Comprehensive peptide marker identification for the detection of multiple nut allergens using a non-targeted LC-HRMS multi-method

Food allergies have emerged as a global problem over the last few decades; therefore, reliable and sensitive analytical methods to ensure food safety for allergic consumers are required. The application of mass spectrometry is of growing interest in this field and several procedures based on low resolution tandem mass spectrometry using single tryptic peptides as analytical targets have recently been described. However, a comprehensive survey of marker peptides for the development of multi-methods is still missing, as is a consensus guide to marker identification. In this study, we therefore report a consistent approach to the development of liquid chromatography-mass spectrometry (LC-MS) multi-screening methods for the detection of allergens in food matrices. Proteotypic peptides were identified by a shotgun proteomics approach and verified through a thorough investigation of specificity and sensitivity. On the basis of this procedure, we identified 44 suitable tryptic marker peptides from six allergenic nut species and developed the first analytical LC-MS method for the detection of trace nut contaminations in processed foods using high resolution mass spectrometry (HRMS). The analysis of spiked matrix samples gave limits of detection (LODs) below 10 μg/g for several nuts; these LODs are comparable with routinely used methods such as ELISA and PCR. Notably, the HRMS approach can be used in an untargeted fashion to identify multiple allergens also retrospectively. In conclusion, we present here the so far largest consensus set of analytical markers from nut allergens and to the best of our knowledge the first multi-allergen method based on LC-HRMS.

Targeted and non-targeted detection of lemon juice adulteration by LC-MS and chemometrics

Economically motivated adulteration (EMA) of lemon juice was detected by LC-MS and principal component analysis (PCA). Twenty-two batches of freshly squeezed lemon juice were adulterated by adding an aqueous solution containing 5% citric acid and 6% sucrose to pure lemon juice to obtain 30%, 60% and 100% lemon juice samples. Their total titratable acidities, °Brix and pH values were measured, and then all the lemon juice samples were subject to LC-MS analysis. Concentrations of hesperidin and eriocitrin, major phenolic components of lemon juice, were quantified. The PCA score plots for LC-MS datasets were used to preview the classification of pure and adulterated lemon juice samples. Results showed a large inherent variability in the chemical properties among 22 batches of 100% lemon juice samples. Measurement or quantitation of one or several chemical properties (targeted detection) was not effective in detecting lemon juice adulteration. However, by using the LC-MS datasets, including both chromatographic and mass spectrometric information, 100% lemon juice samples were successfully differentiated from adulterated samples containing 30% lemon juice in the PCA score plot. LC-MS coupled with chemometric analysis can be a complement to existing methods for detecting juice adulteration.

New Approach for Differentiating Sessile and Pedunculate Oak: Development of a LC-HRMS Method To Quantitate Triterpenoids in Wood

Oak aging is a crucial step in winemaking during which the organoleptic properties of wine are modified. Various parameters affect the chemical composition of oak wood including botanical origin, which has been previously shown to be a determinant factor. This study focused on the development of a LC-HRMS method to assay four recently discovered taste-active triterpenes (three sweet and one bitter). The method was applied to evaluate the effect of oak species (Quercus petraea and Quercus robur) on the concentration of these molecules in wood. The results showed that sessile oak was richer in sweet triterpenes and poorer in the bitter one than pedunculate oak, with high interindividual variations within species. Furthermore, a triterpenoid index was calculated to reveal the triterpenoid composition of oak wood. This index appears to be a promising tool for the unambiguous discrimination of oak species and could offer new insights into oak wood selection by coopers and the monitoring of oak aging by winemakers.

Fully automated semi-quantitative toxicological screening in three biological matrices using turbulent flow chromatography/high resolution mass spectrometry

BACKGROUND

In clinical and forensic toxicology, fast and specific methods are needed for the screening of different classes of drugs. A complete general unknown screening procedure was developed using turbulent flow chromatography with electrospray ionization and Orbitrap mass spectrometry.

METHODS

After protein precipitation, samples were injected directly into the turbulent flow chromatographic system and analyzed with an Orbitrap mass spectrometer. The Exactive® operated in positive and negative modes with alternated high collision dissociation in order to obtain characteristic fragments. We built a library containing 616 compounds by analyzing a reference standard for all the molecules.

RESULTS

Identification was based on retention time, accurate measured mass, isotopic pattern and presence of specific fragments. For each substance, we set a calibration range encompassing infra-therapeutic, therapeutic, supra-therapeutic and toxic concentrations in order to generate semi-quantitative result. For 65% of the components, the limit of detection was below 5 ng/mL. The validation process showed the approach to be selective, sensitive, accurate and precise.

CONCLUSION

The method has been accredited by COFRAC (French Accreditation Committee) according to the ISO 15189 standard. Applicability was successfully tested by analyzing authentic serum, urine and whole blood samples.

Fourier Transform Mass Spectrometry: The Transformation of Modern Environmental Analyses

Unknown compounds in environmental samples are difficult to identify using standard mass spectrometric methods. Fourier transform mass spectrometry (FTMS) has revolutionized how environmental analyses are performed. With its unsurpassed mass accuracy, high resolution and sensitivity, researchers now have a tool for difficult and complex environmental analyses. Two features of FTMS are responsible for changing the face of how complex analyses are accomplished. First is the ability to quickly and with high mass accuracy determine the presence of unknown chemical residues in samples. For years, the field has been limited by mass spectrometric methods that were based on knowing what compounds of interest were. Secondly, by utilizing the high resolution capabilities coupled with the low detection limits of FTMS, analysts also could dilute the sample sufficiently to minimize the ionization changes from varied matrices.

High-Resolution Mass Spectrometry for Untargeted Drug Screening

While gas chromatography-mass spectrometry (GC/MS) continues to be the forensic standard for toxicology, liquid chromatography coupled to tandem MS offers significant operational advantages for targeted confirmatory analysis. LC-high-resolution (HR)-MS has recently been available that offers advantages for untargeted analysis. HR-MS analyzers include the Orbitrap and time-of-flight MS. These instruments are capable of detecting 1 ppm mass resolution. Following soft ionization, this enables the assignment of exact molecular formula, limiting the number of candidate compounds. With this technique, presumptive identification of unknowns can be conducted without the need to match MS library spectra or comparison against known standards. For clinical toxicology, this can greatly expand on the number of drugs and metabolites that can be detected and reported on a presumptive basis. Definitive assignments of the compound's identity can be retrospectively determined with acquisition of the appropriate reference standard.

Neutral Loss Ion Mapping Experiment Combined with Precursor Mass List and Dynamic Exclusion for Screening Unstable Malonyl Glucoside Conjugates

Malonates are one type of the acylation conjugates and found abundantly in ginseng and soybean. Malonyl conjugates of ginsenosides and isoflavone glycosides were often considered as the characteristic components to evaluate various species and different forms of ginseng and soybean products because of their thermal instability. Another famous isoflavonoid-rich leguminous traditional Chinese medicine (TCM), named Puerarin lobata (Gegen), has also been reported to contain malonyl daidzin and malonyl genistin. However, the conjugates were found to present in very low amount and particularly unstable in the negative ion mode scan using LTQ Orbitrap mass spectrometry with electrospray ionization (ESI). In order to screen and characterize the malonyl conjugates in Gegen, a specific method was designed and developed combining neutral loss ion mapping (NLIM) experiment and precursor mass list (PL) triggered data dependent acquisition (DDA). Along with the activation of dynamic exclusion (DE), the method was proven to be specific and efficient for searching the malonate derivatives from Gegen. Two samples were examined by the established method. A total of 66 compounds were found, and 43 of them were malonates of isoflavone glycoside. Very few compounds were reported previously in Gegen. The results are helpful to understand the constituents of Gegen with more insight. The study not only provided a method for analyzing the malonyl conjugates from complex matrices but also explored a way to trace other low amount components in TCMs.

Negative ion electrospray high-resolution tandem mass spectrometry of polyphenols

Representative compounds with a 1,3-dihydroxybenzene substructure belonging to different important polyphenol classes (stilbenes, flavones, isoflavones, flavonols, flavanones, flavanols, phloroglucinols, anthraquinones and bisanthraquinones) were investigated based on detailed high-resolution tandem mass spectrometry measurements with an Orbitrap system under negative ion electrospray conditions. The mass spectral behaviour of these compound classes was compared among each other not only with respect to previously described losses of CO, CH2 CO and C3 O2 but also concerning the loss of CO2 and successive specific fragmentations. Furthermore, some unusual fragmentations such as the loss of a methyl radical during mass spectral decomposition are discussed. The obtained results demonstrate both similarities and differences in their mass spectral fragmentation under MS(n) conditions, allowing a characterization of the corresponding compound type. Copyright © 2015 John Wiley & Sons, Ltd.

Top-Down Mass Spectrometry: Proteomics to Proteoforms

This chapter highlights many of the fundamental concepts and technologies in the field of top-down mass spectrometry (TDMS), and provides numerous examples of contributions that TD is making in biology, biophysics, and clinical investigations. TD workflows include variegated steps that may include non-specific or targeted preparative strategies, orthogonal liquid chromatography techniques, analyte ionization, mass analysis, tandem mass spectrometry (MS/MS) and informatics procedures. This diversity of experimental designs has evolved to manage the large dynamic range of protein expression and diverse physiochemical properties of proteins in proteome investigations, tackle proteoform microheterogeneity, as well as determine structure and composition of gas-phase proteins and protein assemblies.

Identification of urinary proteins potentially associated with diabetic kidney disease

Diabetic nephropathy (DN) is the most common cause of chronic kidney disease. Although several parameters are used to evaluate renal damage, in many instances, there is no pathological change until damage is already advanced. Mass spectrometry-based proteomics is a novel tool to identify newer diagnostic markers. To identify urinary proteins associated with renal complications in diabetes, we collected urine samples from 10 type 2 diabetes patients each with normoalbuminuria, micro- and macro-albuminuria and compared their urinary proteome with that of 10 healthy individuals. Urinary proteins were concentrated, depleted of albumin and five other abundant plasma proteins and in-gel trypsin digested after prefractionation on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The peptides were analyzed using a nanoflow reverse phase liquid chromatography system coupled to linear trap quadrupole-Orbitrap mass spectrometer. We identified large number of proteins in each group, of which many were exclusively present in individual patient groups. A total of 53 proteins were common in all patients but were absent in the controls. The majority of the proteins were functionally binding, biologically involved in metabolic processes, and showed enrichment of alternative complement and blood coagulation pathways. In addition to identifying reported proteins such as α2-HS-glycoprotein and Vitamin D binding protein, we detected novel proteins such as CD59, extracellular matrix protein 1 (ECM1), factor H, and myoglobin in the urine of macroalbuminuria patients. ECM1 and factor H are known to influence mesangial cell proliferation, and CD59 causes microvascular damage by influencing membrane attack complex deposition, suggestive their biological relevance to DN. Thus, we have developed a proteome database where various proteins exclusively present in the patients may be further investigated for their role as stage-specific markers and possible therapeutic targets.

Ion-molecule adduct formation in tandem mass spectrometry

Nowadays most LC-MS methods rely on tandem mass spectrometry not only for quantitation and confirmation of compounds by multiple reaction monitoring (MRM), but also for the identification of unknowns from their product ion spectra. However, gas-phase reactions between charged and neutral species inside the mass analyzer can occur, yielding product ions at m/z values higher than that of the precursor ion, or at m/z values difficult to explain by logical losses, which complicate mass spectral interpretation. In this work, the formation of adduct ions in the mass analyzer was studied using several mass spectrometers with different mass analyzers (ion trap, triple quadrupole, and quadrupole-Orbitrap). Heterocyclic amines (AαC, MeAαC, Trp-P-1, and Trp-P-2), photo-initiators (BP and THBP), and pharmaceuticals (phenacetin and levamisole) were selected as model compounds and infused in LCQ Classic, TSQ Quantum Ultra AM, and Q-Exactive Orbitrap (ThermoFisher Scientific) mass spectrometers using electrospray as ionization method. The generation of ion-molecule adducts depended on the compound and also on the instrument employed. Adducts with neutral organic solvents (methanol and acetonitrile) were only observed in the ion trap instrument (LCQ Classic), because of the ionization source on-axis configuration and the lack of gas-phase barriers, which allowed inertial entrance of the neutrals into the analyzer. Adduct formation (only with water) in the triple quadrupole instruments was less abundant than in the ion trap and quadrupole-Orbitrap mass spectrometers, because of the lower residence time of the reactive product ions in the mass analyzer. The moisture level of the CID and/or damper gas had a great effect in beam-like mass analyzers such as triple quadrupole, but not in trap-like mass analyzers, probably because of the long residence time that allowed adduct formation even with very low concentrations of water inside the mass spectrometer.

Erythrina excelsa exhibits estrogenic effects in vivo and in vitro and is cytotoxic on breast and colon cancer cell lines

CONTEXT

Eythrina excelsa Baker (Fabaceae) is a medicinal plant used to treat various ailments including those of the female genital tract.

OBJECTIVE

The objective of this study is to investigate the estrogenic and cytotoxic effects of the ethanol extract of the stem bark of E. excelsa.

MATERIALS AND METHODS

Erythrina excelsa was evaluated in vitro using the yeast estrogen screen (YES). The extract was then tested in a 3-day uterotrophic assay on ovariectomised Wistar rats at doses of 50 and 100 mg/kg BW/d. Cytotoxic effects were assessed on breast (MCF-7) and colon (HT-29) cancer cell lines using the MTT cell viability assay. Additionally, a LC-PDA-ESI (+)-HRMS and HRMS/MS method was developed and applied for the identification of representative secondary metabolites scaffolds in the extract.

RESULTS

In the YES, the extract stimulated the transactivation of the estrogen receptor in a dose-dependent manner with an EC50 value of 1.8 μg/mL. In rats, E. excelsa increased uterine wet weight, uterine epithelial height, and the mRNA expression of estrogen-responsive genes in the uterus and liver at 50 whereas at 100 mg/kg BW/d anti-estrogenic effects were observed. In the MTT-assay, a dose-dependent decrease of the viability of both cell lines was observed with EC50 values of 13.6 μg/mL (MCF-7) and 27.7 μg/mL (HT-29). The phytochemical analysis revealed that the extract is rich in isoflavonoids, mainly prenylated and pyran-derivatives thereof.

CONCLUSION

Erythrina excelsa is rich in prenylated and pyran-substituted isoflavonoids, exhibits estrogenic/anti-estrogenic and cytotoxic effects and warrant sufficient interest for deeper investigations.

Degradation of the anticancer drug erlotinib during water chlorination: Non-targeted approach for the identification of transformation products

Erlotinib is a highly potent tyrosine kinase inhibitor used in the treatment of the most common type of lung cancer. Due to its recent introduction, very scarce information is available on its occurrence, environmental fate and toxicological effects on aquatic organisms. During chlorination processes normally carried out in wastewater treatment plants and in the pretreatment of hospital effluents, chlorinated transformation products can be formed with an enhanced toxicity relative to the parent compound. Thus, the reactivity of the cytostatic drug erlotinib in free chlorine-containing water was investigated for the first time in the present work. A non-targeted screening approach based on the use of differential profiling tools was applied in order to reveal its potential transformation products. Structural elucidation of the detected transformation products was performed by ultra-performance liquid chromatography coupled to high-resolution hybrid quadrupole-Orbitrap tandem mass spectrometry. The proposed approach allowed detecting a total of nineteen transformation products, being eighteen of them described for the first time in this work, which demonstrates its potential in environmental analysis. Among them, six compounds presented chlorine atoms in their structures, which may be of major concern. Other transformation products involved hydroxylation and oxidation reactions. Time-course profiles of erlotinib and its transformation products were followed in real wastewater samples under conditions that simulate wastewater disinfection. Although the structures of these transformation products could not be positively confirmed due to lack of standards, their chemical formulas and product ions can be added to databases, which will allow their screening in future monitoring studies.

Transformation of tamoxifen and its major metabolites during water chlorination: Identification and in silico toxicity assessment of their disinfection byproducts

The selective estrogen receptor modulator tamoxifen is the most commonly used drug for the treatment and prevention of breast cancer. Tamoxifen is considered as a pro-drug since it is known to exert its pharmacological effect through its major active metabolites, 4-hydroxy-tamoxifen and 4-hydroxy-N-desmethyl-tamoxifen, which are mainly excreted in the urine in the days following administration. In the present work, the reactivity of tamoxifen and its major active metabolites in free chlorine-containing water was investigated for the first time. Under the studied chlorination conditions, tamoxifen was fairly stable whereas its metabolites were quickly degraded. A total of thirteen chlorinated byproducts were tentatively identified by ultra-high performance liquid chromatography coupled to high-resolution hybrid quadrupole-Orbitrap tandem mass spectrometry. Time-course profiles of the identified byproducts were followed in real wastewater samples under conditions that simulate wastewater disinfection. A preliminary assessment of their acute aquatic toxicity at two trophic levels by means of quantitative structure-activity relationship models showed that the identified byproducts were up to 110-fold more toxic than the parent compounds.

Quantitative LC-MS determination of liposomal encapsulated prednisolone phosphate and non-encapsulated prednisolone concentrations in murine whole blood and liver tissue

The underlying pharmacokinetic profile of liposomal drug delivery systems is not yet fully known. This is primarily due to a lack of suitable quantitative bioanalytical methodology to simultaneously determine separate liposomal-encapsulated and non-encapsulated drug tissue concentrations in complex biological samples. Here, an LC-MS method was developed which enables the simultaneous quantification of separate liposomal-encapsulated prednisolone phosphate and non-encapsulated prednisolone concentrations in whole blood and liver tissue. Liquid chromatography, negative electrospray ionization and Orbitrap-MS analysis allowed highly accurate and sensitive detection of prednisolone phosphate (PP) and prednisolone (P) in complex matrix. Using dexamethasone phosphate and dexamethasone as internal standards, the quantitative LC-MS method was optimized and validated for high selectivity, sensitivity and quantitative accuracy of PP and P from liposomes. The lower limits of quantitation were 0.99μmol/L blood and 0.53nmol/g liver for PP, and 229nmol/L blood and 0.514nmol/g liver for P. Quantitative accuracies of 84-118% were observed. The intra-run precision was ≤11%. Application of this new LC-MS method will yield the first liposomal pharmacokinetic profile showing accurate encapsulated and non-encapsulated drug tissue concentrations separately. This is also the first quantitative LC-MS method for the simultaneous quantification of the prodrug PP and its parent drug P in whole blood and liver tissue samples.

A calibration routine for efficient ETD in large-scale proteomics

Electron transfer dissociation (ETD) has been broadly adopted and is now available on a variety of commercial mass spectrometers. Unlike collisional activation techniques, optimal performance of ETD requires considerable user knowledge and input. ETD reaction duration is one key parameter that can greatly influence spectral quality and overall experiment outcome. We describe a calibration routine that determines the correct number of reagent anions necessary to reach a defined ETD reaction rate. Implementation of this automated calibration routine on two hybrid Orbitrap platforms illustrate considerable advantages, namely, increased product ion yield with concomitant reduction in scan rates netting up to 75% more unique peptide identifications in a shotgun experiment. Graphical Abstract ᅟ.

Application to the Danube river basin on the Romanian territory

The occurrence of 67 pharmaceutical and antifungal residues in the Danube river on the Romanian territory was studied by using solid-phase extraction (SPE) and LC-Q Exactive Orbitrap high resolution MS in both full scan (FS) MS and targeted MS/MS modes. A single-laboratory validation procedure was carried out for the determination of 67 compounds in FSMS mode evaluating selectivity, sensitivity, linearity, precision and accuracy. The method showed satisfactory analytical performance. The evaluation of the recovery concluded that 75% of the compounds show recoveries between 85 and 115% and 10% of the compounds show recoveries between 85% and 65%. The level of detection was lower than 5 ng l(-1) for 66% of the compounds, between 5 and 10 ng l(-1) for 22% and between 10 and 25 ng l(-1) for 14% of the compounds. The coefficients of determination R(2) were higher than 0.99 for 79% of the compounds, over a linearity range of 2.5-50 ng l(-1). Targeted MS/MS analysis, performed in addition to the full scan acquisition was used for confirmatory purpose. Twenty samples of Danube water and three of the main tributaries were collected in May, July, August and October 2014. Analysis of the selected water samples revealed the occurrence of 23 compounds such as diclofenac, carbamazepine, sulfamethoxazole, tylosin, indomethacin, ketoprofen, piroxicam, together with antifungals like thiabendazole, and carbendazim. Carbamazepine was detected in 17 samples, the maximum concentration being 40 ng l(-1). The highest concentration reached was 166 ng l(-1) for diclofenac.

Use of 'dilute-and-shoot' liquid chromatography-high resolution mass spectrometry in preclinical research: application to a DMPK study of perhexiline in mouse plasma

This work describes a simple, sensitive and rapid liquid chromatography-high resolution mass spectrometry method for the quantitation of perhexiline and the simultaneous detection of perhexiline metabolites in C57bl/6 mice plasma. Only 5 μL of plasma was used for analysis. Pretreatment was limited to a 100-fold dilution ('dilute-and-shoot'). The analyte was detected by high resolution mass spectrometry (Orbitrap™ technology). Three scan events were performed over the entire chromatogram. Targeted single ion monitoring with data dependent acquisition was employed for perhexiline quantitation and confirmation, while full scan was used to perform untargeted detection of perhexiline phase I and phase II circulating metabolites. The calibration curve was linear (r(2)=0.990) ranging from 0.305 ng/mL (LLOQ) to 10000 ng/mL. Matrix effect was limited to 6.1%. The method was applied to a pharmacokinetic study of perhexiline in mouse plasma and the results obtained were compared to a standard sample preparation method based on protein precipitation and liquid chromatography-tandem mass spectrometry (MRM mode) detection. The new approach provided comparable results in terms of pharmacokinetics parameters estimate with a high sensitivity, additional information on perhexiline circulating metabolites and a low consumption of biological sample. The combination of the 'dilute-and-shoot' approach together with HRMS targeted and untargeted detection represents a suitable alternative to classic bioanalytical approaches in preclinical research.

Paper-Based Electrochemical Cell Coupled to Mass Spectrometry

On-line coupling of electrochemistry (EC) to mass spectrometry (MS) is a powerful approach for identifying intermediates and products of EC reactions in situ. In addition, EC transformations have been used to increase ionization efficiency and derivatize analytes prior to MS, improving sensitivity and chemical specificity. Recently, there has been significant interest in developing paper-based electroanalytical devices as they offer convenience, low cost, versatility, and simplicity. This report describes the development of tubular and planar paper-based electrochemical cells (P-EC) coupled to sonic spray ionization (SSI) mass spectrometry (P-EC/SSI-MS). The EC cells are composed of paper sandwiched between two mesh stainless steel electrodes. Analytes and reagents can be added directly to the paper substrate along with electrolyte, or delivered via the SSI microdroplet spray. The EC cells are decoupled from the SSI source, allowing independent control of electrical and chemical parameters. We utilized P-EC/SSI-MS to characterize various EC reactions such as oxidations of cysteine, dopamine, polycyclic aromatic hydrocarbons, and diphenyl sulfide. Our results show that P-EC/SSI-MS has the ability to increase ionization efficiency, to perform online EC transformations, and to capture intermediates of EC reactions with a response time on the order of hundreds of milliseconds. The short response time allowed detection of a deprotonated diphenyl sulfide intermediate, which experimentally confirms a previously proposed mechanism for EC oxidation of diphenyl sulfide to pseudodimer sulfonium ion. This report introduces paper-based EC/MS via development of two device configurations (tubular and planar electrodes), as well as discusses the capabilities, performance, and limitations of the technique.

A strategy for fast screening and identification of sulfur derivatives in medicinal Pueraria species based on the fine isotopic pattern filtering method using ultra-high-resolution mass spectrometry

Sulfurous compounds are commonly present in plants, fungi, and animals. Most of them were reported to possess various bioactivities. Isotopic pattern filter (IPF) is a powerful tool for screening compounds with distinct isotope pattern. Over the past decades, the IPF was used mainly to study Cl- and Br-containing compounds. To our knowledge, the algorithm was scarcely used to screen S-containing compounds, especially when combined with chromatography analyses, because the (34)S isotopic ion is drastically affected by (13)C2 and (18)O. Thus, we present a new method for a fine isotopic pattern filter (FIPF) based on the separated M + 2 ions ((12)C(x)(1)H(y)(16)O(z)(32)S(13)C2(18)O, (12)C(x+2)(1)H(y)(16)O(z+1)(34)S, tentatively named M + 2OC and M + 2S) with an ultra-high-resolution mass (100,000 FWHM @ 400 m/z) to screen sulfur derivatives in traditional Chinese medicines (TCM).This finer algorithm operates through convenient filters, including an accurate mass shift of M + 2OC and M + 2S from M and their relative intensity compared to M. The method was validated at various mass resolutions, mass accuracies, and screening thresholds of flexible elemental compositions. Using the established FIPF method, twelve S-derivatives were found in the popular medicinal used Pueraria species, and 9 of them were tentatively identified by high-resolution multiple stage mass spectrometry (HRMS(n)). The compounds were used to evaluate the sulfurous compounds' situation in commercially purchased Pueraria products. The strategy presented here provides a promising application of the IPF method in a new field.

High-abundant protein depletion strategies applied on dog cerebrospinal fluid and evaluated by high-resolution mass spectrometry

As the number of fully sequenced animal genomes and the performance of advanced mass spectrometry-based proteomics techniques are continuously improving, there is now a great opportunity to increase the knowledge of various animal proteomes. This research area is further stimulated by a growing interest from veterinary medicine and the pharmaceutical industry. Cerebrospinal fluid (CSF) is a good source for better understanding of diseases related to the central nervous system, both in humans and other animals.

In this study, four high-abundant protein depletion columns, developed for human or rat serum, were evaluated for dog CSF. For the analysis, a shotgun proteomics approach, based on nanoLC-LTQ Orbitrap MS/MS, was applied. All the selected approaches were shown to deplete dog CSF with different success. It was demonstrated that the columns significantly improved the coverage of the detected dog CSF proteome. An antibody-based column showed the best performance, in terms of efficiency, repeatability and the number of proteins detected in the sample. In total 983 proteins were detected. Of those, 801 proteins were stated as uncharacterized in the UniProt database. To the best of our knowledge, this is the so far largest number of proteins reported for dog CSF in one single study.

We evaluated four high-abundant protein depletion kits on dog CSF.

High abundant depletion kit developed for humans/rats can be used for dog CSF.

Protein depletion of dog CSF gives extended coverage of the CSF proteome.

In total, 983 dog proteins were identified in this study.

Application of single-stage Orbitrap mass spectrometry and differential analysis software to nontargeted analysis of contaminants in dog food: detection, identification, and quantification of glycoalkaloids

The objective of this study was to perform a preliminary investigation of the nontargeted search and quantitative capabilities of a single-stage Exactive High-Resolution Mass Spectrometer (HRMS). To do this, the instrument and its associated software performed a non-targeted search for deleterious substances in a dog food sample suspected of causing gastrointestinal problems in dogs. A single-stage Orbitrap/high-performance liquid chromatography method and differential expression analysis software (Sieve) was used to detect and identify, and subsequently quantify, nontargeted compounds occurring only in the suspect dog food sample. When combined with an online database (ChemSpider), a preliminary identification of one of the nontargeted compounds was determined to be potato glycoalkaloids. The diagnostic product ion ratios and quantitative data accuracy generated by the single-stage Orbitrap MS were shown to be similar to results obtained using a triple quadrupole LC-MS/MS. Additionally, the ability of the single-stage Orbitrap instrument to provide precursor and product ion accurate masses and isotope patterns was also investigated.

Development of a quantitative method for the simultaneous analysis of the boar taint compounds androstenone, skatole and indole in porcine serum and plasma by means of ultra-high performance liquid chromatography coupled to high resolution mass spectrometry

Boar taint is an off-odour occurring while heating meat or fat from boars. A method detecting the three compounds (androstenone, skatole and indole) simultaneously in blood would offer substantial advantages since it would allow monitoring the impact of rearing strategies. Therefore, a UHPLC-HR-Orbitrap-MS analysis method is optimized and validated for the quantification of these compounds in plasma or serum. Sample pre-treatment involved an extraction with diethylether followed by a centrifugal filtration (30 kDa). Limits of detection and quantification varied between 0.5 and 1 μg L(-1) and 2 and 3 μg L(-1) for the three compounds, respectively. Besides, an excellent repeatability (RSD < 7.6%), within-laboratory reproducibility (RSD<10.5%), recovery (87-97%) and linearity (R(2)>0.99) were recorded. Correlations between serum/plasma and fat levels of the boar taint compounds were positive for skatole (r(serum) = 0.39 and r(plasma) = 0.84) and androstenone (r(serum) = 0.73-0.78 and r(plasma) = 0.32-0.80).

Accurate and reliable quantification of 25-hydroxy-vitamin D species by liquid chromatography high-resolution tandem mass spectrometry

In general, mass spectrometric quantification of small molecules in routine laboratory testing utilizes liquid chromatography coupled to low mass resolution triple-quadrupole mass spectrometers (QQQs). Here we introduce high-resolution tandem mass spectrometry (quadrupole-Orbitrap) for the quantification of 25-hydroxy-vitamin D [25(OH)D], a marker of the vitamin D status, because the specificity of 25(OH)D immunoassays is still questionable and mass spectrometric quantification is becoming increasingly important. Liquid chromatography coupled to high-resolution tandem mass spectrometry (LC-MS/HR-MS) was used to quantify 25-hydroxy-cholecalciferol [25(OH)D3], 25-hydroxy-ergocalciferol [25(OH)D2], and their C3-epimers 3-epi-25(OH)D3 and 3-epi-25(OH)D2. The method has a run time of 5 min and was validated according to the US Food and Drug Administration and the European Medicines Agency guidelines. High mass resolution was advantageously applied to separate a quasi-isobaric interference of the internal standard D6-25(OH)D2 with 3-epi-25(OH)D3. All analytes showed an imprecision of below 10% coefficient of variation (CV), trueness between 90% and 110%, and limits of quantification below 10 nM. Concentrations measured by LC-MS/HR-MS are in good agreement with those of the National Institute of Standards and Technology reference methods using LC-MS/MS (QQQ). In conclusion, quantification of 25(OH)D by LC-MS/HR-MS is applicable for routine testing and also holds promise for highly specific quantification of other small molecules.

Analysis of veterinary drug and pesticide residues in animal feed by high-resolution mass spectrometry: comparison between time-of-flight and Orbitrap

The use of medium-high-resolution mass spectrometers (M-HRMS) provides many advantages in multi-residue analysis. A comparison between two mass spectrometers, medium-resolution (MRMS) time-of-flight (TOF) and high-resolution (HRMS) Orbitrap, has been carried out for the analysis of toxic compounds in animal feed. More than 300 compounds belonging to several classes of veterinary drugs (VDs) and pesticides have been determined in different animal feed samples using a generic extraction method. The use of a clean-up procedure has been evaluated in both instruments, and several validation parameters have been established, such as the matrix effect, linearity, recovery and sensitivity. Finally, both instruments have been used during the analysis of 18 different feed samples (including chicken, hen, rabbit and horse). Some VDs (sulfadiazine, trimethoprim, robenidine and monensin sodium) and one pesticide (chlorpyrifos) have been identified. In general, better results were obtained using the Orbitrap, such as sensitivity (1-12.5 µg kg(-1)) and recovery values (60-125%). Moreover, this analyser had several software tools, which reduced the time for data processing and were easy to use, performing quick screening for more than 450 compounds in less than 5 min. However, some disadvantages such as the high cost and a decrease in the number of detected compounds at low concentrations must be taken into account.

Ion tree-based structure elucidation of acetophenone dimers (AtA) from Acronychia pedunculata and their identification in extracts by liquid chromatography electrospray ionization LTQ-Orbitrap mass spectrometry

Acronychia-type acetophenones (AtA) is a chemical group of compounds of important structural and biological interest, abundant in Acronychia species. However, there are no data available for their characterization using mass spectrometry. In the current work, AtA have been investigated by multistage high resolution mass spectrometry and both electrospray ionization and atmospheric pressure chemical ionization, in positive and negative mode, were utilized for their structure elucidation and identification. The analysis of AtA using a linear ion trap-Orbitrap analyzer enabled the structural determination of key fragment ions and cleavages, which can be used for the structural characterization thereof. A systematic nomenclature based on protonated and deprotonated fragment ions under collision-induced dissociation conditions and decision trees for the structural determination of AtA are proposed. Furthermore, taking advantage of the characteristic fragmentation patterns, a selective Ultra High Performance Liquid Chromatography Electrospray Ionization multistage Mass Spectrometry (UHPLC-ESI(-)-MS(n)) method was developed and successfully applied for the dereplication of known AtA and the identification of potentially new ones in Acronychia extracts. Despite the structure similarity and the presence of isomers, accurate characterization of known and unknown AtA derivatives was possible.

Multi-analyte high performance liquid chromatography coupled to high resolution tandem mass spectrometry method for control of pesticide residues, mycotoxins, and pyrrolizidine alkaloids

A new reliable and highly sensitive method based on high performance liquid chromatographic (HPLC) separation and high resolution tandem mass spectrometric detection (HRMS/MS) has been developed and validated for determination of 323 pesticide residues, 55 mycotoxins, and 11 plant toxins represented by pyrrolizidine alkaloids. The method was validated for three matrices, leek, wheat, and tea differing in nature/amount of co-extracts that may cause various matrix effects. For target analytes isolation, optimized QuEChERS-based (quick, easy, cheap, effective, rugged, and safe) extraction procedure was employed. Spectral HRMS/MS library has been established providing an entire spectrum of fragment ions for each analyte, which allows unbiased identification and confirmation of target compounds. The limits of quantification (LOQs) of target analytes were below 10 μg kg(-1) for 82%, 81%, and 61% for matrices leek, wheat, and tea, respectively. Recoveries were in the acceptable range (70-120%) according to SANCO/12571/2013 for most of target analytes, except for highly polar 'masked' mycotoxin deoxynivalenol-3-glucoside with recoveries 35%, 47%, and 42% for matrices leek, wheat, and tea, respectively. The linearities of calibration curves expressed as coefficients of determination were in the range of 0.9661-1.000, and repeatabilities expressed as relative standard deviations (RSDs) at LOQs lied in the range of 0.25-13.51%. The trueness of the method was verified using several certified reference materials (CRMs) and proficiency test samples.

Development of a sensitive method for the determination of acrylamide in coffee using high-performance liquid chromatography coupled to a hybrid quadrupole Orbitrap mass spectrometer

The emerging trend towards high-resolution mass spectrometry (MS) alternatives was evaluated by the application of Orbitrap MS for the determination of acrylamide in coffee samples. The high resolving power of the Orbitrap MS provided the high selectivity and sensitivity that enabled quantitative analysis of acrylamide in complex matrices, such as coffee. Several sample preparation methods and scanning modes of the MS (full MS, t-SIM, t-MS2) were assessed in order to optimise parameters of the analytical method. The final procedure involved the extraction of acrylamide with acetonitrile, solid-phase extraction with dispersive primary secondary amine (PSA) and amino columns, and the detection by ultra-performance liquid chromatography coupled to a hybrid quadrupole-Orbitrap MS (HPLC-Q-Orbitrap) operated in targeted MS2 scanning mode. The repeatability of the method at the lowest calibration level (10 μg kg(-1)), expressed as relative standard deviation, was 7.8% and the average recovery of acrylamide was 111%. The proposed method was applied to the determination of acrylamide in 22 samples of roasted coffee obtained from the Latvian retail market. Acrylamide concentration in coffee samples was in the range of 166-503 μg kg(-1).

Aerobic activated sludge transformation of methotrexate: identification of biotransformation products

This study describes the biotransformation of cytostatic and immunosuppressive pharmaceutical methotrexate. Its susceptibility to microbiological breakdown was studied in a batch biotransformation system, in presence or absence of carbon source and at two activated sludge concentrations. The primary focus of the present study are methotrexate biotransformation products, which were tentatively identified by the ultra-high performance liquid chromatography-quadrupole--Orbitrap-MS. Data-dependent experiments, combining full-scan MS data with product ion spectra were acquired, in order to identify the molecular ions of methotrexate transformation products, to propose the molecular formulae and to elucidate their chemical structures. Among the identified transformation products 2,4-diamino-N10-methyl-pteroic acid is most abundant and persistent. Other biotransformation reactions involve demethylation, oxidative cleavage of amine, cleavage of C-N bond, aldehyde to carboxylate transformation and hydroxylation. Finally, a breakdown pathway is proposed, which shows that most of methotrexate breakdown products retain the diaminopteridine structural segment. In total we propose nine transformation products, among them eight are described as methotrexate transformation products for the first time.

High resolution mass spectrometry based techniques at the crossroads of metabolic pathways

The metabolome is the set of small molecular mass compounds found in biological media, and metabolomics, which refers to as the analysis of metabolome in a given biological condition, deals with the large scale detection and quantification of metabolites in biological media. It is a data driven and multidisciplinary approach combining analytical chemistry for data acquisition, and biostatistics, informatics and biochemistry for mining and interpretation of these data. Since the middle of the 2000s, high resolution mass spectrometry is widely used in metabolomics, mainly because the detection and identification of metabolites are improved compared to low resolution instruments. As the field of HRMS is quickly and permanently evolving, the aim of this work is to review its use in different aspects of metabolomics, including data acquisition, metabolite annotation, identification and quantification. At last, we would like to show that, thanks to their versatility, HRMS instruments are the most appropriate to achieve optimal metabolome coverage, at the border of other omics fields such as lipidomics and glycomics.

Advances in mass spectrometry driven O-glycoproteomics

BACKGROUND

Global analyses of proteins and their modifications by mass spectrometry are essential tools in cell biology and biomedical research. Analyses of glycoproteins represent particular challenges and we are only at the beginnings of the glycoproteomic era. Some of the challenges have been overcome with N-glycoproteins and proteome-wide analysis of N-glycosylation sites is accomplishable today but only by sacrificing information of structures at individual glycosites. More recently advances in analysis of O-glycoproteins have been made and proteome-wide analysis of O-glycosylation sites is becoming available as well.

SCOPE OF REVIEW

Here we discuss the challenges of analysis of O-glycans and new O-glycoproteomics strategies focusing on O-GalNAc and O-Man glycoproteomes.

MAJOR CONCLUSIONS

A variety of strategies are now available for proteome-wide analysis of O-glycosylation sites enabling functional studies. However, further developments are still needed for complete analysis of glycan structures at individual sites for both N- and O-glycoproteomics strategies.

GENERAL SIGNIFICANCE

The advances in O-glycoproteomics have led to identification of new biological functions of O-glycosylation and a new understanding of the importance of where O-glycans are positioned on proteins.

A facile means for the identification of indolic compounds from plant tissues

The bulk of indole-3-acetic acid (IAA) in plants is found in the form of conjugated molecules, yet past research on identifying these compounds has largely relied on methods that were both laborious and inefficient. Using recent advances in analytical instrumentation, we have developed a simple yet powerful liquid chromatography-mass spectrometry (LC-MS)-based method for the facile characterization of the small IAA conjugate profile of plants. The method uses the well-known quinolinium ion (m/z 130.0651) generated in MS processes as a signature with high mass accuracy that can be used to screen plant extracts for indolic compounds, including IAA conjugates. We reinvestigated Glycine max (soybean) for its indoles and found indole-3-acetyl-trytophan (IA-Trp) in addition to the already known indole-3-acetyl-aspartic acid (IA-Asp) and indole-3-acetyl-glutamic acid (IA-Glu) conjugates. Surprisingly, several organic acid conjugates of tryptophan were also discovered, many of which have not been reported in planta before. These compounds may have important physiological roles in tryptophan metabolism, which in turn can affect human nutrition. We also demonstrated the general applicability of this method by identifying indolic compounds in different plant tissues of diverse phylogenetic origins. It involves minimal sample preparation but can work in conjunction with sample enrichment techniques. This method enables quick screening of IAA conjugates in both previously characterized as well as uncharacterized species, and facilitates the identification of indolic compounds in general.

Simultaneous identification, confirmation and quantitation of illegal adulterated antidiabetics in herbal medicines and dietary supplements using high-resolution benchtop quadrupole-Orbitrap mass spectrometry

This paper presents an application of ultrahigh-performance liquid chromatography and quadrupole Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HR MS) for the screening, confirmation and quantification of 11 antidiabetics in herbal medicines and dietary supplements. The mass spectrometer was operated in Full MS/dd-MS(2) (data-dependent MS(2)) mode. The full MS scan acquired data for identification and quantification, and dd-MS(2) scan obtained product ion spectra for confirmation. UHPLC-Q-Orbitrap MS quantification was achieved using matrix-matched standard calibration curves with phenacetin as internal standard. The method validation that included selectivity, sensitivity, calibration curve, accuracy and precision, recovery, matrix effect and stability was evaluated. The response showed good linear relationship with the concentrations of analytes over wide ranges (e.g., 0.0004-1 μg/g for metformin) with all the coefficients of correlation (r(2)) >0.9991. The detection limits (LODs) were in the range of 0.05-0.5 ng/g for different analytes. The recoveries yielded results higher than 74.3% for all compounds. The accuracy was in the range of -6.75 to 3.85%, while the intra- and inter-day precision ranged from 0.048 to 11.5%. Among 63 batches of herbal medicines and 34 batches of dietary supplements samples, 7 batches of dietary supplements were positive, while all the herbal medicines were negative. Overall, the novel UHPLC-Q-Orbitrap has demonstrated great performance for identification, confirmation and quantification of antidiabetics in herbal medicines and dietary supplements, ensuring food safety and public health.

Identification of phase II pharmaceutical metabolites in reclaimed water using high resolution benchtop Orbitrap mass spectrometry

This study described an analytical method for the identification of common phase II pharmaceutical metabolites in reclaimed water using liquid chromatography high resolution Orbitrap mass spectrometry after solid phase extraction (SPE). Orbitrap mass spectrometer was operated at resolution of 70000 in MS mode and 35000 in data-dependent MS/MS mode, without using lock mass. Firstly, parent drugs and their metabolites were tentatively identified based on accurate mass using a mass tolerance of 5 ppm. A detailed examination of the extracted ion chromatograms (XICs) for all potential metabolites revealed the presence of two phase II metabolites of sulfamethoxazole, acetylsulfamethoxazole and sulfamethoxazole glucuronide in reclaimed water. Secondly, the high resolution data-dependent MS/MS spectra of each compound were further investigated using metabolic profiling software. After comparing characteristic ions obtained in MS/MS mode with those predicted by the software and reported in previous studies, the two phase II metabolites were positively identified in reclaimed water. Lastly, the two metabolites were detected and quantified in the reclaimed water samples collected during a period of one month. As a result, averaged concentrations of sulfamethoxazole, acetylsulfamethoxazole and sulfamethoxazole glucuronide were calculated at 2848 ± 1367 ng L(-)(1), 1980 ± 1410 ng L(-)(1), and 2859 ± 1526 ng L(-)(1), respectively. The two metabolites represented 54% of the source of sulfamethoxazole in reclaimed water suggesting the importance of measuring pharmaceutical metabolites in the environment. To our knowledge, this is the first known report of sulfamethoxazole glucuronide surviving intact through wastewater treatment plants and occurring in environmental water samples.

Overcoming challenges and opening new opportunities in glycoproteomics

Glycoproteomics has emerged as a prime area of interest within the field of proteomics because glycoproteins have been shown to function as biomarkers for disease and as promising therapeutic targets. A significant challenge in the study of glycoproteins is the fact that they are expressed in relatively low abundance in cells. In response, various enrichment methods have been developed to improve the detection of glycoproteins. One such method involves their capture via oxidation of their glycan chains and covalent attachment with hydrazide resins which, when catalyzed by PNGase F, release N-linked glycans and convert the glycosite Asn to Asp; this conversion is identifiable with LC/ESI-MS/MS as a corresponding increase of 0.984 Da in molecular weight. The present study builds on this body of work, providing evidence of three additional strategies that improve glycoprotein identification: (1) use of a high resolution mass spectrometer—the Q Exactive MS—which delivers 2–3 times more glycoprotein identifications than a low resolution MS; (2) optimization of instrument settings and database search parameters to reduce misidentification of N-linked glycopeptides to ~1 percent; and (3) labeling glycopeptides with ¹⁸O during PNGase F treatment to locate N-linked glycosites within peptides containing multiple N-linked sequons.

Identification and quantification of the main isoflavones and other phytochemicals in soy based nutraceutical products by liquid chromatography-orbitrap high resolution mass spectrometry

The specific phytochemicals composition of soy nutritional supplements is usually not labelled. Hence, 12 dietary supplements were analyzed in order to detect and identify the main phytochemicals present in these samples, using a database containing 60 compounds. Ultra-high performance liquid chromatography coupled to single-stage Orbitrap high resolution mass spectrometry (UHPLC-Orbitrap-MS) has been used. Two consecutive extractions, using as extraction solvent a mixture of methanol:water (80:20, v/v), were employed, followed by two dilutions (10 or 100 times depending on the concentration of the components in the sample) with a mixture of an aqueous solution of ammonium acetate 30mM:methanol (50:50, v/v). The method was validated, obtaining adequate recovery and precision values. Limits of detection (LODs) and quantification (LOQs) were calculated, ranging from 2 to 150μgL(-1). Isoflavones were the predominant components present in the analyzed supplements with values higher than 93% of the total amount of phytochemicals in all cases. The aglycones (genistein, daidzein, glycitein and biochanin A) as well as their three conjugated forms, β-glucosides (genistin, daizin and glycitin) were detected and quantified, being daidzein the isoflavone detected at higher concentration in 8 out of 12 samples reported, with values ranging from 684 to 35,970mgkg(-1), whereas biochanin A was detected at very low concentrations, ranging from 18 to 50mgkg(-1). Moreover, other phytochemicals as flavones, flavonols, flavanones and phenolic acids were also detected and quantified.

Multiresidue analysis of 22 sulfonamides and their metabolites in animal tissues using quick, easy, cheap, effective, rugged, and safe extraction and high resolution mass spectrometry (hybrid linear ion trap-Orbitrap)

A new high performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS) method was developed for a simultaneous multi-residue analysis of 22 sulfonamides (SAs) and their metabolites in edible animal (pig, beef, sheep and chicken) tissues. Sample preparation was optimized on the basis of the "QuEChERS" protocol. The analytes were identified using their LC retention times and accurate mass; the identification was further confirmed by multi-stage high mass accuracy (<5ppm) mass spectrometry. The performance of the method was evaluated according to the EU guidelines for the validation of screening methods for the analysis of veterinary drugs residues. Acceptable values were obtained for: linearity (R(2)<0.99), limit of detection (LOD, 3-26μg/kg), limit of quantification (LOQ, 11-88μg/kg), accuracy (recovery 88-112%), intra- and inter-day precision 1-14 and 1-17%, respectively, decision limit (CCα) and detection capability (CCβ) around the maximum residue limits (MRL) of SAs (100μg/kg). The method was validated by analysis of a reference material FAPAS-02188 "Pig kidney" with ǀ Z-scoreǀ<0.63. The method was applied to various matrices (kidney, liver, muscle) originated from pig, beef, sheep, and chicken) allowing the simultaneous quantification of target sulfonamides at concentration levels above the MRL/2 and the identification of untargeted compounds such as N(4)-acetyl metabolites using multi-stage high mass accuracy mass spectrometry.

Characterization of green fluorescent proteins by 193 nm ultraviolet photodissociation mass spectrometry

We investigate the utility of 193 nm ultraviolet photodissociation (UVPD) in comparison to CID, higher energy CID (HCD), and electron transfer dissociation (ETD) for top down fragmentation of highly homologous green fluorescent proteins (GFP) in the gas phase. Several GFP variants were constructed via mutation of surface residues to charged moieties, demonstrating different pIs and presenting a challenge for identification by mass spectrometry. Presented is a comparison of fragmentation techniques utilized for top down characterization of four variants with varying levels of surface charge. UVPD consistently resulted in identification of more fragment ions relative to other MS/MS methods, allowing higher confidence identification. In addition to the high number of fragment ions, the sites of fragmentation were more evenly spread throughout the protein backbone, which proved key for localizing the point mutations.

Investigation of urinary excretion of hydroxyethyl starch and dextran by uhplc-hrms in different acquisition modes

Plasma volume expanders (PVEs) such as hydroxyethyl starch (HES) and dextran are misused in sports because they can prevent dehydration and reduce haematocrit values to mask erythropoietin abuse. Endogenous hydrolysis generates multiple HES and dextran oligosaccharides which are excreted in urine. Composition of the urinary metabolic profiles of PVEs varies depending on post-administration time and can have an impact on their detectability. In this work, different mass spectrometry data acquisition modes (full scan with and without in-source collision-induced dissociation) were used to study urinary excretion profiles of HES and dextran, particularly by investigating time-dependent detectability of HES and dextran urinary oligosaccharide metabolites in post-administration samples. In-source fragmentation yielded the best results in terms of limit of detection (LOD) and detection times, whereas detection of HES and dextran metabolites in full scan mode with no in-source fragmentation is related to recent administration (< 24 hours). Urinary excretion studies showed detection windows for HES and dextran respectively of 72 and 48 hours after administration. Dextran concentrations were above the previously proposed threshold of 500 µg · mL(-1) for 12 hours. A "dilute-and-shoot" method for the detection of HES and dextran in human urine by ultra-high-pressure liquid chromatography-electrospray ionization-high resolution Orbitrap™ mass spectrometry was developed for this study. Validation of the method showed an LOD in the range of 10-500 µg · mL(-1) for the most significant HES and dextran metabolites in the different modes. The method allows retrospective data analysis and can be implemented in existing high-resolution mass spectrometry-based doping control screening analysis.

Quantitation of acrylamide in foods by high-resolution mass spectrometry

Acrylamide detection still represents one of the hottest topics in food chemistry. Solid phase cleanup coupled to liquid chromatography separation and tandem mass spectrometry detection along with GC-MS detection are nowadays the gold standard procedure for acrylamide quantitation thanks to high reproducibility, good recovery, and low relative standard deviation. High-resolution mass spectrometry (HRMS) is particularly suitable for the detection of low molecular weight amides, and it can provide some analytical advantages over other MS techniques. In this paper a liquid chromatography (LC) method for acrylamide determination using HRMS detection was developed and compared to LC coupled to tandem mass spectrometry. The procedure applied a simplified extraction, no cleanup steps, and a 4 min chromatography. It proved to be solid and robust with an acrylamide mass accuracy of 0.7 ppm, a limit of detection of 2.65 ppb, and a limit of quantitation of 5 ppb. The method was tested on four acrylamide-containing foods: cookies, French fries, ground coffee, and brewed coffee. Results were perfectly in line with those obtained by LC-MS/MS.

Analytical approaches for size and mass analysis of large protein assemblies

Analysis of the size and mass of nanoparticles, whether they are natural biomacromolecular or synthetic supramolecular assemblies, is an important step in the characterization of such molecular species. In recent years, electrospray ionization (ESI) has emerged as a technology through which particles with masses up to 100 MDa can be ionized and transferred into the gas phase, preparing them for accurate mass analysis. Here we review currently used methodologies, with a clear focus on native mass spectrometry (MS). Additional complementary methodologies are also covered, including ion-mobility analysis, nanomechanical mass sensors, and charge-detection MS. The literature discussed clearly demonstrates the great potential of ESI-based methodologies for the size and mass analysis of nanoparticles, including very large naturally occurring protein assemblies. The analytical approaches discussed are powerful tools in not only structural biology, but also nanotechnology.

Comprehensive identification of walnut polyphenols by liquid chromatography coupled to linear ion trap-Orbitrap mass spectrometry

Epidemiologic studies and clinical trials have demonstrated consistent benefits of walnut consumption on coronary heart disease risk and other chronic diseases. Walnuts (Juglans regia L.) have been described previously as a rich source of polyphenols with a broad array of different structures. However, an accurate screening of its complete phenolic profile is still lacking. In the present work, liquid chromatography coupled with electrospray ionization hybrid linear trap quadrupole-Orbitrap mass spectrometry (LC-LTQ-Orbitrap) was applied for a comprehensive identification of phenolic compounds in walnuts. A total of 120 compounds, including hydrolysable and condensed tannins, flavonoids and phenolic acids were identified or tentatively identified on the base of their retention times, accurate mass measurements and subsequent mass fragmentation data, or by comparing with reference substances and literature. The peak area of each signal in mass chromatograms was used to provide semiquantitative information for comparison purposes. The most abundant ions were observed for ellagitannins, ellagic acid and its derivatives. Furthermore, the high-resolution MS analysis revealed the presence of eight polyphenols that have never been reported in walnuts: stenophyllanin C, malabathrin A, eucalbanin A, cornusiin B, heterophylliin E, pterocarinin B, reginin A and alienanin B.

Holistic approach based on high resolution and multiple stage mass spectrometry to investigate ergot alkaloids in cereals

A holistic approach based on high resolution and multiple stage mass spectrometry was developed for identification of less studied or novel ergot alkaloid derivatives. Initially, the fragmentation of nine known ergot alkaloids was studied to establish a strategy for the identification of novel ergot alkaloids. Ions with m/z 223 and m/z 251 were found to be common for all ergopeptines, ergoamides and ergopeptams. Subsequently, parent scan experiments using these ions were performed to screen grain samples for the presence of possible ergot alkaloid derivatives. Besides the six most common ergot alkaloids and their corresponding epimers (for which reference standards were available), eleven other ergot alkaloid derivatives were identified following the proposed strategy.

Mining the O-mannose glycoproteome reveals cadherins as major O-mannosylated glycoproteins

The metazoan O-mannose (O-Man) glycoproteome is largely unknown. It has been shown that up to 30% of brain O-glycans are of the O-Man type, but essentially only alpha-dystroglycan (α-DG) of the dystrophin-glycoprotein complex is well characterized as an O-Man glycoprotein. Defects in O-Man glycosylation underlie congenital muscular dystrophies and considerable efforts have been devoted to explore this O-glycoproteome without much success. Here, we used our SimpleCell strategy using nuclease-mediated gene editing of a human cell line (MDA-MB-231) to reduce the structural heterogeneity of O-Man glycans and to probe the O-Man glycoproteome. In this breast cancer cell line we found that O-Man glycosylation is primarily found on cadherins and plexins on β-strands in extracellular cadherin and Ig-like, plexin and transcription factor domains. The positions and evolutionary conservation of O-Man glycans in cadherins suggest that they play important functional roles for this large group of cell adhesion glycoproteins, which can now be addressed. The developed O-Man SimpleCell strategy is applicable to most types of cell lines and enables proteome-wide discovery of O-Man protein glycosylation.

Enzymatic oxidation of rutin by horseradish peroxidase: kinetic mechanism and identification of a dimeric product by LC-Orbitrap mass spectrometry

Flavonoid oxidation is important issue in food processing and quality. The kinetic mechanism of enzymatic oxidation of rutin by horseradish peroxidase (HRP) was studied. Rutin oxidation reaction was followed by recording of spectral changes over the time at 360 nm. The studied oxidation is mostly enzymatic and less part non-enzymatic. The reaction with HRP has a higher rate compared with the reaction without of HRP, whereby is part of non-enzymatic reaction about 10% of the total reaction. Kinetic parameters were determined from graphics of linear Michaelis-Menten equation, and it was found that investigated reactions of rutin oxidation by HRP take place in a ping-pong kinetic mechanism. High resolution HPLC-MS analysis of the mixture of oxidized products of rutin revealed the presence of rutin dimer. Because of widely distribution of rutin as well as presence of peroxidases and hydrogen peroxide in fresh foods identification of this enzymatic modification product can be beneficial for foods quality and safety.

Insight into virgin olive oil secoiridoids characterization by high-resolution mass spectrometry and accurate mass measurements

With the aim to enhance characterization of virgin olive oil (VOO), high resolution mass spectrometry (HRMS) and high resolution tandem mass spectrometry (HRMS/MS), in positive and negative electrospray ionization (ESI) modes, coupled to fused-core reverse phase chromatography, were applied to distinct VOO phenolic extracts after the optimization of chromatographic conditions, ESI and fragmentation parameters. HRMS, but also HRMS/MS resulted fundamental to progress in secoiridoids structural elucidation. The former revealed that the secoiridoid composition of VOO was far more complicated than previously reported, while the latter helped clarify product ion elemental composition allowing new fragmentations, in addition to those reported in the literature, to be put forward. In particular, for the first time, different product ions with the same nominal mass were unequivocally identified in the spectra of secoiridoid compounds, confirming the greater capacity of HRMS/MS to clarify structure than low-resolution MS. Furthermore, and differing from previous studies, the multiple isomers of the main VOO secoiridoids could be differentiated on the basis of their HR product ion spectra in positive mode.

Optimisation of Downscaled Tandem Affinity Purifications to Identify Core Protein Complexes

In this study we show that via stable, retroviral-expression of tagged EGFR del (L747-S752 deletion mutant) in the PC9 lung cancer cell line and stable doxycycline-inducible expression of tagged Grb2 using a Flp-mediated recombination HEK293 cell system, the SH-TAP can be downscaled to 5 to 12.5 mg total protein input (equivalent to 0.5 - 1 × 15 cm culture plate or 4 - 8 × 10⁶ cells). The major constituents of the EGFR del complex (USB3B, GRB2, ERRFI, HSP7C, GRP78, HSP71) and the Grb2 complex (ARHG5, SOS1, ARG35, CBL, CBLB, PTPRA, SOS2, DYN2, WIPF2, IRS4) were identified. Adjustment of the quantity of digested protein injected into the mass spectrometer reveals that optimisation is required as high quantities of material led to a decrease in protein sequence coverage and the loss of some interacting proteins. This investigation should aid other researchers in performing tandem affinity purifications in general, and in particular, from low quantities of input material.