Fourier Transform Ion Cyclotron Mass Research Articles

N-containing dissolved organic matter promotes dissolved inorganic carbon supersaturation in the Yangtze River, China

Dissolved inorganic carbon (DIC) represents a major global carbon pool and the flux from rivers to oceans has been observed to be increasing. The effect of weathering with respect to increasing DIC has been widely studied in recent decades; however, the influence of dissolved organic matter (DOM) on increasing DIC in large rivers remains unclear. This study employed stable carbon isotopes and Fourier transform ion cyclotron mass spectrometry (FT-ICR MS) to investigate the effect of the molecular composition of DOM on the DIC in the Yangtze River. The results showed that organic matter is an important source of DIC in the Yangtze River, accounting for 40.0 ± 12.1 % and 32.0 ± 7.2 % of DIC in wet and dry seasons, respectively, and increased along the river by approximately three times. Nitrogen (N)-containing DOM, an important composition in DOM with a percentage of ∼40 %, showed superior oxidation state than non N-containing DOM, suggesting that the presence of N could improve the degradable potential of DOM. Positive relationship between organic sourced DIC (DICOC) and N-containing DOM formulae indicated that N-containing DOM is crucial to facilitate the mineralization of DOM to DICOC. N-containg molecular formular with low H/C and O/C ratio were positively correlated with DICOC further verified these energy-rich and biolabile compounds are preferentially decomposed by bacteria to produce DIC. N-containing components significantly accelerated the degradation of DOM to DICOC, which is important for understanding the CO2 emission and carbon cycling in large rivers.

Concealed by darkness: Combination of NMR and HRMS reveal the molecular nature of dissolved organic matter in fractured-rock groundwater and connected surface waters.

Detailed molecular composition of solid phase extracted dissolved organic matter (SPEDOM) collected from fractured-rock groundwater was compared to connected surface river water at two different watersheds in the unconfined chalk aquifer of Champagne in France using full scan ultrahigh resolution electrospray and photoionization Fourier transform ion cyclotron mass spectrometry (FT-ICR MS), Orbitrap tandem MS (MS/MS) and 1H magnetic resonance spectroscopy (NMR). 1H NMR spectroscopy indicated that groundwater SPEDOM carried a higher contribution of aliphatic compounds while surface river waters SPEDOM were enriched in carboxyl-rich alicyclic molecules (CRAM), acetate derivatives and oxygenated units. Furthermore, we show here that use of photoionization (APPI(+)) in aquifer studies is key, ionizing about eight times more compounds than ESI in surface river water samples, specifically targeting the dissolved organic nitrogen pool, accounting for more than 50% of the total molecular space, as well as a non-polar, more aromatic fraction; with little overlap with compounds detected by ESI(-) FT-ICR MS. On the other hand, groundwater SPEDOM samples did not show similar selectivity as less molecular diversity was observed in APPI compared to ESI. Mass-difference transformation networks (MDiNs) applied to ESI(-) and APPI(+) FT-ICR MS datasets provided an overview of the biogeochemical relationships within the aquifer, revealing chemical diversity and microbial/abiotic reactions. Finally, the combination of ESI(-) FT-ICR MS and detailed Orbitrap MS/MS analysis revealed a pool of polar, anthropogenic sulfur-containing surfactants in the groundwaters, likely originating from agricultural runoff. Overall, our study shows that in this aquifer, groundwater SPEDOM contains a significantly reduced pool of organic compounds compared to surface river waters, possibly related to a combination of lack of sunlight and adsorption of high O/C formulas to mineral surfaces.

Contribution of LDI and MALDI for the Characterization of a Lignocellulosic-Based Pyrolysis Bio-Oil.

In recent years, various alternatives to fossil fuels have been developed. One of them involves the production of bio-oils from lignocellulosic-based biomass through pyrolysis. However, bio-oils present numerous heteroatoms and, in particular, oxygen atoms that need to be removed by an upgrading process. To optimize these processes, it is necessary to have good knowledge of the composition of the bio-oils at the molecular level. This work aims to establish the usefulness of laser desorption ionization (LDI) and matrix-assisted laser desorption/ionization (MALDI) techniques on lignocellulosic biomass-based bio-oils. Using a Fourier transform ion cyclotron mass spectrometer (FTICR MS), we showed that MALDI gives more information than LDI. The selectivity of a series of MALDI matrices was investigated, showing that some matrices are selective toward compound families and others ionize a wider range of compounds. In this study, nine proton-transfer matrices and three electron-transfer matrices were used and compared to results obtained in LDI. Dithranol, acetosyringone, and graphene oxide were the three promising matrices selected from all matrices, giving an overall characterization of oxygenated classes in a bio-oil. They allowed the ionization of many more species covering a wide range of polarity, aromaticity, and mass with a homogeneous relative intensity for all molecular classes such as lignin-derivative species, sugars, and lipid-derivative species.

FT-ICR-MS combined with fluorescent spectroscopy reveals the driving mechanism of the spatial variation in molecular composition of DOM in 22 plateau lakes

Dissolved organic matter (DOM) is the largest carbon pool and directly affects the biogeochemistry in lakes. In the current study, fourier transform ion cyclotron mass spectrometry (FT-ICR-MS) combined with fluorescent spectroscopy was used to assess the molecular composition and driving mechanism of DOM in 22 plateau lakes in Mongolia Plateau Lakes Region (MLR), Qinghai Plateau Lakes Region (QLR) and Tibet Plateau Lakes Region (TLR) of China. The limnic dissolved organic carbon (DOC) content ranged from 3.93 to 280.8 mg L−1 and the values in MLR and TLR were significantly higher than that in QLR. The content of lignin was the highest in each lake and showed a gradually decreasing trend from MLR to TLR. Random forest model and structural equation model implied that altitude played an important role in lignin degradation while the contents of total nitrogen (TN) and chlorophyll a (Chl-a) have a great influence on the increase of DOM Shannon index. Our results also suggested that the inspissation of DOC and the promoted endogenous DOM production caused by the inspissation of nutrient resulted in a positive relationship between limnic DOC content and limnic factors such as salinity, alkalinity and nutrient concentration. From MLR to QLR and TLR, the molecular weight and the number of double bonds gradually decreased but the humification index (HIX) also decreased. In addition, from the MLR to the TLR, the proportion of lignin gradually decreased, while the proportion of lipid gradually increased. Both above results suggested that photodegradation was dominated in lakes of TLR, while microbial degradation was dominated in lakes of MLR.

Molecular transformation of organic nitrogen in Antarctic penguin guano-affected soil

Organic nitrogen (ON) is an important participant in the Earth’s N cycle. Previous studies have shown that penguin feces add an abundance of nutrients including N to the soil, significantly changing the eco-environment in ice-free areas in Antarctica. To explore the molecular transformation of ON in penguin guano-affected soil, we collected guano-free weathered soil, modern guano-affected soil from penguin colonies, ancient guano-affected soil from abandoned penguin colonies, and penguin feces from the Ross Sea region, Antarctica, and Fourier transform ion cyclotron mass spectrometry (FT-ICR MS) was used to investigate the chemical composition of water-extractable ON. By comparing the molecular compositions of ON among different samples, we found that the number of ON compounds (>4,000) in weathered soil is minimal, while carboxylic-rich alicyclic-like molecules (CRAM-like) are dominant. Penguin feces adds ON into the soil with > 10,000 CHON, CHONS and CHN compounds, including CRAM-like, lipid-like, aliphatic/ peptide-like molecules and amines in the guano-affected soil. After the input of penguin feces, macromolecules continue to degrade, and other ON compounds tend to be oxidized into relatively stable CRAM-like molecules, this is an important transformation process of ON in guano-affected soils. We conclude the roles of various forms of ON in the N cycle are complex and diverse. Combined with previous studies, ON eventually turns into inorganic N and is lost from the soil. The lost N ultimately returns to the ocean and the food web, thus completing the N cycle. Our study preliminarily reveals the molecular transformation of ON in penguin guano-affected soil and is important for understanding the N cycle in Antarctica.

Molecular Diversity and Biochemical Content in Two Invasive Alien Species: Looking for Chemical Similarities and Bioactivities.

The biochemical composition, molecular diversity, and two different bioactivities of Asparagopsis armata and Rugulopteryx okamurae (two alien species with different invasive patterns in the southern Iberian Peninsula) were analyzed through spectrophotometric methods and Fourier transform ion cyclotron mass spectroscopy (FT-ICR-MS). A total of 3042 molecular formulas were identified from the different extracts. The dH2O extracts were the most molecularly different. A. armata presented the highest content of nitrogenous compounds (proteins, CHON) and sulphur content, whereas R. okamurae was rich in carbonated compounds (total carbon, lipids, CHO, and CHOP). Antioxidant capacity and phenolic content were higher in R. okamurae than in A. armata. Antimicrobial activity was detected from both species. A. armata showed capacity to inhibit human and fish pathogens (e.g., Staphylococcus aureus or Vibrio anguillarum), whereas R. okamurae only showed inhibition against human bacteria (Staphylococcus aureus and Cutibacterium acnes). In R. okamurae, molecules with a great number of pharmaceutical activities (e.g., anti-inflammatory or antitumoral), antibacterial, biomaterial, and other utilities were found. The main molecules of A. armata had also pharmaceutical applications (e.g., antimalarian, antithrombotic, anti-inflammatory, or antiarthritis). The valorization of these species can help to counteract the environmental effects of the bioinvasions.

Gut Microbiota Associated with Gestational Health Conditions in a Sample of Mexican Women.

Gestational diabetes (GD), pre-gestational diabetes (PD), and pre-eclampsia (PE) are morbidities affecting gestational health which have been associated with dysbiosis of the mother's gut microbiota. This study aimed to assess the extent of change in the gut microbiota diversity, short-chain fatty acids (SCFA) production, and fecal metabolites profile in a sample of Mexican women affected by these disorders. Fecal samples were collected from women with GD, PD, or PE in the third trimester of pregnancy, along with clinical and biochemical data. Gut microbiota was characterized by high-throughput DNA sequencing of V3-16S rRNA gene libraries; SCFA and metabolites were measured by High-Pressure Liquid Chromatography (HPLC) and (Fourier Transform Ion Cyclotron Mass Spectrometry (FT-ICR MS), respectively, in extracts prepared from feces. Although the results for fecal microbiota did not show statistically significant differences in alfa diversity for GD, PD, and PE concerning controls, there was a difference in beta diversity for GD versus CO, and a high abundance of Proteobacteria, followed by Firmicutes and Bacteroidota among gestational health conditions. DESeq2 analysis revealed bacterial genera associated with each health condition; the Spearman's correlation analyses showed selected anthropometric, biochemical, dietary, and SCFA metadata associated with specific bacterial abundances, and although the HPLC did not show relevant differences in SCFA content among the studied groups, FT-ICR MS disclosed the presence of interesting metabolites of complex phenolic, valeric, arachidic, and caprylic acid nature. The major conclusion of our work is that GD, PD, and PE are associated with fecal bacterial microbiota profiles, with distinct predictive metagenomes.

Urban and agricultural land use regulates the molecular composition and bio-lability of fluvial dissolved organic matter in human-impacted southeastern China

AbstractUrbanization and agricultural land use can increase the transport of nutrients to fluvial ecosystems; yet, the overall impact of urban and nonpoint agricultural inputs on the composition, bio-lability, and the fate of fluvial dissolved organic matter (DOM) remains poorly understood. We investigated the optical and molecular composition and bio-lability of DOM in 76 streams and rivers with varying sizes of catchment area (1 ~ 4850 km2) along large gradients of urban and agricultural land use. Optical spectroscopy and Fourier transform ion cyclotron mass spectrometry (FT-ICR MS) were used to determine the chemical composition of DOM, and laboratory bio-incubations were used to assess DOM bio-lability. We found that urban and agricultural land use intensification was associated with the reduced relative contribution of DOM from pristine soils, enriched dissolved organic carbon (DOC), and higher contributions of aliphatic and peptide-like DOM, as well as enrichment of N- and S-containing molecular formulae. Specifically, FT-ICR MS revealed that the relative abundance of CHO-containing formulae decreased while that of CHOS-containing formulae increased with increasing urban land use. DOM bio-availability was higher in rivers draining urbanized and agricultural landscapes and was related to decreased DOM aromaticity and increased proportions of energy-rich aliphatic formulae. Our results suggested that DOM from urbanized and agricultural catchments significantly altered the chemical composition and bio-availability of DOM with potential effects on ecosystem metabolism and the fate of organic carbon in the downstream-linked streams and rivers. Anthropogenic disturbances may thus boost the microbial processing of organic carbon, including uptake, retention, and outgassing in the impacted ecosystems. Graphical Abstract

Substantial Biogeochemical and Biomolecular Processing of Dissolved Organic Matter in an Anticyclonic Eddy in the Northern South China Sea Down to Bathypelagic Depths

Solid-phase extracted dissolved organic matter (SPE-DOM) was isolated from two depth profiles at the core and at the edge of an anticyclonic eddy (ACE) in the northern South China Sea. Non-target nuclear magnetic resonance (NMR) spectroscopy and Fourier transform ion cyclotron mass spectrometry (FTICR/MS) of SPE-DOM revealed a higher uniformity of DOM molecules within the ACE than at the edge of the ACE. Small-scale upwelling of external nutrients may have contributed to higher productivity and production of fresher DOM, with higher proportions of CHNO and CHNOS compounds and low molecular weight species at the edge of the eddy. Common SPE-DOM molecules of supposedly biological origin such as carbohydrates and olefins were most abundant in the chlorophyll maximum layer in both stations. An unusual suite of ~10 abundant and ~35 less abundant tert-butyl benzene derivatives with potential to act as endocrine disruptors within a marine food chain and ~two dozen ketones of putative bacterial origin was recognized at meso- and bathypelagic depths in single-digit micromolar concentrations, with a distinct maximum at 1000 m depth at the edge of ACE. Downwelling might bring temporary large volumes of productive marine waters into deep waters, with micromolar concentration of abundant, microbial food web-specific metabolites (e.g. 2,4-di-tert-butylphenol et al.). In our study, these eventually added up to one quarter of common background biogeochemical marine organic matter even at bathypelagic depths and beneath and are significant food and energy sources for marine biota. Mesoscale chemical heterogeneity of marine water columns might extend to larger depths than currently anticipated and may create activity hotspots influencing biota, processing of DOM, and cycling of nutrients and trace elements.

Imaging of Corticosteroids in Mouse Kidney Using Mass Spectrometry

Aldosterone regulates renal sodium reabsorption which is important for blood pressure homeostasis. Glucocorticoids may also contribute to this process although this is less well understood. Analysis of steroid hormones and the metabolites in the plasma and urine gives insights into corticosteroid biology but steroid concentrations at a cellular level are largely unknown, and the kidney remains a “black box”. Mass spectrometry imaging (MSI) permits localisation of steroids in histological zones based on regional markers. This approach has been previously applied to localise steroids in brain and testes, and here is applied to kidney. Our aim was to map and quantify glucocorticoids and aldosterone in different histological zones (cortex, medulla) of kidneys from mice receiving different dietary salt, to provide new information relevant to the physiological actions of these hormones.Cryosections kidney from male C57BL6 mouse (age 12 weeks, n=6: dietary salt low 0.03% vs normal 0.3% vs high 3%) were subject to MSI analysis following Girard T reagent derivatisation and α‐cyano‐4‐hydroxycinnamic acid matrix application. Matrix assisted laser desorption/ionisation (MALDI) was used as a sampling method, coupled to Fourier Transform Ion cyclotron mass spectrometry.Ions with m/z 458.3010 (Δppm=0.65), 460.3166 (Δppm=0.65), and 474.2957 (Δppm=1.05) were detected, using MALDI, in renal sections for derivatives of 11‐dehydrocorticosterone, corticosterone and aldosterone respectively. Untargeted evaluation of ions was conducted to find regional markers that would allow definition of kidney histological zones. Heat maps indicated that corticosterone intensity was higher in the inner cortex than the rest of the kidney. In contrast 11‐dehydrocorticosterone, a metabolite produced by the enzymic activity of 11β‐hydroxysteroid dehydrogenase type II, was detected at highest levels in the medulla. The aldosterone signal was equally strong in medulla and outer cortex. Steroid localisation after treatment with different salt intakes indicated that the intensity of the corticosterone signal increases in the outer cortex in kidneys from mice receiving low salt diet, while 11‐dehydrocorticosterone was not affected. The intensity of the aldosterone signal within the kidney was not changed by different salt intakes. Our approach shows that it is feasible to image corticosteroids at 75μm spatial resolution within the kidney. This technology provides new insights into the physiological control of sodium transport by steroids and opens doors to understanding changes in disorders of blood pressure.

Unraveling the Role of Anthropogenic and Natural Drivers in Shaping the Molecular Composition and Biolability of Dissolved Organic Matter in Non-pristine Lakes.

Lakes receive and actively process terrestrial dissolved organic matter (DOM) and play an important role in the global carbon cycle. Urbanization results in elevated inputs of nonpoint-source DOM to headwater streams. Retention of water in lakes allows time for alteration and transformation of the chemical composition of DOM by microbes and UV radiation. Yet, it remains unclear how anthropogenic and natural drivers impact the composition and biolability of DOM in non-pristine lakes. We used optical spectroscopy, Fourier transform ion cyclotron mass spectrometry, stable isotopic measurements, and laboratory bioincubations to investigate the chemical composition and biolability of DOM across two large data sets of lakes associated with a large gradient of urbanization in lowland Eastern China, encompassing a total of 99 lakes. We found that increased urban land use, gross domestic products, and population density in the catchment were associated with an elevated trophic level index, higher chlorophyll-a, higher bacterial abundance, and a higher amount of organic carbon with proportionally higher contribution of aliphatic and peptide-like DOM fractions, which can be highly biolabile. Catchment areas, water depth, lake area: catchment area, gross primary productivity, δ18O-H2O, and bacterial abundance, however, had comparatively little linkage with DOM composition and biolability. Urban land use is currently intensifying in many developing countries, and our results anticipate an increase in the level of biolabile aliphatic DOM from nonpoint sources and accelerated carbon cycling in lake ecosystems in such regions.

Compositional analysis of essential oil and solvent extracts of Norway spruce sprouts by ultrahigh-resolution mass spectrometry.

Coniferous trees, especially their needles and bark, are a rich source of bioactive compounds. The developing needles of Norway spruce (Picea abies), also known as spruce sprouts, are enriched with vitamin C and other antioxidants, and thus they are used as a dietary supplement and have been traditionally used to treat various inflammatory disorders such as rheumatism and gout. Their chemical composition is only limitedly known, however. The main objective of this work was to have a deeper understanding on the chemical composition of spruce sprouts to assess their full potential in different pharmaceutical, nutraceutical, or technochemical applications. Ultrahigh-resolution Fourier-transform ion cyclotron (FT-ICR) mass spectrometry, coupled to direct-infusion electrospray ionisation (ESI) or atmospheric pressure photoionisation (APPI) techniques, was used for in-depth compositional analysis of solvent extracts and essential oil of spruce sprouts. A combined use of ESI and APPI techniques offered a great complementary insight into the rich chemistry of different spruce sprout extracts, allowing detection of thousands of chemical constituents with over 200 secondary metabolites tentatively identified. These compounds belonged to different classes such as organic acids, terpenes, flavonoids, stilbenes, sterols, and nitrogen alkaloids. Spruce sprouts have a complex metabolite profile that differs considerably from that of the old, developed needles.

Improved coverage of plant metabolites using powder laser desorption/ionization coupled with Fourier-transform ion cyclotron mass spectrometry

In this study, the effectiveness of powder laser desorption/ionization (LDI) coupled with Fourier-transform ion cyclotron mass spectrometry (FT-ICR MS) was evaluated for the improved coverage of plant metabolites. Ground plant (powder) was fixed on a metal plate using double-sided tape. Compared with the conventional approach involving liquid extraction, which is followed by electrospray ionization MS analysis, a smaller amount of sample (∼200 µg) was required in the proposed method. Additionally, the laborious steps of liquid extraction, concentration, and solid-phase extraction were avoided. Employing the proposed method in Centella asiatica leaves analysis, higher number of reproducible molecular formulas (>5000) and metabolites (>650) were obtained than the conventional methods. Flavonoids, phenolic acids, xanthones, lipids, carbohydrates, terpenoids, and alkaloids compounds were detected from leaves, stems, and roots of C. asiatica. This study indicates that LDI FT-ICR MS is a quick and effective tool for enhanced plant metabolite profiling in the solid phase.

Conditioning Film and Early Biofilm Succession on Plastic Surfaces.

In the context of environmental plastic pollution, it is still under debate if and how the "plastisphere", a plastic-specific microbial community, emerges. In this study, we tested the hypothesis that the first conditioning film of dissolved organic matter (DOM) sorbs selectively to polymer substrates and that microbial attachment is governed in a substrate-dependent manner. We investigated the adsorption of stream water-derived DOM to polyethylene terephthalate (PET), polystyrene (PS), and glass (as control) including UV-weathered surfaces by Fourier-transform ion cyclotron mass spectrometry. Generally, the saturated, high-molecular mass and thus more hydrophobic fraction of the original stream water DOM preferentially adsorbed to the substrates. The UV-weathered polymers adsorbed more polar, hydrophilic OM as compared to the dark controls. The amplicon sequencing data of the initial microbial colonization process revealed a tendency of substrate specificity for biofilm attachment after 24 h and a clear convergence of the communities after 72 h of incubation. Conclusively, the adsorbed OM layer developed depending on the materials' surface properties and increased the water contact angles, indicating higher surface hydrophobicity as compared to pristine surfaces. This study improves our understanding of molecular and biological interactions at the polymer/water interface that are relevant to understand the ecological impact of plastic pollution on a community level.

On the Trail of the German Purity Law: Distinguishing the Metabolic Signatures of Wheat, Corn and Rice in Beer.

Here, we report a non-targeted analytical approach to investigate the influence of different starch sources on the metabolic signature in the final beer product. An extensive sample set of commercial beers brewed with barley, wheat, corn and/or rice were analyzed by both direct infusion Fourier transform ion cyclotron mass spectrometry (DI-FTICR MS, 400 samples) and UPLC-ToF-MS (100 samples). By its unrivaled mass resolution and accuracy, DI-FTICR-MS was able to uncover the compositional space of both polar and non-polar metabolites that can be traced back to the use of different starch sources. Reversed phase UPLC-ToF-MS was used to access information about molecular structures (MS2-fragmentation spectra) and isomeric separation, with a focus on less polar compounds. Both analytical approaches were able to achieve a clear statistical differentiation (OPLS-DA) of beer samples and reveal metabolic profiles according to the starch source. A mass difference network analysis, applied to the exact marker masses resolved by FTICR, showed a network of potential secondary metabolites specific to wheat, corn and rice. By MS2-similarity networks, database and literature search, we were able to identify metabolites and compound classes significant for the use of the different starch sources. Those were also found in the corresponding brewing raw materials, confirming the potential of our approach for quality control and monitoring. Our results also include the identification of the aspartic acid-conjugate of N-β-D-glucopyranosyl-indole-3-acetic acid as a potential marker for the use of rice in the brewing industry regarding quality control and food inspection purposes.

Hidden in its color: A molecular-level analysis of the beer’s Maillard reaction network

We here report a comprehensive non-targeted analytical approach to describe the Maillard reaction in beer. By Fourier-transform ion cyclotron mass spectrometry (FT-ICR-MS), we were able to assign thousands of unambiguous molecular formulae to the mass signals and thus directly proceed to the compositional space of 250 analyzed beer samples. Statistical data analyses of the annotated compositions showed that the Maillard reaction is one of the driving forces of beer’s molecular diversity leading to key compositional changes in the beer metabolome. Different visualization methods allowed us to map the systematic nature of Maillard reaction derived compounds. The typical molecular pattern, validated by an experimental Maillard reaction model system, pervades over 2,800 (40%) of the resolved small molecules. The major compositional changes were investigated by mass difference network analysis. We were able to reveal general reaction sequences that could be assigned to successive Maillard intermediate phase reactions by shortest path analysis.

Mapping of Corticosteroids in Murine Kidneys Using Mass Spectrometry Imaging

Renal sodium reabsorption is important for blood pressure homeostasis and is physiologically regulated by aldosterone; glucocorticoids may also contribute. Abnormal steroid hormone activity within the kidney contributes to hypertension but the mechanisms are not fully defined. Molecular profiling of receptors and metabolising enzymes indicates that steroid hormone action is compartmentalised within the kidney. Ambient steroid concentrations are a critical factor governing bioactivity at a cellular level, but this is largely unknown, and the kidney remains a “black box”. Mass spectrometry imaging (MSI) was applied recently to localise steroids in brain and testes, and here is applied to kidney. Image reconstruction permits characterisation and co-registration of kidney histological regions based on regional markers detectable by MSI. Our aim was to map and quantify glucocorticoids and aldosterone in different histological zones (cortex, medulla) of murine kidneys, using an optimised MSI method. This approach has the potential to map steroids within functional zones of the kidney, providing fundamental new information relevant to hormone action in health and in disease. Cryosections of male C57BL6 mouse kidneys (age 12 weeks, n=6) were subject to MSI following derivatisation using Girard T reagent and α-cyano-4-hydroxycinnamic acid matrix application. Images were reconstructed, and methods optimised to enhance signal and limit diffusion of analytes of interest. Matrix assisted laser desorption/ionisation (MALDI) was used as a sampling method, coupled to Fourier Transform Ion cyclotron mass spectrometry. Ions with m/z 458.3010, 460.3166 and 474.2957 were detected, using MALDI, in renal sections, close to the predicted masses of 458.3013 (Δppm=0.65), 460.3169 (Δppm=0.65), and 474.2962 (Δppm=1.05), for derivatives of 11-dehydrocorticosterone, corticosterone and aldosterone respectively. Untargeted evaluation of ions was conducted to find regional markers that would allow definition of kidney histological zones. The Heat maps generated indicated that corticosterone intensity was higher in the inner cortex area close to the corticomedullary junction than the rest of the kidney. In contrast 11-dehydrocorticosterone was detected mainly in medulla and aldosterone signal was equally strong in medulla and outer cortex. Thus, MSI can be used map the sites where glucocorticoid and mineralocorticoids are most active in regulating renal tubular function. Co-localisation of steroids of interest with zonal markers by MSI permits steroid mapping in functional renal zones of the kidney. This approach provides fundamental new insights into the physiological control of sodium transport by steroids and opens doors to understanding changes in disorders of blood pressure. The project was supported and funded by Kidney Research UK.

The importance of nutrients for microbial priming in a bog rhizosphere

Wetlands host anaerobic microbes which convert organic carbon into methane (CH4), a powerful greenhouse gas. Wetland plants can influence which carbon compounds are available for microbial processing by exuding freshly fixed carbon from their roots. Exudation of carbon from plant roots can trigger microbial priming: the process of new carbon stimulating the microbial community into processing more soil carbon than they otherwise would have. This study utilized high resolution Fourier transform ion cyclotron mass spectrometry (FT-ICR-MS) analysis to probe the composition of soil organic compounds from the rhizosphere of Carex aquatillis, a common wetland sedge, which is known to have stimulated microbial priming within peat soil. The goal was to identify what types of molecules were created or lost during microbial priming in the wetland rhizosphere and thus advance mechanistic understanding of the process. FT-ICR-MS analysis demonstrated that more microbial transformations of carbon occurred among water-soluble compounds than among hydrophobic compounds, but that some hydrophobic compounds were processed. Crucially for understanding microbial priming, the root exudates triggered increased processing of high molecular weight molecules regardless of nutrient content but processed low molecular weight compounds only if they contained nitrogen or sulfur, essential nutrients for plant growth. The importance of sulfur in determining molecular utilization is noteworthy because priming literature typically focuses on nitrogen-mining. The fact that some molecules were processed and others were not is evidence for a selective priming effect in which some carbon compounds with specific properties are used at an increased rate, while others are left unaltered.

Molecular Characterization of Strongly and Weakly Interfacially Active Asphaltenes by High-Resolution Mass Spectrometry

Asphaltenes are a complex mixture of molecular structures with a variety of functionalities, which in turn impacts their physical properties. Discriminating between asphaltenes that are strongly and weakly interfacially active is providing a new direction to mitigate asphaltene-related problems. Whole asphaltenes (WA) were extracted from a South American heavy crude oil, further fractionated into interfacially active asphaltenes (IAA) and remaining asphaltenes (RA), and molecularly characterized by positive-ion (+) atmospheric pressure photoionization (APPI) using a 9.4 T Fourier transform ion cyclotron mass spectrometer (FT-ICR MS). The IAA fraction was found to contain a greater abundance of heteroatoms with >50% of IAA containing two or more heteroatoms as compared to ∼30% for RA. The IAA fraction was enriched in oxygen-containing species, more specifically higher-order Ox and OxSy groups that were predominantly of low DBE. Gas-phase fragmentation of RA and IAA precursor ions (m/z 650) by infrared multiphoton dissociation (IRMPD) revealed an abundance of multi-core motifs in IAA, while RA was found to be a mixture of single-core and multi-core structures. Analysis of the fragmented ions showed a prevalence of nitrogen-containing species of high DBE (aromatic molecular structures), while oxygen-containing species were most likely associated with aliphatic side chains. Extrography fractionation of RA and IAA verified the abundance of multi-core motifs in IAA, which were highly polar and of low DBE and carbon number. These “atypical” structures of IAA are classified as asphaltenes as a result of their functionality and polarity rather than high aromaticity.

Structure of protonated heterodimer of proline and phenylalanine: Revealed by infrared multiphoton dissociation spectroscopy and theoretical calculations

The infrared multiphoton dissociation (IRMPD) spectrum of the protonated heterodimer of ProPheH+, in the range of 2700-3700 cm−1, has been obtained with a Fourier-transform ion cyclotron mass spectrometer combined with an IR OPO laser. The experimental spectrum shows one peak at 3565 cm−1 corresponding to the free carboxyl O-H stretching vibration, and two broad peaks centered at 2935 and 3195 cm−1. Theoretical calculations were performed on the level of M062X/6-311++G(d,p). Results show that the most stable isomer is characterized by a charge-solvated structure in which the proton is bound to the unit of proline. Its predicted spectrum is in good agreement with the experimental one, although the coexistence of salt-bridged structures cannot be entirely excluded.