Project description:Advances in software and high resolution, high mass accuracy mass spectrometers have expanded their functionality beyond traditional data dependent acquisition (DDA) methods. Using a single platform, an orthogonal quadrupole time-of flight (QqTOF) mass spectrometer, the TripleTOF 5600, we have investigated the feasibility of implementing large-scale targeted quantitative assays, derived from discovery type data sets, using scheduled, high resolution multiple reaction monitoring (sMRM-HR) mass spectrometry. We assessed the selectivity and reproducibility of MRM-HR, also referred to as parallel reaction monitoring (PRM), measuring standard peptide concentration curves as well as system suitability assays. We specifically compared the robustness and accuracy of MRM-HR assays to traditional SRM workflows on triple quadrupole instruments. To determine the utility of sMRM-HR for large-scale targeted quantitative assays, we retention time scheduled over 500 peptides in a single LC-MS acquisition. High resolution and high mass accuracy of the full scan MS/MS spectra resulted in sufficient selectivity to monitor numerous MS/MS fragment ions per analyte precursor and provided flexibility for post-acquisition assay refinement and optimization. To demonstrate its applicability to biological samples, whole cell lysates from several E. coli wild-type and mutant strains were quantitatively assayed by sMRM-HR to confirm a previously generated candidate list of differentially expressed proteins. The ease of developing and implementing sMRM-HR assays derived directly from DDA discovery workflows on the same high resolution instrument platform facilitates downstream validation studies targeting many peptides for MS/MS level quantitation. This work provides a robust MRM-HR workflow for rapidly moving from discovery analysis to large-scale, multiplexed, targeted quantitation.
Project description:Acetaminophen (N-acetyl-p-aminophenol; APAP) is a mild analgesic and antipyretic used commonly worldwide. Although APAP is considered a safe and effective over-the-counter medication, it is also the leading cause of drug-induced acute liver failure. Its hepatotoxicity has been linked to the covalent binding of its reactive metabolite, N-acetyl p-benzoquinone imine (NAPQI), to proteins. The aim of this in vivo study was to identify APAP-protein targets in both rat and mouse liver, and to compare the results from both species, using bottom-up proteomics and targeted multiple reaction monitoring (MRM) experiments. Livers from rats and mice, treated with APAP, were homogenized and digested by trypsin. Digests were then fractionated by mixed-mode solid-phase extraction prior to liquid chromatography-tandem mass spectrometry (LC-MS/MS) using scheduled multiple reaction monitoring (MRM) acquisition. The targeted assays were optimized based on high-resolution MS/MS data from information-dependent acquisition (IDA) using control liver homogenates treated with a custom alkylating reagent forming a positional isomer of the APAP modification on all cysteine residues, in order to build an in-house modified peptide database for targeted analysis. A list of putative in vivo targets of APAP were screened from previous in vitro studies, data-dependent high-resolution MS/MS analyses of liver digests, as well as selected proteins from the target protein database (TPDB), an online resource which references previous reports of proteins found to be modified by acetaminophen. Multiple protein targets of APAP in each species were found, while confirming modification sites.
Project description:Establishment and maintenance of pregnancy is dependent on progesterone synthesized by the corpus luteum (CL). The CL is known for the prominent presence of intracellular lipid droplets (LDs). However relatively little is known about the composition and function of these luteal LDs. Our objective was to identify the lipid composition of LDs from fully functional bovine CLs. Luteal LDs were isolated by flotation through a discontinuous sucrose gradient, lipids were then extracted using a standard Bligh and Dyer protocol, dried, and sent to Avanti Polar Lipids for lipidomics analysis. The samples were provided for lipidomic profiling of free sterols, cholesteryl esters, triglycerides, diacylglycerols, phospholipids, and sphingolipids. Molecular species were resolved by reversed-phase liquid chromatography in the presence of class and sub-class specific internal standard compounds added to each sample. The compounds were detected by tandem mass spectrometry (MS/MS) with scheduled multiple reaction monitoring (MRM) for mass-specific fragment ions according to the lipid class and molecular weight of the compound. Quantification of cholesterol, cholesteryl esters, triglycerides, and diglycerides were directly calculated with standards and internal standards from calibration response curves. The remaining lipid species were semi-quantization using the integrated area of each analyte’s MRM peak, divided by the appropriate internal standard peak area, and multiplied by the standard’s known concentration. Lipid concentrations were normalized to the corresponding protein concentration of each sample and as a mol % relative to total lipids or within each lipid class. Isolated luteal LDs were composed primarily of triglyceride (88%, mol% of lipid class to total lipids). Other neutral lipids included diacylglycerol, 2.9%; and cholesteryl esters, 1.5%. Polar lipids were primarily composed of phosphatidylcholine (3.1%), sphingomyelin (1.5%), phosphatidylinositol (0.9%), phosphatidylethanolamine (0.8%) and phosphatidylserine (0.4%). A number of other minor lipids representing less than 0.32% of the total lipid pool were also detected including phosphatidylglycerol, lysophospholipids, ceramides, and glycosylated ceramides. Lipid composition of bovine luteal LDs are distinct from LDs isolated from other tissues and in other species.
Project description:In the present study, we developed a novel targeted proteomics approach for quantification of allele-specific protein expression (ASPE) based on scheduled high resolution multiple reaction monitoring (sMRM-HR) with a heavy stable isotope-labeled quantitative concatamer (QconCAT) internal protein standard. This strategy was applied to the determination of the ASPE of UGT2B15 in human livers using the common UGT2B15 nonsynonymous variant rs1902023 (i.e. Y85D) as the marker to differentiate expressions from the two alleles. This novel ASPE approach has the potential to be widely utilized for the identification of cis-genetic variants capable of regulating gene expression at the protein level.
Project description:Top-Down proteomics pilot experiment of unfractionated Bovine Heart Mitochondria (BHM) using ultra high resolution Q-ToF tandem mass spectrometry (maXis 4G ETD, Bruker Daltonics).
Project description:We profiled the transcriptomes of latency-competent cells derived from the human cancer cell lines H2087 (lung adenocarcinoma) and HCC1954 (breast adenocarcinoma) in mitogen-rich and mitogen-low media (MRM and MLM, respectively). In addition, we analyzed the epigenetic landscape of these cell lines under MLM conditions.
Project description:An important question for the use of the mouse as a model for studying human disease is the degree of functional conservation of genetic control pathways from human to mouse. The human and mouse placenta show structural similarities but there have been no systematic attempt to assess their molecular similarities or differences. We built a comprehensive database of protein and microarray data for the highly vascular exchange region micro-dissected from the human and mouse placenta near-term. Abnormalities in this region are associated with two of the most common and serious complications of human pregnancy, maternal preeclampsia (PE) and fetal intrauterine growth restriction (IUGR), each disorder affecting ~5% of all pregnancies. Over 7,000 orthologs were detected with 70% co-expressed and over 80% of genes known to cause placental phenotypes in mouse were co-expressed. These genes form a tight protein-protein interaction network with novel candidate genes likely to be important in placental structure and/or function. The entire data is available as a web-accessible database to guide the informed development of mouse models to study human disease This experiment is now fully represented in NCBI Peptidome database with accession PSE115; http://www.ncbi.nlm.nih.gov/peptidome/search/index.shtml?acc=PSE115 Microdissection of human villous trees and mouse placental labyrinth. Tissues were split for microarray and protein analysis. For protein analysis samples were first fractionated by differential sucrose gradients into mitochrondria, cytosol, microsomes and nuclei. Mitochrondira and neuclei were each extracted by two different methods for soluble and insoluble material. Each subcellular fraction for each tissue was analysed in quintuplet by 9 step 2 dimensional LC/MSMS. This generated a total of 270 mzXML files for each tissue.