Reversed-phase Liquid Chromatography Mass Spectrometry Research Articles

Determination of the decapping efficiency of THIOMAB™ antibodies with the engineered cysteine in the Fc region for making antibody-drug conjugates by specific hinge fragmentation-liquid chromatography.

The site-specific antibody-drug conjugates (ADCs), particularly those utilizing the engineered cysteine in Fc fragments of mAbs (THIOMAB™ antibodies), have emerged as a novel class of biotherapeutics for cancer treatment. The engineered cysteine residues in these antibodies are capped by cysteine or glutathione through a disulfide bond. Prior to conjugation with linker-payloads, these caps need to be removed through a reduction process. However, monitoring the efficiency of the decapping process has been challenging due to the lack of effective analytical methods. Intact reversed-phase liquid chromatography-mass spectrometry and hydrophobic interaction chromatography methods failed to separate decapped and capped intact THIOMAB™ mAbs in our study. Instead the fragmentation of mAbs provided a novel strategy to analyze the decapping effiency. After cleavage using a hinge specific enzyme, the generated Fc fragments with and without cysteine and/or glutathione caps displayed different hydrophobicity and were well separated by RPLC, allowing quantitative determination of the decapping efficiency. Enzymes that cleave both above and below the hinge disulfide bonds were tested. The use of FabALATICA can determine percentages of molecules with 0, 1, and 2 cysteine and/or glutathione caps, respectively, regardless of whether the antibody contains the hinge LALA mutations. On the other hand, FabRICATOR enzyme can only be utilized for antibodies without LALA mutations for the overall decapping percentage and cannot be used to estimate intact antibody each with 0, 1, and 2 caps. Therefore, FabALACTICA cleavage followed by RPLC provides a wider application of monitoring the decapping efficiency of all antibodies with the engineered cysteine in Fc.

Discovering oxidized polar lipids in microalgae lipidome using liquid chromatography mass spectrometry approaches

Microalgae are rich in polar lipids, such as glycolipids, phospholipids and betaine lipids esterified with omega-3 polyunsaturated fatty acids (PUFA), which are prone to oxidation. Under stress conditions, the redox balance in microalgae is altered, leading to an abnormal production of reactive oxygen species (ROS) that can affect surrounding lipids. While few oxidized polar lipids have been described to play important roles in mammals and possess interesting bioactive properties, their occurrence in microalgae is poorly described, hindering their exploitation as novel bioactive compounds. To enhance our understanding of these lipids, we conducted a targeted analysis of oxidized polar lipids in lipid extracts obtained from five microalgae species: Chlorella vulgaris, Chlorococcum amblystomatis, Scendesmus obliquus, Nanochloropsis oceanica and Phaeodactylum ticornutum, using reverse-phase liquid chromatography mass spectrometry (RP-LC-MS). A detailed analysis of the LC-MS data identified 150 oxidized polar lipid species across different classes of phospholipids, glycolipids and betaine lipids in the five microalgae species. These modified oxidized lipids featured oxygenated species with 1–3 additional oxygen atoms in the fatty acyl chains. The predominant oxidized fatty acids esterified to these lipids were omega-3 eicosapentaenoic acid (EPA, 20:5 n-3) and α-linonelic acid (ALA, 18:3 n-3). Notably, most oxidized lipid species were identified in diacylglyceryl-N,N,N-trimethylhomoserine (DGTS) in C. amblystomatis, S. obliquus and N. oceanica, monogalactosyldiacylglycerol (MGDG) in P. tricornutum, and phosphatidylethanolamine (PE) in C. vulgaris. Furthermore, distinct fragmentation patterns across lipid classes allowed the unequivocal identification of oxidized polar lipids. These findings reveal a diverse array of oxidized polar lipids in microalgae, predominantly enriched with oxidized omega-3 PUFA, highlighting microalgae as a natural source of oxidized polar lipids that may serve as a natural reservoir of bioactive omega-3 oxylipins.

Selective Enrichment via TiO2 Magnetic Nanoparticles Enables Deep Profiling of Circulating Neutral Glycosphingolipids.

Circulating neutral glycosphingolipids (neutral GSLs (nGSLs)) are a unique subset of nGSLs that detach from organs or cell membranes and enter the bloodstream. Altered molecular distribution of circulating nGSL is increasingly associated with diseases. However, profiling of circulating nGSLs presents a lasting challenge due to their low abundances and structural complexity. Although TiO2 magnetic nanoparticles (TiO2 MNPs) were effective for the enrichment of nGSLs in brain tissue, the protocol showed limited selectivity for circulating nGSLs because their abundances were 100-times lower in human plasma than in brain tissue. In this work, we optimized the key parameters of selective enrichment by TiO2 MNPs and achieved 1:10,000 selectivity for nGSLs over interfering phospholipids, while maintaining ∼70% recovery for different subclasses of nGSLs. By integrating TiO2 MNP-based selective enrichment with reversed-phase liquid chromatography mass spectrometry and charge-tagging Paternò-Büchi derivatization, we achieved deep profiling of over 300 structures of nGSLs and sulfatides across 5 orders of magnitude in relative abundances, a significant leap regarding lipid coverage. We also depicted the structural atlas of nGSLs with defined headgroup, long-chain base, N-acyl chain, the location of desaturation, and 2-hydroxylation. Such information provides a valuable resource for lipidomic studies concerning the roles of circulating nGSLs in health and diseases.

Reversed-Phase Ultrahigh-Performance Liquid Chromatography-Mass Spectrometry Method for High-Throughput Lipidomic Quantitation.

Reversed-phase ultrahigh-performance liquid chromatography-mass spectrometry (RP-UHPLC/MS) method is optimized for the quantitation of a large number of lipid species in biological samples, primarily in human plasma and serum. The method uses a C18 bridged ethylene hybrid (BEH) column (150×2.1mm; 1.7μm) for the separation of lipids from 23 subclasses with a total run time of 25min. Lipid species separation allows the resolution of isobaric and isomeric lipid forms. A triple quadrupole mass spectrometer is used for targeted lipidomic analysis using multiple reaction monitoring (MRM) in the positive ion mode. Data are evaluated by Skyline software, and the concentrations of analytes are determined using internal standards per each individual lipid class.

Characterization of HphA: The First Enzyme in the Homologation Pathway of l-Phenylalanine and l-Tyrosine.

Homologation of amino acids is the insertion or deletion of a methylene group to their side chain, which is a relatively uncommon chemical transformation observed in peptide natural product (NP) structure. Homologated amino acids can potentially make the NP more stable in a biological system, but its biosynthesis is yet to be understood. This study biochemically characterized the first of three unexplored enzymes in the homologation pathway of l-phenylalanine and l-tyrosine. Previously proposed reactions catalyzed by HphA were confirmed by reversed-phase high-performance liquid chromatography and tandem mass spectrometry analysis. The substrate profile and kinetic parameters showed high selectivity for the natural substrates and their close analogs. The comparability of HphA to homologous enzymes in primary metabolic pathways, 2-isopropylmate synthase and homocitrate synthase which are involved in l-leucine and l-lysine biosynthesis, respectively, was validated by bioinformatical and site-directed mutagenesis studies. The knowledge obtained from this study has deepened the understanding of the homologation of amino acids, which can lead to future combinatorial biosynthesis and metabolic engineering studies.

Comprehensive characterization of bacterial glycoconjugate vaccines by liquid chromatography - mass spectrometry

Bacterial pathogens can cause a broad range of infections with detrimental effects on health. Vaccine development is essential as multi-drug resistance in bacterial infections is a rising concern. Recombinantly produced proteins carrying O-antigen glycosylation are promising glycoconjugate vaccine candidates to prevent bacterial infections. However, methods for their comprehensive structural characterization are lacking. Here, we present a bottom-up approach for their site-specific characterization, detecting N-glycopeptides by nano reversed-phase liquid chromatography-mass spectrometry (RP-LC-MS). Glycopeptide analyses revealed information on partial site-occupancy and site-specific glycosylation heterogeneity and helped corroborate the polysaccharide structures and their modifications. Bottom-up analysis was complemented by intact glycoprotein analysis using nano RP-LC-MS allowing the fast visualization of the polysaccharide distribution in the intact glycoconjugate. At the glycopeptide level, the model glycoconjugates analyzed showed different repeat unit (RU) distributions that spanned from 1 to 21 RUs attached to each of the different glycosylation sites. Interestingly, the intact glycoprotein analysis displayed a RU distribution ranging from 1 to 28 RUs, showing the predominant species when the different glycopeptide distributions are combined in the intact glycoconjugate. The complete workflow based on LC-MS measurements allows detailed and comprehensive analysis of the glycosylation state of glycoconjugate vaccines.

Metabolic features of adolescent major depressive disorder: A comparative study between treatment-resistant depression and first-episode drug-naive depression

Major depressive disorder (MDD) is a psychiatric illness that can jeopardize the normal growth and development of adolescents. Approximately 40% of adolescent patients with MDD exhibit resistance to conventional antidepressants, leading to the development of Treatment-Resistant Depression (TRD). TRD is associated with severe impairments in social functioning and learning ability and an elevated risk of suicide, thereby imposing an additional societal burden. In this study, we conducted plasma metabolomic analysis on 53 adolescents diagnosed with first-episode drug-naïve MDD (FEDN-MDD), 53 adolescents with TRD, and 56 healthy controls (HCs) using hydrophilic interaction liquid chromatography-mass spectrometry (HILIC-MS) and reversed-phase liquid chromatography-mass spectrometry (RPLC-MS). We established a diagnostic model by identifying differentially expressed metabolites and applying cluster analysis, metabolic pathway analysis, and multivariate linear support vector machine (SVM) algorithms. Our findings suggest that adolescent TRD shares similarities with FEDN-MDD in five amino acid metabolic pathways and exhibits distinct metabolic characteristics, particularly tyrosine and glycerophospholipid metabolism. Furthermore, through multivariate receiver operating characteristic (ROC) analysis, we optimized the area under the curve (AUC) and achieved the highest predictive accuracy, obtaining an AUC of 0.903 when comparing FEDN-MDD patients with HCs and an AUC of 0.968 when comparing TRD patients with HCs. This study provides new evidence for the identification of adolescent TRD and sheds light on different pathophysiologies by delineating the distinct plasma metabolic profiles of adolescent TRD and FEDN-MDD.

Characterization of PEGylation sites in Neulasta and a biosimilar candidate with a combined fragmentation strategy in mass spectrometry analysis.

In the development of biosimilar products to Neulasta, it is essential to determine the intact molecular mass and confirm precise PEGylation sites. In this study, we applied a combination of techniques, including post-column addition of triethylamine in reversed-phase liquid chromatography-mass spectrometry (RPLC-MS) to determine the intact molecular mass, and in-source fragmentation (ISF) and higher-energy collision dissociation-tandem mass spectrometry (HCD-MS/MS) to identify the PEGylation site. Our results show that both the pegfilgrastim biosimilar candidate and Neulasta lots are mono-PEGylated at the N-terminal end. Furthermore, we show that the combined ISF and HCD-MS/MS method can be used for identifying the PEGylation sites in the diPEGylated variant of pegfilgrastim. The diPEGylated variant has modification sites at the N-terminal end and a lysine at position 35 in the protein sequence.

Optimization of elution conditions and comparison of emerging biocompatible columns on the resolving power and detection sensitivity of oligonucleotides by ion-pairing reversed-phase liquid chromatography mass spectrometry

A generic performance comparison strategy has been developed to evaluate the impact of mobile-phase additives (ion-pairing agent / counter ion systems), distinct stationary phases on resulting resolving power, and MS detectability of oligonucleotides and their critical impurities in gradient IP-RPLC. Stationary-phase considerations included particle type (core-shell vs. fully porous particles), particle diameter, and pore size. Separations were carried out at 60°C to optimize mass transfer (C-term). The incorporation of an active column preheater mitigated thermal mismatches, leading to narrower peaks and overcoming peak splitting. Acetonitrile as organic modifier outweighed methanol in terms of peak-capacity generation and yielded a 30% lower back pressure. Performance screening experiments were conducted varying ion-pairing agents and counter ions, while adjusting gradient span achieved an equivalent effective retention window. Hexafluoromethylisopropanol yielded superior chromatographic resolution, whereas hexafluoroisopropanol yielded significantly higher MS detection sensitivity. The 1.7 µm core-shell particle columns with 100 Å pores provided maximum resolving power for small (15–35 mers) oligonucleotides. Sub-min analysis for 15–35 polyT ladders was achieved operating a 50 mm long column at the kinetic performance limits. High-resolution separations between a 21-mer modified RNA sequence oligonucleotides and its related (shortmer and phosphodiester) impurities and complementary strand were obtained using a coupled column set-up with a total length of 450 mm.

Dimethyl sulfoxide as a gas phase charge-reducing agent for the determination of PEGylated proteins' intact mass.

Determination of PEGylated proteins' intact mass by mass spectrometry is challenging due to the molecules' large size, excessive charges, and instrument limitations. Previous efforts have been reported. However, signal variability, ion coalescence, and a generally low degree of robustness have been observed. In this work, we have explored the capabilities of post-column infusion of dimethyl sulfoxide (DMSO) following reversed-phase liquid chromatography-mass spectrometry (RP-LCMS) to determine PEG-filgrastim' intact mass, and to characterize its PEG moiety. The method was optimized around reproducibility (six preparations, and three injection replicates) with an in-house prepared PEG-filgrastim standard. The method showed a mass accuracy of ≤1.2 Da. The average molecular weight (MWEO=483) was 40 147.9 Da. The number average molecular weight (Mn) and the weight average molecular weight (Mw) were observed to be 40 101.1 and 40 113.9 Da, respectively, both with an RSD of 0.03%. The molecular weight distribution of ethylene oxide (EO), the polydispersity index (PDI), was 1.0003 for all preparations with a minimum and maximum number of EO units of 448 ± 2 and 516 ± 2, respectively. The method was finally applied to commercially available Neulasta® lots where the Mn and Mw were 39 995.8 and 40 008.8 Da, respectively, both with an RSD of 0.1%. The minimum and maximum EO units across the lots were observed to be 444.5 ± 1.5 and 514 ± 3, respectively. The PDI for all Neulasta® lots was 1.0003. This study provides an insightful characterization of Neulasta® and describes a robust LC-MS methodology for the characterization of the PEGylated proteins.

Untargeted plasma metabolomics and risk of colorectal cancer—an analysis nested within a large-scale prospective cohort

BackgroundColorectal cancer (CRC) is a leading cause of cancer-related death worldwide, but if discovered at an early stage, the survival rate is high. The aim of this study was to identify novel markers predictive of future CRC risk using untargeted metabolomics.MethodsThis study included prospectively collected plasma samples from 902 CRC cases and 902 matched cancer-free control participants from the population-based Northern Sweden Health and Disease Study (NSHDS), which were obtained up to 26 years prior to CRC diagnosis. Using reverse-phase liquid chromatography–mass spectrometry (LC–MS), data comprising 5015 metabolic features were obtained. Conditional logistic regression was applied to identify potentially important metabolic features associated with CRC risk. In addition, we investigated if previously reported metabolite biomarkers of CRC risk could be validated in this study population.ResultsIn the univariable analysis, seven metabolic features were associated with CRC risk (using a false discovery rate cutoff of 0.25). Two of these could be annotated, one as pyroglutamic acid (odds ratio per one standard deviation increase = 0.79, 95% confidence interval, 0.70–0.89) and another as hydroxytigecycline (odds ratio per one standard deviation increase = 0.77, 95% confidence interval, 0.67–0.89). Associations with CRC risk were also found for six previously reported metabolic biomarkers of prevalent and/or incident CRC: sebacic acid (inverse association) and L-tryptophan, 3-hydroxybutyric acid, 9,12,13-TriHOME, valine, and 13-OxoODE (positive associations).ConclusionsThese findings suggest that although the circulating metabolome may provide new etiological insights into the underlying causes of CRC development, its potential application for the identification of individuals at higher risk of developing CRC is limited.

Identification of novel antioxidant collagen peptides for preventing and treating H2 O2 -induced oxidative stress in HepG2 cells through in vitro and in silico approaches.

Nowadays, the prevalence of oxidative stress-related chronic diseases is increasing. The identification of novel antioxidant collagen peptides to counteract oxidative stress for individuals' health has gained significant attention. In this study, collagen peptides with antioxidant activities were separated and identified by ion chromatography, reversed-phase high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry. The identified antioxidant collagen peptides were further screened by molecular docking for Keap1-targeted peptide inhibitors and their theoretical interaction mechanisms were investigated. Four novel antioxidant collagen peptides, GPAGPIGPVG, GPAGPpGPIG, ISGPpGPpGPA and IDGRPGPIGPA, with high binding affinity to Keap1 were selected. Molecular docking results demonstrated that the putative antioxidant mechanism of the four antioxidant collagen peptides contributed to their blockage of Keap1-Nrf2 interactions. The results of antioxidant activity of the four antioxidant collagen peptides proved that IDGRPGPIGPA exerted a high scavenging capacity for DPPH and ABTS free radicals, while GPAGPpGPIG improved the resistance of cells to hydrogen peroxide-induced oxidative damage by promoting the activation of intracellular antioxidant enzymes and the production of reduced glutathione in human hepatoma (HepG2) cells. The antioxidant collagen peptides (GPAGPIGPVG, GPAGPpGPIG, ISGPpGPpGPA and IDGRPGPIGPA) will be developed as novel functional food for human health in the near future. © 2023 Society of Chemical Industry.

Native SEC and Reversed-Phase LC-MS Reveal Impact of Fab Glycosylation of Anti-SARS-COV-2 Antibodies on Binding to the Receptor Binding Domain.

The binding affinity of monoclonal antibodies (mAbs) for their intended therapeutic targets is often affected by chemical and post-translational modifications in the antigen binding (Fab) domains. A new two-dimensional analytical approach is described here utilizing native size exclusion chromatography (SEC) to separate populations of antibodies and bound antibody-antigen complexes for subsequent characterization of these modifications by reversed-phase (RP) liquid chromatography-mass spectrometry (LC-MS) at the intact antibody level. Previously, we utilized peptide mapping to measure modifications impacting binding. However, in this study, the large size of the modification (N-glycosylation) allowed assessing its impact from small amounts (∼20 ug) of intact antibody, without the need for peptide mapping. Here, we apply the native SEC-based competitive binding assay to quickly and qualitatively investigate the effects of Fab glycosylation of four antispike protein mAbs that were developed for use in the treatment of COVID-19 disease. Three of the mAbs were observed to have consensus N-glycosylation sites (N-X-T/S) in the Fab domains, a relatively rare occurrence in therapeutic mAbs. The goal of the study was to characterize the levels of Fab glycosylation present, as well as determine the impact of glycosylation on binding to the spike protein receptor binding domain (RBD) and the ability of the mAbs to inhibit RBD-ACE2 interaction at the intact antibody level, with minimal sample treatment and preparation. The three mAbs with Fab N-glycans were found to have glycosylation profiles ranging from full occupancy at each Fab (in one mAb) to partially glycosylated with mixed populations of two, one, or no glycan moieties. Competitive SEC analysis of mAb-RBD revealed that the glycosylated antibody populations outcompete their nonglycosylated counterparts for the available RBD molecules. This competitive SEC binding analysis was applied to investigate the three-body interaction of a glycosylated mAb blocking the interaction between endogenous binding partners RBD-ACE2, finding that both glycosylated and nonglycosylated mAb populations bound to RBD with high enough affinity to block RBD-ACE2 binding.

In-Depth Characterization of Sphingoid Bases via Radical-Directed Dissociation Tandem Mass Spectrometry.

Sphingoid base (SPH) is a basic structural unit of all classes of sphingolipids. A sphingoid base typically consists of an aliphatic chain that may be desaturated between C4 and C5, an amine group at C2, and a variable number of OH groups located at C1, C3, and C4. Variations in the chain length and the occurrence of chemical modifications, such as methyl branching, desaturation, and hydroxylation, lead to a large structural diversity and distinct functional properties of sphingoid bases. However, conventional tandem mass spectrometry (MS/MS) via collision-induced dissociation (CID) faces challenges in characterizing these modifications. Herein, we developed an MS/MS method based on CID-triggered radical-directed dissociation (RDD) for in-depth characterization of sphingoid bases. The method involves derivatizing the sphingoid amine with 3-(2,2,6,6-tetramethylpiperidin-1-yloxymethyl)-picolinic acid 2,5-dioxopyrrolidin-1-yl ester (TPN), followed by MS2 CID to unleash the pyridine methyl radical moiety for subsequent RDD. This MS/MS method was integrated on a reversed-phase liquid chromatography-mass spectrometry workflow and further applied for in-depth profiling of total sphingoid bases in bovine heart and Caenorhabditis elegans. Notably, we identified and relatively quantified a series of unusual sphingoid bases, including SPH id17:2 (4,13) and SPH it19:0 in C. elegans, revealing that the metabolic pathways of sphingolipids are more diverse than previously known.

Perioperative exposure to volatile organic compounds in neonates undergoing cardiac surgery

ObjectiveVolatile organic compounds (VOCs) are used in the sterilization and manufacture of medical equipment. These compounds have high vapor pressures with low water solubility and are emitted as gases from solids or liquids. They can be mutagenic, neurotoxic, genotoxic, and/or carcinogenic. Safe limits of exposure are not known for neonates. This study examined determinants of exposure in newborns undergoing cardiac surgery. MethodsTwenty metabolites of 16 VOCs (eg, xylene, cyanide, acrolein, acrylonitrile, N, N-dimethylformamide, 1,3-butadiene, styrene, and benzene) were measured as metabolites in daily urine samples collected from 10 neonates undergoing cardiac operations (n = 150 samples). Metabolites were quantified using reversed-phase ultra-high performance liquid chromatography and electrospray ionization tandem mass spectrometry. Repeated measures analysis of covariance was performed for each metabolite to examine associations with use of medical devices. ResultsAt least 3 metabolites were detected in every sample. The median number of metabolites detected in each sample was 14 (range, 3-15). In a model controlling for other factors, the use of extracorporeal membrane oxygenation was associated with significantly (P ≤ .05) greater metabolite levels of acrolein, acrylonitrile, ethylene oxide, propylene oxide, styrene, and ethylbenzene. Patients breathing ambient air had greater levels of metabolites of acrolein, xylene, N,N-dimethylformamide, methyl isocyanate, cyanide, 1,3-butadiene (all P ≤ .05). ConclusionsExposure to volatile organic compounds is pervasive in newborns undergoing cardiac surgery. Sources of exposure likely include medical devices and inhalation from the air in the intensive care unit. The contribution of VOC exposure during cardiac surgery in newborns to adverse outcomes warrants further evaluation.

Simultaneous separation and detection of nine kynurenine pathway metabolites by reversed-phase liquid chromatography-mass spectrometry: Quantitation of inflammation in human cerebrospinal fluid and plasma

BackgroundThe kynurenine pathway (KP) generates eight tryptophan (TRP) metabolites collectively called kynurenines, which have gained enormous interest in clinical research. The importance of KP for different disease states calls for developing a low-cost and high-throughput chromatography-mass spectrometry method to evaluate the potential of different kynurenines. Simultaneous separation of TRP and its eight metabolites is challenging because they have substantial polarity differences (log P = −2.5 to +1.3). ResultsA low-cost, reversed-phase LC-MS/MS method based on polarity partitioning was established to simultaneously separate and quantitate all nine kynurenine pathway metabolites (KPMs) in a single run for the first time in the open literature. Based on stationary phase screening and ternary mobile phase optimization strategy, high polarity KPMs were retained while medium and low polarity KPMs were eluted in a shorter time. After method validation, we demonstrated the applicability of this LC/MS/MS method by quantitative measurement of all nine KPM in cerebrospinal fluid (CSF) and plasma among two groups of human subjects diagnosed with depression. Furthermore, we measured the differential KPMs in these two groups of low and high inflammation and correlated the results with CRP or TNF-α markers for depression. SignificanceOur proposed LC-MS/MS provides a new metabolite assay that can be easily applied in various clinical applications to simultaneously quantify multiple biomarkers in KP dysfunction.

Assessing the hydrophobicity of glycopeptides using reversed-phase liquid chromatography and tandem mass spectrometry

Retention time is one of the most important parameters that has been widely used to demonstrate the separation results obtained from liquid chromatography (LC) platforms. However, retention time can shift when samples are tested with different instruments and laboratories, which hinders the identification process of analytes when comparing data collected from different LC systems. To address this problem, hydrophobicity index was introduced for retention time normalization of the glycopeptides separated by reversed-phase LC (RPLC). Tandem MS was used for the detection and identification of glycopeptides. In addition, the influence of different types of glycans on the hydrophobicity of peptide backbones was studied by comparing the retention time of glycopeptides with their non-glycosylated counterparts. The hydrophobicity of tryptic digested glycopeptides derived from model glycoproteins, including bovine fetuin, α1-acid glycoprotein, and haptoglobin from human plasma, were evaluated based on the hydrophobicity index of the standard peptides from a peptide retention time calibration mixture. The reduction of hydrophobicity of multiple peptide backbones was observed due to the hydrophilic glycan structures. By comparing the hydrophobicity index of glycopeptides collected from different time and instruments, the day-to-day and lab-to-lab comparisons suggested high reliability and reproducibility of this approach. The RSD% of hydrophobicity index from inter-lab experiments was 1.2%, while the RSD% of retention time was 5.1%. Then, the applications of this method were demonstrated on complex glycopeptide samples extracted from human blood serum. The hydrophobicity index can be applied to address the retention time shift when using different instruments, thereby boosting confidence of the characterization of glycopeptides.

Characterization of Oxidized Glycerophosphoethanolamines via Radical-Directed Dissociation Tandem Mass Spectrometry and the Paternò-Büchi Derivatization.

Oxidized glycerophosphoethanolamines (oxPEs) represent a subclass of bioactive lipids that have intricate roles in various physiological and pathological events. Conventional mass spectrometric methods cannot provide unambiguous information to locate the OH group and the sites of unsaturation. Herein, we report a combined strategy for in-depth structural characterization of oxPEs, including radical-directed dissociation tandem mass spectrometry (RDD-MS/MS) for localizing the OH group and the Paternò-Büchi derivatization coupled with tandem mass spectrometry for pinpointing carbon-carbon double-bond locations. The RDD-MS/MS method has been integrated on a reversed-phase liquid chromatography-mass spectrometry workflow. It enables the profiling of 24 distinct oxPE molecules with unequivocal assignment of the OH sites at nM sensitivity in bovine liver lipid extract treated by soybean 15-lipoxygenase. These findings showcase that the developed method has a good potential in analyzing biological systems where oxPEs may play important roles.

Liquid chromatography separation and identification of new oxidative degradation impurity in edoxaban tosylate hydrate drug substance by using liquid chromatography with tandem mass spectrometry.

Edoxaban is an anti-coagulant medication and a director factor Xa inhibitor. A novel reverse phase liquid chromatography-mass spectrometry compatible method developed for separation and identification of new oxidative degradation impurities in edoxaban tosylate hydrate drug substance. The separation of three oxidative degradation impurities was achieved by using YMC Triart phenyl (250 × 4.6) mm, 5 µm column with mobile phase containing gradient elution of mobile phase-A as 10 mM ammonium acetate and mobile phase-B as acetonitrile:methanol (1:1)% (v/v). The flow rate of the mobile phase is 0.7 mL/min with a column temperature of 40 °C and detection wavelength of 290 nm. Edoxaban tosylate hydrate shows significant degradation in oxidative stress conditions and forms three oxidative degradation products. The degradation products were identified and characterized by using a high-resolution mass spectrometry quadrupole-time of flight mass detector. The three oxidative degradation impurities of Edoxaban drug substance were well resolved with each other and along with Edoxaban drug substance peak. Among the three oxidative degradation impurities di-N-oxide impurity was the new oxidative degradation impurity identified for the first time and a novel reverse-phase high-performance liquid chromatography method was developed for separation of the three oxidative degradation impurities.

Exploring the Metabolic Differences between Cisplatin- and UV Light-Induced Apoptotic Bodies in HK-2 Cells by an Untargeted Metabolomics Approach.

Among the extracellular vesicles, apoptotic bodies (ABs) are only formed during the apoptosis and perform a relevant role in the pathogenesis of different diseases. Recently, it has been demonstrated that ABs from human renal proximal tubular HK-2 cells, either induced by cisplatin or by UV light, can lead to further apoptotic death in naïve HK-2 cells. Thus, the aim of this work was to carry out a non-targeted metabolomic approach to study if the apoptotic stimulus (cisplatin or UV light) affects in a different way the metabolites involved in the propagation of apoptosis. Both ABs and their extracellular fluid were analyzed using a reverse-phase liquid chromatography-mass spectrometry setup. Principal components analysis showed a tight clustering of each experimental group and partial least square discriminant analysis was used to assess the metabolic differences existing between these groups. Considering the variable importance in the projection values, molecular features were selected and some of them could be identified either unequivocally or tentatively. The resulting pathways indicated that there are significant, stimulus-specific differences in metabolites abundancies that may propagate apoptosis to healthy proximal tubular cells; thus, we hypothesize that the share in apoptosis of these metabolites might vary depending on the apoptotic stimulus.