ionization-Fourier Transform Ion Cyclotron Resonance-mass Research Articles

Mechanistic Insights into the Biodegradation of Carbon Dots by Fungal Laccase.

While carbon dots (CDs) have the potential to support the agricultural revolution, it remains obscure about their environmental fate and bioavailability by plants. Fungal laccase-mediated biotransformation of carbon nanomaterials has received little attention despite its known capacity to eliminate recalcitrant contaminants. Herein, we presented the initial investigation into the transformation of CDs by fungal laccase. The degradation rates of CDs were determined to be first-order in both substrate and enzyme. Computational docking studies showed that CDs preferentially bonded to the pocket of laccase on the basal plane rather than the edge through hydrogen bonds and hydrophobic interactions. Electrospray ionization-Fourier transform-ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS) and other characterizations revealed that the phenolic/amino lignins and tannins portions in CDs are susceptible to laccase transformation, resulting in graphitic structure damage and smaller-sized fragments. By using the 13C stable isotope labeling technique, we quantified the uptake and translocation of 13C-CDs by mung bean plants. 13C-CDs (10 mg L-1) accumulated in the root, stem, and leaf were estimated to be 291, 239, and 152 μg g-1 at day 5. We also evidenced that laccase treatment alters the particle size and surface chemistry of CDs, which could facilitate the uptake of CDs by plants and reduce their nanotoxicity to plants.

Comparison of Sample Preparation Techniques for the (−)ESI-FT-ICR-MS Analysis of Humic and Fulvic Acids

Soil organic matter (SOM) plays a key role in the global carbon and nitrogen cycles. Soil biogeochemistry is regularly studied by extracting the base-soluble fractions of SOM: acid-insoluble humic acid (HA) and acid-soluble fulvic acid (FA). Electrospray ionization-Fourier transform-ion cyclotron resonance-mass spectrometry (ESI-FT-ICR-MS) is commonly utilized for molecularly characterizing these fractions. Different sample preparation techniques exist for the analysis of HA and FA though questions remain regarding data comparability following different preparations. Comparisons of different sample preparation techniques here revealed that the negative-mode ESI-FT-ICR-MS analytical window can be skewed to detect different groups of molecules, with primary differences in oxygenation, aromaticity, and molecular weight. It was also observed that HA and FA from soils versus an aquatic matrix behaved very differently. Thus, we conclude that sample preparation techniques determined to be "most optimal" in our study are in no way universal. We recommend that future studies of HA and FA involve similar comparative studies for determining the most suitable sample preparation technique for their particular type of HA or FA matrices. This will enhance data comparability among different studies and environmental systems and ultimately allow us to better understand the complex composition of environmental matrices.

Hydrothermal liquefaction of cellulose in ammonia/water

In order to obtain the N-containing organics from cellulose under mild conditions, hydrothermal liquefaction of cellulose in the presence of ammonia was conducted in this study. The results showed that the increasing reaction temperature and prolonging time facilitated the conversion of cellulose in hydrothermal liquefaction (HTL) with NH3·H2O and decreased the amount of solid residue. Reaction temperature showed more influence than reaction time on solid residue formation. The components of bio-oil were significantly affected by reaction temperature and reaction time. Electrospray ionization-Fourier transform-ion cyclotron resonance-mass spectrometry (ESI FT-ICR MS) provided an insight for understanding the distribution of the different kinds of N-heterocycle compounds in the bio-oil. The possible reaction pathway of N-heterocycle compounds formation from cellulose during hydrothermal liquefaction with NH3·H2O was proposed.

Investigating organic matter properties affecting the binding behavior of heavy metals in the rhizosphere of wetlands

Soil organic matter (SOM) is a crucial factor affecting the immobilization of heavy metal in wetlands. Recent studies have shown that the rhizosphere SOM has great ability to immobilize heavy metals. However, there existed few works on studying molecular characteristics of SOM to explore the mechanisms. Electrospray ionization–Fourier transform ion cyclotron resonance–mass spectrometry (ESI-FTICR-MS) combined with FTIR spectroscopy were applied to investigate the characteristics of SOM in rhizosphere and nonrhizosphere samples and to find out what characteristics the rhizosphere SOM embodies conducive to metal binding in this paper. The rhizosphere contained higher C, P, Mn, and other metal concentrations. The adsorption of Cr on rhizosphere SOM was greater than that on nonrhizosphere SOM. Compared to nonrhizosphere SOM, rhizosphere SOM contained less saturated and more oxidized compounds, greater overall molecular weights (MW), more condensed aromatic structures (56.59% VS 51.56% by peak intensity), less carboxylate and N-containing COO functional groups (25.98% VS 56.63% by peak intensity), more hydrophilicity, and the latter four are conducive to metal binding. This study showed that the rhizosphere SOM had unique compositional and structural characteristics. These results provided evidence for the phytoremediation technologies of heavy metal contaminated wetlands.

Novel detection of post-translational modifications in human monocyte-derived dendritic cells after chronic alcohol exposure: Role of inflammation regulator H4K12ac

Previous reports on epigenetic mechanisms involved in alcohol abuse have focus on hepatic and neuronal regions, leaving the immune system and specifically monocyte-derived dendritic cells (MDDCs) understudied. Our lab has previously shown histone deacetylases are modulated in cells derived from alcohol users and after in vitro acute alcohol treatment of human MDDCs. In the current study, we developed a novel screening tool using matrix assisted laser desorption ionization-fourier transform-ion cyclotron resonance mass spectrometry (MALDI-FT-ICR MS) and single cell imaging flow cytometry to detect post-translational modifications (PTMs) in human MDDCs due to chronic alcohol exposure. Our results demonstrate, for the first time, in vitro chronic alcohol exposure of MDDCs modulates H3 and H4 and induces a significant increase in acetylation at H4K12 (H4K12ac). Moreover, the Tip60/HAT inhibitor, NU9056, was able to block EtOH-induced H4K12ac, enhancing the effect of EtOH on IL-15, RANTES, TGF-β1, and TNF-α cytokines while restoring MCP-2 levels, suggesting that H4K12ac may be playing a major role during inflammation and may serve as an inflammation regulator or a cellular stress response mechanism under chronic alcohol conditions.

Hydroconversion Behavior of Asphaltenes under Liquid-Phase Hydrogenation Conditions

To fully utilize deoiled end-cut (DOE) from selective asphaltene extraction process, Venezuela n-pentane DOE was subjected to hydroconversion in an autoclave reactor using tetralin as hydrogen donor. Venezuela DOE and its hydroconversion products were separated into gas, n-heptane maltenes (HM), n-heptane asphaltenes (HAs), and coke. The effects of reaction conditions including reaction temperature, solvent-to-feedstock (S/F) weight ratio, and reaction time on product distribution were investigated. High temperature, large S/F ratio, and long time benefited the generation of gas, HM, and coke to some extent. Under optimal conditions, over 50 wt % HAs in DOE was converted into HM fraction, with less than 3 wt % coke yield. The elemental compositions and molecular weights of HAs and HM, along with reaction time, were also analyzed. The hydrogen-to-carbon (H/C) ratio of HAs declined from 1.115 to 0.871, indicating that HAs underwent dehydrogenation and dealkylation reactions. However, the H/C ratio of HM initially increased from 1.405 to 1.548, showing that hydrogenation reaction occurred, and then decreased to 1.374 because of the cracking of HAs into HM and/or the secondary cracking of HM. The average molecular-weight decrease both for HAs and HM confirmed disaggregation and cracking reactions. The molecular composition and transformation of nitrogen and sulfur compounds before and after hydroconversion were determined by negative- and positive-ion electrospray ionization Fourier transform ion-cyclotron–resonance mass spectrometry, respectively. N1, S1, and O2 classes were dominant in the feedstock. After hydroconversion, N1 and S2 compounds decreased in HAs, indicating that they were reactive species. N1 compounds mainly cracked into small N1 compounds and also condensed into N2 compounds, while S2 compounds generally decomposed into S1 compounds.

Hydrothermal liquefaction of isolated cuticle of Agave americana and Capsicum annuum: Chemical characterization of petroleum-like products

Abstract Hydrothermal liquefaction (HTL) of cuticular materials from Agave americana and Capsicum annuum was performed for extended periods of time (72 h) at 360 °C meant to simulate long-term maturation of the organic matter. Both cuticular materials displayed evidence for possible oil production from the amounts of polymethylenic carbons in 13 C solid-state nuclear magnetic resonance spectra. The bio-oil yields were approximately 35 wt.% and exhibited heating values of 40.5 MJ kg −1 , comparable to those of typical crude petroleum. Analysis by two dimensional gas chromatography indicated that the A . americana bio-oil was dominated by a homologous series of n -alkanes, whereas cyclic and aromatic compounds were the major compounds identified in the C . annumm bio-oil. Further analysis using electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry revealed the bio-oil samples were predominantly lipid-like in character. The result of this study demonstrate that one can utilize highly aliphatic biopolymeric components of certain plant materials to produce bio-oils that have the potential to be utilized as alternative fuels.

Transgenic petunia with the iron(III)-phytosiderophore transporter gene acquires tolerance to iron deficiency in alkaline environments.

Iron is an essential nutrient for all plants. However, terrestrial plants often suffer from iron deficiency in alkaline soil due to its extremely low solubility. Alkaline soil accounts for about 30% of all cultivated ground in the world. Plants have evolved two distinct strategies, I and II, for iron uptake from the soil. Dicots and non-graminaceous monocots use Strategy I, which is primarily based on the reduction of iron(III) to iron(II) and the uptake of iron(II) by the iron-regulated transporter, IRT1. In contrast, graminaceous plants use Strategy II to efficiently acquire insoluble iron(III). Strategy II comprises the synthesis and secretion of iron-chelating phytosiderophores, such as mugineic acids and the Yellow Stripe 1 transporter proteins of the iron(III)-phytosiderophore complex. Barley, which exhibits the highest tolerance to iron deficiency in alkaline soil among graminaceous plants, utilizes mugineic acids and the specific iron(III)-mugineic acids transporter, HvYS1. In this study, we established the transgenic plant Petunia hybrida, which originally had only Strategy I, by introducing the HvYS1 transporter gene derived from barley. When the transgenic plants were grown hydroponically in media containing the iron(III)-2′-deoxymugineic acid complex, free 2′-deoxymugineic acid and its iron(III) complex were detected in the root extract of the transgenic plant by electrospray ionization-Fourier transform-ion cyclotron resonance mass spectrometry. The growth of the transgenic petunia was significantly better than that of the control host in alkaline conditions. Consequently, the transgenic plant acquired a significantly enhanced tolerance to alkaline hydroponic media in the presence of the iron(III)-2′-deoxymugineic acid complex. Furthermore, the flower color of the transgenic plant deepened. The results showed that iron-phytosiderophore complexes and their transporters can potentially be utilized to overcome the worldwide iron uptake problems to diverse plant species that are found in areas with alkaline conditions.

Valuable Crude Oil from Hydrothermal Liquefaction of an Aliphatic Coal

Artificial maturation techniques, such as hydrothermal liquefaction (HTL), have demonstrated the ability to generate petroleum-like products, termed bio-oils, from feedstocks including manure, algae and agricultural wastes; however, the oxygen, nitrogen, and sulfur content of bio-oils often requires upgrading. The objective of this study was to utilize HTL on a low rank coal to produce a high quality crude oil sample that can be used as a transportation fuel. Coal from the Wyodak-Anderson coal seam was selected for HTL due to its predominant aliphatic character and low heteroatom content. HTL was performed at 360 °C for 72 h. The untreated coal, spent solid, and expelled oil were analyzed using several advance analytical techniques including solid-state 13C NMR, two-dimensional gas chromatography–mass spectrometry and electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry to achieve a comprehensive molecular characterization. Solid-state 13C NMR analyses of the untreated and spent coal estimate that 22% of the untreated coal, mostly the aliphatic portion, is lost as expelled hydrocarbon products. The expelled oil exhibits molecular characteristics similar to high quality crude oils, including low heteroatom content, n-alkanes ranging from C9–C32, and other desirable crude oil components such as cycloalkanes, alkyl benzenes and naphthalenes. It is suggested here that upon thermal maturation of the coal, preserved ester bonds in refractory biopolymers present in the coal are being cracked to yield fatty acids, which upon heating undergo decarboxylation, and finally random cleavage of C–C bonds to yield the lower molecular weight n-alkanes. Our results confirm that HTL is an effective technique for the production of a high quality crude oil from a low rank coal.

Manganese speciation in paired serum and CSF samples using SEC-DRC-ICP-MS and CE-ICP-DRC-MS

Occupational manganese (Mn) overexposure leads to accumulation in the brain and has been shown to cause progressive, permanent, neuro-degenerative damage with syndromes similar to idiopathic Parkinsonism. Mn is transported by an active mechanism across neural barriers (NB) finally into the brain; but to date, modes of Mn neurotoxic action are poorly understood. This paper investigates the relevant Mn-carrier species which are responsible for widely uncontrolled transport across NB. Mn speciation in paired serum/cerebrospinal fluid (CSF) samples was performed by size exclusion chromatography-inductively coupled plasma-dynamic reaction cell-mass spectrometry (SEC-ICP-DRC-MS) and capillary zone electrophoresis coupled to ICP-DRC-MS in a 2D approach for clear identification. For additional species verification, electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry was used after SEC-ICP-DRC-MS (second 2D approach). The Mn species from the different sample types were interrelated and correlation coefficients were calculated. In serum protein-bound Mn species like Mn-transferrin/albumin (Mn-Tf/HSA) were dominant, which had the main influence on total Mn in serum if Mn(total) was <1.5 μg/L. Above serum Mn(total) concentration of 1.6 μg/L the serum Mn(total) concentration was correlated with increasing Mn-citrate (Mn-Cit) concentration. In parallel Mn(total) and Mn species in CSF were determined. It turned out that Mn(total) from CSF was about half of Mn(total) in serum; Mn-Tf/HSA was only about 10% compared to serum. It turned out that above 1.6 μg/L Mn(total) in serum Mn-Cit was not only the leading Mn species in serum but also was the main influencing factor of both Mn(total) and Mn-Cit concentration in CSF. These results were further investigated using two statistical models (orthogonal partial least squares discriminant analysis, canonical discriminant analysis). Both models discriminated the samples in two groups where CSF samples were either correlated to Mn(total) and Mn-Cit (samples with serum Mn(total) > 1,550 ng/L) or correlated to Mn-Tf/HSA (samples with serum Mn(total) < 1,550 ng/L). We conclude that elevated Mn-Cit(serum) could be a valuable marker for increased total Mn in CSF (and brain), i.e., it could be a marker for elevated risk of Mn-dependent neurological disorders such as manganism in occupational health.

Promiscuity of Carbonic Anhydrase II. Unexpected Ester Hydrolysis of Carbohydrate-Based Sulfamate Inhibitors

Carbonic anhydrases (CAs) are enzymes whose endogenous reaction is the reversible hydration of CO(2) to give HCO(3)(-) and a proton. CA are also known to exhibit weak and promiscuous esterase activity toward activated esters. Here, we report a series of findings obtained with a set of CA inhibitors that showed quite unexpectedly that the compounds were both inhibitors of CO(2) hydration and substrates for the esterase activity of CA. The compounds comprised a monosaccharide core with the C-6 primary hydroxyl group derivatized as a sulfamate (for CA recognition). The remaining four sugar hydroxyl groups were acylated. Using protein X-ray crystallography, the crystal structures of human CA II in complex with four of the sulfamate inhibitors were obtained. As expected, the four structures displayed the canonical CA protein-sulfamate interactions. Unexpectedly, a free hydroxyl group was observed at the anomeric center (C-1) rather than the parent C-1 acyl group. In addition, this hydroxyl group is observed axial to the carbohydrate ring while in the parent structure it is equatorial. A mechanism is proposed that accounts for this inversion of stereochemistry. For three of the inhibitors, the acyl groups at C-2 or at C-2 and C-3 were also absent with hydroxyl groups observed in their place and retention of stereochemistry. With the use of electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry (ESI-FTICR-MS), we observed directly the sequential loss of all four acyl groups from one of the carbohydrate-based sulfamates. For this compound, the inhibitor and substrate binding mode were further analyzed using free energy calculations. These calculations suggested that the parent compound binds almost exclusively as a substrate. To conclude, we have demonstrated that acylated carbohydrate-based sulfamates are simultaneously inhibitor and substrate of human CA II. Our results suggest that, initially, the substrate binding mode dominates, but following hydrolysis, the ligand can also bind as a pure inhibitor thereby competing with the substrate binding mode.

Formation of nitrogenated organic aerosols in the Titan upper atmosphere

Many aspects of the nitrogen fixation process by photochemistry in the Titan atmosphere are not fully understood. The recent Cassini mission revealed organic aerosol formation in the upper atmosphere of Titan. It is not clear, however, how much and by what mechanism nitrogen is incorporated in Titan's organic aerosols. Using tunable synchrotron radiation at the Advanced Light Source, we demonstrate the first evidence of nitrogenated organic aerosol production by extreme ultraviolet-vacuum ultraviolet irradiation of a N(2)/CH(4) gas mixture. The ultrahigh-mass-resolution study with laser desorption ionization-Fourier transform-ion cyclotron resonance mass spectrometry of N(2)/CH(4) photolytic solid products at 60 and 82.5 nm indicates the predominance of highly nitrogenated compounds. The distinct nitrogen incorporations at the elemental abundances of H(2)C(2)N and HCN, respectively, are suggestive of important roles of H(2)C(2)N/HCCN and HCN/CN in their formation. The efficient formation of unsaturated hydrocarbons is observed in the gas phase without abundant nitrogenated neutrals at 60 nm, and this is confirmed by separately using (13)C and (15)N isotopically labeled initial gas mixtures. These observations strongly suggest a heterogeneous incorporation mechanism via short lived nitrogenated reactive species, such as HCCN radical, for nitrogenated organic aerosol formation, and imply that substantial amounts of nitrogen is fixed as organic macromolecular aerosols in Titan's atmosphere.

Investigating a New Type of Hydrogen Bond

A novel complexation of neutral cavitands and anions is discussed. Resorcin­arene-based cavitands 2-11 all have acetal hydrogen atoms oriented into the cavity. Electrospray ionization Fourier-transform ion-cyclotron resonance mass spectrometry (ESI-FTICR-MS) was used to analyze the anion binding because solvent and counter ion effects could be ruled out. Collision-induced decomposition studies along with quantum chemical calculations reveal the nonaromatic C-H···anion coordination to be quite strong.

The structure of salmochelins: C-glucosylated enterobactins of Salmonella enterica.

Salmochelins represent novel carbohydrate containing catecholate siderophores, which are excreted by Salmonella enterica and uropathogenic Escherichia coli strains under low-iron stress. While previous analytical data showed salmochelins to contain 2,3-dihydroxybenzoyl-L-serine and glucose, the molecular structure remained elusive. Structure elucidation with electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry (ESI-FTICR-MS), GC-MS and 2D-NMR now revealed that salmochelins are enterobactin-related compounds, which are beta-C-glucosylated at the 5-position of a 2,3-dihydroxybenzoyl residue. The key compound salmochelin S4 is a twofold beta-C-glucosylated enterobactin analogue. Comparison of partial structures of salmochelin with a C-glycosylated compound previously characterized by another group strongly suggest that salmochelins represent the long sought compounds termed Salmonella resistance factors (SRF) or pacifarins. Transformation of iro-genes into enterobactin-producing E. coli K12 confers the ability to produce salmochelins. A detailed analysis proved iroB to be the sole gene with glycosyltransferase activity necessary for salmochelin production. Salmochelins compared to enterobactin are the better siderophores in the presence of serum albumin. This may indicate for salmochelins a considerably more important role for pathogenic processes in certain Escherichia coli and Salmonella infections than formerly assigned to enterobactin. This conclusion is supported by the location of the iro genes on pathogenicity islands of uropathogenic E. coli strains.

Mass-selective ion accumulation and fragmentation in a linear octopole ion trap external to a fourier transform ion cyclotron resonance mass spectrometer

Electrosprayed protein ions are accumulated and mass selected in an external linear octopole trap before injection into a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Mass selection is performed by application of superimposed rf and dc octopole electric potentials during ion accumulation. Ion trajectory stability and mass selection in the octopole field are explained qualitatively by analogy to a quadrupole mass filter. Accumulation of ions from a selected m/z range is demonstrated experimentally for 7 and 9.4 T electrospray ionization (ESI) FTICR mass spectrometers. Ion fragmentation in the octopole may occur under certain operating conditions.

Probing RegA/RNA Interactions Using Electrospray Ionization–Fourier Transform Ion Cyclotron Resonance–Mass Spectrometry

The interactions of bacteriophage T4 regA protein, a unique translational regulator, with RNAs of various size and sequence were studied using electrospray ionization–Fourier transform ion cyclotron resonance–mass spectrometry. Using very gentle interface conditions, regA/RNA complexes with a 1:1 binding stoichiometry were observed for all four target RNAs studied, consistent with solution binding studies. Competitive binding of target RNAs and their degradation products with regA demonstrated that the loss of a single nucleotide resulted in a dramatic change in binding affinity in some cases. Competitive binding of regA with four target RNAs revealed similar relative binding affinity order to that suggested by previousin vitrorepression experiments. The use of sustained off-resonance irradiation for collisionally induced dissociation of a regA/RNA complex suggested the potential for directly obtaining information regarding the regA binding domain.