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Selected Reaction Monitoring Facility

The Sealy Center for Molecular Medicine (SCMM) Selected Reaction Monitoring Mass Spectrometry (SRM MS) Facility aims to provide UTMB investigators and trainees with state-of-the-art mass spectrometry-based proteomics and metabolomics technologies and services.


The SRM facility provides the following technologies and services:


  • SRM-based targeted proteomics analysis
    Selected reaction monitoring (SRM; plural, MRM, multiple reaction monitoring) is a ‘targeted’ MS approach for the detection and quantification of a predetermined set of proteins in a complex background. In a SRM-MS assay (Figure 1), one or two signature proteotypic peptides, which are unique to the protein of interest, are selected to stoichiometrically represent the protein. SRM-MS analysis of these signature peptides is performed on a triple quadrupole mass spectrometer (QQQ-MS), an instrument with the capability of selectively isolating precursor ions corresponding to the m/z of the signature peptides and to selectively monitor peptide-specific fragment ions (the combination of m/z of precursor ion and its product ions are called precursor-product ion transitions). SRM-MS assay can be thought of as the MS equivalent of the traditional Western blot, in that specific proteins are targeted and quantified. However, SRM assays do not require the generation of high-affinity antibodies, and yet have better specificity of quantification. Specifically, SRM-MS can be used for studying the dynamics of signaling pathways and biomarker verification. 

    The SRM facility's proteomics analysis services include:
  • Development of new SRM assays for proteins
  • Quantification of a set of pre-selected proteins
  • Biomarker verification
  • Quantitative proteomics and phosphoproteomics profiling
    Quantitative proteomics and phosphoproteomics is a technique to determine the relative abundance changes of proteome and phosphoproteome. It usually refers to shotgun proteomics approach in which high-resolution, high mass accuracy mass spectrometer and label-free or stable isotope methods, such as iTRAQ and H218O, are used. The phosphorylated peptides are enriched with immobilized metal affinity chromatography (IMAC) technology. The quantification is achieved by measuring the intensity of MS signal of the precursors of peptides or iTRAQ reporter ion (Figure 2). The SRM facility provides this service using high-resolution, high-mass accuracy Q Exactive Orbitrap mass spectrometer and label-free or stable isotope methods such as iTRAQ and H218O. Please inquire about experiment design and cost.
  • Posttranslational Modification (PTM) profiling
    The SRM facility provides services for identification of other PTMs. Please contact us for more information and other types of posttranslational modification analyses that can be performed.
  • Protein and PTMs Identification
    Protein and PTMs Identification can be performed from SDS-PAGE gel.


  • Quantitative metabolomics profiling
    The SRM facility provides global metabolomics profiling using accurate mass measurements with a high-resolution, high mass accuracy Q Exactive Orbitrap mass spectrometer. The schematic workflow for metabolomics profiling is shown in Figure 3.
  • Targeted metabolites and small molecules analysis
    • Development of new SRM assays for metabolites or other small molecules
    • Quantification of a set of pre-selected metabolites or small molecules. The SRM facility has established SRM assays for amino acids, biological acids and bases, and some lipids
    • Pharmacokinetics analysis









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