Should We Think Positive or Negative About Dihydrobenzofuran Neolignans? an ESI-MS/MS Study

2020 ◽  
Author(s):  
Herbert Dias ◽  
Eduardo Crevelin ◽  
Vinicius Palaretti ◽  
Ricardo Vessecchi ◽  
Antônio Eduardo Crotti
Keyword(s):  
Structural Features ◽  
Biologically Active ◽  
Negative Ion ◽  
Esi Ms ◽  
Product Ions ◽  
Sequential Mass Spectrometry ◽  
Negative Ion Mode ◽  
Gas Phase Fragmentation ◽  
Protonated Molecules ◽  
Positive Ion

<p>This study elucidates the gas-phase fragmentation pathways of a series of biologically active benzofuran neolignans (BNs) and dihydrobenzofuran neolignans (DBNs) by means of electrospray ionization accurate-mass tandem and sequential mass spectrometry (ESI-MS/MS and ESI-MS<sup>n</sup>) and thermochemical data estimated by using Computational Chemistry and the B3LYP/6-31+G(d,p) model. In their deprotonated forms, these compounds produced more diagnostic product ions as compared to the corresponding protonated molecules. Moreover, a series of odd-electron product ions (radical anions) were detected, which has not been reported for protonated DBNs. Direct C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>• elimination from the precursor ion (deprotonated molecule) only occurred for the BNs and can help to distinguish these compounds from the DBNs. Although the product ion [M‒CH<sub>3</sub>OH]<sup>‒</sup> emerged in the spectrum of all the DBNs analyzed here, the mechanism through which this ion originates strongly depends on specific structural features, so that further [M‒CH<sub>3</sub>OH]<sup>‒</sup> fragmentation generates important diagnostic product ions. Comparison between the ESI-MS/MS data of these compounds in the negative ion mode (deprotonated molecule) and in the positive ion mode (protonated molecule) revealed that the negative ion mode provides much more information (at least one diagnostic product ion emerged for all the analyzed compounds) and does not require the use of additives to produce the precursor ions (deprotonated molecules). </p>

Should We Think Positive or Negative About Dihydrobenzofuran Neolignans? an ESI-MS/MS Study

2020 ◽  
Author(s):  
Herbert Dias ◽  
Eduardo Crevelin ◽  
Vinicius Palaretti ◽  
Ricardo Vessecchi ◽  
Antônio Eduardo Crotti
Keyword(s):  
Structural Features ◽  
Biologically Active ◽  
Negative Ion ◽  
Esi Ms ◽  
Product Ions ◽  
Sequential Mass Spectrometry ◽  
Negative Ion Mode ◽  
Gas Phase Fragmentation ◽  
Protonated Molecules ◽  
Positive Ion

<p>This study elucidates the gas-phase fragmentation pathways of a series of biologically active benzofuran neolignans (BNs) and dihydrobenzofuran neolignans (DBNs) by means of electrospray ionization accurate-mass tandem and sequential mass spectrometry (ESI-MS/MS and ESI-MS<sup>n</sup>) and thermochemical data estimated by using Computational Chemistry and the B3LYP/6-31+G(d,p) model. In their deprotonated forms, these compounds produced more diagnostic product ions as compared to the corresponding protonated molecules. Moreover, a series of odd-electron product ions (radical anions) were detected, which has not been reported for protonated DBNs. Direct C<sub>2</sub>H<sub>3</sub>O<sub>2</sub>• elimination from the precursor ion (deprotonated molecule) only occurred for the BNs and can help to distinguish these compounds from the DBNs. Although the product ion [M‒CH<sub>3</sub>OH]<sup>‒</sup> emerged in the spectrum of all the DBNs analyzed here, the mechanism through which this ion originates strongly depends on specific structural features, so that further [M‒CH<sub>3</sub>OH]<sup>‒</sup> fragmentation generates important diagnostic product ions. Comparison between the ESI-MS/MS data of these compounds in the negative ion mode (deprotonated molecule) and in the positive ion mode (protonated molecule) revealed that the negative ion mode provides much more information (at least one diagnostic product ion emerged for all the analyzed compounds) and does not require the use of additives to produce the precursor ions (deprotonated molecules). </p>

Identification of Aflatoxins by Quadrupole Mass Spectrometry/Mass Spectrometry

1984 ◽  
Vol 67 (4) ◽  
pp. 734-738 ◽  
Author(s):  
Ronald D Plattner ◽  
Glenn A Bennett ◽  
Robert D Stubblefield
Keyword(s):  
Mass Spectrometry ◽  
Aflatoxin B1 ◽  
Impact Ionization ◽  
Negative Ion ◽  
Quadrupole Mass ◽  
Molecular Anion ◽  
Negative Ion Mode ◽  
Protonated Molecules ◽  
Positive Ion ◽  
Mass Spectrometry Mass Spectrometry

Abstract MS/MS daughter experiments were recorded for aflatoxins B1, B2, G1, G2, M1, M2, and aflatoxicol, using 3 ionization modes. Daughters were recorded from the molecular ion (M+) using electron impact ionization (EI). Daughters from the protonated molecules (MH+) were recorded in the positive ion mode and the daughters from the molecular anion (M+) were recorded in the negative ion mode using chemical ionization (CI). These daughter spectra are all relatively simple. The EI daughters are quite similar to conventional EI spectra. The yield of (M-) is about 100 times greater than the yield of M+ in EI or MH+ in isobutane CI spectrum. Negative ion daughter spectra were used to demonstrate the feasibility of determining the presence of aflatoxin B1 in crude extracts of contaminated corn. Aflatoxin B1 could be detected at 10 ppb.

Dependence of matrix effect on ionization polarity during LC–ESI–MS analysis of derivatized amino acids in some natural samples

2017 ◽  
Vol 23 (5) ◽  
pp. 245-253 ◽  
Author(s):  
Maarja-Liisa Oldekop ◽  
Riin Rebane ◽  
Koit Herodes
Keyword(s):  
Amino Acids ◽  
Matrix Effect ◽  
Negative Ion ◽  
Herbal Extracts ◽  
Esi Ms ◽  
Ms Analysis ◽  
The Matrix ◽  
Negative Ion Mode ◽  
Positive Ion ◽  
Sample Dilution

Matrix effect, the influence of co-eluting components on the ionization efficiency of the analyte, affects the trueness and precision of the LC–ESI–MS analysis. Derivatization can reduce or eliminate matrix effect, for example, diethyl ethoxymethylenemalonate (DEEMM) derivatives have shown less matrix effect compared to other derivatives. Moreover, the use of negative ion mode can further reduce matrix effect. In order to investigate the combination of derivatization and different ionization modes, an LC–ESI–MS/MS method using alternating positive/negative ion mode was developed and validated. The analyses in positive and negative ion modes had comparable limit of quantitation values. The influence of ESI polarity on matrix effect was investigated during the analysis of 22 DEEMM-derivatized amino acids in herbal extracts and honeys. Sample dilution approach was used for the evaluation of the presence of matrix effect. Altogether, 4 honeys and 11 herbal extracts were analyzed, and the concentrations of 22 amino acids in the samples are presented. In the positive ion mode, matrix effect was observed for several amino acid derivatives and the matrix effect was stronger in honey samples compared to the herbal extracts. The negative ion mode was free from matrix effect, with only few exceptions in honeys (average relative standard deviation over all analytes and matrices was 8%; SD = 7%). The matrix effect was eliminated in the positive ion mode by sample dilution and agreement between concentrations from the two ion modes was achieved for most amino acids. In conclusion, it was shown that the combination of derivatization and negative ion mode can be a powerful tool for minimizing matrix effect in more complicated applications.

Serum Lipids Profiling Perturbances in Patients with Ischemic Heart Disease and Ischemic Cardiomyopathy

2020 ◽  
Author(s):  
Lin Yang ◽  
Liang Wang ◽  
Yangyang Deng ◽  
Lizhe Sun ◽  
Bowen Low ◽  
...  
Keyword(s):  
Heart Disease ◽  
Ischemic Heart Disease ◽  
Ischemic Cardiomyopathy ◽  
Serum Lipids ◽  
Ischemic Heart ◽  
Negative Ion ◽  
Serum Samples ◽  
Cross Sectional ◽  
Negative Ion Mode ◽  
Positive Ion

Abstract Background: Ischemic heart disease (IHD) is a common cardiovascular disorder associated with inadequate blood supply to the myocardium. Chronic coronary ischemia leads to ischemic cardiomyopathy (ICM). Despite their rising prevalence and morbidity, few studies have discussed the lipids alterations in these patients. Methods: In this cross-sectional study, we analyzed serum lipids profile in IHD and ICM patients using a lipidomics approach. Consecutive consenting patients admitted to the hospital for IHD and ICM were enrolled. Serum samples were obtained after overnight fasting. Non-targeted metabolomics was applied to demonstrate lipids metabolic profile in control, IHD and ICM patients. Results: A total of 63 and 62 lipids were detected in negative and positive ion mode respectively. Among them, 16:0 Lyso PI, 18:1 Lyso PI in negative ion mode, and 19:0 Lyso PC, 12:0 SM d18:1/12:0, 15:0 Lyso PC, 17:0 PC, 18:1-18:0 PC in positive ion mode were significantly altered both in IHD and ICM as compared to control. 13:0 Lyso PI, 18:0 Lyso PI, 16:0 PE, 14:0 PC DMPC, 16:0 ceramide, 18:0 ceramide in negative ion mode, and 17:0 PE, 19:0 PC, 14:0 Lyso PC, 20:0 Lyso PC, 18:0 PC DSPC, 18:0-22:6 PC in positive ion mode were significantly altered only in ICM as compared to IHD and control. Conclusion: Using non-targeted lipidomics profiling, we have successfully identified a group of circulating lipids that were significantly altered in IHD and ICM. The lipids metabolic signatures shed light on potential new biomarkers and therapeutics for preventing and treating ICM.

Structural investigation of perfluorocarboxylic acid derivatives formed in the reaction with N,N-dimethylformamide dialkylacetals

2019 ◽  
Vol 26 (2) ◽  
pp. 131-143 ◽  
Author(s):  
Monika Stróżyńska ◽  
Jürgen H. Gross ◽  
Katrin Schuhen
Keyword(s):  
Structural Investigation ◽  
Direct Analysis ◽  
Dimethyl Acetal ◽  
Negative Ion ◽  
Cluster Ions ◽  
Perfluorocarboxylic Acid ◽  
Reaction Products ◽  
Salt Structure ◽  
Negative Ion Mode ◽  
Positive Ion

A structural investigation of perfluorocarboxylic acid derivatives formed in the reaction with N,N-dimethylformamide dialkylacetals employing several techniques of mass spectrometry (MS) is described. Two derivatizing reagents, dimethylformamide dimethyl acetal (DMF-DMA) and dimethylformamide diethylacetal (DMF-DEA) were used. In contrast to carboxylic acids, perfluorocarboxylic acids are not able to form alkyl esters as the main product in this reaction. We found that perfluorooctanoic acid (PFOA) forms a salt with N,N-dimethylformamide dialkylacetals. This salt undergoes a further reaction inside the injection block of a gas chromatograph (GC) by loss of CO2 and then forms 1,1-perfluorooctane-(N,N,N,N-tetramethyl)-diamine. The GC-MS experiments using both electron ionization (EI) and positive-ion chemical ionization (PCI) revealed that the same reaction products are formed with either derivatizing reagent. Subjecting the perfluorocarboxylic acid derivative to electrospray ionization (ESI) and direct analysis in real time (DART), both positive- and negative-ion modes indicated that cluster ions are formed. In the positive-ion mode, this cluster ion consists of two iminium cations and one PFOA anion, while in the negative-ion mode, it comprises two PFOA anions and one cation. The salt structure was further confirmed by liquid injection field desorption/ionization (LIFDI) as well as infrared (IR) spectroscopy. We propose a simple mechanism of N,N,N′,N′-tetramethylformamidinium cation formation. The structure elucidation is supported by specific fragment ions as obtained by GC-EI-MS and GC-PCI-MS analyses.

scholarly journals Sensing Precursors of Illegal Drugs—Rapid Detection of Acetic Anhydride Vapors at Trace Levels Using Photoionization Detection and Ion Mobility Spectrometry

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1852
Author(s):  
Victor Bocos-Bintintan ◽  
George-Bogdan Ghira ◽  
Mircea Anton ◽  
Aurel-Vasile Martiniuc ◽  
Ileana-Andreea Ratiu
Keyword(s):  
Acetic Anhydride ◽  
Ion Mobility Spectrometry ◽  
Ion Mobility ◽  
Operation Mode ◽  
Analytical Techniques ◽  
Negative Ion ◽  
Illegal Drugs ◽  
Product Ions ◽  
Ultra Trace ◽  
Negative Ion Mode

Sensitive real-time detection of vapors produced by the precursors, reagents and solvents used in the illegal drugs manufacture represents a priority nowadays. Acetic anhydride (AA) is the key chemical used as acetylation agent in producing the illegal drugs heroin and methaqualone. This study was directed towards quick detection and quantification of AA in air, using two fast and very sensitive analytical techniques: photoionization detection (PID) and ion mobility spectrometry (IMS). Results obtained indicated that both PID and IMS can sense AA at ultra-trace levels in air, but while PID produces a non-selective response, IMS offers richer information. Ion mobility spectrometric response in the positive ion mode presented one product ion, at reduced ion mobility K0 of 1.89 cm2 V−1 s−1 (almost overlapped with positive reactant ion peak), while in the negative ion mode two well separated product ions, with K0 of 1.90 and 1.71 cm2 V−1 s−1, were noticed. Our study showed that by using a portable, commercial IMS system (model Mini IMS, I.U.T. GmbH Berlin) AA can be easily measured at concentrations of 0.05 ppmv (0.2 mg m−3) in negative ion mode. Best selectivity and sensitivity of the IMS response were therefore achieved in the negative operation mode.

Positive and negative ion mode ESI-MS and MS/MS for studying drug–DNA complexes

2006 ◽  
Vol 253 (3) ◽  
pp. 156-171 ◽  
Author(s):  
Frédéric Rosu ◽  
Sophie Pirotte ◽  
Edwin De Pauw ◽  
Valérie Gabelica
Keyword(s):  
Negative Ion ◽  
Dna Complexes ◽  
Esi Ms ◽  
Negative Ion Mode

scholarly journals Comparative transcriptome and metabolome analysis of Ostrinia furnacalis female adults under UV-A exposure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Li Su ◽  
Changli Yang ◽  
Jianyu Meng ◽  
Lv Zhou ◽  
Changyu Zhang
Keyword(s):  
Immune Defense ◽  
Negative Ion ◽  
Comparative Transcriptome ◽  
Ostrinia Furnacalis ◽  
Metabolome Analysis ◽  
Dna Libraries ◽  
Important Pest ◽  
Negative Ion Mode ◽  
And Control ◽  
Positive Ion

AbstractUltraviolet A (UV-A) radiation is a significant environmental factor that causes photoreceptor damage, apoptosis, and oxidative stress in insects. Ostrinia furnacalis is an important pest of corn. To understand the adaptation mechanisms of insect response to UV-A exposure, this study revealed differentially expressed genes (DEGs) and differently expressed metabolites (DEMs) in O. furnacalis under UV-A exposure. Three complementary DNA libraries were constructed from O. furnacalis adult females (CK, UV1h, and UV2h), and 50,106 expressed genes were obtained through Illumina sequencing. Of these, 157 and 637 DEGs were detected in UV1h and UV2h after UV-A exposure for 1 and 2 h, respectively, compared to CK, with 103 and 444 upregulated and 54 and 193 downregulated genes, respectively. Forty four DEGs were detected in UV2h compared to UV1h. Comparative transcriptome analysis between UV-treated and control groups revealed signal transduction, detoxification and stress response, immune defense, and antioxidative system involvement. Metabolomics analysis showed that 181 (UV1h vs. CK), 111 (UV2h vs. CK), and 34 (UV2h vs. UV1h) DEMs were obtained in positive ion mode, while 135 (UV1h vs. CK), 93 (UV2h vs. CK), and 36 (UV2h vs. UV1h) DEMs were obtained in negative ion mode. Moreover, UV-A exposure disturbed amino acid, sugar, and lipid metabolism. These findings provide insight for further studies on how insects protect themselves under UV-A stress.

scholarly journals Evaluation of 6 MALDI-Matrices for 10 μm lipid imaging and on-tissue MSn with AP-MALDI-Orbitrap

2021 ◽  
Author(s):  
Tina B. Angerer ◽  
Jerome Bour ◽  
Jean-Luc Biagi ◽  
Eugene Moskovets ◽  
Gilles Frache
Keyword(s):  
Spatial Resolution ◽  
Tissue Sample ◽  
Additional Treatment ◽  
Negative Ion ◽  
High Mass ◽  
Lipid Species ◽  
High Mass Resolution ◽  
Matrix Additives ◽  
Negative Ion Mode ◽  
Positive Ion

Mass spectrometry imaging (MSI) is a technique uniquely suited to localize and identify lipids in a tissue sample. Using an AP-MALDI UHR source coupled to an Orbitrap Elite, numerous lipid locations and structures can be determined in high mass resolution spectra and at cellular spatial resolution, but careful sample preparation is necessary. We tested 11 protocols on serial brain sections for the commonly used MALDI matrices, CHCA, Norharmane, DHB, DHAP, THAP, and DAN, in combination with tissue washing and matrix additives, to determine the lipid coverage, signal intensity, and spatial resolution achievable with AP-MALDI. In positive ion mode, the most lipids could be detected with CHCA and THAP, while THAP and DAN without additional treatment offered the best signal intensities. In negative ion mode, DAN showed the best lipid coverage and DHAP performed superior for Gangliosides. DHB produced intense cholesterol signals in the white matter. 155 lipids were assigned in positive (THAP), 137 in negative ion mode (DAN) and 76 lipids were identified using on tissue tandem-MS. The spatial resolution achievable with DAN was 10 μm, confirmed with on tissue line-scans. This enabled the association of lipid species to single neurons in AP-MALDI images. The results show that the performance of AP-MALDI is comparable to vacuum MALDI techniques for lipid imaging.

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