J. Proteome Res. 2004, 3, 61. 

Smith, R.D., Anderson, G.A., Lipton, M.S., Pasa-Tolic, L., Shen, Y., Conrads, T.P., Veenstra, T.D., and Udseth, H.R. 2002. An accurate mass tag strategy for quantitative and high-throughput measurements. Proteomics 2, 513-523. 

Top-down proteomics. This strategy deals with intact protein molecules no proteolytic cleavage is performed [41], It involves the accurate molecular mass measurement of the intact protein nsing high-resolution mass spectrometry within 2 Da, followed by a molecular mass database search. The identity of... 

Orbitrap-based MS systems are predominantly used for bottom-up and middle-down proteomic measurements, (Cannon et al. 2010) where the peptides are fragmented in the linear ion trap and fragments mass analyzed in the orbitrap. In addition, orbitrap-MS systems are used for accurate mass determination of intact proteins (McFarland et al. 2014). These measurements are particularly useful for the detection and differentiation of closely related microorganisms since this methodology allows the detection of a wide range of proteins in the sample, beyond the detection of ribosomal proteins. 

MS instruments measure the mass-to-charge ratio (m/z) values of the smallest of molecules very accurately. In addition, the development of translated genomic databases and specialized software algorithms that rapidly search MS data against theoretical spectra of known or predicted proteins within databases is an important component that greatly facilitated the emergence of mass spectrometry-based proteomics as a key approach for large-scale proteomic analysis.15... 

Mass spectrometry provides a wealth of information for proteomics research, enzymology, and protein chemistry in general. The techniques require only miniscule amounts of sample, so they can be readily applied to the small amounts of protein that can be extracted from a two-dimensional electrophoretic gel. The accurately measured molecular mass of a protein is one of the critical parameters in its identification. Once the mass of a protein is accurately known, mass spectrometry is a convenient and accurate method for detecting changes in mass due to the presence of bound cofactors, bound metal ions, covalent modifications, and so on. 

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