Reversed-phase Liquid Chromatography Mass Spectrometry Research Articles

Composition mapping of highly substituted cellulose-ether monomers by liquid chromatography–mass spectrometry and probability-based data deconvolution

Cellulose ethers (CEs) are semi-synthetic polymers produced by derivatization of natural cellulose, yielding highly substituted products such as ethyl hydroxyethyl cellulose (EHEC) or methyl ethyl hydroxyethyl cellulose (MEHEC). CEs are commonly applied as pharmaceutical excipients and thickening agents in paints and drymix mortars. CE properties, such as high viscosity in solution, solubility, and bio-stability are of high interest to achieve required product qualities, which may be strongly affected by the substitution pattern obtained after derivatization. The average and molar degree of substitution often cannot explain functional differences observed among CE batches, and more in-depth analysis is needed. In this work, a new method was developed for the comprehensive mapping of the substitution degree and composition of β-glucose monomers of CE samples. To this end, CEs were acid-hydrolyzed and then analyzed by gradient reversed-phase liquid chromatography-mass spectrometry (LC-MS) using an acid-stable LC column and time-of-flight (TOF) mass spectrometer. LC-MS provided monomer resolution based on ethylene oxide, hydroxyl, and terminating methyl/ethyl content, allowing the assignment of detailed compositional distributions. An essential further distinction of constitutional isomer distributions was achieved using an in-house developed probability-based deconvolution algorithm. Aided by differential heat maps for visualization and straightforward interpretation of the measured LC-MS data, compositional variation between bio-stable and non-bio-stable CEs could be identified using this new approach. Moreover, it disclosed unexpected methylations in EHEC samples. Overall, the obtained molecular information on relevant CE samples demonstrated the method's potential for the study of CE structure-property relationships.

Metabolites, elemental profile and chemical activities of Pinus strobus high temperature-derived pyroligneous acid

BackgroundPyroligneous acid (PA) is an aqueous smoky fraction produced during pyrolysis of biomass. The chemical composition of PA from different plant biomass has been studied, but reports on PA metabolites and elemental profiles are rare. In this study, we examined the metabolites, elemental profiles and the associated chemical activities of PA derived from white pine (Pinus strobus) at 1100 °C compared to similar work done elsewhere using different biomass at lower temperatures.ResultsPA from P. strobus biomass exhibited a lower electrical conductivity (2.05 mS/cm), salinity (1.03 g/L) and total dissolved solids (1.42 g/L) but higher oBrix content (9.35 ± 0.06) compared to PA from other feedstock. The P. strobus PA showed a higher antioxidant activity characterized by enhanced radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl free-radical (78.52%) and accumulation of higher total phenolic (95.81 ± 1.45 gallic acid equivalents (GAE)/mL) and flavonoid content (49.46 µg quercetin/mL). Metabolite profiling by direct injection mass spectrometry with a reverse-phase liquid chromatography–mass spectrometry (DI/LC–MS/MS) identified a total of 156 metabolites. Four (4) main groups including organic acids (90.87%), hexose (8.60%), carnitine (0.3%) and phospholipids (0.24%) were found in the PA. Mineral element analysis revealed that the P. strobus PA contained high concentrations of nitrogen (N), potassium (K), calcium (Ca) and zinc (Zn), while the content of sodium (Na) and trace/heavy metals were present at levels below the reported limit.ConclusionThis study indicates that P. strobus PA is a valuable product that can be used in agriculture to improve plant growth and productivity under normal and environmentally stressful conditions.Graphical

Identification and molecular mechanisms of novel antioxidative peptides from fermented camel milk (Kachchi breed, India) with anti‐inflammatory activity in raw macrophages cell lines

The investigation was aimed at assessing anti‐inflammatory and antioxidative activities along with the release of peptides with antioxidative properties during the fermentation of camel milk by Lacticaseibacillus casei (NK9). Reverse‐phase high‐performance liquid chromatography (RP‐HPLC) was used to separate the bioactive peptides of 3 and 10 kDa (permeates and retentates). Reverse‐phase liquid chromatography–mass spectrometry (RPLC/MS) was used to identify and characterise the pure bioactive peptides, and the effect of fermented camel milk on inflammation produced by lipopolysaccharide (LPS)/endotoxin in RAW 264.7 (Ralph and William's cell line) was also examined. Furthermore, docking revealed that peptides (LLNEK and IYTFPQPQSL) were predicted to inhibit myeloperoxidase (nMPO) activity by engaging with different residues in and around the human myeloperoxidase (hMPO) active site.

Metabolomics Analysis of Aqueous Humor Based on Liquid Chromatography-Mass Spectrometry.

Aqueous humor (AH) is a transparent fluid that fills the anterior segment of the eye. The composition and level of metabolites in AH are important for understanding its physiology and changes caused by the occurrence of eye disease. A simple method for the preparation and analysis of AH samples was developed using the liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) technique. The analyses were performed using two types of chromatography: reversed-phase liquid chromatography-mass spectrometry (LC-RP-MS) and hydrophilic interaction liquid chromatography-mass spectrometry (LC-HILIC-MS), in the sample prepared by one protocol.

Purification and Characterization of Novel Antihypertensive and Antioxidative Peptides From Whey Protein Fermentate: In Vitro, In Silico, and Molecular Interactions Studies

Objective The goal of this research was to purify and characterize the novel angiotensin-converting enzyme (ACE)–inhibitory and antioxidant peptides from fermented whey protein concentrate produced by Lactobacillus paracasei and Saccharomyces cerevisiae in a co-fermentation system. Method Whey protein fermented with lactic acid bacteria and yeast culture was analyzed for antioxidative, ACE inhibition, as well as anti-inflammatory activity followed by SDS-PAGE, isoelectric focusing, and 2-dimensional (2D) analysis. Anti-inflammatory activity of whey protein fermentate was also studied on the RAW 264.7 cell line. The bioactive peptides were separated from the whey protein fermentate using reverse-phase high-performance liquid chromatography (RP-HPLC) and reverse-phase liquid chromatography mass spectrometry (RPLC/MS), and thus identification and characterization of purified bioactive peptide was performed. Results Whey protein fermentate samples’ bioactivity was analyzed at specific time intervals at 12, 24, 36, and 48 hours at 37 °C for M11 and at 25 °C for WBS2A. The development settings (incubation time [12, 24, 36, and 48 hours) and inoculation rates [1.5%, 2.0%, and 2.5%]) were optimized for peptide synthesis via the o-phthaldialdehyde (OPA) method (proteolytic activity). Maximum proteolytic activity was observed at 37 °C for M11 (6.50 mg/mL) and at 25 °C for WBS2A (8.59 mg/mL) for 48 hours of incubation. Protein profiling was carried out using SDS-PAGE and 2D gel electrophoresis, in which Sodium dodecyl-sulfate (SDS) exhibited protein bands in the 10- to 55-kDa range, while 2D showed protein bands varying from 10 to 70 kDa. Every spot from 2D was digested by trypsin and identified by RPLC/MS. Protein fractionations (3- and 10-kDa permeates) were carried out employing RP-HPLC. Whey protein fermentate has anti-inflammatory action in RAW 264.7 macrophages that have been exposed to lipopolysaccharide. A molecular docking system was also used to investigate the interactions of peptides (AFLDSRTR, ILGAFIQIITFR) with human myeloperoxidase enzyme. Conclusions The antihypertensive and antioxidative peptides discovered from whey protein fermentate may be helpful in the design of pharmacologically active healthy ingredients in the upcoming years.

Proteomic analysis of infected root canals with apical periodontitis in patients with type 2 diabetes mellitus: A cross-sectional study.

This study aimed to quantitatively and qualitatively determine the proteomic profile of apical periodontitis (AP) in type 2 diabetes mellitus (T2DM) patients in comparison with systemically noncompromised patients and to correlate the protein expression of both groups with their biological functions. The sample consisted of 18 patients with asymptomatic AP divided into two groups according to the presence of T2DM: diabetic group-patients with T2DM (n=9) and control group-systemically healthy patients (n=9). After sample collection, the root canal samples were prepared for proteomic analysis using reverse-phase liquid chromatography-mass spectrometry. Label-free quantitative proteomic analysis was performed by Protein Lynx Global Service software. Differences in protein expression between groups were calculated using t-test (p < .05). Biological functions were analysed using the Homo sapiens UniProt database. A total of 727 human proteins were identified in all samples. Among them, 124 proteins common to both groups were quantified, out of which 65 proteins from the diabetic group showed significant differences compared with the control: 43 upregulated (p < .05) and 22 downregulated (p < .05) proteins. No significant differences in protein expression were seen for the remaining 59 proteins (p > .05). Most proteins with differences in expression were related to immune/inflammatory response. Neutrophil gelatinase-associated lipocalin, Plastin-2, Lactotransferrin and 13 isoforms of immunoglobulins were upregulated. In contrast, Protein S100-A8, Protein S100-A9, Histone H2B, Neutrophil defensin 1, Neutrophil defensin 3 and Prolactin-inducible protein were downregulated. Quantitative differences were demonstrated in the expression of proteins common to diabetic and control groups, mainly related to immune response, oxidative stress, apoptosis and proteolysis. These findings revealed biological pathways that provide the basis to support clinical findings on the relationship between AP and T2DM.

Comprehensive metabolite quantitative assay based on alternate metabolomics and lipidomics analyses

Metabolomics-based precision medicine is facing several obstacles including cross-platform data comparison issue and the lack of metabolome benchmark values of healthy population, one of main reasons is the shortage of comprehensive metabolome quantitation methods. Here, we developed an alternate reversed-phase liquid chromatography-mass spectrometry (RPLC-MS) method to quantitatively determine metabolites and lipids. Assisted by a wide set of reference standards and real samples, up to 397 multiple reaction monitoring (MRM) transitions (239 for positive and 158 for negative ion modes) and 1080 MRM transitions (607 for positive and 473 for negative ion modes) were defined respectively in the metabolomic and lipidomic analyses with more than 1000 metabolites and lipids being quantified. Among them, 144 analytes including amines, amino acids, benzenoids, peptides, nucleobases and related, bile acids, carboxylic acids, fatty acids, hormones, indoles and others were absolutely quantified, while carnitines, lyso-phosphatidylcholines, lyso-phosphatidylethanolamines, free fatty acids, sphingomyelins, phosphatidylcholines (PCs), alkyl and alkenyl substituted PCs, phosphatidylethanolamines (PEs), alkyl and alkenyl substituted PEs and triacylglycerols were semiquantified. The developed method was validated to have good analytical characteristics. Analytical results of standard reference material 1950 human plasma had a good agreement with literature data. As a proof of application, this method was used to study serum metabolic pattern changes of patients with hyperuricemia and nonalcoholic fatty liver. This alternate RPLC-MS method for quantitative metabolites and lipids analysis can further be used to provide technology and large-scale data support for precision medicine and life sciences.

Urinary metabolites as a predictive marker for perinatal depression: A secondary analysis of the mothers, Omega-3 &amp; Mental Health Study

Background:Perinatal depression has been associated with unfavorable pregnancy and childhood development outcomes; however, no objective markers exist to identify perinatal mood disorders. We investigated whether metabolites in maternal urine during pregnancy can predict increased depressive symptoms in late pregnancy and postpartum among pregnant women at risk for perinatal depression.Methods:We evaluated metabolomic markers in urine collected at 12–20 and 34–36 weeks’ gestation. We analyzed 49 urinary metabolites using ion pairing reversed-phase liquid chromatography-mass spectrometry. Depressive symptom severity was identified using Beck Depression Inventory (BDI) scores from 105 participants at 12–20 and 34–36 weeks’ gestation, and 6–8 weeks’ postpartum. Mixed model repeated measures analysis evaluated associations between changes in maternal urinary metabolites and BDI scores across pregnancy.Results:Increases in urinary xanthine and hypoxanthine were positively associated with increases in maternal depressive symptoms throughout pregnancy (p = 0.03 and 0.02, respectively). This finding did not persist after false discovery rate correction. None of the urinary metabolites examined were significantly associated with development of postpartum depressive symptoms.Limitations:This study is an exploratory secondary biologic sample analysis from a trial whose sample size was determined by a different primary outcome and expected effect size, which may have limited statistical power to detect associations between urinary metabolites, depressive symptoms, and mood trajectory over time.Conclusions:Increasing concentrations of xanthine and hypoxanthine were associated with increasing depressive symptoms throughout pregnancy. Further research is needed to evaluate the utility of these metabolic markers in identifying women at risk for perinatal depressive symptoms.

Comparative study on retention behaviour and enantioresolution of basic and neutral structurally unrelated compounds with cellulose-based chiral stationary phases in reversed phase liquid chromatography-mass spectrometry conditions

A comparative study on the retention behaviour and enantioresolution of 54 structurally unrelated neutral and basic compounds using five commercial cellulose-based chiral stationary phases (CSPs) and hydro-organic mobile phases compatible with MS detection is performed. Four phenylcarbamate-type cellulose CSPs (cellulose tris(3,5-dimethylphenylcarbamate), Cell1; cellulose tris(3-chloro-4-methylphenylcarbamate), Cell2; cellulose tris(4-chloro-3-methylphenylcarbamate), Cell4 and cellulose tris(3,5- dichlorophenylcarbamate), Cell5) and one benzoate-type cellulose CSP (cellulose tris(4-methylbenzoate), Cell3) are assayed. Mobile phases consist of binary mixtures of methanol (30–90% MeOH) or acetonitrile (10-98% ACN) with 5 mM ammonium bicarbonate (pH = 8.0).The existence of reversed phase (RPLC) and hydrophilic interaction liquid chromatography (HILIC) retention behaviour domains is explored. In MeOH/H2O mobile phases, for all compounds and CSPs, the typical RPLC retention behaviour is observed. When using ACN/H2O mobile phases, for all compounds in all CSPs (even in the non-chlorinated CSPs) a U-shaped retention behaviour depending on the ACN/H2O content is observed which indicates the coexistence of the RPLC- (< 80% ACN) and HILIC- (∼80–98% ACN) domains. The magnitude of retention changes in both domains is related to the hydrophobicity of the compound as well as to the nature of the CSP.The study of the effect of the nature and concentration of the organic solvent, as well as the nature of the CSP on the enantioresolution reveals that: (i) the use of MeOH/H2O or ACN/H2O greatly affects the enantioselectivity and enantioresolution degree of the chromatographic systems, being, in general, better the results obtained with ACN/H2O mobile phases. (ii) The ACN-RPLC-domain provides much better enantioresolution than HILIC-domain. (iii) Cell2, especially with ACN/H2O mobile phases, is the CSP that allows baseline enantioresolution for a higher number of compounds. (iv) Phenylcarbamate-type CSPs do not offer clear complementary enantioselectivity to that of Cell2. (v) Cell3 is the only CSP that provides marked complementary enantioselectivity to that of Cell2, almost orthogonal in MeOH/H2O mobile phases.

Method for absolute quantification of short chain fatty acids via reverse phase chromatography mass spectrometry.

Short chain fatty acids (SCFAs; including acetate, propionate, and butyrate) are an important class of biological molecules that play a major role in modulating host-microbiome interactions. Despite significant research into SCFA-mediated biological mechanisms, absolute quantification of these molecules in their native form by liquid chromatography mass spectrometry is challenging due to their relatively poor chromatographic properties. Herein, we introduce SQUAD, an isotope-based strategy for absolute quantification of SCFAs in complex biological samples. SQUAD uses aniline derivatization in conjunction with isotope dilution and analysis by reverse-phase liquid chromatography mass spectrometry. We show that SQUAD enables absolute quantification of biologically relevant SCFAs in complex biological samples with a lower limit of detection of 40 nM and a lower limit of quantification ranging from 160 nM to 310 nM. We observed an intra- and inter-day precision under 3% (relative standard deviation) and errors in intra- and inter-day accuracy under 10%. To demonstrate this quantification strategy, we analyzed SCFAs in the caecal contents of germ free versus conventionally raised specific pathogen free (SPF) mice. We showed that acetate was the most abundant SCFA in both types of mice and was present at 200-fold higher concentration in the SPF mice. We also illustrated the use of our quantification strategy in in vitro microbial cultures from five different species of bacteria grown in Mueller Hinton media. This study illustrates the diverse SCFA production rates across microbial taxa with acetate production serving as one of the key differentiating factors across the species. In summary, we introduce an isotope dilution strategy for absolute quantification of aniline-dativized SCFAs and illustrate the utility of this approach for microbiome research.

Sex-specific differences in plasma lipid profiles are associated with Gulf War Illness

BackgroundNearly 250,000 veterans from the 1990–1991 Gulf War have Gulf War Illness (GWI), a condition with heterogeneous pathobiology that remains difficult to diagnose. As such, availability of blood biomarkers that reflect the underlying biology of GWI would help clinicians provide appropriate care to ill veterans. In this study, we measured blood lipids to examine the influence of sex on the association between blood lipids and GWI diagnosis.MethodsPlasma lipid extracts from GWI (n = 100) and control (n = 45) participants were subjected to reversed-phase nano-flow liquid chromatography-mass spectrometry analysis.ResultsAn influence of sex and GWI case status on plasma neutral lipid and phospholipid species was observed. Among male participants, triglycerides, diglycerides, and phosphatidylcholines were increased while cholesterol esters were decreased in GWI cases compared to controls. In female participants, ceramides were increased in GWI cases compared to controls. Among male participants, unsaturated triglycerides, phosphatidylcholine and diglycerides were increased while unsaturated cholesterol esters were lower in GWI cases compared to controls. The ratio of arachidonic acid- to docosahexaenoic acid-containing triglyceride species was increased in female and male GWI cases as compared to their sex-matched controls.ConclusionDifferential modulation of neutral lipids and ratios of arachidonic acid to docosahexaenoic acid in male veterans with GWI suggest metabolic dysfunction and inflammation. Increases in ceramides among female veterans with GWI also suggest activation of inflammatory pathways. Future research should characterize how these lipids and their associated pathways relate to GWI pathology to identify biomarkers of the disorder.

Development of an ion pairing reversed-phase liquid chromatography-mass spectrometry method for characterization of clustered regularly interspaced short palindromic repeats guide ribonucleic acid

Guide ribonucleic acid (gRNA) is a critical reagent in clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 genome editing. The single stranded guide RNA (sgRNA) is the most commonly used gRNA in application. Evaluation of the impurity profile of synthetic sgRNA is important for any CRISPR genome editing experiments. However, the large molecular size, complex impurity profile and unique secondary structure pose many challenges in the analysis of sgRNA by ion pairing reversed-phase liquid chromatography (IP-RPLC), the commonly used method. In this work, we developed a generic IP-RPLC method for guide RNA analysis. We found that large pore size of stationary phase was the most critical column parameter to achieve high resolution separation of sgRNA while particle structure, particle size and surface chemistry had less impact. Our results indicated that charge interaction was the most critical mechanism for retention and mass transfer had less impact on the performance of separation. An IP-RPLC/mass spectrometry (MS) method was also developed with a specific practice to reduce adducts and enable intact MS analysis of sgRNAs. The generic IP-RPLC method demonstrates its feasibility to serve as a release, stability, characterization and in-process control testing method for synthetic sgRNA products.

Reduction of residual topical diclofenac in waste water by a wiping procedure before hand washing

Diclofenac is non-steroidal anti-inflammatory drug (NSAID) with widespread usage as a topical treatment for relief of pain and inflammation in soft-tissue injuries. While the permeation mechanisms of topically applied diclofenac are well documented, the fate of residual diclofenac not retained at the site of pain following subsequent hand-washing is still not well characterized. The aim of this study quantifies the amount of diclofenac present in rinse water after the application of a topical pain gel containing 23.2mg/g diclofenac diethylamine, and subsequent washing of the hands. A comparison of two different hand washing techniques was completed with and without wiping hands directly after product application and before washing. A pilot study was completed to optimize the analytical procedures used in the quantification of diclofenac in the rinse water, followed by a main study with 24 test subjects. The data were first analyzed separately and subsequently pooled for statistical analysis. To determine the amount of diclofenac in the rinse water samples, we used reverse phase-liquid chromatography-mass spectrometry (RP-LC-MS/MS). It was determined that a hand washing procedure with a pre-wash wipe of the hands with a paper towel resulted in a 66% reduction in diclofenac released into the waste water system (7.43±3.02mg/L). This study shows for the first time that a wiping procedure before hand washing will have a significant impact on the amount of diclofenac in the rinse water. Thus, it is possible to significantly impact the release of non-absorbed residual diclofenac after product application.

Dimethylcysteine (DiCys)/o-Phthalaldehyde Derivatization for Chiral Metabolite Analyses: Cross-Comparison of Six Chiral Thiols.

Metabolomics profiling using liquid chromatography-mass spectrometry (LC-MS) has become an important tool in biomedical research. However, resolving enantiomers still represents a significant challenge in the metabolomics study of complex samples. Here, we introduced N,N-dimethyl-l-cysteine (dimethylcysteine, DiCys), a chiral thiol, for the o-phthalaldehyde (OPA) derivatization of enantiomeric amine metabolites. We took interest in DiCys because of its potential for multiplex isotope-tagged quantification. Here, we characterized the usefulness of DiCys in reversed-phase LC-MS analyses of chiral metabolites, compared against five commonly used chiral thiols: N-acetyl-l-cysteine (NAC); N-acetyl-d-penicillamine (NAP); isobutyryl-l-cysteine (IBLC); N-(tert-butoxycarbonyl)-l-cysteine methyl ester (NBC); and N-(tert-butylthiocarbamoyl)-l-cysteine ethyl ester (BTCC). DiCys and IBLC showed the best overall performance in terms of chiral separation, fluorescence intensity, and ionization efficiency. For chiral separation of amino acids, DiCys/OPA also outperformed Marfey’s reagents: 1-fluoro-2-4-dinitrophenyl-5-l-valine amide (FDVA) and 1-fluoro-2-4-dinitrophenyl-5-l-alanine amide (FDAA). As proof of principle, we compared DiCys and IBLC for detecting chiral metabolites in aqueous extracts of rice. By LC–MS analyses, both methods detected twenty proteinogenic l-amino acids and seven d-amino acids (Ala, Arg, Lys, Phe, Ser, Tyr, and Val), but DiCys showed better analyte separation. We conclude that DiCys/OPA is an excellent amine-derivatization method for enantiomeric metabolite detection in LC-MS analyses.

Hydrophilic interaction chromatography – mass spectrometry for metabolomics and proteomics: state-of-the-art and current trends

Among all the –omics approaches, proteomics and metabolomics have received increased attention over the last decade. Both approaches have reached a certain level of maturity, showing their relevance in numerous clinical applications, including biomarkers discovery, improved diagnosis, staging, and prognosis of diseases, as well as a better knowledge on various (patho-)physiological processes. Analytically, reversed-phase liquid chromatography – mass spectrometry (RPLC-MS) is considered the golden standard in proteomics and metabolomics, due to its ease of use and reproducilibity. However, RPLC-MS alone is not sufficient to resolve the complexity of the proteome, while very polar metabolites are typically poorly retained. In this context, hydrophilic interaction chromatography (HILIC) represents an attractive complementary approach, due to its orthogonal separation mechanism. This review presents an overview of the literature reporting the application of HILIC-MS in metabolomics and proteomics. For metabolomics the focus is on the analysis of bioactive lipids, amino acids, organic acids, and nucleotides/nucleosides, whereas for proteomics the analysis of complex samples and protein post-translational modifications therein using bottom-up, middle up/down proteomics and intact protein analysis is discussed. The review handles the technological aspects related to the use of HILIC-MS in both proteomics and metabolomics, paying attention to stationary phases, mobile phase conditions, injection volume and column temperature. Recent trends and developments in the application of HILIC-MS in proteomics and metabolomics are also presented and discussed, highlighting the advantages the technique can provide in addition or complementary to RPLC-MS, as well as the current limitations and possible solutions.

Development of a method for dansylation of metabolites using organic solvent-compatible buffer systems for amine/phenol submetabolome analysis

Metabolomics, which serves as a readout of biological processes and diseases monitoring, is an informative research area for disease biomarker discovery and systems biology studies. In particular, reversed-phase liquid chromatography-mass spectrometry (RPLC-MS) has become a powerful and popular tool for metabolomics analysis, enabling the detection of most metabolites. Very polar and ionic metabolites, however, are less easily detected because of their poor retention in RP columns. Dansylation of metabolites simplifies the sub-metabolome analysis by reducing its complexity and increasing both hydrophobicity and ionization ability. However, the various metabolite concentrations in clinical samples have a wide dynamic range with highly individual variation in total metabolite amount, such as in saliva. The bicarbonate buffer typically used in dansylation labeling reactions induces solvent stratification, resulting in poor reproducibility, selective sample loss and an increase in false-determined metabolite peaks. In this study, we optimized the dansylation protocol for samples with wide concentration range of metabolites, utilizing diisopropylethylamine (DIPEA) or tri-ethylamine (TEA) in place of bicarbonate buffer, and presented the results of a systemic investigation of the influences of individual processes involved on the overall performance of the protocol. In addition to achieving high reproducibility, substitution of DIPEA or TEA buffer resulted in similar labeling efficiency of most metabolites and more efficient labeling of some metabolites with a higher pKa. With this improvement, compounds that are only present in samples in trace amounts can be detected, and more comprehensive metabolomics profiles can be acquired for biomarker discovery or pathway analysis, making it possible to analyze clinical samples with limited amounts of metabolites.

Hydrophilic-interaction-based magnetically assisted matrix solid-phase dispersion extraction of carbadox and olaquindox in feeds.

Carbadox and olaquindox have been banned from feeds since 1998 by the EU because of their mutagenic, photoallergic, and carcinogenic effects. Unfortunately, owing to their outstanding effect, they are frequently abused or misused in animal husbandry. There is an urgent need to develop a sensitive and reliable method for monitoring these drugs in animal feeds. This work reported a new method of hydrophilic-interaction-based magnetically assisted matrix solid-phase dispersion (MMSPD) extraction coupled with reversed-phase liquid chromatography-mass spectrometry for simultaneous determination of carbadox and olaquindox in animal feeds. 3-Trimethoxysilylpropyl methacrylate (γ-MAPS)-modified attapulgite (ATP) was crosslinked with γ-MAPS-modified iron(II,III) oxide (Fe3 O4 ), 1-vinyl-3-(butyl-4-sulfonate) imidazolium (VBSIm), acrylamide (AM), and N,N'-methylene-bis(acrylamide) (MBA) to synthesize ATP@Fe3 O4 @poly(VBSIm-AM-MBA) particles. The resultant particles were characterized by scanning electron microscopy, energy dispersive spectrometer, transmission electron microscopy, vibrating sample magnetometer, and Fourier transform infrared spectroscopy. Crosslinking of ATP into the magnetic particles has significantly increased the adsorption capacity of the particles. Under optimum conditions, the limits of detection (S/N=3) were 0.3μg kg-1 and 0.9μg kg-1 for carbadox and olaquindox respectively. The intra-day and inter-day recoveries of the spiked targets in feed samples were in the range 83.5-98.3% with relative standard deviations of 1.0-8.3%. With a simplified procedure and a low amount of sample, the proposed hydrophilic-interaction-based MMSPD method is not only useful for the determination of carbadox and olaquindox in feeds but also holds great promise for the analysis of other polar targets in solid or semisolid matrices. © 2021 Society of Chemical Industry.

Exploratory Metabolomic Analysis Based on Reversed-Phase Liquid Chromatography-Mass Spectrometry to Study an In Vitro Model of Hypoxia-Induced Metabolic Alterations in HK-2 Cells.

Oxygen deficiency in cells, tissues, and organs can not only prevent the proper development of biological functions but it can also lead to several diseases and disorders. In this sense, the kidney deserves special attention since hypoxia can be considered an important factor in the pathophysiology of both acute kidney injury and chronic kidney disease. To provide better knowledge to unveil the molecular mechanisms involved, new studies are necessary. In this sense, this work aims to study, for the first time, an in vitro model of hypoxia-induced metabolic alterations in human proximal tubular HK-2 cells because renal proximal tubules are particularly susceptible to hypoxia. Different groups of cells, cultivated under control and hypoxia conditions at 0.5, 5, 24, and 48 h, were investigated using untargeted metabolomic approaches based on reversed-phase liquid chromatography–mass spectrometry. Both intracellular and extracellular fluids were studied to obtain a large metabolite coverage. On the other hand, multivariate and univariate analyses were carried out to find the differences among the cell groups and to select the most relevant variables. The molecular features identified as affected metabolites were mainly amino acids and Amadori compounds. Insights about their biological relevance are also provided.

Abstract 459: Lipidomic analysis of extracellular vesicles and its potential for the identification of body fluid-based biomarkers for breast cancer diagnosis

Abstract Background: Tumor-derived Extracellular Vesicles (EVs) are found in body fluids of cancer patients. These EVs include exosomes and microvesicles, which play an important role in tumor development and metastasis. Although EVs have great potential as liquid biopsies for early detection of breast cancer, the lipid composition of breast cancer-derived EVs is unknown. Here, we studied the lipid composition of EVs and its potential for the identification of body fluid-based biomarkers for breast cancer diagnosis. Methods: The lipid composition of EVs and their parental cells were evaluated for nine breast cancer and two non-cancerous mammary cell lines. EVs were isolated by size-exclusion chromatography (SEC). Furthermore, ten blood plasma samples were studied from women diagnosed with primary breast cancer before surgery, nine samples from patients with progressive metastatic breast cancer and ten samples from healthy women who neither had pre-existing medical conditions nor infections at the time the samples were collected or in the previous weeks. EVs were obtained from blood plasma samples by a combination of density gradient ultracentrifugation and SEC. Lipids were extracted from EVs and analyzed by reverse-phase liquid chromatography mass-spectrometry (LC-MS). Results: We found that EVs produced by breast cancer cell lines were enriched in sphingomyelins and ceramides when compared to their parental cells. Furthermore, phospholipids such as phosphatidylcholine and phosphatidylethanolamine were found to be abundant in these EVs. Multivariate analyses showed that EVs released by breast cancer cells can be distinguished from those released by non-cancerous cells based on their phospholipid and sphingolipid composition (AUCROC=0.99, p&amp;lt;0.001). A key finding of this study is that we also found significant differences in the phospholipid and sphingolipid composition between EVs found in blood plasma from breast cancer patients and healthy volunteers (AUCROC=0.99, p&amp;lt;0.001). Importantly with respect to the practical applications of this study for early diagnosis of breast cancer, these differences in EV's lipid content were also significant between EVs from primary breast cancer patients and healthy volunteers (AUCROC=0.99, p&amp;lt;0.001). Annotation of specific lipid species are currently being carried out by MS/MS analysis. Conclusion: Our findings demonstrate the potential of the lipid content of cancer-derived EVs for the identification of lipid biomarkers for breast cancer diagnosis and its use for the development of non-invasive (or minimally invasive) diagnostic methods based on blood plasma analysis. Citation Format: Erika Dorado, M Luisa Doria, Anika Nagelkerke, James S McKenzie, Stefania Maneta-Stavrakaki, Charlotte Ion, Thomas Whittaker, Jeremy Nicholson, Molly M Stevens, R Charles Coombes, Zoltan Takats. Lipidomic analysis of extracellular vesicles and its potential for the identification of body fluid-based biomarkers for breast cancer diagnosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 459.

O-glycoforms of polymeric immunoglobulin A1 in the plasma of patients with IgA nephropathy are associated with pathological phenotypes.

Immunoglobulin A1 (IgA1) O-glycosylation plays an important role in the pathogenesis of IgA nephropathy (IgAN). However, variations in IgA1 O-glycoforms have not been explored. We aimed to investigate the IgA1 O-glycoforms in the hinge region (HR) of polymeric IgA1 (pIgA1) and then evaluate the association between IgA1 O-glycoforms and crescent formation in IgAN. The discovery cohort (Cohort 1) comprised 11 crescentic IgAN patients, 10 noncrescentic IgAN patients and 10 healthy controls and the validation cohort (Cohort 2) comprised 11 crescentic IgAN patients, 9 noncrescentic IgAN patients and 9 healthy controls. A total of 143 IgAN patients with different crescent percentages (Cohort 3) were also included. pIgA1 was purified from the plasma of the participants. The variation in O-glycoforms was evaluated by estimating the molecular weights of IgA1 hinge glycopeptides using reversed-phase liquid chromatography and tandem mass spectrometry under electron-transfer/higher-energy collision dissociation fragmentation mode. In the discovery cohort (Cohort 1), the number of N-acetylgalactosamine (GalNAc) bound to one HR was lower in IgAN patients. The proportions of GalNAc3 (defined as O-glycans bound to one HR at three sites) and GalNAc4 were highest in crescentic IgAN patients, followed by noncrescentic IgAN patients, and were lowest in healthy controls [GalNAc 3: 9.92 ± 3.37% versus 6.65 ± 1.53% versus 4.05 ± 1.24% (P < 0.001); GalNAc4: 45.91 ± 4.75% versus 41.13 ± 2.95% versus 40.98 ± 2.95% (P = 0.004), respectively]. The proportions of GalNAc5 and GalNAc6 were lowest in crescentic IgAN patients followed by noncrescentic IgAN patients and were highest in healthy controls [GalNAc5: 50.15 ± 4.27% versus 47.92 ± 4.09% versus 45.87 ± 3.79% (P = 0.028); GalNAc6: 6.58 ± 2.53% versus 6.04 ± 1.35% versus 4.65 ± 2.27% (P = 0.034), respectively]. These results were consistent in the validation cohort (Cohort 2). In another cohort with 143 patients with different crescent percentages (Cohort 3), the number of GalNAc in pIgA1 decreased with an increasing percentage of crescents. The number of GalNAc in IgA1 HRs was lower in IgAN patients, especially in crescentic IgAN patients, and may be associated with a severe IgAN phenotype.