Study of Double Bond Equivalents and the Numbers of Carbon and Oxygen Atom Distribution of Dissolved Organic Matter with Negative-Mode FT-ICR MS

Top-down lignomic matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry analysis of lignin oligomers extracted from date palm wood

RATIONALE

We report for the first time the top-down lignomic analysis of the virgin released lignin (VRL) oligomers obtained from the Saudi date palm wood (SDPW), using a matrix-assisted laser desorption/ionization time-of-flight/time-of-flight (MALDI-TOF/TOF) instrument. In addition, we are proposing new collision-induced dissociation tandem mass spectrometry (CID-MS/MS) fragmentation routes for this series of unreported VRL oligomers.

METHODS

We have used direct MALDI-TOF-MS analysis of the mixture of lignin oligomers without any chromatographic pre-separation. High-energy CID-MS/MS analyses were used to confirm the precursor ion structures.

RESULTS

Six protonated lignin oligomer molecules were identified: [C₁₉ H₂₄ O₈  + H]⁺ as H(8-O-4')G; [C₅₀ H₅₂ O₁₉  + H]⁺ as H(8-O-4')H(8-O-4'')S(8-O-4''')S(8-O-4'''')G; [C₅₈ H₅₄ O₁₈ + H]⁺ as H(8-O-4')H(8-O-4'')H(8-O-4''')G(8-O-4'''')S(8-O-4''''')G; [C₅₈ H₅₄ O₁₉  + H]⁺ as H(8-O-4')H(8-O-4'')H(8-O-4''')S(8-O-4'''')S(8-O-4''''')G; [C₆₁ H₆₈ O₂₅  + H]⁺ as H(8-O-4')G(8-O-4'')G(8-O-4''')S(8-O-4'''')S(8-O-4''''')G; and [C₆₁ H₆₈ O₂₆  + H]⁺ as C(8-O-4')G(8-O-4'')G(8-O-4''')S(8-O-4'''')S(8-O-4''''')G units (H = coniferyl, S = sinapyl, and G = p-coumaryl). Two distonic cations were identified as [C₃₉ H₄₃ O₁₅  + H]^+• and [C₄₀ H₄₃ O₁₆  + H]^+• deriving from two tetrameric lignin oligomers. The high-energy MS/MS analyses allowed the confirmation of the proposed structures of this series of lignin oligomers.

CONCLUSIONS

To our knowledge, this is the first elucidation of the lignin structure of the Saudi seedling date palm wood that was accomplished using a top-down lignomic strategy that has not previously been published. The complex high-energy CID-MS/MS fragmentations presented herein are novel and have never been described before.

Organic sulfur fingerprint indicates continued injection fluid signature 10 months after hydraulic fracturing

Hydraulic fracturing requires the injection of large volumes of fluid to extract oil and gas from low permeability unconventional resources (e.g., shale, coalbed methane), resulting in the production of large volumes of highly complex and variable waste fluids. Shale gas fluid samples were collected from two hydraulically fractured wells in Morgantown, WV, USA at the Marcellus Shale Energy and Environment Laboratory (MSEEL) and analyzed using ultrahigh resolution mass spectrometry to investigate the dissolved organic sulfur (DOS) pool. Using a non-targeted approach, ions assigned DOS formulas were analyzed to identify dominant DOS classes, describe their temporal trends and their implications, and describe the molecular characteristics of the larger DOS pool. The average molecular weight of organic sulfur compounds in flowback decreased and was lowest in produced waters. The dominant DOS classes were putatively assigned to alcohol sulfate and alcohol ethoxysulfate surfactants, likely injected as fracturing fluid additives, on the basis of exact mass and homolog distribution matching. This DOS signature was identifiable 10 months after the initial injection of hydraulic fracturing fluid, and an absence of genes that code for alcohol ethoxysulfate degrading proteins (e.g., sulfatases) in the shale well genomes and metagenomes support that these additives are not readily degraded biologically and may continue to act as a chemical signature of the injected fluid. Understanding the diversity, lability, and fate of organic sulfur compounds in shale wells is important for engineering productive wells and preventing gas souring as well as understanding the consequences of unintended fluid release to the environment. The diversity of DOS, particularly more polar compounds, needs further investigation to determine if the identified characteristics and temporal patterns are unique to the analyzed wells or represent broader patterns found in other formations and under other operating conditions.

Naphthenic Acid Mixtures and Acid-Extractable Organics from Oil Sands Process-Affected Water Impair Embryonic Development of Silurana (Xenopus) tropicalis

Naphthenic acids (NAs) are carboxylic acids naturally occurring in crude oils and bitumen and are suspected to be the primary toxic substances in wastewaters associated with oil refineries and mining of oil sands. Oil sands process-affected water (OSPW) generated by the extraction of bitumen from oil sands are a major source of NAs and are currently stored in tailings ponds. We report on the acute lethality and teratogenic effects of aquatic exposure of Silurana (Xenopus) tropicalis embryos to commercial NA extracts and from the acid extractable organics (AEOs) fraction of a Canadian OSPW. Using electrospray ionization-high resolution mass spectrometry, we determined that the O₂ species proportion were 98.8, 98.9 and 58.6% for commercial mixtures Sigma 1 (S1M) and Sigma 2 (S2M), and AEOs, respectively. The 96h LC₅₀ estimates were 10.4, 11.7, and 52.3 mg/L for S1M, S2M, and the AEOs, respectively. The 96h EC₅₀ estimates based on frequencies of developmental abnormalities were 2.1, 2.6, and 14.2 mg/L for S1M, S2M, and the AEOs, respectively. The main effects observed were reduced body size, edema, and cranial, heart, gut and ocular abnormalities. Increasing concentrations of the mixtures resulted in increased severity and frequency of abnormalities ( p < 0.05). The rank-order potency was S1M > S2M > AEO based on LC₅₀ and EC₅₀ estimates. These data provide insight into the effects NAs in amphibian embryos and can contribute to the development of environmental guidelines for the management of OSPW.

Yellowstone Hot Springs are Organic Chemodiversity Hot Spots

Yellowstone National Park hydrothermal springs were investigated according to their organic geochemistry with a special focus on the Yellowstone hot spring dissolved organic matter (YDOM) that was solid-phase extracted. Here we show that YDOM has a unique chemodiversity that has not yet been observed anywhere else in aquatic surface environments and that Yellowstone hot springs are organic chemodiversity hot spots. Four main geochemically classified hot spring types (alkaline-chloride, mixed alkaline-chloride, acid-chloride-sulfate and travertine-precipitating) exhibited distinct organic molecular signatures that correlated remarkably well with the known inorganic geochemistry and manifested themselves in excitation emission matrix fluorescence, nuclear magnetic resonance, and ultrahigh resolution mass spectra. YDOM contained thousands of molecular formulas unique to Yellowstone of which 80% contained sulfur, even in low hydrogen sulfide containing alkaline-chloride springs. This unique YDOM reflects the extreme organic geochemistry present in the hydrothermal features of Yellowstone National Park.

Transformations of dissolved organic matter induced by UV photolysis, Hydroxyl radicals, chlorine radicals, and sulfate radicals in aqueous-phase UV-Based advanced oxidation processes

Considering the increasing identification of trace organic contaminants in natural aquatic environments, the removal of trace organic contaminants from water or wastewater discharge is an urgent task. Ultraviolet (UV) and UV-based advanced oxidation processes (AOPs), such as UV/hydrogen peroxide (UV/H₂O₂), UV/free chlorine and UV/persulfate, are attractive and promising approaches for the removal of these contaminants due to the high reactivity of active radical species produced in these UV-AOPs with a wide variety of organic contaminants. However, the removal efficiency of trace contaminants is greatly affected by the presence of background dissolved organic matter (DOM). In this study, we use ultrahigh resolution mass spectrometry to evaluate the transformation of a standard Suwanee River fulvic acid DOM isolate in UV photolysis and UV-AOPs. The use of probe compounds allows for the determination of the steady-state concentrations of active radical species in each UV-AOP. The changes in the H/C and O/C elemental ratios, double bond equivalents, and the low-molecular-weight transformation product concentrations of organic acids reveal that different DOM transformation patterns are induced by each UV-AOP. By comparison with the known reactivities of each radical species with specific organic compounds, we mechanistically and systematically elucidate the molecular-level DOM transformation pathways induced by hydroxyl, chlorine, and sulfate radicals in UV-AOPs. We find that there is a distinct transformation in the aliphatic components of DOM due to HO• in UV/H₂O₂ and UV/free chlorine. Cl• induced transformation of olefinic species is also observed in the UV/free chlorine system. Transformation of aromatic and olefinic moieties by SO₄^•- are the predominant pathways in the UV/persulfate system.

Molecular Chemistry of Atmospheric Brown Carbon Inferred from a Nationwide Biomass Burning Event

Lag Ba'Omer, a nationwide bonfire festival in Israel, was chosen as a case study to investigate the influence of a major biomass burning event on the light absorption properties of atmospheric brown carbon (BrC). The chemical composition and optical properties of BrC chromophores were investigated using a high performance liquid chromatography (HPLC) platform coupled to photo diode array (PDA) and high resolution mass spectrometry (HRMS) detectors. Substantial increase of BrC light absorption coefficient was observed during the night-long biomass burning event. Most chromophores observed during the event were attributed to nitroaromatic compounds (NAC), comprising 28 elemental formulas of at least 63 structural isomers. The NAC, in combination, accounted for 50-80% of the total visible light absorption (>400 nm) by solvent extractable BrC. The results highlight that NAC, in particular nitrophenols, are important light absorption contributors of biomass burning organic aerosol (BBOA), suggesting that night time chemistry of •NO₃ and N₂O₅ with particles may play a significant role in atmospheric transformations of BrC. Nitrophenols and related compounds were especially important chromophores of BBOA. The absorption spectra of the BrC chromophores are influenced by the extraction solvent and solution pH, implying that the aerosol acidity is an important factor controlling the light absorption properties of BrC.

Application of phase correction to improve the characterization of photooxidation products of lignin using 7 Tesla Fourier-transform ion cyclotron resonance mass spectrometry

Lignin is the second most abundant natural biopolymer and potentially a valuable alternative energy source for conventional fossil fuels. In this study, Fourier-transform ion cyclotron resonance-mass spectrometry (FTICR-MS) in conjunction with phase correction was applied to study photooxidation products of lignin using a 7 Tesla (T) mass spectrometer. The application of 7 T FTICR-MS has often been inadequate for the analysis of complex natural organic matter because of insufficient resolving power as compared with high-field FTICR, which led to incorrect assignments of elemental formulae and discontinuous plots in graphical and statistical analyses. Here, the application of phase correction to the FTICR mass spectra of lignin oxidation products greatly improved the spectral quality, and thus, readily permitted characterization of photooxidation processes of lignin compounds under simulated solar radiation conditions.

Shedding light on the structures of lignin compounds: photo-oxidation under artificial UV light and characterization by high resolution mass spectrometry

Lignin is the second most abundant natural polymer and a promising alternative energy source for conventional fossil fuels. In this study, we investigated transformations of lignin compounds under artificial UV light conditions at the molecular level. Such light-induced changes of composition profiles in nature after sun exposure have been studied for crude oil in the petroleomics field. We applied a similar high resolution mass spectrometry experimental strategy to lignin and demonstrated various data processing methods to reveal the characteristic differences between the extremely complex data sets of two sample sets, one native control before and one sample after photo-irradiation, using Fourier transform ion cyclotron resonance-mass spectrometry. Graphical abstract Kendrick mass defect versus nominal Kendrick mass for mass spectra of a control and UV-oxidized lignin sample.

Molecular diversity of riverine alkaline-extractable sediment organic matter and its linkages with spectral indicators and molecular size distributions

Few studies have been conducted to examine the spatial heterogeneity of riverine sediment organic matter (SOM) at the molecular level. The present study explored the chemical and molecular heterogeneity of alkaline-extractable SOM from riverine sediments via multiple analytical tools including molecular composition, absorption and fluorescence spectra, and molecular size distributions. The riverine SOM revealed complex and diverse characteristics, exhibiting a great number of non-redundant formulas and high spatial variations. The molecular diversity was more pronounced for the sediments affected by a higher degree of anthropogenic activities. Unlike the cases of aquatic dissolved organic matter, highly-unsaturated structures with oxygen (HUSO) of SOM were more associated with the spectral and size features of humic-like (or terrestrial) substances than aromatic molecules were, cautioning the interpretation of the SOM molecules responsible for apparent indicators. Noting that a higher detection rate (DR) produces fewer common molecules, the common molecules of 23 different SOMs were determined at a reasonable DR value of 0.35, which accounted for a small portion (5.8%) of all detected molecules. They were mainly CHO compounds (>98%), which positively correlated with spectral indicators of biological production. Despite the low abundance, however, the ratios of aromatic to aliphatic substances could be indexed to classify the common molecules into several geochemical molecular groups with different degrees of the associations with the apparent spectral and size indicators.

Two-dimensional mass defect matrix plots for mapping genealogical links in mixtures of lignin depolymerisation products

Lignin is the second most abundant natural biopolymer, and lignin wastes are therefore potentially significant sources for renewable chemicals such as fuel compounds, as alternatives to fossil fuels. Waste valorisation of lignin is currently limited to a few applications such as in the pulp industry, however, because of the lack of effective extraction and characterisation methods for the chemically highly complex mixtures after decomposition. Here, we have implemented high resolution mass spectrometry and developed two-dimensional mass defect matrix plots as a data visualisation tool, similar to the Kendrick mass defect plots implemented in fields such as petroleomics. These 2D matrix plots greatly simplified the highly convoluted lignin mass spectral data acquired from Fourier transform ion cyclotron resonance (FTICR)–mass spectrometry, and the derived metrics provided confident peak assignments and strongly improved structural mapping of lignin decomposition product series from the various linkages within the lignin polymer after electrochemical decomposition.

Graphical Abstract

Molecular-Scale Investigation with ESI-FT-ICR-MS on Fractionation of Dissolved Organic Matter Induced by Adsorption on Iron Oxyhydroxides

Adsorption by minerals is a common geochemical process of dissolved organic matter (DOM) which may induce fractionation of DOM at the mineral-water interface. Here, we examine the molecular fractionation of DOM induced by adsorption onto three common iron oxyhydroxides using electrospray ionization coupled with Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). Ferrihydrite exhibited higher affinity to DOM and induced more pronounced molecular fractionation of DOM than did goethite or lepidocrocite. High molecular weight (>500 Da) compounds and compounds high in unsaturation or rich in oxygen including polycyclic aromatics, polyphenols and carboxylic compounds had higher affinity to iron oxyhydroxides and especially to ferrihydrite. Low molecular weight compounds and compounds low in unsaturation or containing few oxygenated groups (mainly alcohols and ethers) were preferentially maintained in solution. This study confirms that the double bond equivalence and the number of oxygen atoms are valuable parameters indicating the selective fractionation of DOM at mineral and water interfaces. The results of this study provide important information for further understanding the behavior of DOM in the natural environment.

Indexing Permafrost Soil Organic Matter Degradation Using High-Resolution Mass Spectrometry

Microbial degradation of soil organic matter (SOM) is a key process for terrestrial carbon cycling, although the molecular details of these transformations remain unclear. This study reports the application of ultrahigh resolution mass spectrometry to profile the molecular composition of SOM and its degradation during a simulated warming experiment. A soil sample, collected near Barrow, Alaska, USA, was subjected to a 40-day incubation under anoxic conditions and analyzed before and after the incubation to determine changes of SOM composition. A CHO index based on molecular C, H, and O data was utilized to codify SOM components according to their observed degradation potentials. Compounds with a CHO index score between -1 and 0 in a water-soluble fraction (WSF) demonstrated high degradation potential, with a highest shift of CHO index occurred in the N-containing group of compounds, while similar stoichiometries in a base-soluble fraction (BSF) did not. Additionally, compared with the classical H:C vs O:C van Krevelen diagram, CHO index allowed for direct visualization of the distribution of heteroatoms such as N in the identified SOM compounds. We demonstrate that CHO index is useful not only in characterizing arctic SOM at the molecular level but also enabling quantitative description of SOM degradation, thereby facilitating incorporation of the high resolution MS datasets to future mechanistic models of SOM degradation and prediction of greenhouse gas emissions.

Structural characterization of organic aerosol using Fourier transform ion cyclotron resonance mass spectrometry: aromaticity equivalent approach

RATIONALE

A challenge of atmospheric particulate matter (PM) analysis is the understanding of the sources and chemistry of complex organic aerosols, especially the water-soluble organic compounds (WSOC) fraction, a key component of atmospheric fine PM (PM(2.5)). The sources of WSOC are not well understood and, thus, the molecular characterization of WSOC is important because it provides insight into aerosol sources and the underlying mechanisms of secondary organic aerosols formation and transformation.

METHODS

In this study, molecular characterization of WSOC was achieved using Fourier transform ion cyclotron resonance mass spectrometry. The aromaticity equivalent (X(c)), a new parameter calculated from the assigned molecular formula, is introduced to improve the identification and characterization of aromatic and condensed aromatic compounds in WSOC. Diesel PM (DPM) and atmospheric PM samples were used to study the applicability of the proposed method.

RESULTS

Threshold values of X(c) ≥2.5000 and X(c) ≥2.7143 are proposed as unambiguous minimum criteria for the presence of aromatics and condensed aromatics, respectively. By using these criteria, 36% of precursors were defined as aromatics and condensed aromatics in the DPM. For comparison, 21% of aromatic and condensed aromatic compounds were defined using the Aromaticity Index (AI) classification. The lower estimates by the AI approach are probably due to the failure to recognize aromatics and condensed aromatics with longer alkyl chains. The estimated aromatic and condensed aromatic fractions in the atmospheric aerosol samples collected in an industrial area affected by biomass burning events were 51.2 and 50.0%, respectively.

CONCLUSIONS

The advantage of employing this parameter is that X(c) would have a constant value for each proposed core structure regardless of the degree of alkylation, and thus visual representation and structural interpretations of the spectra become advantageous for characterizing and comparing complex samples. In addition, the proposed parameter complements the AI classification and identification of aromatic and condensed aromatic structures in complex matrices.

Structural characterization of dissolved organic matter: a review of current techniques for isolation and analysis

Natural dissolved organic matter (DOM) in aquatic systems plays many environmental roles: providing building blocks and energy for aquatic biota, acting as a sunscreen in surface water, and interacting with anthropogenic compounds to affect their ultimate fate in the environment. Such interactions are a function of DOM composition, which is difficult to ascertain due to its heterogeneity and the co-occurring matrix effects in most aquatic samples. This review focuses on current approaches to the chemical structural characterization of DOM, ranging from those applicable to bulk samples and in situ analyses (UV-visible spectrophotometry and fluorescence spectroscopy) through the concentration/isolation of DOM followed by the application of one or more analytical techniques, to the detailed separation and analysis of individual compounds or compound classes. Also provided is a brief overview of the main techniques used to characterize isolated DOM: mass spectrometry (MS), nuclear magnetic resonance mass spectrometry (NMR) and Fourier transform infrared spectroscopy (FTIR).

Evaluation of biologically mediated changes in oil sands naphthenic acid composition by Chlamydomonas reinhardtii using negative-ion electrospray orbitrap mass spectrometry

Industrial activity associated with oil-sands extraction in Canada's Athabasca region produces a variety of contaminants of concern, including naphthenic acid fraction components (NAFCs). NAFCs are a complex mixture of organic compounds that are poorly understood both in terms of their chemical composition and effects on the environment. NAFC toxicity in the unicellular green algae Chlamydomonas reinhardtii P.A.Dangeard was correlated with the presence of the algal cell wall. It was suggested that the toxicity of NAFCs in C. reinhardtii was due to surfactant effects. Surfactant-cell wall interactions are specific and governed by the compound class and structure, and by the nature of the biological material. Here, we investigate the effects of wildtype (WT) C. reinhardtii and two cell-wall mutants on specific classes of NAFCs when growing cultures were treated with a 100 mg · L(-1) solution of NAFCs. Changes in the NAFC composition in the media were examined using high resolution mass spectrometry over a period of 4 d. Algal mediated changes in the NAFCs were limited to specific classes of NAFCs. In particular, the removal of large, classical naphthenic acids, with a double bond equivalent of 8, was observed in WT C. reinhardtii cultures. The observed algal mediated changes in NAFC composition would have been masked by low resolution mass spectrometry and highlight the importance of this tool in examining bioremediation of complex mixtures of NAFCs.

Atmospheric pressure photo ionization hydrogen/deuterium exchange mass spectrometry--a method to differentiate isomers by mass spectrometry

In this report, a method for in-source hydrogen/deuterium (H/D) exchange at atmospheric pressure is reported. The method was named atmospheric pressure photo ionization hydrogen/deuterium exchange mass spectrometry (APPI HDX MS). H/D exchange was performed by mixing samples dissolved in toluene with CH3OD solvent and analyzing the mixture using atmospheric pressure photo ionization mass spectrometry (APPI-MS). The APPI HDX spectra obtained with contact times between the analyte solution and methanol-OD (CH3OD) of < 0.5 s or 1 h showed the same pattern of H/D exchange. Therefore, it was concluded that APPI HDX occurred in the source but not in the solution. The proposed method does not require a specific type of mass spectrometer and can be performed at atmospheric pressure. H/D exchange can be performed in any laboratory with a mass spectrometer and a commercial APPI source. Using this method, multiple H/D exchanges of aromatic hydrogen and/or H/D exchange of active hydrogen were observed. These results demonstrated that H/D exchange can be used to distinguish between isomers containing primary, secondary, and tertiary amines, as well as pyridine and pyrrole functional groups.

Fourier transform ion cyclotron resonance mass spectrometric analysis of the green fraction of soil humic acids

RATIONALE

The green fraction of soil humic acids (HAs), designated Pg, contains 4,9-dihydroxyperylene-3,10-quinone (DHPQ) as a chromophore. Although various naturally occurring DHPQ derivatives are known to occur and Pg-like absorption is observed in the UV-visible spectra of HAs from various types of soils worldwide, the chemical structure of Pg is still unknown.

METHODS

For a better understanding of the chemical composition of Pg, the pre-isolated (crude Pg) and purified Pg (G2) samples and three soil HAs with different degrees of humification were analyzed using negative-mode electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) at 12 Tesla. The Pg samples were characterized using H/C-O/C ratios and based on the type and magnitude of the molecular formulae having DHPQ or related compounds as a potential structure.

RESULTS

The H/C-O/C diagram indicated that most of the lipids, proteins, other aliphatics, and lignin-like components were removed, while condensed aromatic components were concentrated during the purification process of crude Pg to G2 using Sephadex G-50. More than 27 molecular formulae resembling DHPQ, DHPQ substituted with varying numbers of carboxyl and/or hydroxyl groups, and phenyl-DHPQ derivatives were identified in both Pg samples. The peak magnitudes of these formulae in G2 (accounting for 40% of the total assigned magnitude) were greater than that in the crude Pg (21%). Most of the 27 molecular formulae were also detected in the three soil HAs, suggesting a common existence of Pg-related compounds in various soil HAs.

CONCLUSIONS

The important molecular formulae of Pg components were estimated utilizing FTICRMS. Copyright © 2013 John Wiley & Sons, Ltd.

Ultrahigh resolution mass spectrometry-based metabolic characterization reveals cerebellum as a disturbed region in two animal models

In the previous reports about cognitive dysfunction, cerebellum was thought to be a less affected tissue by genetic or environmental alterations in comparison to other tissues in the brain including hippocampus under the same conditions. In this work, we investigated two types of metabolomic alterations inside the cerebellum tissue. The first one addressed the differences in the metabolomics profiles between Transgenic (Tg) CRND8 of Alzheimer's disease mice and non-transgenic (non-Tg) littermates. The second one addressed the metabolic differences between wild type mice exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and wild type mice which are not exposed to this toxic compound. For these two investigations, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS) was implemented. As a result, the significant changes of each comparison were tentatively annotated by the high mass accuracy generated from the measurements in the negative ion mode. The biosynthesis of amino acids was also enhanced pronouncedly, and perturbation of purine metabolism was also observed in Tg mice compared to non-Tg littermates. In another animal model, the reduced levels of amino acids were found whereas the intermediate levels in purine metabolism and fatty acids including fatty acid conjugated metabolites were elevated in cerebellar tissues of mice exposed to TCDD compared to control group. Collectively, it was demonstrated that FT-ICR/MS was a powerful tool for interpretation of the elemental compositions of the peaks, revealing that the metabolic perturbations in cerebellar tissues of mice were induced by either genetic manipulation or environmental factor. Therefore, the non-targeted approach, alternatively, provides various metabolic phenotypes for the systems-level mirror of the complex etiology of neurotoxicity in the cerebellum.

Hippocampal metabolomics using ultrahigh-resolution mass spectrometry reveals neuroinflammation from Alzheimer's disease in CRND8 mice

In the wake of genomics, metabolomics characterizes the small molecular metabolites revealing the phenotypes induced by gene mutants. To address the metabolic signatures in the hippocampus of the amyloid-beta (Aβ) peptides produced in transgenic (Tg) CRND8 mice, high-field ion cyclotron resonance-Fourier transform mass spectrometry supported by LC-LTQ-Orbitrap was introduced to profile the extracted metabolites. More than 10,000 ions were detected in the mass profile for each sample. Subsequently, peak alignment and the 80% rule followed by feature selection based on T score computation were performed. The putative identification was also conducted using the highly accurate masses with isotopic distribution by interfacing the MassTRIX database as well as MS/MS fragmentation generated in the LTQ-Orbitrap after chromatographic separation. Consequently, 58 differentiating masses were tentatively identified while up to 44 differentiating elemental compositions could not be biologically annotated in the databases. Nonetheless, of the putatively annotated masses, eicosanoids in arachidonic acid metabolism, fatty acid beta-oxidation disorders as well as disturbed glucose metabolism were highlighted as metabolic traits of Aβ toxicity in Tg CRND8 mice. Furthermore, a web-based bioinformatic tool was used for simulation of the metabolic pathways. As a result of the obtained metabolic signatures, the arachidonic acid metabolism dominates the metabolic perturbation in hippocampal tissues of Tg CRND8 mice compared to non-Tg littermates, indicating that Aβ toxicity functions neuroinflammation in hippocampal tissue and new theranostic opportunities might be offered by characterization of altered arachidonic acid metabolism for Alzheimer's disease.