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Background It is essential to identify the chemical components for the quality control methods establishment of Chinese Classical Formula (CCF). However, CCF are complex mixture of several herbal medicines with huge number of different compounds and they are not equal to the combination of chemical components from each herb due to particular formula ratio and preparation techniques. Therefore, it is time-consuming to identify compounds in a CCF by analyzing the LC–MS/MS data one by one, especially for unknown components. Methods An ultra-high pressure liquid chromatography-linear ion trap-orbitrap high resolution mass spectrometry (UHPLC-LTQ-Orbitrap-MS/MS) approach was developed to comprehensively profile and characterize multi-components in CCF with Erdong decoction composed of eight herbal medicines as an example. Then the MS data of Erdong decoction was analyzed by MS/MS-based molecular networking and these compounds with similar structures were connected to each other into a cluster in the network map. Then the unknown compounds connected to known compounds in a cluster of the network map were identified due to their similar structures. Results Based on the clusters of the molecular networking, 113 compounds were rapidly tentative identification from Erdong decoction for the first time in the negative mode, which including steroidal saponins, triterpenoid saponins, flavonoid O-glycosides and flavonoid C-glycosides. In addition, 10 alkaloids were tentatively identified in the positive mode from Nelumbinis folium by comparison with literatures. Conclusion MS/MS-based molecular networking technique is very useful for the rapid identification of components in CCF. In Erdong decoction, this method was very suitable for the identification of major steroidal saponins, triterpenoid saponins, and flavonoid C-glycosides.

Physical review / D 104(9), 096009 (1-13) (2021). doi:10.1103/PhysRevD.104.096009, We study negative modes around the Coleman���de Luccia bounce solution. The conditions for the appearance of an infinite number of negative modes do not coincide between Lagrangian and Hamiltonian formulations in the literature, and we discuss the origin of this difference in detail. We show how different choices of the variable for the fluctuation around the bounce solution affect the negative mode condition in the Hamiltonian approach, and point out that there exists a choice that gives the same negative mode condition as the Lagrangian approach., Published by Inst., Melville, NY

Using structures of subwavelength metallic capped helices with both negative electric and magnetic couplings, we demonstrate a broadband negative mode index metasurface. Numerical and experimental results are presented for the structure with negative dispersion bandwidth of 44% compared to the resonant frequency of individual capped helices. Optimisation of such structures in terms of their size, element geometry and operational passband width is demonstrated.

Electrospray ionization (ESI) operating in the negative mode coupled to high-resolution mass spectrometry is the most popular technique for the characterization of dissolved organic matter (DOM). The vast molecular heterogeneity and the functional group diversity of this complex mixture prevents the efficient ionization of the organic material by a single ionization source, so the presence of uncharacterized material is unavoidable. The extent of this poorly ionizable pool of carbon is unknown, is presumably variable between samples, and can only be assessed by the combination of analysis with a uniform detection method. Charged aerosol detection (CAD), whose response is proportional to the amount of nonvolatile material and is independent from the physicochemical properties of the analytes, is a suitable candidate. In this study, a fulvic acid mixture was fractionated and analyzed by high-pressure liquid chromatography–mass spectrometry in order to investigate the polarity and size distributions of highly and poorly ionizable material in the sample. Additionally, DOM samples of terrestrial and marine origins were analyzed to evaluate the variability of these pools across the land–sea aquatic continuum. The relative response factor values indicated that highly ionizable components of aquatic DOM mixtures are more hydrophilic and have lower molecular weight than poorly ionizable components. Additionally, a discrepancy between the samples of terrestrial and marine origins was found, indicating that marine samples are better represented by ESI than terrestrial samples, which have an abundant portion of hydrophobic poorly ionizable material. Title in thesis list of papers: Investigating the ionisation of dissolved organic matter by electrospray ionisation

Glycosaminoglycans (GAGs) are polysaccharides produced by most mammalian cells and involved in a variety of biological processes. However, due to the size and complexity of GAGs, detailed knowledge about the structure and expression of GAGs by cells, the glycosaminoglycome, is lacking. Here we report a straightforward and versatile approach for structural domain mapping of complex mixtures of GAGs, GAGDoMa. The approach is based on orthogonal enzymatic depolymerization of the GAGs to generate internal, terminating, and initiating domains, and nanoflow reversed-phase ion-pairing chromatography with negative mode higher-energy collision dissociation (HCD) tandem mass spectrometry (MS/MS) for structural characterization of the individual domains. GAGDoMa provides a detailed structural insight into the glycosaminoglycome, and offers an important tool for deciphering the complexity of GAGs in cellular physiology and pathology.

The characterization of plant compounds with pharmacological activity is a field of great relevance in research and development. As such, identification techniques with the goal of developing new drugs or even validating the bioactive properties of extracts must be explored in order to further expand the knowledge of plant extract composition. Most works in this field employ HPLC, when exploring non-structural and cell wall carbohydrates from Rhynchelytrum repens. Phenolic compounds were studied by classical chromatography techniques and UV-vis spectrophotometry, with C-glycosylated flavonoids being detected but with no further details regarding the chemical structure of these compounds. In this work we employ paper spray ionization mass spectrometry (PS-MS) for the evaluation of the chemical profile of R. repens methanol extract. Positive ionization mode identified 15 compounds, belonging to flavonoids, fatty acids, and other classes of compounds; negative mode ionization was able to identify 20 compounds comprising the classes of quinic acids, stilbenes and flavonoids. PS-MS proved effective for the evaluation of R. repens extracts, making it possible to identify a total of thirty-five compounds. The bioactive properties attributed to R. repens were confirmed by the identification and characterization of compounds identified by PS-MS.

In this paper, first the fracture load, the crack initiation angle and the crack trajectory are experimentally measured for the round-tip V-notched Brazilian disk specimen made of polymethyl-methacrylate under compressive-shear loading. Then, the fracture load and the crack initiation angle are predicted by using the extended finite element method on the basis of the linear cohesive crack criterion. The fracture trajectory of the round-tip V-notched Brazilian disk specimens is also estimated by means of the extended finite element method and the incremental methods. Both the experimental observations and the theoretical fracture models indicate that although the notch bisector line is under compressive-shear loading, one half of the notch border still sustains tensile stresses and fracture takes place from this half. A very good agreement is shown to exist between the theoretical predictions and the experimental results for various notch opening angles and different notch radii.

This work reports the theoretical and experimental study of fragmentation reactions in the gas phase of five phenolic acids using triple quadrupole mass spectrometry by electrospray ionization in negative ionic mode, as well as the isotope exchange experiments. MS/MS spectra were analyzed to suggest the fragmentation mechanisms, while theoretical calculations at the theory level B3LYP/6-311+G** were performed to expose the proposed mechanisms viability for this class of compounds. As expected, compounds with aromatic methoxy substitution presented •CH3 radical elimination as the principal fragmentation pathway, forming dystonic ions. Compounds without methoxy substituents dissociate with higher energies losing the CO2, CO and H2O. The isotopic marking experiments indicated the exchange of hydrogens by deuterases in the hydroxyl protons, which corroborates with the proposed mechanisms.

Non-targeted and suspect analyses with liquid chromatography/electrospray/high-resolution mass spectrometry (LC/ESI/HRMS) are gaining importance as they enable identification of hundreds or even thousands of compounds in a single sample. Here, we present an approach to address the challenge to quantify compounds identified from LC/HRMS data without authentic standards. The approach uses random forest regression to predict the response of the compounds in ESI/HRMS with a mean error of 2.2 and 2.0 times for ESI positive and negative mode, respectively. We observe that the predicted responses can be transferred between different instruments via a regression approach. Furthermore, we applied the predicted responses to estimate the concentration of the compounds without the standard substances. The approach was validated by quantifying pesticides and mycotoxins in six different cereal samples. For applicability, the accuracy of the concentration prediction needs to be compatible with the effect (e.g. toxicology) predictions. We achieved the average quantification error of 5.4 times, which is well compatible with the accuracy of the toxicology predictions.

No analytical assay is currently available for the simultaneous determination of CBD major metabolites in serum or urine samples of individuals treated with medical cannabis or CBD-based pharmaceuticals. We developed and validated a method using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) for quantifying cannabidiol (CBD) and its metabolites, cannabidiol-7-oic acid (7-COOH-CBD), 7hydroxycannabidiol (7-OH-CBD), 6-alpha-hydroxycannabidiol (6-alpha-OH-CBD) and 6-beta-hydroxycannabidiol (6-beta-OH-CBD) in serum and urine samples of an individual treated with medical cannabis. The ionization was performed by electrospray in negative mode to reach the sensitivity required to detect trace amounts, with limits of quantification ranging from 0.05 to 0.1 ng/mL. The method is accurate (average inter/intra-day error

Brittle failure of key-hole notches is investigated experimentally and theoretically under mixed mode I/II loading with negative mode I contributions. The key-hole notched Brazilian disk specimen made of the general-purpose Polystyrene is utilized for conducting the fracture experiments. To predict the experimental results, the key-hole notch maximum tangential stress and key-hole notch mean stress criteria are utilized. It is shown that both criteria could provide good predictions to the experimental results of the fracture load. Moreover, the key-hole notch mean stress criterion with the experimentally determined critical distance is shown to be the most accurate failure criterion.

RATIONALE An application of microdialysis sampling for evaluation of the interaction property of small molecules to macromolecules is presented. Microdialysis combined with liquid chromatography coupled to quadrupole time-of-flight tandem mass spectrometry (LC/QTOF-MS/MS) was established for the purpose of screening of the multiple bioactive compounds in traditional Chinese medicines (TCMs). METHODS Microdialysis experiments were performed in vitro using a syringe pump and probes. Separation was achieved via liquid chromatography, and MS analysis was conducted by electrospray ionization quadrupole time-of-flight mass spectrometry in negative mode. The interaction property of compounds in TCMs with aldose reductase can be deduced from the comparison of the peak areas in chromatograms using a stable internal standard. RESULTS In this work, 23 compounds including iridoids, flavonoids, monoterpenoids, carotenoids and phenolic acids were identified by comparison with reference compounds, characteristic high-resolution mass spectrometry and the MS/MS fragmentations simultaneously. Binding degrees of 23 compounds in Gardenia jasminoides Eliis (G. jasminoide) with aldose reductase ranged from 13.91% to 66.25%. Also, microdialysis recoveries of 23 compounds in G. jasminoides were determined. CONCLUSIONS The Interaction properties of 23 compounds in G. jasminoides with aldose reductase were investigated and they are potential bioactive ingredients. Microdialysis coupled to LC/QTOF-MS/MS can be used for screening of bioactive multicomponents from TCMs with appropriate targets. Copyright © 2016 John Wiley & Sons, Ltd.

"Zhu She Yong Xue Shuan Tong" lyophilized powder (ZSYXST), consists of a series of saponins extracted from Panax notoginseng, which has been widely used in China for the treatment of strokes. In this study, an ultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) combined with preparative high performance liquid chromatography (PHPLC) method was developed to rapidly identify both major and minor saponins in ZSYXST. Some high content components were removed through PHPLC in order to increase the sensitivity of the trace saponins. Then, specific characteristic fragment ions in both positive and negative mode were utilized to determine the types of aglycone, saccharide, as well as the saccharide chain linkages. As a result, 94 saponins, including 20 pairs of isomers and ten new compounds, which could represent higher than 98% components in ZSYXST, were identified or tentatively identified in commercial ZSYXST samples.

ent-Kaurenoic acid (KA) is a key intermediate connected to a phytohormone gibberellin. To date, the general procedure for quantifying KA is by using traditional gas chromatography–mass spectrometry (GC–MS). In contrast, gibberellins, which are more hydrophilic than KA, can be easily quantified by liquid chromatography-tandem mass spectrometry (LC–MS/MS). In this study, we have established a new method to quantify KA by LC–MS/MS by taking advantage of a key feature of KA, namely the lack of fragmentation that occurs in MS/MS when electrospray ionization (ESI) is in the negative mode. Q1 and Q3 were adopted as identical channels for the multiple reaction monitoring of KA. The method was validated by comparing with the results obtained by selected ion monitoring in GC–MS. This new method could be applicable for the quantification of other hydrophobic compounds., Highlights • ent-Kaurenoic acid (KA) can be quantified by LC–MS/MS. • Detection limit of KA acid was 0.59 ng ml−1. • We set Q1 and Q3 to the same MRM channel. • Endogenous KA in a moss was detected and quantified.

Rationale Mass calibration in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is currently obtained using mixtures of individual peptides. This procedure has several drawbacks, including laborious preparation, limited shelf life and unequal calibration mass spacing. Polyalanine, a simple to prepare polydisperse molar mass standard, alleviates these problems. Methods Polyalanine is prepared by the typical protocols for biological sample analytics. Results Polyalanine is the first polymeric standard providing abundant signals in both, positive and negative polarity mode with the typical matrices DHB and HCCA. Conclusions Facile MS as well as MS/MS calibration is thus enabled for the first time in both polarity modes by employing this polydisperse standard. Copyright © 2016 John Wiley & Sons, Ltd.

Triterpenoids are the major secondary metabolites and active substances in Ganoderma, considered as the “marker compounds” for the chemical evaluation or standardization of Ganoderma. A response surface methodology was used to optimize the ultrasonic-assisted extraction of triterpenoids. The extraction rate was 7.338 ± 0.150 mg/g under the optimum conditions: 87% ethanol, ratio of solid to liquid (w : v) 1 : 28, and ultrasound extraction time 36 min. Based on the high sensitivity and selectivity of HPLC-LTQ-Orbitrap-MSn, 24 components of triterpenoids were tentatively identified in the negative mode. Then, the global chemical profiling consisting of HPLC and TLC fingerprints generated by ChemPattern™ software was developed for evaluation of Ganoderma species. For fingerprint analysis, 11 peaks of triterpenoids were selected as the characteristic peaks to evaluate the similarities of different samples. The correlation coefficients of similarity were greater than 0.830. The cluster analysis showed a clear separation of three groups, and 11 peaks played key roles in differentiating these samples. The developed global chemical profiling method could be applied for rapid evaluation, quality control, and authenticity identification of Ganoderma and other herbal medicines.

European common ash, Fraxinus excelsior, is currently threatened by Ash dieback (ADB) caused by the fungus, Hymenoscyphus fraxineus. To detect and identify metabolites that may be products of pathways important in contributing to resistance against H. fraxineus, we performed untargeted metabolomic profiling on leaves from five high-susceptibility and five low-susceptibility F. excelsior individuals identified during Danish field trials. We describe in this study, two datasets. The first is untargeted LC-MS metabolomics raw data from ash leaves with high-susceptibility and low-susceptibility to ADB in positive and negative mode. These data allow the application of peak picking, alignment, gap-filling and retention-time correlation analyses to be performed in alternative ways. The second, a processed dataset containing abundances of aligned features across all samples enables further mining of the data. Here we illustrate the utility of this dataset which has previously been used to identify putative iridoid glycosides, well known anti-herbivory terpenoid derivatives, and show differential abundance in tolerant and susceptible ash samples.

In nontarget screening, structure elucidation of small molecules from high resolution mass spectrometry (HRMS) data is challenging, particularly the selection of the most likely candidate structure among the many retrieved from compound databases. Several fragmentation and retention prediction methods have been developed to improve this candidate selection. In order to evaluate their performance, we compared two in silico fragmenters (MetFrag and CFM-ID) and two retention time prediction models (based on the chromatographic hydrophobicity index (CHI) and on log D). A set of 78 known organic micropollutants was analyzed by liquid chromatography coupled to a LTQ Orbitrap HRMS with electrospray ionization (ESI) in positive and negative mode using two fragmentation techniques with different collision energies. Both fragmenters (MetFrag and CFM-ID) performed well for most compounds, with average ranking the correct candidate structure within the top 25% and 22 to 37% for ESI+ and ESI- mode, respectively. The rank of the correct candidate structure slightly improved when MetFrag and CFM-ID were combined. For unknown compounds detected in both ESI+ and ESI-, generally positive mode mass spectra were better for further structure elucidation. Both retention prediction models performed reasonably well for more hydrophobic compounds but not for early eluting hydrophilic substances. The log D prediction showed a better accuracy than the CHI model. Although the two fragmentation prediction methods are more diagnostic and sensitive for candidate selection, the inclusion of retention prediction by calculating a consensus score with optimized weighting can improve the ranking of correct candidates as compared to the individual methods. Graphical abstract Consensus workflow for combining fragmentation and retention prediction in LC-HRMS-based micropollutant identification.

International audience; For the first time, the electrospray ionization efficiency (IE) scales in positive and negative mode are united into a single system enabling,direct comparison of IE values across ionization modes. This is made possible by the use of a reference Compound that ionizes to a similar extent in both positive, and negative modes. Thus, choosing the optimal (i.e., most sensitive) ionization conditions for a given set of analytes is enabled. Ionizatiori efficiencies of 33 compounds ionizing in both modes demonstrate that, contrary to general practice, negative mode allows, better sensitivity for 46% of such compounds Whereas the positive mode is preferred for only 18%, and for 36%, the results for both modes are comparable.

The combined and interactive effects of the bolt-hole fit conditions and the preloads of the fasteners on the load carrying capacity of single-lap composite-to-titanium bolted joints have been investigated both experimentally and numerically. Quasi-static tests of the hybrid joints with different fit conditions are implemented, and a three dimensional finite element progressive failure analysis model is proposed to predict the influences of the bolt-hole fit conditions and fastener’s preloads on the mechanical behaviors of the joints. Based on the experimental validated simulation method, a multi-factor, mixed levels orthogonal design table and the analysis of variance method are used to arrange the simulation conditions and to further study the interactive effects of preloads and fit conditions. Through the analysis of the results, for the researched double bolt, single-lap composite-titanium joints, it is found that: the effects of both the interference fit and the preloads change from positive into negative mode with the increase of the interference fit values or preload values; appropriate bolt-hole fit conditions and preloads can improve the bolt-hole contact conditions of the loaded joints, and then retard the fiber failures around the fastener holes, and increase the load carrying capacity of the joints eventually; the interactive effect of the bolt-hole interference fit conditions and preloads cannot be ignored and the parameters need to be considered together and synthetically as the joints are being optimized.

This study was conducted to determine the content of 7 mycotoxins (aflatoxin B 1 , B 2 , G 1 , G 2 , M 1 , ochratoxin A and zearalenone) using LC-MS/MS in pork available on the Korean markets. The analysis was carried out using following conditions; C 18 column (2.1×100 mm, 1.7 μm), mobile phase composed of H 2 O (0.1 mM NH 4 Ac 0.01% HCOOH)：Methanol (0.1 mM NH 4 Ac 0.01% HCOOH), binary pump at a flow rate of 0.5 mL/min and 2 μL of injection volume, MS/MS detector with ESI positive and negative mode. The quantication of mycotoxins was based on matrix-matched calibration curves with a correlation coefficient in excess of 0.99 for the 7 mycotoxins. The dectection limits were ranged 0.74∼2.13 ng/g, with mean recoveries between 73.10∼97.46% except aflatoxin B 1 (61.31%). We also monitored mycotoxin residues in 208 pork samples. The test results, mycotoxins were not found except one sample. Ochratoxin A in one sample of the test samples was detected below the quantification limit.

We report how electrochemiluminescence (ECL) of rubrene can be utilized for enhancing the visualization of latent fingerprints in two different modes. The enhancement arises from the spatially selective ECL generation either from the substrate surface uncovered by the fingerprint or the fingerprint itself, designated negative or positive imaging mode, respectively. The negative mode is performed directly in an electrolyte solution containing rubrene and co-reactant. Given that organic residues in the fingerprint deposit make the underlying surface electrochemically inert or less active, ECL reaction occurs only on the surface untouched by the fingertip, generating a negative impression with a dark ridge pattern against the illuminated background. The positive imaging mode is based on the preferential adsorption of rubrene aggregates to the ridge materials via physical attraction; then the fingerprint can glow via ECL reaction in a solution containing co-reactant under an appropriate applied potential. Keywords: Latent fingerprints, Electrochemiluminescene, Rubrene, Negative mode, Positive mode

Glucose is a common medical analyte measuring in human serum or blood samples. The development of a primary method is necessary for the establishment of traceability in measurements. We have developed an isotope dilution liquid chromatography tandem mass spectrometry as a primary method for the measurement of glucose in human serum. Glucose and glucose- 13 C6 in sample were ionized in ESI negative mode and monitored at mass transfers of m/z 179/89 and 185/92 in MRM, respectively. Glucose was separated on NH2P50 2D column, and the mobile phase was 20 mM NH4OAc in 30% acetonitrile/70% water. Verification of this method was performed by the comparison with NIST SRMs. Our results agreed well with the SRM values. We have developed two levels of glucose serum certified reference material using this method and distributed them to the clinical laboratories in Korea as samples for proficiency testings. The expended uncertainty was about 1.2% on 95% confidence level. In proficiency testings, the results obtained from the clinical laboratories showed about 3.6% and 3.9% RSD to the certified values. Primary method can provide the traceability to the field laboratories through proficiency testings or certified reference materials.

The (CO) elimination reaction of cyclopropylmethoxy (fluoro/chloro) carbenes (C–X, X=H, F, Cl) and its consequent rearrangement products are studied computationally using B3LYP/6-311++G** method. Results of this study show that the reaction proceeds via a first TS corresponding to the cyclopropylmethoxy (chloro/fluoro) carbenes (C–X, X=H, F, Cl). The negative mode of this TS species corresponds to the elimination of the CO molecule, consistent with the experimentally proposed mechanism. Effects of the X substitution on the electronic and energetic properties of this conversion which is an intermediate step of the conversion of 3-cyclopropylmethoxy-3-(fluoro/chloro) diazirines (D–X, X=H, F, Cl) to different products are also investigated. Calculations are also carried out for reactants and products of this reaction at the same level of theory. Nuclear quadrupole coupling constants and asymmetry parameter of the 35Cl and 14N nuclei have also been calculated and analyzed for reactants, TSs and products, as probes of the reaction coordinate.

We describe a novel improved approach to the synthesis of the important and well-known heat shock protein 70 inhibitor (HSP70), pifithrin-μ, with corresponding and previously unreported characterisation. The first example of a combination study comprising HSP70 inhibitor pifithrin-μ and cisplatin or oxaliplatin is reported. We have determined, using the Chou-Talalay method, (i) moderate synergistic and synergistic effects in co-treating PC-3 prostate cancer cells with pifithrin-μ and cisplatin and (ii) significant synergistic effects including strong synergism in cotreating HT29 colorectal cancer cells with oxaliplatin and pifithrin-μ.

Negative electron-transfer dissociation (NETD) has emerged as a premier tool for peptide anion analysis, offering access to acidic post-translational modifications and regions of the proteome that are intractable with traditional positive-mode approaches. Whole-proteome scale characterization is now possible with NETD, but proper informatic tools are needed to capitalize on advances in instrumentation. Currently only one database search algorithm (OMSSA) can process NETD data. Here we implement NETD search capabilities into the Byonic platform to improve the sensitivity of negative-mode data analyses, and we benchmark these improvements using 90 min LC-MS/MS analyses of tryptic peptides from human embryonic stem cells. With this new algorithm for searching NETD data, we improved the number of successfully identified spectra by as much as 80% and identified 8665 unique peptides, 24 639 peptide spectral matches, and 1338 proteins in activated-ion NETD analyses, more than doubling identifications from previous negative-mode characterizations of the human proteome. Furthermore, we reanalyzed our recently published large-scale, multienzyme negative-mode yeast proteome data, improving peptide and peptide spectral match identifications and considerably increasing protein sequence coverage. In all, we show that new informatics tools, in combination with recent advances in data acquisition, can significantly improve proteome characterization in negative-mode approaches.

Nastajanje negativnih iona elektroraspršenjem za cijelu klasu biomakromolekula (peptidi, proteini, DNA, RNA, ugljikohidrati) je energetski nepovoljnije od nastajanja pozitivnih iona u ionskom izvoru spektrometra masa. Jedan od razloga je vezan uz nemogućnost postizanja stabilnog elektroraspršenja u negativnom načinu rada spektrometra masa. Nastajanje i analiza negativnih iona peptida i proteina ima izraziti značaj u području proteomike, gdje bi se takvom primjenom pospješila uspješnost analize ukupnog aminokiselinskog slijeda proteina i njegovih posttranslacijskih modifikacija. Prijašnja istraživanja pokazala su pozitivan utjecaj formaldehida na formiranje negativnih iona selektivnih modulatora androgenih receptora. Smatra se da bi sličan utjecaj mogli imati i drugi aldehidi, ketoni i esteri jer podliježu sličnoj reakciji u kiselom mediju kao i formaldehid. Proučavana je ionizacija negativnih iona peptida i proteina nano-elektroraspršenjem na hibridnom spektrometru masa koji se sastoji od T-vala, kvadrupola i analizatora vremena leta u neprekinutom slijedu (T-val Q-TOF MS). Tijekom predselekcije poboljšivača ionizacije (aldehida, ketona i estera) pokazalo se da su najveći utjecaj na nastajanje negativnih iona imali 2,2-dimetilpropanal, etil-metanoat i 2-fenil-2-oksoetanal. Da bi se pospješila ionizacija, odabrani poboljšivači ionizacije negativnih iona su umiješani u tok pokretne faze pri protoku od 0,4 L min-1 uz pomoć poslijekolonskog injekcijskog sustava. Rezultati su pokazali da se umiješavanjem mikromolarnih količina navedenih spojeva u matičnicu pokretne faze postiže ionizacija negativnih iona peptida i proteina u ESI-MS-u. For a wide variety of biological compounds (peptides, proteins, DNA, RNA, carbohydrates),negative ion formation by electrospray ionization is energetically less favorable than positive ion formation in mass spectrometer ion source. One of the reasons is inability to maintain stable electrospray in negative ion mode. Formation and analysis of negative ions of peptides and proteins is of great importance in proteomics research, as they would significantly improve amino acid sequence analysis of proteins and analysis of their posttranslational modifications. Previous research showed favorable effects of formaldehyde on the negative-ion formation of selective androgen receptor modulators. It is assumed that other aldehydes, ketones and esters would have similar effect because their reaction mechanism in acidic medium is similar to the reaction mechanism of formaldehyde. Hybrid T-wave quadrupole time-of-flight mass spectrometer (T-wave Q-TOF MS) was used for the study of nano electrospray formation of negative ions of peptides and proteins. Preselection of the negative-ion enhancers (aldehydes, ketones and esters) showed that the greatest effect on negative-ion formation had 2,2-dimethylpropanal, ethyl methanoate and 2-oxo-2-phenylethanal. The selected negative-ion enhancers were added postcolumn at a flow rate of 0,4 L min-1 to a mobile phase flow to enhance ionization. Results showed that formation of negativeions of peptides and proteins in ESI-MS was achieved by addition of micromolar quantities of the mentioned negative-ion enhancers to the mobile phase flow.

Pearson correlation coefficients were applied for the objective comparison of 30 black gel pen inks analysed by laser desorption ionization mass spectrometry (LDI-MS). The mass spectra were obtained for ink lines directly on paper using positive and negative ion modes at several laser intensities. This methodology has the advantage of taking into account the reproducibility of the results as well as the variability between spectra of different pens. A differentiation threshold could thus be selected in order to avoid the risk of false differentiation. Combining results from positive and negative mode yielded a discriminating power up to 85%, which was better than the one obtained previously with other optical comparison methodologies. The technique also allowed discriminating between pens from the same brand. © 2011 Elsevier Ireland Ltd.

Usually, the differentiation of inks on questioned documents is carried out by optical methods and thin layer chromatography (TLC). Therefore, spectrometric methods were also proposed in forensic literature for the analysis of dyes. Between these techniques, laser desorption/ionization mass spectrometry (LDI-MS) has demonstrated a great versatility thanks to its sensitivity to blue ballpoint ink dyes and minimal sample destruction. Previous researches concentrated mostly on the LDI-MS positive mode and have shown that this analytical tool offers higher discrimination power than high performance TLC (HPTLC) for the differentiation of blue ballpoint inks. Although LDI-MS negative mode has already been applied in numerous forensic domains like the studies of works of art, automotive paints or rollerball pens, its potential for the discrimination of ballpoint pens was never studied before. The aim of the present paper is therefore to evaluate its potential for the discrimination of blue ballpoint inks. After optimization of the method, ink entries from 33 blue ballpoint pens were analyzed directly on paper in both positive and negative modes by LDI-MS. Several cationic and anionic ink components were identified in inks; therefore, pens were classified and compared according to their formulations. Results show that additional information provided by anionic dyes and pigments significantly increases the discrimination power of positive mode. In fact, it was demonstrated that classifications obtained by the two modes were, to some extent, complementary (i.e., inks with specific cationic dyes not necessarily contained the same anionic components).

A statistical methodology for the objective comparison of LDI-MS mass spectra of blue gel pen inks was evaluated. Thirty-three blue gel pen inks previously studied by RAMAN were analyzed directly on the paper using both positive and negative mode. The obtained mass spectra were first compared using relative areas of selected peaks using the Pearson correlation coefficient and the Euclidean distance. Intra-variability among results from one ink and inter-variability between results from different inks were compared in order to choose a differentiation threshold minimizing the rate of false negative (i.e. avoiding false differentiation of the inks). This yielded a discriminating power of up to 77% for analysis made in the negative mode. The whole mass spectra were then compared using the same methodology, allowing for a better DP in the negative mode of 92% using the Pearson correlation on standardized data. The positive mode results generally yielded a lower differential power (DP) than the negative mode due to a higher intra-variability compared to the inter-variability in the mass spectra of the ink samples.

Some analytical characteristics of ion-mobility increment spectrometry (IMIS) in the negative and positive modes were compared in detecting diacetylmorphine vapors. It was shown experimentally that the sensitivity of IMIS in the negative mode to diacetylmorphine depends on the concentration of the water vapors in the drift gas: the lower the concentration, the higher the sensitivity. Data for cocaine are presented for comparison. Sampling diacetylmorphine and cocaine in the ionization chamber of the ion-mobility increment spectrometer was performed using a chromatograph with a multicapillary gas-chromatographic column.

A rapid discrimination method of amino acid drinks (AADs) by microscopic Fourie-transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS) was studied for forensic identification. The ten descriptions of PET bottle AADs (several tens μL) were used as samples. Types of saccharides contained mainly in the drinks were given by the FT-IR analysis. The results by the ESI-MS analysis of samples diluted twice with acetonitrile were as follows : amino acids and saccharides were mainly detected as [M+H]+and [M+Na(or K)]+, respectively, in the positive mode. Acidity regulators and saccharides were mainly detected as [M−H]− and [M+Cl]−, respectively, in the negative mode. The FT-IR and ESI-MS analyses used in this study rapidly discriminated all samples of the AADs, and could be applied to screening tests of the AADs.

As a new emerging environmental contaminant, perchlorate has prompted people to pay more attention. The presence of perchlorate in the human body can result in improper regulation of metabolism for adults. Furthermore, it also causes developmental and behavioral problems for infants and children because it can interfere with iodide uptake into the thyroid tissue. In this paper, perchlorate in sewage sludge, rice, bottled drinking water and milk was detected for investigating the perchlorate pollution status in China. The places, where the samples were collected, cover most regions of China. Therefore, the final data on perchlorate levels will give an indication of the perchlorate pollution status in China. The final determination of perchlorate was performed by ion chromatography–electrospray tandem mass spectrometry with negative mode. The concentration of perchlorate in sewage sludge, rice, bottled drinking water and milk was in the range of 0.56–379.9 μg/kg, 0.16–4.88 μg/kg, 0.037–2.013 μg/L and 0.30–9.1 μg/L, respectively. The results show that perchlorate has been widespread in China. Keywords: Perchlorate, IC-ESI-MS/MS, Sewage sludge, Bottled water, Rice, Milk

It is more crucial than ever to consider the elderly when designing products. One of the important things to remember is the legibility of characters, since this influences the accessibility and usability of products. We studied the effects of character attributes on legibility using 70 subjects (60 aged 46-79 with no apparent ocular problems except presbyopia, and 10 aged 68-80 with cataracts). Thirty 10-key television remote control models were made. The characters on each were different, and were based on combinations of three attributes-height (5 levels), thickness (3 levels), and display mode (2 levels; positive: black characters on a white background, negative: white characters on a black background). Participants subjectively evaluated the legibility of the characters for each 10-key sample under two ambient illuminance conditions: 500 lx and 50 lx. They also performed paired comparisons on samples with the same height and thickness but different display modes. Subjective data were analyzed using a three-way factorial ANOVA for character height, thickness, and display mode. Legibility was significantly affected by all factors for those without cataracts under both illuminance conditions, and the interaction between thickness and display mode was significant. A two-way factorial ANOVA was performed for height and display mode for each thickness. Legibility was, in general, better for thinner characters in negative mode and was better in negative mode under dark illuminance for those with and without cataracts. This tendency was more pronounced in the elderly (over 65 years old). Paired comparisons showed that legibility was better in negative mode under both illuminance conditions, especially with medium and thin characters, for those with and without cataracts. Although there are few accounts of the effects of positive and negative modes in various existing guidelines, this finding would suggest that legibility can be enhanced by using the negative mode.

We investigated the relationship between individual subjects’ functional connectomes and 280 behavioral and demographic measures, in a single holistic multivariate analysis relating imaging to non-imaging data from 461 subjects in the Human Connectome Project. We identified one strong mode of population co-variation; subjects were predominantly spread along a single “positive-negative” axis, linking lifestyle, demographic and psychometric measures to each other and to a specific pattern of brain connectivity.

Zusammenfassung: Die Klimavariabilitat im europaischen Alpenraum auf der Zeitskala von Jahren bis Jahrhunderten Neue Zeitreihen von Proxydaten und friihen Instrumentenmessungen aus den Alpen erlauben eine prazisere Interpretation der Klimavariabilitat sowie der dahinter verborgenen Prozesse. Die Studie zeigt, daB wahrend Phasen mit unterschiedlichen Antriebscharakteristiken (forcings) des Klimasystems spezifische Temperatur- und Niederschlagsanomalien auftreten. So wurde wahrend der schwachen Solaraktivitat des Maunder Minimums eine Tendenz zu kalten und trockenen Wintern sowie feuchten Sommern registriert. Nach tropischen Vulkanausbruchen waren die Sommer mehrheitlich kalt, und in der rezenten Phase der zunehmenden Treibhausgase werden vor allem warme Winter beobachtet. Die Korrelationen zwischen den natiir lichen und anthropogenen Forcing-Faktoren und dem Nordatlantischen Oszillationsindex zeigen kein eindeutiges Bild. Immerhin kann festgestellt werden, daB der Index wahrend der trockenkalten Winter des spaten Maunder Minimums mit geringer Solaraktivitat betont negativ war. Die VorstoBphasen der zwei betrachteten Alpengletscher sind bedingt durch ein komplexes Temperatur- und Niederschlagsmuster in Winter und Sommer. Es wird vorgeschlagen, diese VorstoBphasen mit dem englischen Ausdruck "Little Ice Age Type Events" zu benennen. Summary: New sets of proxy and early instrumental data from the European Alps allow deeper insights into climate variability and its underlying processes on varying timescales. The study indicates that periods with different forcing character istics show specific temperature and precipitation anomalies: Cold and dry winters as well as wet summers during the low solar activity period of the Maunder Minimum, cold summers after tropical volcanic eruptions and warm winters in the recent period with an increasing greenhouse gas concentration. The relation between periods with a prevailing positive or negative mode of the North Atlantic Oscillation (NAO) and this natural or anthropogenic forcing is very complex. At least it can be stated that the negative or meridional mode of NAO dominated during the low solar activity period with the cold and dry winters of the late Maunder Minimum. The advance periods of the two selected Alpine glaciers are obviously driven by characteristic but varying temperature and precipitation courses during winter and summer. It is suggested to call these periods Little Ice Age Type Events (LIATE's).

Peanuts (Arachis hypogaea) contain numerous phenolic compounds with antimicrobial and antioxidant properties. These secondary metabolites may be isolated as co-products from peanut skins or testae during peanut processing and have potential use in functional food or feed formulations. Peanut skins were extracted in ethanol and analyzed by mass spectrometry to identify major phenolic compounds. Extracts were analyzed by LC-MS (Accela-MSQ,ThermoFisher Scientific,Waltham, Massachusetts, USA). Separations were performed using a PFP column in reverse phase. The MS detector was scanned from 50 – 500 m/z in negative mode (ESI). Additional analysis of extracts was performed by GC-TOF (Leco Corp., St. Joseph, Michigan, USA). Spectral data collected by both instruments were used to obtain a profile of the phenolic compounds that included catechin, epicatechin, and several anthocyanidins. These results are expected to promote the use of phenolics obtained from inexpensive agricultural sources.

Milk composition has been known to change during lactation. To help understand the changes in metabolic profile throughout the whole lactation, liquid chromatography mass-spectrometry was used to analyze 306 milk samples from 82 primi- and multiparous dairy cows. Changes in metabolic profile common to all cows throughout lactation were ascertained based on principal component and general linear model analysis. Sets of specific markers; for instance, 225, 397, and 641–642 m / z (positive mode), and 186, 241, and 601–604 (negative mode), with at least a 1.5-fold higher intensity during the first 60d compared with the last 60d of lactation were observed. The metabolome was affected by parity and milking time. Markers, identified as peptides differentiating parity, were observed. A significant increase for citrate was observed in evening milk. Milk coagulation traits were strongly animal specific. The curd firmness values were influenced by milking time. Sets of markers were associated with curd firmness in positive (197 m / z ) and negative (612, 737, 835, 836, 902, 1000, 1038, and 1079 m / z ) ion mode.

This study summarises the results of the levels of 21 perfluoroalkyl substances (PFASs) in 50 selected pooled samples representing 15 food commodities with the special focus on those of animal origin, as meat, seafood, fish, milk, dairy products and hen eggs, which are commonly consumed in various European markets, e.g. Czech, Italian, Belgian and Norwegian. A new, rapid sample preparation approach based on the QuEChERS extraction procedure was applied. Ultra-performance liquid chromatography (UHPLC) coupled to tandem mass spectrometry (MS/MS) employing electrospray ionisation (ESI) in negative mode was used for the quantification of target analytes. Method quantification limits (MQLs) were in the range of 1–10 ng kg−1 (ng l−1) for fish, meat, hen eggs, cheese and milk, and in the range of 2.5–125 ng kg−1 for butter. Only 16 of the group of 21 PFASs were found in at least one analysed sample. From 16 PFASs, perfluorooctane sulfonate (PFOS) was the most frequently detected analyte present in approximately 50% of samples (in the range of 0.98–2600 ng kg−1). PFCAs with C8–C14 carbon chain were presented in approximately 20% of samples. The concentration ranges of individual compounds in the respective groups of PFASs were: 2.33–76.3 ng kg−1 for PFSAs (without PFOS), 4.99–961 ng kg−1 for PFCAs, 10.6–95.4 ng kg−1 for PFPAs, and 1.61–519 ng kg−1 for FOSA. The contamination level in the analysed food commodities decreased in the following order: seafood > pig/bovine liver >> freshwater/marine fish > hen egg > meat >> butter. When comparing the total contamination and profiles of PFASs in food commodities that originated from various sampling countries, differences were identified, and the contents decreased as follows: Belgium >> Norway, Italy > Czech Republic.

This study describes determination of chloramphenicol (CAP) in honey, milk, and egg by LC-electrospray ionization (ESI)-MS. CAP was extracted with ethyl acetate from honey, and with acetonitrile from milk and egg. d5-CAP was used as the internal standard. Separation was achieved on a ZORBAX Eclipse C18 2.1 id, 150 mm, 2.1 μm column. The mass spectrometer was equipped with an ESI interface in negative mode. Mass determination of CAP and d5-CAP was carried out in selected ion monitoring mode by scanning m/z 321 for CAP and m/z 326 for d5-CAP as quantification ions, and m/z 323 as the confirmation ion. The validation of the analytical method was performed by carrying out linearity, LOD, LOQ, accuracy, precision, and recovery. Calibration curve was linear between 0.1 and 20.0 ng/g with correlation coefficient >0.998. Accuracy of the method for the honey sample was 95%, and for the milk powder sample 106%. Precision of the method, expressed as CV%, varied between 1.60 and 4.37 for intraday and 2.00 to 5.67 for interday. Quantification limits of method were 0.05, 0.08, and 0.09 ng/g for egg, milk, and honey, respectively. Recovery of the method ranged between 86 and 103% for all three matrixes and two different concentrations. Finally, the method was checked by participating proficiency tests from the Food Analysis Performance and Assessment Scheme 0281 and 0298 honey samples. Z scores were –1.0 and 0.4, respectively.

Electrospray ionization mass spectrometry (ESI-MS) measurements were performed under a variety of solution conditions on a highly acidic sub-fragment (B3C) of the C-terminal carbohydrate-binding repeat region of Clostridium difficile toxin B, and two mutants (B4A and B4B) containing fewer acidic residues. ESI-MS measurements performed in negative ion mode on aqueous ammonium acetate solutions of B3C at low ionic strength (I 80 mM) revealed evidence, based on the measured charge state distribution, of protein unfolding. In contrast, no evidence of unfolding was detected from ESI-MS measurements made in positive ion mode at low I or in either mode at higher I. The results of proton nuclear magnetic resonance and circular dichroism spectroscopy measurements and gel filtration chromatography performed on solutions of B3C under low and high I conditions suggest that the protein exists predominantly in a folded state in neutral aqueous solutions with I 10 mM. The results of ESI-MS measurements performed on B3C in a series of solutions with high I at pH 5 to 9 rule out the possibility that the structural changes are related to ESI-induced changes in pH. It is proposed that unfolding of B3C, observed in negative mode for solutions with low I, occurs during the ESI process and arises due to Coulombic repulsion between the negatively charged residues and liquid/droplet surface charge. ESI-MS measurements performed in negative ion mode on B4A and B4B also reveal a shift to higher charge states at low I but the magnitude of the changes are smaller than observed for B3C.

A simple method using a liquid chromatograph with a mass spectrometer has been developed for the determination of chlorophenols in food. mass spectral acquisition was performed in the negative mode by applying sungle ion monitoring. In LC separation, Cadenza CD-C18 and 10 mmol/L ammonium acetate-methanol were used as the column and mobile phase, respectively. Chlorophenols in food were extracted with methanol, and cleaned up with an Oasis HLB cartridge. The quantification limits were 0.2 ng/g for 4-chlorophenol, 2 ng/g for 2,6-dichlorophenol, 1 ng/g for 2,4-dichlorophenol and 0.5 ng/g for 2,4,6-trichlorophenol. The average rocoveries of chlorophenols from food at the spiked level of 20 ng/g were in the range of 70-85%. The relative standard deviations of all examined compounds were within 10%.

A negative-mode mass spectrometry approach characterizes intractable parts of the proteome.

Purpose Our aim was to identify obvious different metabolites and metabolic pathways to elucidate the etiology of rhegmatogenous retinal detachment associated with choroidal detachment (RRDCD) so as to provide direction toward diagnosis and treatment of RRDCD. Methods We used a liquid chromatography-quadrupole-time-of-flight/mass spectrometer (LC-Q-TOF/MS) to obtain the metabolome from the vitreous tissue of patients with rhegmatogenous retinal detachment (RRD) and RRDCD. The metabolomes from 29 samples (14 from RRD patients and 15 from RRDCD patients) were analyzed by principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). A one-way analysis of variance with a Bonferroni correction was used to test significance. The Biofluid Metabolites Database and Human Metabolome Database were used to identify ions. Results The PLS-DA identified 265 (variable importance in the project >1) ions whose levels were significantly different in vitreous from patients with RRD and RRDCD. Among the 265 ions, 24 (23 observed in the positive mode and 1 observed in the negative mode) were identified by searching MS and MS/MS fragments in the Biofluid Metabolites Database and Human Metabolome Database. Metabolites found were associated with pathways related to proliferation, inflammatory reactions, and hemodynamic changes. Conclusions Metabolites have been identified that were present in vitreous at significantly different levels between RRDCD and RRD. These metabolites are likely to be involved in the pathology of each disease and may potentially be used to diagnose and treat RRDCD and RRD.

To the Editor: We appreciate the opportunity to clarify and expand on our publication further. Human milk oligosaccharides have become an important area of research, primarily because of the pioneering efforts of several researchers and, particularly, of Professor Kunz. This publication [1] is one in a string of manuscripts that were submitted around the same time summarizing our efforts in measuring human milk oligosaccharides rapidly in several biological fluids. The paper published in this journal is best considered along with two other manuscripts in this area. With this in mind, we respond to the comments in each point. Points 1 and 2. Reproducibility and precision for the MALDI/MS was illustrated in this paper but the ESI LC/MS was not rigorously shown. We have published an additional paper [2] that shows the reproducibility and the repeatability of the LC/MS method using both isotopic labeling and peak areas. We show very good correlation between isotopic labeling and peak areas and now use primarily chromatographic peak areas for quantitation. We have also published a recent comprehensive paper [3] that shows high repeatability of LC/MS for oligosaccharides in terms of retention times, chromatographic peak area, and total ion abundances for the same sample injected nearly 30 times over a 3-d period. Point 3. We are very familiar with ion suppression in oligosaccharide analysis as demonstrated by an early paper on ion suppression onMALDI [4], where we show that native sialylated species are suppressed by neutral species in the positive mode by nearly a factor of 10, whereas in the negative mode sialylated species suppress neutral species. Similar suppression is observed in the ESI; however, when LC is performed, the components are separated and much less suppression occurs. In the earlier paper, we show that when the sialylated species and the neutral species are separated, their MS responses are very similar. Point 4. The water content is an issue with every biological fluid, whether it is serum, spinal fluid, saliva, or milk. It is an issue that everyone in this research needs to deal with carefully by freezing the sample as soon as possible and keeping the samples in −80 °C freezers in sealed containers. This is, in our opinion, standard operating procedure for nearly all laboratories working in this area, and we felt no need to comment on it further. Point 5. We agree that more descriptions should have been provided. However, taking into account the recommended length of the manuscript, we felt compelled to leave out This article is a response to the ‘Letter to the Editor’ to be found at DOI: 10.1007/s00216-013-7145-1