Multiple Reaction Monitoring Tandem Mass Research Articles

Profiling of Oxylipins as Markers of Oxidative Stress in Biological Samples.

Oxylipins are oxidized metabolites of polyunsaturated fatty acids (PUFAs). They represent a class of risk markers and/or therapeutic targets for diseases associated with inflammation, including cardiovascular disease and brain disorders. Because the biological activities of free PUFAs and oxylipins depend on their chemical structures and concentrations, monitoring PUFAs and oxylipin levels in biological systems is critical for understanding their roles in health and disease. Traditionally, accurate quantification of free PUFAs and oxylipins in biological samples was performed separately, as PUFAs are often 1000-fold more abundant than the derived oxidized fatty acids (oxylipins). This article describes a liquid chromatography multiple reaction monitoring tandem mass spectrometry method for the quantitative analysis of five free PUFAs and 88 oxylipins in various biological fluids, including plasma, platelet supernatants, and tissues. The same approach can also be used in conjunction with an alkaline hydrolysis step to quantify total oxylipins in fish oils. We observed that in some samples, linoleic acid levels in plasma and eicosapentaenoic acid and arachidonic acid levels in brain tissue were above the upper limit of quantification. To address this issue, we developed a data analysis method to obtain PUFA and oxylipin concentrations in these samples without additional sample preparation, thus significantly saving time and labor. © 2024 Wiley Periodicals LLC. Basic Protocol: Quantification of polyunsaturated fatty acids (PUFAs) and oxylipins using liquid chromatography multiple reaction monitoring tandem mass spectrometry Support Protocol 1: Preparation of internal standard mixed working solution Support Protocol 2: Preparation of standard mixed stock solution Support Protocol 3: Preparation of standard mixed working solution Alternate Protocol 1: Extraction and quantitation of free PUFAs and oxylipins from mouse brain tissue Alternate Protocol 2: Extraction and quantitation of total PUFAs and oxylipins from fish oil.

A High-Throughput Absolute Quantification of Protein-Bound Tryptophan from Model and Crop Seeds.

This protocol describes a high-throughput absolute quantification protocol for the aromatic essential amino acid, tryptophan (Trp). This procedure consists of a milligram-scale alkaline hydrolysis followed by an absolute quantification step using a multiple reaction monitoring tandem mass spectrometric (LC-MS/MS) detection method. The approach facilitates the analysis of a few hundred samples per week by using a 96-well plate extraction setup. Importantly, the method uses only ∼4 mg of tissue per sample and uses the common alkaline hydrolysis protocol, followed by water extraction that includes L-Trp-d5 as an internal standard to enable the quantification of the absolute level of the bound Trp with high precision, accuracy, and reproducibility. The protocol described herein has been optimized for seed samples for Arabidopsis thaliana, Glycine max, and Zea mays but could be applied to other plant tissues. © 2023 Wiley Periodicals LLC. Basic Protocol: Analysis of protein-bound tryptophan from seeds.

A High-Throughput Absolute Quantification of Protein-Bound Sulfur Amino Acids from Model and Crop Plant Seeds.

In this procedure, we describe a high-throughput absolute quantification protocol for the protein-bound sulfur amino acids, cysteine (Cys) and methionine (Met), from plant seeds. This procedure consists of performic acid oxidation that transforms bound Cys into cysteic acid (CysA) and bound Met into methionine sulfone (MetS) followed by acid hydrolysis. The absolute quantification step is performed by multiple reaction monitoring tandem mass spectrometry (LC-MS/MS). The approach facilitates the analysis of a few hundred samples per week by using a 96-well plate extraction setup. Importantly, the method uses only ∼4 mg of tissue per sample and uses the common acid hydrolysis protocol, followed by water extraction that includes DL-Ser-d3 and L-Met-d3 as internal standards to enable the quantification of the absolute levels of the protein-bound Cys and Met with high precision, accuracy, and reproducibility. The protocol described herein has been optimized for seed samples from Arabidopsis thaliana, Glycine max, and Zea mays but could be applied to other plant tissues. © 2023 Wiley Periodicals LLC. Basic Protocol: Analysis of protein-bound cysteine and methionine from seeds.

CFTR protein quantification as a cystic fibrosis diagnostic biomarker in dried blood spots using multiple reaction monitoring tandem mass spectrometry

The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel found on the apical surface of epithelial cells in the airway and gastrointestinal tract. A mutation in the CFTR protein is responsible for developing cystic fibrosis (CF) disease. Therefore, circulating CFTR protein could be a promising biomarker of CF disease.Multiple methodological challenges are associated with CF's available diagnostic and screening methods, such as low specificity and potential false discovery rate, mainly for ethnic groups whose CFTR mutations are not covered in the mutation panels.Herein, we have developed an absolute quantification (AQUA) method based on two CFTR signature peptides (SPs). A liquid chromatography-tandem spectrometry (LC-MS/MS) method in multiple reaction monitoring (MRM) mode (MRM transitions 1168.90 > 85.929 and 707.19 > 85.93 of SP1 and SP2, respectively) enabled the accurate quantification of CFTR protein in a dried blood spot (DBS). The method was validated successfully based on international guidelines in terms of signal linearity, precision (within-run CV 3.37–8.54%; between-run CV 5.15–11.06% for the selected SPs), and accuracy (within-run 93.4–105.59%; between-run 97.45–103.28% for the selected SPs). The level of soluble CFTR protein was evaluated as a potential biomarker for CF using patients (n = 39) and healthy controls (n = 30), were found to be in CF patients lower than controls. For instant, the level of signature peptide 1 (SP1) was 2.09 ± 0.55 nM, 68.77 ± 1.40 nM in CF patients compared to Ctrl, respectively; p < 0.0001.This study is the first to report CFTR levels in DBS using signature peptides by LC-MS/MS as a diagnostic marker for CF. The receiver operating characteristic (ROC) for CFTR SP1 and SP2 showed a significant area under the curves (AUC) 0.7714 (99% CI, p < 0.0001), and 0.8234 (99% CI, p < 0.0001), respectively. The presented MRM method provides a highly specific and sensitive approach to CFTR quantification in a DBS and could be applied in CF screening.

Screening and analysis of potentially active components in Shenxiong glucose injection using UHPLC coupled with photodiode array detection and MS/MS.

Shenxiong glucose injection, a pharmaceutical preparation containing a water extract of the roots of Salvia miltiorrhizae and ligustrazine hydrochloride, is widely used in clinical to treat cardiovascular diseases in China. The chemical components of the water extract have been reported and the cardioprotective effects of the injection have been evaluated. However, the chemical constituents of the injection and their correlations with its pharmacological effects have not been established. In this study, 13 chemical constituents of the injection have been identified or characterized by ultra-high performance liquid chromatography with diode array detection and electrospray ionization quadrupole time-of-flight tandem mass spectrometry. Besides, the potentially active compounds of this preparation that directly act on cardiac cells have been screened by cell extraction and ultra high performance liquid chromatography targeted multiple reaction monitoring. As a result, eight potentially active compounds, danshensu (1), ligustrazine hydrochloride (4), salvianolic acid I/H (7), lithospermic acid (8), salvianolic acid D (9), rosmarinic acid (10), salvianolic acid B (12), and salvianolic acid C (13), were obtained and structurally characterized from the 11 target compounds used for screening. The liquid chromatography with quadrupole time-of-flight mass spectrometry and liquid chromatography with multiple reaction monitoring tandem mass spectrometry combination method has demonstrated its potency for the screening, detection, and structural identification of bioactive compounds in a complex matrix.

Quantitative determination of free D-Asp, L-Asp and N-methyl-D-aspartate in mouse brain tissues by chiral separation and Multiple Reaction Monitoring tandem mass spectrometry.

Several studies have suggested that free d-Asp has a crucial role in N-methyl d-Asp receptor-mediated neurotransmission playing very important functions in physiological and pathological processes. This paper describes the development of an analytical procedure for the direct and simultaneous determination of free d-Asp, l-Asp and N-methyl d-Asp in specimens of different mouse brain tissues using chiral LC-MS/MS in Multiple Reaction Monitoring scan mode. After comparing three procedures and different buffers and extraction solvents, a simple preparation procedure was selected the analytes of extraction. The method was validated by analyzing l-Asp, d-Asp and N-methyl d-Asp recovery at different spiked concentrations (50, 100 and 200 pg/μl) yielding satisfactory recoveries (75–110%), and good repeatability. Limits of detection (LOD) resulted to be 0.52 pg/μl for d-Asp, 0.46 pg/μl for l-Asp and 0.54 pg/μl for NMDA, respectively. Limits of quantification (LOQ) were 1.57 pg/μl for d-Asp, 1.41 pg/μl for l-Asp and 1.64 pg/μl for NMDA, respectively. Different concentration levels were used for constructing the calibration curves which showed good linearity. The validated method was then successfully applied to the simultaneous detection of d-Asp, l-Asp and NMDA in mouse brain tissues. The concurrent, sensitive, fast, and reproducible measurement of these metabolites in brain tissues will be useful to correlate the amount of free d-Asp with relevant neurological processes, making the LC-MS/MS MRM method well suited, not only for research work but also for clinical analyses.

Quantitative analysis of the major linkage region tetrasaccharides in heparin

Heparin is a polysaccharide based anticoagulant drug composed of a complex mixture of glycosaminoglycan chains and peptidoglycosaminoglycan chains. In an effort to better characterize this important polysaccharide based drug, we examined the peptide components of the minor peptidoglycosaminoglycan chains comprising heparin. Three different the glycan-peptide linkage regions tetrasaccharide fragments were isolated from pharmaceutical heparin using heparin lyase II and characterized the structure of these tetrasaccharides using nuclear magnetic resonance spectroscopy and mass spectrometry. A sensitive and quantitative assay was developed for these linkage regions using multiple reaction-monitoring tandem mass spectrometry. These three different linkage regions were found in heparins coming from porcine intestine and bovine lung. Two of these were also present in the low molecular weight heparin, enoxaparin.

Comprehensive Proteomics Approach in Characterizing and Quantifying Allergenic Proteins from Northern Shrimp: Toward Better Occupational Asthma Prevention

Occupational asthma is a major chronic health dilemma among workers involved in the seafood industry. Several proteins notoriously known to cause asthma have been reported in different seafood. This work involves the application of an allergenomics strategy to study the most potent allergens of northern shrimp. The proteins were extracted from shrimp tissue and profiled by gel electrophoresis. Allergenic proteins were identified based on their reactivity to patient sera and were structurally identified using tandem mass spectrometry. Northern shrimp tropomyosin, arginine kinase, and sarcoplasmic calcium-binding protein were found to be the most significant allergens. Multiple proteolytic enzymes enabled 100% coverage of the sequence of shrimp tropomyosin by tandem mass specrometry. Only partial sequence coverage was obtained, however, for the shrimp allergen arginine kinase. Signature peptides, for both tropomyosin and arginine kinase, were assigned and synthesized for use in developing the multiple reaction monitoring tandem mass spectrometric method. Subsequently, air samples were collected from a shrimp processing plant and two aerosolized proteins quantified using tandem mass specrometry. Allergens were detected in all areas of the plant, reaching levels as high as 375 and 480 ng/m(3) for tropomyosine and arginine kinase, respectively. Tropomyosine is much more abundant than arginine kinase in shrimp tissues, so the high levels of arginine kinase suggest it is more easily aerosolized. The present study shows that mass spectrometric analysis is a sensitive and accurate tool in identifying and quantifying aerosolized allergens.

Quantification of Cry1Ab in genetically modified maize leaves by liquid chromatography multiple reaction monitoring tandem mass spectrometry using 18O stable isotope dilution

Cry1Ab is one of the most common Bacillus thuringiensis (Bt) proteins in genetically modified crops, which exhibits strong resistance against insect pests. In the present study, a sensitive and precise liquid chromatography stable isotope dilution multiple reaction monitoring tandem mass spectrometry (LC-SID-MRM-MS) assay was developed and validated to quantify the amount of Cry1Ab expression in transgenic maize leaves. The measurement of protein was converted to measurement of unique peptides to Cry1Ab protein. Two peptides unique to Cry1Ab were synthesized and labeled in H(2)(18)O to generate (18)O stable isotope peptides as internal standards. The validated method obtained superior specificity and good linearity. And the inter- and intra-day precision and accuracy for all samples were satisfactory. The results demonstrated Cry1Ab protein was 31.7 ± 4.1 μg g(-1) dry weight in Bt-176 transgenic maize leaves. It proved that the novel LC-SID-MRM-MS method was sensitive and selective to quantify Cry1Ab in the crude extract without time-consuming pre-separation or purification procedures.

Application of 13C stable isotope labeling liquid chromatography–multiple reaction monitoring–tandem mass spectrometry method for determining intact absorption of bioactive dipeptides in rats

The liquid chromatography–multiple reaction monitoring–tandem mass spectrometry (LC–MRM–MS/MS) method using 13C stable isotope-labeled dipeptides was newly developed to simultaneously determine the absorption of three antihypertensive peptides (Val-Tyr, Met-Tyr, and Leu-Tyr) into blood of spontaneously hypertensive rats in one run-in assay. After extracting 13C-labeled peptides in blood sample with a C 18 cartridge, the extract was applied to a 13C monoisotopic transition LC–MRM–MS/MS system with d-Val-Tyr included as internal standard. An excellent separation of each dipeptide in LC was achieved at the elution condition of 5–100% methanol in 0.1% formic acid at a flow rate of 0.25 ml/min. The 13C-labeled peptides ionized by electron spray were detected in the positive ion mode within 15 min. The established method showed high reproducibility with less than 10% coefficient of variation as well as high accuracy of more than 85%. After the administration of a mixture containing the three 13C-labeled dipeptides to rats at each dose of 30 mg/kg, we could successfully determine the intact absorption of each 13C-labeled peptide with the maximal absorption amount of 1.1 ng/ml plasma for Val-Tyr by the proposed LC–MRM–MS/MS method.

Site-Preferential Dissociation of Peptides with Active Chemical Modification for Improving Fragment Ion Detection

Multiple reaction monitoring tandem mass spectrometry becomes an important strategy for measuring protein targets in complex biomatrixes. Active chemical modification of peptides like phenylthiocarbamoylation has unique potential for improving the measurement. This potential is enabled by active participation of a modifying group in site-preferential dissociation of modified peptides, which produces certain fragment ions at very high yields and in a sequence-independent manner. In this work, a novel combination of energy-resolved mass spectrometry with substituent effect investigation is used to analyze important factors that control the specificity of the site-preferential dissociation of phenylthiocarbamoyl peptides. On the basis of the linear correlation between collision energy and the Hammett constant as well as computational studies, it is found that the initial enhanced capture of a mobile proton and the subsequent, site-directed intramolecular proton transfer are important to the high yields (approximately 70-90%) for producing two types of fragment ions of phenylthiocarbamoyl peptides: the modified b(1) ion and the complementary y(n-1) ion. This understanding will help the design of new modification reagents. When integrated with the throughput and the signal-enhancing potential of peptide modification, active chemical modification of peptides will significantly advance mass spectrometry-based, targeted proteome analysis.

A novel mass spectrometric assay for the cerebroside sulfate activator protein (saposin B) and arylsulfatase A

A mass spectrometric method is described for monitoring cerebrosides in the presence of excess concentrations of alkali metal salts. This method has been adapted for use in the assay of arylsulfatase A (ASA) and the cerebroside sulfate activator protein (CSAct or saposin B). Detection of the neutral glycosphingolipid cerebroside product was achieved via enhancement of ionization efficiency in the presence of lithium ions. Assay samples were extracted into the chloroform phase as for the existing assays, dried, and diluted in methanol-chloroform-containing lithium chloride. Samples were analyzed by electrospray ionization mass spectrometry with a triple quadrupole mass spectrometer in the multiple reaction monitoring tandem mass spectrometric mode. The assay has been used to demonstrate several previously unknown or ambiguous aspects of the coupled ASA/CSAct reaction, including an absolute in vitro preference for CSAct over the other saposins (A, C, and D) and a preference for the non-hydroxylated species of the sulfatide substrate over the corresponding hydroxylated species. The modified assay for the coupled ASA/CSAct reaction could find applicability in settings in which the assay could not be performed previously because of the need for radiolabeled substrate, which is now not required.