FT-ICR MS Analysis Research Articles

The impact of natural sunlight irradiation on the biotoxicities of different molecular sizes EfOM/SRNOM and its relationship with spectral and molecular level parameters

Natural sunlight irradiation is regarded as an efficient and low-carbon method for controlling the biotoxicity of effluents from domestic wastewater treatment plants (WWTPs). Dissolved organic matter in WWTPs effluent (EfOM) is responsible for the non-specific biotoxicity of effluent. In the present study, the variation in spectral characteristics, molecular composition, luminescent bacteria toxicity, and genotoxicity of EfOM of different molecular sizes (MOSs) during natural sunlight irradiation were investigated from a systematic perspective, and the standard natural organic matter from the Suwannee River (SRNOM) was synchronously assessed for comparative purposes. To further explore the cause of the biotoxicity changes, the relationships between the spectral or molecular level parameters (obtained from FT-ICR MS analysis) and biotoxicity were assessed using correlation analysis. The molecules in <1 kDa EfOM with lower molecular weight, higher unsaturation degree, and higher humification and fluorescence had higher luminescent bacteria toxicity under sunlight irradiation. However, in the <1 kDa SRNOM, the molecules which were characterized by higher humification and fluorescence had higher luminescent bacteria toxicity. The notable genotoxicity reduction of EfOM under sunlight irradiation was attributed to the photochemical degradation of components with a high unsaturation degree. Such findings could enable ecological safety improvement of aquatic environments using natural sunlight.

Insight into the mechanisms of trichloronitromethane formation by vacuum ultraviolet: QSAR model and FTICR-MS analysis

Vacuum ultraviolet (VUV) photolysis is recognized as an environmental-friendly treatment process. Nitrate (NO3−) and natural organic matter (NOM) are widely present in water source. We investigated trichloronitromethane (TCNM) formation during chlorination after VUV photolysis, because TCNM is an unregulated highly toxic disinfection byproduct. In this study: (1) we found reactive nitrogen species that is generated under VUV photolysis of NO3− react with organic matter to form nitrogen-containing compounds and subsequently form TCNM during chlorination; (2) we found the mere presence of 0.1 mmol/L NO3− can result in the formation of up to 63.96 µg/L TCNM; (3) we found the changes in pH (6.0-8.0), chloride (1-4 mmol/L), and bicarbonate (1-4 mmol/L) cannot effectively diminish TCNM formation; and, (4) we established the quantitative structure-activity relationship (QSAR) model, which indicated a linear relationship between TCNM formation and the Hammett constant (σ) of model compounds; and, (5) we characterized TCNM precursors in water matrix after VUV photolysis and found 1161 much more nitrogen-containing compounds with higher aromaticity were generated. Overall, this study indicates more attention should be paid to reducing the formation risk of TCNM when applying VUV photolysis process at scale.

PFAS Analysis with Ultrahigh Resolution 21T FT-ICR MS: Suspect and Nontargeted Screening with Unrivaled Mass Resolving Power and Accuracy.

Per- and polyfluoroalkyl substances (PFASs) are a large family of thousands of chemicals, many of which have been identified using nontargeted time-of-flight and Orbitrap mass spectrometry methods. Comprehensive characterization of complex PFAS mixtures is critical to assess their environmental transport, transformation, exposure, and uptake. Because 21 tesla (T) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers the highest available mass resolving power and sub-ppm mass errors across a wide molecular weight range, we developed a nontargeted 21 T FT-ICR MS method to screen for PFASs in an aqueous film-forming foam (AFFF) using suspect screening, a targeted formula database (C, H, Cl, F, N, O, P, S; ≤865 Da), isotopologues, and Kendrick-analogous mass difference networks (KAMDNs). False-positive PFAS identifications in a natural organic matter (NOM) sample, which served as the negative control, suggested that a minimum length of 3 should be imposed when annotating CF2-homologous series with positive mass defects. We putatively identified 163 known PFASs during suspect screening, as well as 134 novel PFASs during nontargeted screening, including a suspected polyethoxylated perfluoroalkane sulfonamide series. This study shows that 21 T FT-ICR MS analysis can provide unique insights into complex PFAS composition and expand our understanding of PFAS chemistries in impacted matrices.

Enhanced chemodiversity, distinctive molecular signature and diurnal dynamics of dissolved organic matter in streams of two headwater catchments, Southeastern China

Dissolved organic matter (DOM) is a complicated assembly of organic molecules, including thousands of molecules with various structures and properties. However, how the stream DOM sources respond to carbon compositions and the transformation processes remains unclear. In this study, the chemical characteristics and spectral and mass spectrometry (FT-ICR MS) of DOM were analyzed. Six sampling points of headwater stream (HWSs) were sampled, and an effluent polluted stream (WSR) and a main stream of the Changjiang River (DT) were also sampled for comparison. In situ degradation experiments and FT-ICR MS analysis were also performed to observe the dynamic processes of DOM in HWS. The results showed that the anthropogenic markers of sewage (i.e. sulfur (S) compounds and marker from antibiotics and estrogen) in HWS were higher than those in DT. The molecular weight decreased while the degradation products (S-containing compounds and unsaturated compounds (HU)) increased after in situ degradation due to the influence of both the photodegradation and biodegradation process. In addition, the KMD plots showed that the DOM homologue intensities in range 400–600 Da changed significantly after demethylation by biodegradation. The components of highly refractory substances and the degradation degree of DOM in DT was higher than that in HWS. We extracted the refractory DOM pool in HWS, which was mainly small molecular with molecular weights < 600 Da. These molecular will be difficult to remove in traditional drinking water treatment processes and easily produced disinfection byproducts (DBPs). This study emphasized the necessity of identifying the sources and transformation processes of DOM in HWS and clarified the types and characteristics of DOM that should be considered in future drinking water treatment.

Chromophoric dissolved organic carbon cycle and its molecular compositions and optical properties in precipitation in the Guanzhong basin, China

The investigation of water-soluble organic carbon (WSOC), which is important in the biogeochemical cycle of precipitation, can provide a comprehensive view of chromophores within the atmospheric boundary layer. In this work, the optical properties and molecular characteristics of WSOC in precipitation over the Guanzhong Basin (GB) of North China were investigated using ultraviolet-visible (UV–vis) absorption and excitation-emission matrix (EEM) fluorescence spectra, and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with electrospray ionization (ESI). Furthermore, sources and wet deposition of WSOC were estimated using in-situ measurements and modeling. The light-absorption by WSOC at 250–300 nm (UV region) and 400–550 nm (visible region) was 64.17% and 15.36% relative to the estimated total light-absorption, respectively. Parallel factor (PARAFAC) analysis revealed three types of fluorophores in WSOC at Xi'an (XN), including two humic-like substances (HULIS) and one protein-like substance (PRLIS), with HULIS accounting for 79% of total fluorescence intensity. FT-ICR MS analysis revealed that CHO and CHON were the most abundant components of WSOC at XN, each containing a variety of lignins, protein/amino sugars, and lipids. Moreover, the positive matrix factorization (PMF) model identified the contributions from three main sources (secondary precursors and aerosols, and coal combustion) of WSOC in precipitation at XN. The annual wet deposition flux of WSOC in precipitation at XN was estimated as about 0.63 g C m−2 yr−1, lower than that at other polluted cities. These findings add to our understanding of chromophoric dissolved organic carbon budgets, which is critical for accurately assessing the global carbon cycle.

Heavy-Oil Surrogate Formulation Based on Ft-Icr Ms Analysis

Heavy-Oil Surrogate Formulation Based on Ft-Icr Ms Analysis

Molecular characteristics of sulfur compounds in oxidative desulfurization for heavy fuel oil based on APPI FT-ICR MS analysis

Oxidative desulfurization of model oil and heavy fuel oil (HFO) was investigated under mild conditions using H2O2 as an oxidant and acetonitrile as an extractant. The influence factors in the oxidation and extraction processes were evaluated and optimized. The molecular characteristics of the raw feedstock and the desulfurized oils, and the corresponding extraction phases were systematically analyzed by APPI FT-ICR MS, 1H NMR, etc. The results showed that the desulfurization rate of dibenzothiophene reached 97.7% after 10 min reaction, while the sulfur removal efficiency of HFO was 30.7% under optimized conditions. The structures of sulfur compounds were described in heteroatom type, carbon number distribution vs unsaturation degree. The detected main sulfur-containing compounds are S1, S2, S3, NS, OS, O2S, O2S2, and O4S2. Based on the APPI FT-ICR MS results, it can be found that almost all the S1 species have been transformed into sulfone after the oxidation process. Furthermore, the sulfone of O2S1 and O4S2 species in extraction phases were in double bond equivalent (DBE) range from 9 to 25 and carbon number with ≤ 40. 1H NMR results showed that the α to aromatic CH3 combined naphthenic CH-CH2 group accounted for 73.2% in the extraction phase.

Time-dependent molecular progression and acute toxicity of oil-soluble, interfacially-active, and water-soluble species reveals their rapid formation in the photodegradation of Macondo Well Oil

Photodegradation is a significant weathering process that transforms spilled oil, yet, the fate, degradation rate, and molecular transformations that occur through photoinduced pathways remain relatively unknown. The molecular complexity combined with the increased polarity of photoproducts challenges conventional analytical techniques. Here, we catalogue the molecular progression of photochemical transformation products of Macondo Well Oil by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We track the molecular compositions of oil-soluble, interfacially-active, and water-soluble oil species formed at varying time intervals in photomicrocosm experiments. Short photoirradiation periods (<24 h), not previously reported, are included to reveal rapid photooxidation of native oil components. Surface oil films exposed to solar irradiation were shown to increasingly contribute to the dissolved organic carbon pool as a function of increased irradiation time. FT-ICR MS analysis of acidic species of each fraction identifies tens of thousands of oil-soluble, interfacially-active, and water-soluble phototransformation products, including Ox, NOx, and SOx species. Oil-soluble species incorporate oxygen as a function of irradiation periods. After 96 h of irradiation, ~14 wt% of the photooxidized oil film was interfacially active and contained phototransformed species with up to 12 oxygen atoms per molecule. Water-soluble species correspond to highly oxygenated compounds. Importantly, photochemical oxidation is shown to occur within the first hour. Beyond 24 h, photoproducts remain compositionally similar, highlighting the rapid effect of photodegradation to transform oil species into water-soluble compounds. Molecular fingerprints provided by FT-ICR MS highlight the oxygen dependence on oil/water solubility. Microtox® analysis indicates that the toxicity of water-soluble photoproducts rapidly increases at early irradiation time points (first 24 h) compared to the dark control and reaches a maximum at 6 h of irradiation. Results highlight the temporal, molecular progression of photoproducts as they partition from oil-soluble to oil-soluble interfacially-active, and finally to water-soluble species.

Light absorption properties and molecular compositions of water-soluble and methanol-soluble organic carbon emitted from wood pyrolysis and combustion

Organic carbon (OC) emitted from biomass burning (BB) plays an important role in the global radiation budget. In this work, primary OC emitted from wood pyrolysis and combustion under nitrogen (N2) and air conditions in a tube furnace was investigated. The absorption spectra, chemical functional groups, and molecular compositions of OC were analyzed using UV–Vis-NIR spectrophotometer, Fourier transform infrared spectroscopy (FTIR), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. The light absorption properties showed that the mass absorption efficiency at 365 nm (MAE365) of methanol-soluble OC (MSOC) is 3.1–3.8 times higher than that of water-soluble OC (WSOC). Moreover, the MAE365 values derived from the N2 pyrolysis atmosphere are higher than that from the air atmosphere for both MSOC and WSOC. These results indicated that OC extracted by methanol has higher light absorption, especially for the OC emitted from the N2 pyrolysis atmosphere. Although the FTIR spectra showed identical functional groups for the OC from the air and N2 conditions, molecular compositions from the FT-ICR MS analysis presented significant differences. The molecular weight (MW), double bonds equivalent (DBE), DBE/C, and modified aromaticity index (AImod) of extracted OC showed higher values in MSOC than those in WSOC, and higher values under the N2 atmosphere than those under the air atmosphere. In addition, MAE365 showed positive correlations with MW (r = 0.94), DBE (r = 0.88), DBE/C (r = 0.96), and AImod (r = 0.97), whereas negative correlations with H/C (r = −0.97), O/C (r = −0.90), N/C (r = −0.88), and S/C (r = −0.93). These results indicated that molecules with larger MW and a high level of unsaturation and aromaticity present higher light absorption, while molecules with high elemental ratios of H/C, O/C, N/C, and S/C are adverse to light absorption.

Soil Organic Matter Characterization by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR MS): A Critical Review of Sample Preparation, Analysis, and Data Interpretation.

The biogeochemical cycling of soil organic matter (SOM) plays a central role in regulating soil health, water quality, carbon storage, and greenhouse gas emissions. Thus, many studies have been conducted to reveal how anthropogenic and climate variables affect carbon sequestration and nutrient cycling. Among the analytical techniques used to better understand the speciation and transformation of SOM, Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) is the only technique that has sufficient mass resolving power to separate and accurately assign elemental compositions to individual SOM molecules. The global increase in the application of FTICR MS to address SOM complexity has highlighted the many challenges and opportunities associated with SOM sample preparation, FTICR MS analysis, and mass spectral interpretation. Here, we provide a critical review of recent strategies for SOM characterization by FTICR MS with emphasis on SOM sample collection, preparation, analysis, and data interpretation. Data processing and visualization methods are presented with suggested workflows that detail the considerations needed for the application of molecular information derived from FTICR MS. Finally, we highlight current research gaps, biases, and future directions needed to improve our understanding of organic matter chemistry and cycling within terrestrial ecosystems.

Chemical composition overview on two organic residues from the inner part of an archaeological bronze vessel from Cumae (Italy) by GC–MS and FTICR MS analyses

Chemical composition overview on two organic residues from the inner part of an archaeological bronze vessel from Cumae (Italy) by GC–MS and FTICR MS analyses

Novel four-dimensional approach for the structural characterization of neutral nitrogen compounds in vacuum gas oils using UHPLC-IM-QqToF analysis

The molecular analysis of complex matrices such as vacuum gas oils require powerful instruments such as Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). As this technique does not allow the separation of two isomers, ion mobility coupled to mass spectrometry (IMMS) can be used to target a structural detail. However, the resolving power of ion mobility is not sufficient to resolve isomers in such a complex mixture. In this paper, ion mobility-mass spectrometry coupled to separative methods such as Flash-HPLC and UHPLC has been used to characterize the neutral nitrogen compounds found in vacuum gas oils. One vacuum gas oil feedstock as well as different hydrotreated samples have been analyzed through a heart-cutted HPLC-UHPLC-IM-QqToF analysis to target specific compounds that have been found to be problematic within hydrotreatment context thanks to ESI(−)-FT-ICR MS analyses. The extraction of the macroscopic descriptors (mobility, full-width at half-maximum) allowed highlighting first trends about the samples. Then, the chromatographic peaks obtained for a given alkylation degree have been divided into several retention time segments and the corresponding mobilograms have been obtained. Bi-modal distributions have been obtained and the observed Collision Cross Sections and MS/MS spectra suggested the presence of compact and non-compact structures. The evolution of these structures has been followed throughout hydrotreatment to evaluate both the quantity and the reactivity of the groups of isomers. Moreover, this methodology helped giving clues whether the targeted compounds are refractory to the hydrotreatment process or reaction intermediates of the hydrotreatment process.

Chemical Kinetics of Asphaltene Pyrolysis

The research reported in this publication was partially supported by the Saudi Electricity Company (SEC) and the Clean Combustion Research Center (CCRC) of the King Abdullah University of Science and Technology (KAUST). The authors thank Drs. Long Jiang and Aiping Chen for their work on asphaltene separation and analytical chemistry. This research used resources of the Core Labs at the KAUST. We also thank Dr Wen Zhang for the FT ICR-MS analysis and Dr Salvedin Telalovic for the TGA–MS.

Characterisation of copal resin and amber by negative-ion electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry.

Copal resin and amber from Columbia were analysed by negative-ion electrospray ionisation (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), with particular focus on polar compounds with relatively high molecular weights. A total of 4038 and 2755 compounds were identified between m/z 150 and 1,000 in the spectra of the copal resin and amber DCM extracts, respectively. The CHO classes were the most abundant species in the detected polar compounds. The petrochemical process of converting copal resin to amber is accompanied by evaporation and dispersion of volatile molecules and polymerisation of relatively smaller molecules. Thus, the most abundant compounds in copal resin comprised more than one C5 basic unit compared to amber, and the relative abundances of compounds with a high number of carbon and oxygen atoms in amber were higher than those in copal resin. There were strong positive correlations between the double-bond equivalence (DBEav ) values and the number of oxygen atoms in both samples. The slopes and y-intercepts of the linear relationship indicated that the C5 pentadienoic acid is the basic structure of heteroatom compound molecules in copal resin and amber. FT-ICR MS analysis focuses on the characterisation of heteroatom compounds with relatively high molecular weight and is helpful to provide supplementary information on the origin and evolution of complex organic mixtures such as copal resin and amber at the molecular level in a fast and convenient way.

Ionic strength effect on the formation of organonitrate compounds through photochemical degradation of vanillin in liquid water of aerosols

The ionic strength can affect the photochemical reactions occurring in the liquid core of the aerosol deliquescent particles. Yet, the investigations related to ionic strength effect on aqueous-phase reactions are limited. Here we assess the photochemical degradation of a typical lignin-derived compound, vanillin (VL), upon addition of either sodium nitrate (NaNO3) or sodium sulfate (Na2SO4). The UV-VIS absorption spectra of VL exhibits a hyperchromic effect and a bathochromic shift of the n→π* absorption band, in going from λmax = 310 nm in the dilute aqueous phase to λmax = 346 nm at I = 0.3 M adjusted by Na2SO4. A hypsochromic shift of the n→π* absorption band of VL, in going from λmax = 310 nm in the dilute liquid water to λmax = 303 nm at Ieff = 0.124 M is observed when the ionic strength was adjusted with NaNO3.At fixed pH ≈ 4, representing both the cloud droplets and the liquid core of the aerosol particles, the pseudo-first-order rate constant, k1st (Ieff.→0) = (1.5 ± 0.2) x 10−5 s−1, in dilute aqueous solution (Ieff = 0 M, NaNO3), linearly decreases to (k1st = (3.7 ± 0.2) x 10−6 s−1), at Ieff = 0.124 M (NaNO3) with kinetic salting coefficient b = -(4.8 ± 0.2) L mol−1. The very subtle pH change of the absorption spectra of irradiated VL is observed due to the formation of carboxylic acids, hydroxylated compounds and oligomers which presence was confirmed by FT-ICR MS analysis. Most likely aliphatic like CHO compounds are formed upon photodegradation of VL in dilute aqueous phase while the condensed aromatic CHO and CHON compounds are produced in presence of nitrate ions (Ieff = 0.124 M). These results suggest that inorganic ions present in the liquid water of aerosols alters the kinetics and the product formation of photochemical degradation of organic compounds which in turn can affect the light absorption properties of aerosols.

PHYTOCHEMICAL SCREENING, ANTIOXIDANT, ANTI-CYTOTOXIC AND ANTICANCER EFFECTS OF GALINSOGA PARVIFLORA AND VERNONIA POLYANTHES (ASTERACEAE) EXTRACTS

The study was designed to investigate the chemical composition and the biological effects of G. parviflora and V. polyanthes ethanolic extracts in vitro. Total content of phenols, flavonoids and tannins was quantified by spectrophotometry; chemical characterization was permed by mass spectrometry (ESI (-) FT-ICR MS and APCI (+) FT-ICR MS analysis). Antioxidant activities were determined by FRAP and Fe2+ chelating methods. Extracts cytotoxicity was evaluated in human lymphocytes, sarcoma-180 (S-180) and human gastric adenocarcinoma (AGS) cells, by MTT assay. V. polyanthes presented higher total content of tannins and G. parviflora presented higher amount of phenols and flavonoids. Chemical characterization showed the presence of flavonoids, phenolic acids and sesquiterpene lactones in V. polyanthes extract, and steroids, phenolic acids and fatty acids (Poly Unsaturated Fatty Acids - PUFA) in G. parviflora extract. V. polyanthes extract stood out in the Fe2+ chelation test. G. parviflora extract did not present outstanding antioxidant results in the tested protocols. Both species showed a tendency to promote cytotoxicity in human lymphocyte cells. Regarding the antiproliferative effect, both species were able to reduce S-180 cell viability and G. parviflora extract showed high antiproliferative potential in the assay with AGS cells. These findings reinforce the medicinal use of these plants, as well as suggest their potential use for the development of new drugs and for the treatment of cancers.

Fourier-transform ion cyclotron resonance mass spectrometry for characterizing proteoforms.

Proteoforms contribute functional diversity to the proteome and aberrant proteoforms levels have been implicated in biological dysfunction and disease. Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), with its ultrahigh mass-resolving power, mass accuracy, and versatile tandem MS capabilities, has empowered top-down, middle-down, and native MS-based approaches for characterizing proteoforms and their complexes in biological systems. Herein, we review the features which make FT-ICR MS uniquely suited for measuring proteoform mass with ultrahigh resolution and mass accuracy; obtaining in-depth proteoform sequence coverage with expansive tandem MS capabilities; and unambiguously identifying and localizing post-translational and noncovalent modifications. We highlight examples from our body of work in which we have quantified and comprehensively characterized proteoforms from cardiac and skeletal muscle to better understand conditions such as chronic heart failure, acute myocardial infarction, and sarcopenia. Structural characterization of monoclonal antibodies and their proteoforms by FT-ICR MS and emerging applications, such as native top-down FT-ICR MS and high-throughput top-down FT-ICR MS-based proteomics at 21 T, are also covered. Historically, the information gleaned from FT-ICR MS analyses have helped provide biological insights. We predict FT-ICR MS will continue to enable the study of proteoforms of increasing size from increasingly complex endogenous mixtures and facilitate the benchmarking of sensitive and specific assays for clinical diagnostics. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

Refinement of Compound Aromaticity in Complex Organic Mixtures by Stable Isotope Label Assisted Ultrahigh-Resolution Mass Spectrometry

Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) provides a unique opportunity for molecular analysis of natural complex mixtures. In many geochemical and environmental studies structure-propertry relations are based solely on the elemental compositional information. Several calculated parameters were proposed to increase reliability of structural attribution, among which aromaticity indices (AI and AImod) are widely used. Herein, we applied a combination of selective labeling reactions in order to obtain direct structural information on the individual components of lignin-derived polyphenolic material. Carboxylic (COOH), carbonyl (C═O), and hydroxyl (OH) groups were enumerated by esterification, reducing, and acetylation reactions, respectively, followed by FTICR MS analyses. Obtained information was enabled to constrain aromaticity accounting for the carbon skeleton only. We found that actual aromaticity of components may be both higher or lower than approximated values depending on the abundance of COOH, C═O, and OH groups. The results are of importance for the geochemical community studying terrestrial NOM with structural gradients.

Contributions to Lignomics: Stochastic Generation of Oligomeric Lignin Structures for Interpretation of MALDI-FT-ICR-MS Results.

The lack of standards to identify oligomeric molecules is a challenge for the analysis of complex organic mixtures. High-resolution mass spectrometry-specifically, Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS)-offers new opportunities for analysis of oligomers with the assignment of formulae (Cx Hy Oz ) to detected peaks. However, matching a specific structure to a given formula remains a challenge due to the inability of FT-ICR MS to distinguish between isomers. Additional separation techniques and other analyses (e.g., NMR spectroscopy) coupled with comparison of results to those from pure compounds is one route for assignment of MS peaks. Unfortunately, this strategy may be impractical for complete analysis of complex, heterogeneous samples. In this study we use computational stochastic generation of lignin oligomers to generate a molecular library for supporting the assignment of potential candidate structures to compounds detected during FT-ICR MS analysis. This approach may also be feasible for other macromolecules beyond lignin.

Engineering of melanin biopolymer by co-expression of MelC tyrosinase with CYP102G4 monooxygenase: Structural composition understanding by 15 tesla FT-ICR MS analysis

In this study, a novel melanin pigment was synthesized by Escherichia coli cells co-expressing tyrosinase (MelC) and cytochrome P450 monooxygenase (CYP102G4) enzymes simultaneously. The CYP102G4 catalyzes indole C3-specific hydroxylation and generates 3-hydroxyindole (indoxyl) and 3-oxoindole. Additional supply of indole derivatives leads to much darker melanin pigmentation with higher yields (3.4 g/L) of synthesized CYP-Melanin, which showed interesting morphological and electrochemical properties. To understand the correlation between its chemical structure and functions, FT-IRand SEM analysis were attempted. Following 15 T FT-ICR mass spectrometry analysis provided information on the chemical and molecular compositions, characteristics of the synthetic melanins, evidence of higher nitrogen content, and higher degree of unsaturation in the CYP-Melanin structure. Besides, electrical conductivity of CYP-Melanin was determined by cyclic voltammetry (CV) analysis to investigate the feasibility for the application of CYP-Melanin as electrical materials.