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.

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.

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.

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 Retention dependences support highly confident identification of lipid species in human plasma by reversed-phase UHPLC/MS

2021 ◽  
Author(s):  
Zuzana Vankova ◽  
Ondrej Peterka ◽  
Michaea Chocholouskova ◽  
Robert Jirasko ◽  
Denise Wolrab ◽  
...  
Keyword(s):  
Human Plasma ◽  
Reversed Phase ◽  
Mass Accuracy ◽  
Lipid Classes ◽  
Negative Ion ◽  
High Mass ◽  
Chromatographic Retention ◽  
Mass Analyzer ◽  
Lipid Species ◽  
Full Scan

Reversed-phase ultrahigh-performance liquid chromatography - mass spectrometry (RP-UHPLC/MS) method was developed with the aim to unambiguously identify a large number of lipid species from multiple lipid classes in human plasma. The optimized RP-UHPLC/MS method employed the C18 column with sub-2 micrometer particles with the total run time of 25 min. The chromatographic resolution was investigated with 42 standards from 18 lipid classes. The UHPLC system was coupled to high-resolution quadrupole - time-of-flight (QTOF) mass analyzer using electrospray ionization (ESI) measuring full scan and tandem mass spectra (MS/MS) in positive- and negative-ion modes with high mass accuracy. Our identification approach was based on m/z values measured with mass accuracy within 5 ppm tolerance in the full scan mode, characteristic fragment ions in MS/MS, and regularity in chromatographic retention dependences for individual lipid species, which provides the highest level of confidence for reported identifications of lipid species including regioisomeric and other isobaric forms. The graphs of dependences of retention times on the carbon number or on the number of double bond(s) in fatty acyl chains were constructed to support the identification of lipid species in homologous lipid series. Our list of identified lipid species is also compared with previous publications investigating human blood samples by various MS based approaches. In total, we have reported more than 500 lipid species representing 26 polar and nonpolar lipid classes detected in NIST Standard reference material 1950 human plasma.

229 RAPID, UNTARGETED LIPID DETERMINATION IN INDIVIDUAL BOVINE OOCYTES AND PRE-IMPLANTATION EMBRYOS BY HIGH-RESOLUTION DESORPTION ELECTROSPRAY IONIZATION MASS SPECTROMETRY

2013 ◽  
Vol 25 (1) ◽  
pp. 262 ◽  
Author(s):  
A. F. González-Serrano ◽  
C. R. Ferreira ◽  
V. Pirro ◽  
L. S. Eberlin ◽  
J. Heinzmann ◽  
...  
Keyword(s):  
High Resolution ◽  
Desorption Electrospray Ionization ◽  
Fatty Acyl ◽  
Glass Slide ◽  
Negative Ion ◽  
Ionization Mass ◽  
Desi Ms ◽  
Negative Ion Mode ◽  
Bovine Oocytes ◽  
Positive Ion

Lipid structural analysis in individual pre-implantation mammalian embryos is hampered by the small amount of biological material, such that most studies use staining methods or gas chromatography analysis generate information only on the fatty acyl residues. Recent developments in high-resolution desorption electrospray ionization mass spectrometry (DESI-MS) allow the analysis of free fatty acids (FA) and glycerophospholipids (PL) in individual bovine embryos. Here, we report on the use of DESI-MS for the sensitive analysis of triacylglycerol (TAG) species, profiles of FA and PL in individual bovine oocytes and embryos. Bovine oocytes (n = 40) and blastocysts (n = 42) were frozen in a minimal volume of PBS (2 to 5 µL). Samples were directly deposited on glass slides after thawing. After drying, a volume of 500 µL of methanol : water (1 : 1, vol/vol) was carefully deposited on the surface of the glass slide and removed by orienting the glass slide vertically to eliminate PBS salts. An Orbitrap mass spectrometer was used for the experiments. Parameters for the positive ion mode were as follows: acetonitrile (ACN) supplemented with 3 µL mL–1 of AgNO3 at a 5 µL min–1 flow rate, injection time of 1000 ms, and a mass-to-charge range of m/z 400 to 1500. For the negative ion mode, the solvent combination used was acetonitrile + dimethylformamide (1 : 1, vol/vol) at a 1.0 µL min–1 flow rate, a maximum injection time of 1000 ms, and a mass-to-charge range of m/z 150 to 1000. Positive ion mode data for the detection of TAG species were acquired first, followed by acquisition of FA and PL in the negative ion mode. Detection of TAG by DESI, which is extremely useful for bovine embryo cryopreservation and metabolism research, has been performed by adding AgNO3 in the DESI spray to obtain silver adducts, which are easily recognised by the characteristic 1 : 1 abundance ratio of the 107 : 109 Ag isotopes. The most abundant fatty acyl residues present in TAG species were palmitic (P), linoleic (L), oleic (O), and stearic (S) acids, such as TAG of m/z 937, PPL (50 : 2); m/z 965, POO (52 : 1); m/z 967, POS (52 : 2); m/z 989, OOL/LLS (54 : 4); and m/z 991, OOO, SOL (54 : 3). Free FA and PL profiles collected from the same samples in the negative ion mode were similar to those in our recent report (2012 J. Mass Spectrom. 47, 29–33). Lipid attribution has been performed based on high-resolution mass analysis. Multivariate statistics from this data set will allow visualisation of differences observed in the lipid profiles among samples. In conclusion, we report the use of DESI-MS for the sensitive analysis of TAG in individual bovine oocytes and embryos and the creation of profiles of FA, PL, and TAG species in the same sample by DESI-MS.

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