Blood and Plasma Proteomics: Targeted Quantitation and Posttranslational Redox Modifications.

Proteome profiling using mass spectrometry is extensively utilized to understand the physiological characteristics of cells, tissues, fluids, and many other biological matrices. From the earliest days of the proteomics era, exploratory analyses of the blood protein complement have attracted a great deal of interest, owing to the pivotal importance of blood cells and biofluids (serum, plasma) for research and biomedical purposes. Once challenged by the high dynamic range of protein concentrations, low sensitivity of mass spectrometers, and poor annotation of proteomics databases, the techniques in this field have quickly evolved in recent years, particularly in the areas of absolute quantification of proteins and in mapping of posttranslational modifications. Here we describe (a) the design and production of heavy isotope-labeled peptides used as reporter internal standards for absolute protein quantification and (b) a redox proteomics approach to optimize sample preparation and database searching to elucidate oxidative modifications to protein amino acids. The two methods achieve complimentary goals in the field of blood research and pave the way for future translation of next-generation proteomics technologies into clinical practice.