Exploring the capabilities of gas chromatography and liquid chromatography single and tandem mass spectrometry for discriminating and characterizing marine oils by using chemometric tools

Assessing the capabilities of instrumental techniques for discriminating marine oils and studying the positional distribution of fatty acids on the backbone of triacylglycerols (TAG) are of vital importance from commercial, nutritional, biochemical and technological points of view. This represents a great challenge for analysts due to the wide variety of fatty acids and the complexity of naturally occurring TAG species. In this thesis, the potential of gas chromatography (GC) for discriminating full fatty acid methyl ester (FAME) profiles of marine oils (cod liver, salmon, seal and whale oils) is evaluated by means of principal component analysis (PCA). The FAME profiles from plant oils such as rapeseed, linseed and soy oils and seven different brands of omega-3 (ω-3) fatty acids supplements are also used in the discrimination process. The results from the PCA plots can reliably distinguish between plant, ω-3 fatty acids supplements, fish and marine mammal oils. By removing the contribution of the ω-3 fatty acids supplements and plant oils, it is possible to discriminate within every type of fish and marine animal oils. GC offers a rapid, simple and convenient means of discriminating marine oils from different species, brands and grades. The thesis also studies the feasibility of fingerprinting and discriminating marine oils based on their TAG profiles using liquid chromatography electrospray single and tandem mass spectrometry (LC-ESI-MS and LC-ESI-MS2) in conjunction with chemometric tools. Four kinds of profiles, including total ion chromatogram (TIC) and mass spectral profiles derived from LC-ESI-MS and LC-ESI-MS2 experiments, are examined prior to data pretreatment by component detection algorithm (CODA) to reduce the noise and background. These profiles are subsequently subjected to PCA to evaluate their performance for discriminating marine oils and plant oils. The results show that the TIC profiles derived from both LC-ESI-MS and LC-ESI-MS2 experiments turn out to be inadequate for discrimination of complex marine oils. Although the classification results are remarkably improved by using single mass spectral profiles derived from LC-ESI-MS experiments, the differentiation among seal oils of different species and qualities is not achieved. In comparison, the use of tandem mass spectral profiles from LC-ESI-MS2 experiment is demonstrated to be the best strategy for discrimination of marine oils which enables the differentiation not only between marine oils and plant oils but also among the seal oils of different species and qualities. The tandem mass spectral profiles could preferably represent the characteristics of TAG patterns, and could be used as an alternative approach for fingerprinting and detecting of adulteration of marine oils. The final aspect studied in the present thesis is the structural characterization of TAG by using LC-ESI-MS2 for identifying the positional distribution of fatty acids on the glycerol backbone in cod liver oil. A computational algorithm is developed to characterize rapidly and interpret automatically the mass spectra of the various detected TAG species. Three different solvent mixtures are used to dissolve the sample prior to the instrumental analysis. The discrepancies between the results indicate that the choice of the solvent system influences the identification of the TAG species. The results obtained by the proposed LC-ESI-MS2 approach are in agreement with those from the well established lipase method. LC-ESI-MS2 provides a suitable and powerful strategy for the structural characterization of TAG in cod liver oil

Application of liquid chromatographymass spectrometry and chemometrics in the automated characterization of molecular lipid species

Lipidomics is an important field that has attracted extensive interest worldwide, due to the increasing awareness of crucial lipid functions in biological systems. Lipidomics aims at detecting, characterizing and quantifying lipid species comprehensively. In the work for the present thesis, analytical strategies based on liquid chromatography-mass spectrometry (LCMS) and chemometrics were developed for characterization of molecular species of major lipid classes, i.e. triacylglycerols (TAG) and glycerophospholipids (GPL) from marine oils and biological systems. The applicability of liquid chromatography electrospray tandem mass spectrometry (LC-ESIMS2) for the structural characterization of naturally occurring TAG in cod liver oil was investigated. A computational algorithm was developed to automatically interpret mass spectra and elucidate TAG structures, and the results of the algorithm were compared against the lipase benchmark method. It was proved that LC-ESI-MS2 provides a suitable and powerful strategy for the structural characterization of TAG in cod liver oil. The thesis also evaluates different strategies for differentiating marine oils by means of principal component analysis (PCA). The TAG composition and four different types of data, including total ion current (TIC) and total mass spectral (TMS) profiles derived from LC-ESIMS and LC-ESI-MS2, were used as the datasets for PCA. The results show that using the tandem TMS profiles from LC-ESI-MS2 experiments was the most rapid and convenient approach for the differentiation of the various marine and plant oils investigated, and for the representation of the characteristic TAG patterns. The thesis proposes a least square spectral resolution (LSSR) approach for the automated characterization and deconvolution of the main GPL species, i.e., phosphatidylcholine (PC) and phosphatidylethanolamine (PE) in biological extracts. Class-specific scanning methods, such as precursor ion scanning and neutral loss scanning, in LC-MS were applied to acquire the lipidomic dataset. The methodology is based on least squares resolution of spectra and chromatograms from theoretically calculated mass spectra with the isotope distribution. The described algorithm was able to resolve PC and PE species of reference mixtures, porcine brain sphingomyeline, cod and mouse brain lipid extracts. Recent advances in high-resolution mass spectrometry have revolutionized the lipidomics field by providing high-resolution data. The LSSR methodology was further extended to be compatible with this type of data for an accurate identification and quantification of lipid species. The methodology has been expanded to cover the analysis of other major lipid classes such as GPL, sphingolipids, glycerolipids. Examples for the analysis of natural lipids extracts from egg, porcine brain and bovine liver are presented. The flexibility of the methodology allows supporting more lipid classes and more data interpretation functions, which in turn makes LSSR a promising tool for lipidomic data analysis. LSSR methodology was applied on LC-MS data to evaluate the effects of methylmercury (MeHg) and EPA on intact PC and PE species in mouse brain. The effects of EPA and MeHg on PC and PE composition in brain were evaluated by PCA and ANOVA. The results demonstrate that EPA reduces the levels of arachidonic acid (AA) containing PC and PE species in brain, while MeHg tends to elevate the levels of AA containing PC and PE species. EPA also significantly increases the levels of n-3 polyunsaturated fatty acids (PUFA) containing PC and PE species in brain. The results indicate that EPA may counteract the alterations of the PC and PE pattern induced by MeHg, and thus alleviate MeHg neurotoxicity in mouse brain through the inhibition of AA-derived pro-inflammatory factors. The LSSR methodology was further applied to evaluate the effects of MeHg and EPA on the PC and PE composition in mouse liver and plasma by PCA and ANOVA in conjunction with biological and toxicological analyses. Similar to results from brain, EPA significantly elevates the levels of PC and PE species that contain n-3 PUFA and reduces the levels of PC and PE species that contains AA. MeHg increases the levels of PC and PE species with AA to a lower extent. MeHg induces more prostaglandin E2 and less prostaglandin E3, thus increasing proinflammatory factors, while EPA displays the ability to decrease the AA-derived inflammatory factors. The histological analysis of cell damage and necrosis and the measurements of biochemical indexes also indicate that MeHg induced chronic inflammatory symptoms in mice, and that EPA can alleviate the MeHg-induced hepatic toxicity. Collectively, EPA may have protective effects against MeHg-induced toxicity in mice due to the favourable modification of membrane phospholipid composition and the inhibition of inflammatory factors release. In summary, the described strategies and algorithms represent promising tools for the analysis of TAG and GPL species in oils, fats and biological systems. The application of these methodologies on different objects can provide insights into various research areas, such as food and nutrition, health, pharmacology and toxicology

Discrimination of n-3 Rich Oils by Gas Chromatography

Exploring the capabilities of instrumental techniques for discriminating n-3 rich oils derived from animals is a very important though much neglected area that was emphasized more than 100 years ago. In this study the potential of gas chromatography (GC) for discriminating full fatty acid methyl ester (FAME) profiles from fish (cod liver and salmon) and marine mammal (seal and whale) oils is evaluated by means of principal component analysis (PCA). The FAME profiles from plant oils such as rapeseed, linseed and soy oils and seven different brands of n-3 supplements are also used in the discrimination process. The results from the PCA plots can reliably distinguish between plant, n-3 supplements, fish and marine mammal oils. By removing the contribution of the n-3 supplements and plant oils it is possible to discriminate between types of fish and marine animal oils. GC offers a rapid, simple and convenient means of discriminating oils from different species, brands and grades

Influence of Al Coordinates on Hierarchical Structure and T Atoms Redistribution during Base Leaching of ZSM-5

Al coordinates in ZSM-5 showed significant effects on hierarchical structure and T atoms redistribution during NaOH/TPAOH treatment and different catalytic performances in the methanol-to-propylene reaction. NaOH treatment of parent ZSM-5 with a few extra-framework Al sites mainly involved the desilication process, while an additional alumination process was observed when some Al3+ was added into the NaOH solution, which resulted in mesoporous crystals with intact outer shells. Dealumination-realumination and desilication processes occurred with ZSM-5 with distorted four-coordinate, five-coordinate, or six coordinate Al sites. For TPAOH treatment, the desilication recrystallization process occurred with parent ZSM-5 and resulted in hollow crystals with ultrasilica shells via Si redistribution, consequently 2.5 times the lifetime of parent ZSM-5 by restricting external coke deposition. By comparison, desilication, dealumination, and (Si, Al)-recystallization were observed for ZSM-5 with distorted four-coordinate Al sites, involving both Si and Al atoms redistribution processes resulting in abundant mesopores and a high-silica outer surface, which showed almost times the lifetime of parent ZSM-5

Tissue accumulation of polystyrene microplastics causes oxidative stress, hepatopancreatic injury and metabolome alterations in Litopenaeus vannamei

Microplastics (MPs) pose one of the major environmental threats to marine organisms and ecosystems on a global scale. Although many marine crustaceans are highly susceptible to MPs pollution, the toxicological effects and mechanisms of MPs on crustaceans are poorly understood. The current study focused on the impacts of MPs accumulation in shrimp Litopenaeus vannamei at the behavioral, histological and biochemical levels. The results demonstrated the accumulation of polystyrene MPs in various organs of L. vannamei, with highest MPs abundance in the hepatopancreas. The MPs accumulated in shrimp caused growth inhibition, abnormal swimming behavior and reduced swimming performance of L. vannamei. Following MPs exposure, oxidative stress and lipid peroxidation were also observed, which were strongly linked to attenuated swimming activity of L. vannamei. The above MPs-induced disruption in balance of antioxidant system triggered the hepatopancreatic damage in L. vannamei, which was exacerbated with increasing MPs concentrations (from 0.02 to 1 mg L−1). Furthermore, metabolomics revealed that MPs exposure resulted in alterations of metabolic profiles and disturbed glycolysis, lipolysis and amino acid metabolism pathways in hepatopancreas of L. vannamei. This work confirms and expands the knowledge on the sublethal impacts and toxic modes of action of MPs in L. vannamei

Methanol to Olefins Reaction Route Based on Methylcyclopentadienes as Critical Intermediates

Starting from C1 raw material, methanol conversion to hydrocarbons has been realized via a rather complicated pathway. In this contribution, we proposed an alternative methanol reaction route and provided a general understanding of such complex indirect mechanism. The methylcyclopentenyl cations and their deprotonated counterparts (methylcyclopentadienes) were validated to appear on the working H-SAPO-34 catalyst by in situ C-13 MAS NMR spectroscopy and the GC-MS technique, and their catalytic reactivity was revealed by the C-12/C-13-CH3OH isotopic switch experiment. In this context, a cyclopentadienes-based cycle was established, in which light olefins were formed with methylcyclopentadienes as critical intermediates. The feasibility of this alternative route was confirmed by density functional theory calculations. Notably, the cyclopentadienes-based cycle runs in parallel with the traditional alkenes-based and aromatics-based cycles; these three mechanistic cycles are interrelated through interconversion of the involved intermediates, including alkene, cyclopentadiene, and aromatic species. All these three cycles work together for the C-C bond assembly in the methanol-to-olefins reaction system. These findings help to build a more complete methanol conversion network and advance the in-depth understanding of indirect mechanism of methanol conversion

Exercise training improves mitochondrial respiration and is associated with an altered intramuscular phospholipid signature in women with obesity

Aims/hypothesis: We sought to determine putative relationships among improved mitochondrial respiration, insulin sensitivity and altered skeletal muscle lipids and metabolite signature in response to combined aerobic and resistance training in women with obesity. Methods: This study reports a secondary analysis of a randomised controlled trial including additional measures of mitochondrial respiration, skeletal muscle lipidomics, metabolomics and protein content. Women with obesity were randomised into 12 weeks of combined aerobic and resistance exercise training (n = 20) or control (n = 15) groups. Pre- and post-intervention testing included peak oxygen consumption, whole-body insulin sensitivity (intravenous glucose tolerance test), skeletal muscle mitochondrial respiration (high-resolution respirometry), lipidomics and metabolomics (mass spectrometry) and lipid content (magnetic resonance imaging and spectroscopy). Proteins involved in glucose transport (i.e. GLUT4) and lipid turnover (i.e. sphingomyelin synthase 1 and 2) were assessed by western blotting. Results: The original randomised controlled trial showed that exercise training increased insulin sensitivity (median [IQR]; 3.4 [2.0–4.6] to 3.6 [2.4–6.2] x10−5 pmol l−1 min−1), peak oxygen consumption (mean ± SD; 24.9 ± 2.4 to 27.6 ± 3.4 ml kg−1 min−1), and decreased body weight (84.1 ± 8.7 to 83.3 ± 9.7 kg), with an increase in weight (pre intervention, 87.8± 10.9 to post intervention 88.8 ± 11.0 kg) in the control group (interaction p < 0.05). The current study shows an increase in mitochondrial respiration and content in response to exercise training (interaction p < 0.05). The metabolite and lipid signature at baseline were significantly associated with mitochondrial respiratory capacity (p < 0.05) but were not associated with whole-body insulin sensitivity or GLUT4 protein content. Exercise training significantly altered the skeletal muscle lipid profile, increasing specific diacylglycerol(32:2) and ceramide(d18:1/24:0) levels, without changes in other intermediates or total content of diacylglycerol and ceramide. The total content of cardiolipin, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) increased with exercise training with a decrease in the PC:PE ratios containing 22:5 and 20:4 fatty acids. These changes were associated with content-driven increases in mitochondrial respiration (p < 0.05), but not with the increase in whole-body insulin sensitivity or GLUT4 protein content. Exercise training increased sphingomyelin synthase 1 (p < 0.05), with no change in plasma-membrane-located sphingomyelin synthase 2. Conclusions/interpretation: The major findings of our study were that exercise training altered specific intramuscular lipid intermediates, associated with content-driven increases in mitochondrial respiration but not whole-body insulin sensitivity. This highlights the benefits of exercise training and presents putative target pathways for preventing lipotoxicity in skeletal muscle, which is typically associated with the development of type 2 diabetes

Understanding the Fundamentals of Microporosity Upgrading in Zeolites: Increasing Diffusion and Catalytic Performances

Abstract Hierarchical zeolites are regarded as promising catalysts due to their well‐developed porosity, increased accessible surface area, and minimal diffusion constraints. Thus far, the focus has been on the creation of mesopores in zeolites, however, little is known about a microporosity upgrading and its effect on the diffusion and catalytic performance. Here the authors show that the “birth” of mesopore formation in faujasite (FAU) type zeolite starts by removing framework T atoms from the sodalite (SOD) cages followed by propagation throughout the crystals. This is evidenced by following the diffusion of xenon (Xe) in the mesoporous FAU zeolite prepared by unbiased leaching with NH4F in comparison to the pristine FAU zeolite. A new diffusion pathway for the Xe in the mesoporous zeolite is proposed. Xenon first penetrates through the opened SOD cages and then diffuses to supercages of the mesoporous zeolite. Density functional theory (DFT) calculations indicate that Xe diffusion between SOD cage and supercage occurs only in hierarchical FAU structure with defect‐contained six‐member‐ring separating these two types of cages. The catalytic performance of the mesoporous FAU zeolite further indicates that the upgraded microporosity facilitates the intracrystalline molecular traffic and increases the catalytic performance