FT-ICR Mass Spectrometry Research Articles

Molecular characterization of naphthenic acids from heavy crude oils using MALDI FT-ICR mass spectrometry

Naphthenic acid (NA) fractions from heavy crude oils are typically analyzed in mass spectrometry via electrospray ionization (ESI). Here, we show that NA analysis is also possible by MALDI using a highly basic matrix (proton sponge). When compared with ESI, that allowed detection of six compound families, MALDI resulted in the observation of twenty-two compound families. Besides, MALDI analysis affords compositional-dependent information. Unlike ESI, where all NAs are detected as deprotonated molecules, in MALDI we observe both deprotonated molecules and radical anions. This indicates that ion formation in NA by MALDI can occur by either acid-base and electron-capture mechanisms, or both. Interestingly, the preferred ionization channel seems to be compound class dependent; for instance, the acid base mechanism (which allows detection of deprotonated NA species through a Brönsted-Lowry reaction) applies exclusively to NAs with high H/C ratios along the whole O/C range. On the other hand, for less saturated compounds both mechanisms apply, while the electron capture channel occurs exclusively in species with low H/C and high O/C ratios or high H/C and low O/C ratios (envelope of the van Krevelen plots). In summary, we demonstrate that MALDI(-) is an alternative method for the analysis of complex petrochemical samples offering additional advantages, when compared with ESI, such as increasing compositional space accessibility for polar samples, high throughput and exceptional tolerance to the presence of impurities and salts in the samples. Furthermore, exploration on semi-quantitative approaches in MALDI can provide additional advantages such as those offered by LC-ESI MS, currently used to quantify naphthenic acids.

Compact FTICR Mass Spectrometry for Real Time Monitoring of Volatile Organic Compounds.

In this paper, we present a compact Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS) designed for real time analysis of volatile organic compounds (VOCs) in air or in water. The spectrometer is based on a structured permanent magnet made with NdFeB segments. Chemical ionization is implemented inside the ICR cell. The most widely used reaction is the proton transfer reaction using H3O+ precursor ions, but other ionic precursors can be used to extend the range of species that can be detected. Complex mixtures are studied by switching automatically from one precursor to another. The accuracy obtained on the mass to charge ratio (Δm/z 5 × 10−3), allows a precise identification of the VOCs present and the limit of detection is 200 ppb without accumulation. The time resolution is a few seconds, mainly limited by the time necessary to come back to background pressure after the gas pulses. The real time measurement will be illustrated by the monitoring of VOCs produced during the thermal degradation of a polymer and by an example where three different precursor ions are used alternatively to monitor a gas sample.

Structural information of asphaltenes derived from petroleum vacuum residue and its hydrotreated product obtained by FT-ICR mass spectrometry with narrow ion isolation windows

Petroleum asphaltene is a complex natural organic mixture which plays a crucial role in the refining processes. In this work, asphaltenes derived from petroleum vacuum residue and its hydrotreated product were characterized by high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Tandem mass spectra with narrow ion isolation window were realized by increasing the value of collision RF amplitude. Tandem mass spectra with 3 Da and 1 Da isolation windows were compared, which demonstrated the advantages of applying narrow isolation window of 1 Da. The tandem mass spectra of asphaltenes were simplified due to the narrow isolation window. Moreover, a better correlation between the parent and fragment ions obtained by narrow isolation window of 1 Da was suggested by moving the isolation window. Finally, aromatic hydrocarbons with more naphthenic rings were suggested for the molecular structures of the processed asphaltene according to the results.

On the Origin of the Distinctly Different Reactivity of Ruthenium in [MO]+ /CH4 Systems (M=Fe, Ru, Os).

The thermal gas-phase reactions of [RuO]+ with methane have been explored by FT-ICR mass spectrometry and high-level quantum-chemical calculations. In contrast to the previously studied [FeO]+ /CH4 and [OsO]+ /CH4 couples, which undergo oxygen/hydrogen atom transfers and dehydrogenation, respectively, the [RuO]+ /CH4 system produces selectively [Ru(CH)2 ]+ and H2 O, albeit with much lower efficiency. Various mechanistic scenarios were uncovered, and the associated electronic origins were revealed by high-level quantum-chemical calculations. The reactivity differences observed for the [MO]+ /CH4 couples (M=Fe, Ru, Os) are due to the subtle interplay of the spin-orbit coupling efficiency, orbital overlap, and relativistic effects.

Comment on "Laser Desorption/Ionization Coupled to FTICR Mass Spectrometry for Studies of Natural Organic Matter".

Comment on "Laser Desorption/Ionization Coupled to FTICR Mass Spectrometry for Studies of Natural Organic Matter".

Response to Comment on "Laser Desorption/Ionization Coupled to FTICR Mass Spectrometry for Studies of Natural Organic Matter".

Response to Comment on "Laser Desorption/Ionization Coupled to FTICR Mass Spectrometry for Studies of Natural Organic Matter".

Characterization of Molecular Composition of Bacterial Melanin Isolated from Streptomyces glaucescens Using Ultra-High-Resolution FT-ICR Mass Spectrometry

Characterization of Molecular Composition of Bacterial Melanin Isolated from Streptomyces glaucescens Using Ultra-High-Resolution FT-ICR Mass Spectrometry

Characterization of bio-crude from hydrothermal liquefaction of Enteromorpha prolifera by FT-ICR mass spectrometry

Enteromorpha prolifera is a major species of the green tide. In this study, hydrothermal liquefaction of E. rolifera was carried out. The chemical composition of bio-crude was characterized using Fourier transform ion cyclotron resonance mass spectrometry. The acidic O-containing compounds were O2 class compounds, namely hexadecanoic acid and octadecanoic acid. The basic N-containing compounds were mainly nitrogenous heterocyclic compounds with carbon number of 20~40 and high unsaturation degree.

Differential Enzymatic 16O/18O Labeling for the Detection of Cross-Linked Nucleic Acid-Protein Heteroconjugates.

Cross-linking of nucleic acids to proteins in combination with mass spectrometry permits the precise identification of interacting residues between nucleic acid-protein complexes. However, the mass spectrometric identification and characterization of cross-linked nucleic acid-protein heteroconjugates within a complex sample is challenging. Here we establish a novel enzymatic differential 16O/18O-labeling approach, which uniquely labels heteroconjugates. We have developed an automated data analysis workflow based on OpenMS for the identification of differentially isotopically labeled heteroconjugates against a complex background. We validated our method using synthetic model DNA oligonucleotide-peptide heteroconjugates, which were subjected to the labeling reaction and analyzed by high-resolution FTICR mass spectrometry.

Proton-induced reactions of [2.2]-paracyclophane in the gas phase. A study by FT-ICR-spectrometry and DFT calculation.

The reactions of the [2-2]-paracyclophane 1 and the [2-2]-metaparacyclopane 2 in the gas phase after protonation by CI(CH4) or CI(I-C4H10) were studied by FT-ICR mass spectrometry. The ions C16H17+ produced in the external ion source of the FT-ICR instrument were transferred into the ICR cell containing the neutral reactant, and the reactions were analyzed measuring the efficiency of the transfer of a proton to a series of bases with known proton affinity and gas phase basicity as well as the efficiency of the ion-molecule reaction with ethyl vinyl ether. Both reaction types show that the ions C16H17+ produced by chemical ionization (CI) consist of two sets of isomeric ions A and B which exhibit distinctly different behavior on deprotonation and of the reaction with ethyl methyl ether. Isomer(s) A (about 65% of the ion population) react efficiently with this vinyl ether by an addition/elimination process typical of primary and secondary benzylic carbenium ions, while isomer B (about 35% of the ion population) undergoes only an ineffective deprotonation by the vinyl ether. By bracketing deprotonation, it is shown that A is actually composed of two isomers A1 and A2 with slightly different proton affinity and gas phase basicity. These two ions have been identified using CA-mass spectrometry as protonated 3-phenethylstyrene (A1) and protonated 4-phenethylstyrene (A2). The CA-mass spectrum of the isomer B indicated that these ions C16H17+ correspond to protonated 1-(ethyl phenyl)-1-phenyl-ethene. This agrees with the rather strong basicity of the conjugated base of ions B, which results in a slow deprotonation. A protonated 1-(ethyl phenyl)-1-phenyl-ethene can arise from a protonated 2-phenethylstyrene by H- and subsequent phenyl shifts, but requires the preceding rearrangement of the protonated [2.2]-paracyclophane into the protonated isomer "[2.2]-orthocyclophane" - the 1,5-dibenzocyclooctadiene. The possibility of such a deep-sited rearrangement was studied by the computation of the relevant reaction routes applying DFT-methods at the level B3LYP/6-311+g(3d,2p)//B3LYP/3-21g) to analyze the reaction mechanisms.

Chemical characterization of dissolved organic matter in moist acidic tussock tundra soil using ultra-high resolution 15T FT-ICR mass spectrometry

Global warming is considered one of the most serious environmental issues, substantially mediating abrupt climate changes, and has stronger impacts in the Arctic ecosystems than in any other regions. In particular, thawing permafrost in the Arctic region with warming can be strongly contributing the emission of greenhouse gases (CO2 and CH4) that are produced from microbial decomposition of preserved soil organic matter (SOM) or are trapped in frozen permafrost soils, consequently accelerating global warming and abrupt climate changes. Therefore, understanding chemical and physical properties of permafrost SOM is important for interpreting the chemical and biological decomposability of SOM. In this study, we investigated dissolved organic matter (DOM) along the soil depth profile in moist acidic tussock tundra to better understand elemental compositions and distributions of the arctic SOM to evaluate their potential decomposability under climate change. To achieve ultra-high resolution mass profiles, the soil extracts were analyzed using a 15 Tesla Fourier transform ion cyclotron resonance mass spectrometer in positive and negative ion modes via electrospray ionization. The results of this analysis revealed that the deeper organic soil (2Oe1 horizon) exhibits less CHON class and more aromatic class compounds compared to the surface organic soils, thus implying that the 2Oe1 horizon has undergone a more decomposition process and consequently possessed the recalcitrant materials. The compositional features of DOM in the Arctic tundra soils are important for understanding the changes in biogeochemical cycles caused from permafrost changes associated with global warming and climate change.

Untargeted metabolomic analysis and pathway discovery in perinatal asphyxia and hypoxic-ischaemic encephalopathy

Elucidating metabolic effects of hypoxic-ischaemic encephalopathy (HIE) may reveal early biomarkers of injury and new treatment targets. This study uses untargeted metabolomics to examine early metabolic alterations in a carefully defined neonatal population. Infants with perinatal asphyxia who were resuscitated at birth and recovered (PA group), those who developed HIE (HIE group) and healthy controls were all recruited at birth. Metabolomic analysis of cord blood was performed using direct infusion FT-ICR mass spectrometry. For each reproducibly detected metabolic feature, mean fold differences were calculated HIE vs. controls (ΔHIE) and PA vs. controls (ΔPA). Putative metabolite annotations were assigned and pathway analysis was performed. Twenty-nine putatively annotated metabolic features were significantly different in ΔPA after false discovery correction (q < 0.05), with eight of these also significantly altered in ΔHIE. Altered putative metabolites included; melatonin, leucine, kynurenine and 3-hydroxydodecanoic acid which differentiated between infant groups (ΔPA and ΔHIE); and D-erythrose-phosphate, acetone, 3-oxotetradecanoic acid and methylglutarylcarnitine which differentiated across severity grades of HIE. Pathway analysis revealed ΔHIE was associated with a 50% and 75% perturbation of tryptophan and pyrimidine metabolism, respectively. We have identified perturbed metabolic pathways and potential biomarkers specific to PA and HIE, which measured at birth, may help direct treatment.

Investigation of meningioma samples by FTICR mass spectrometry

Investigation of meningioma samples by FTICR mass spectrometry

Mapping the contact surfaces in the Lamin A:AIMP3 complex by hydrogen/deuterium exchange FT-ICR mass spectrometry.

Aminoacyl-tRNA synthetases-interacting multifunctional protein3 (AIMP3/p18) is involved in the macromolecular tRNA synthetase complex via its interaction with several aminoacyl-tRNA synthetases. Recent reports reveal a novel function of AIMP3 as a tumor suppressor by accelerating cellular senescence and causing defects in nuclear morphology. AIMP3 specifically mediates degradation of mature Lamin A (LmnA), a major component of the nuclear envelope matrix; however, the mechanism of how AIMP3 interacts with LmnA is unclear. Here we report solution-phase hydrogen/deuterium exchange (HDX) for AIMP3, LmnA, and AIMP3 in association with the LmnA C-terminus. Reversed-phase LC coupled with LTQ 14.5 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) results in high mass accuracy and resolving power for comparing the D-uptake profiles for AIMP3, LmnA, and their complex. The results show that the AIMP3-LmnA interaction involves one of the two putative binding sites and an adjacent novel interface on AIMP3. LmnA binds AIMP3 via its extreme C-terminus. Together these findings provide a structural insight for understanding the interaction between AIMP3 and LmnA in AIMP3 degradation.

Extension of the Analytical Window for Characterizing Aromatic Compounds in Oils Using a Comprehensive Suite of High-Resolution Mass Spectrometry Techniques and Double Bond Equivalence versus Carbon Number Plot

In this study, comprehensive two-dimensional (2D) gas chromatography–mass spectrometry (GC–MS), atmospheric pressure photoionization (APPI) quadrupole-Orbitrap mass spectrometry (MS), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were used to study the aromatic fractions of crude oil and oil shale pyrolysates (shale oils). The collected data were compared and combined in the double bond equivalence (DBE) versus carbon number plot to obtain a more complete understanding of the composition of the oil fractions. The numbers of peaks observed by each technique followed the order 2D GC–MS < Orbitrap MS < FT-ICR MS. The class distributions observed by Orbitrap MS and FT-ICR MS were similar to each other but different from that observed by 2D GC–MS. The DBE and carbon number distributions of the 2D GC–MS and Orbitrap MS data were similar for crude oil aromatics. The FT-ICR MS plots of DBE and carbon number showed an extended range of higher values relative to the other methods. For ...

Electronic Origin of the Competitive Mechanisms in the Thermal Activation of Methane by the Heteronuclear Cluster Oxide [Al2 ZnO4

The thermal gas-phase reactions of [Al2 ZnO4 ].+ with methane have been explored by using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. Two competitive mechanisms, that is, hydrogen-atom transfer (HAT) and proton-coupled electron transfer (PCET) are operative. Interestingly, while the HAT process is influenced by the polarity of the transition structure, both the ionic nature of the metal-oxygen bond and the structural rigidity of the cluster oxide affect the PCET pathway. As compared to the previously reported homonuclear [Al2 O3 ].+ and [ZnO].+ , the heteronuclear oxide [Al2 ZnO4 ].+ exhibits a much higher chemoselectivity towards methane. The electronic origins of the doping effect have been explored.

Comprehensive qualification and quantification of triacylglycerols with specific fatty acid chain composition in horse adipose tissue, human plasma and liver tissue

High levels of triacylglycerols (TGs) have been linked to cardiovascular disease and liver diseases. Comprehensively analyzing TGs is helpful to understand the TGs functions in these diseases. However, due to the existence of a large number of isomers TGs and the lack of commercial standards, precise analysis of individual triacylglycerol (TG) with specific fatty acid chain composition is full of challenge. In this work, ultra-performance liquid chromatography (UPLC) coupled with electrospray ionization (ESI) mass spectrometry (MS) were employed for comprehensive qualification and quantification of TGs with specific fatty acid chain composition in horse adipose tissue, human plasma and liver tissues including hepatocellular carcinoma (HCC) and para-carcinoma tissues. Multiple MS detection modes from QTRAP MS and FT-ICR MS were utilized, and hundreds of TG species (including many oxidized TG species) with their specific fatty acid chain compositions have been qualified and quantified. The isomer TGs interference, the isobaric interference, and oxidized TG species interference were firstly indicated. Several isomer TGs, for example, 18:1/20:1/18:2 TG and 20:3/18:1/18:0 TG, which were all 56:4 TG, demonstrated different trends in HCC tissue compared with para-carcinoma tissue, which showed the importance of analysis of TG with specific fatty acid chain composition. In addition, 10 TGs with the degree of unsaturation beyond three were significantly decreased, while 16:0/17:0/18:0 TG, no double bond, was significantly increased in the HCC tissue, which firstly revealed aberrant specific TG metabolism in HCC. This is a systematic report about comprehensive analysis of TGs by UPLC-ESI-MS, which is of significance for accurate analysis of these lipids.

Sequential Gas-Phase Activation of Carbon Dioxide and Methane by [Re(CO)2]+: The Sequence of Events Matters!

The potential of carbonyl rhenium complexes in activating and coupling carbon dioxide and methane has been explored by using a combination of gas-phase experiments (FT-ICR mass spectrometry) and high-level quantum chemical calculations. While the complexes [Re(CO)x]+ (x = 0, 1, 3) are thermally unreactive toward CO2, [Re(CO)2]+ abstracts one oxygen atom from this substrate spontaneously at ambient conditions. Based on 13C and 18O labeling experiments, the newly generated CO ligand is preferentially eliminated, and two mechanistic scenarios are considered to account for this unexpected finding. The oxo complex [ORe(CO)2]+ reacts further with CH4 to produce the dihydridomethylene complex [ORe(CO)(CH2)(H)2]+. However, coupling of the CO and CH2 ligands to form CH2═C═O does not take place. Further, the complexes [Re(CO)x(CH2)]+ (x = 1, 2), generated in the thermal reaction of [Re(CO)x]+ (x = 1, 2) with CH4, are inert toward CO2. Mechanistic insight on the origin of this remarkable reactivity pattern has been derived from detailed quantum chemical calculations.

Laser Desorption/Ionization Coupled to FTICR Mass Spectrometry for Studies of Natural Organic Matter.

Laser desorption/ionization (LDI) was investigated as an ionization method for Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) studies of natural organic matter (NOM). Using International Humic Substances Society standards, Suwannee River fulvic acid (SRFA) and Suwannee River natural organic matter (SRNOM), LDI was found to ionize a very similar set of compounds (>90% of molecular formulas identity) to the matrix assisted laser desorption/ionization (MALDI), while producing higher quality spectra. A comparison of electrospray ionization (ESI) and LDI spectra showed that different types of compounds are ionized by these methods with only 9.9% of molecular formulas common to both. The compounds ionized by LDI/MALDI belong to low oxygen classes (maximum number of species for O7-O9), while ESI compounds belong to higher oxygen classes (maximum number of species for O14-O16). Compounds ionized by LDI can be classified as aliphatic, aromatic, and condensed aromatics in approximately equal measure, while aliphatic compounds dominated the ESI spectra of SRFA. In order to maximize the coverage of molecular species, LDI, as a particularly convenient and readily deployable ionization method, should be used routinely in combination with other ionization methods, such as ESI, for FTICR MS studies of NOM.

Chemical Characterization of Polar Species in Colombian Vacuum Residue and Its Supercritical Fluid Extraction Subfractions Using Electrospray Ionization Ft-icr Mass Spectrometry

Compositional changes of Colombian vacuum residue and its supercritical fluid extraction fractionation (SFEF) subfractions were analysed by positive- and negative mode electrospray (ESI) coupled with Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results showed different distribution of compounds among the SFEF subfractions. The most dominant classes were the nitrogen compounds N1 and the SFEF end-cut showed to be enriched in multi-heteroatom species. Detailed analysis of double bond equivalent (DBE) distribution revealed that pyridine compounds were more aromatic than pyrrole ones. Planar limit indicated high condensation degree of carboxylic acids species. Therefore, this work evidenced the utility of SFEF fractionation and ESI FT-ICR MS in the detailed characterization of polar compounds in vacuum residua.