Electrospray Ionization Mass Spectra Research Articles

Purification and Molecular Characterization of Fucoidan Isolated from Ascophyllum nodosum Brown Seaweed Grown in Ireland.

The present study investigates the molecular characteristics of fucoidan obtained from the brown Irish seaweed Ascophyllum nodosum, employing hydrothermal-assisted extraction (HAE) followed by a three-step purification protocol. The dried seaweed biomass contained 100.9 mg/g of fucoidan, whereas optimised HAE conditions (solvent, 0.1N HCl; time, 62 min; temperature, 120 °C; and solid to liquid ratio, 1:30 (w/v)) yielded 417.6 mg/g of fucoidan in the crude extract. A three-step purification of the crude extract, involving solvents (ethanol, water, and calcium chloride), molecular weight cut-off filter (MWCO; 10 kDa), and solid-phase extraction (SPE), resulted in 517.1 mg/g, 562.3 mg/g, and 633.2 mg/g of fucoidan (p < 0.05), respectively. In vitro antioxidant activity, as determined by 1,1-diphenyl-2-picryl-hydrazyl radical scavenging and ferric reducing antioxidant power assays, revealed that the crude extract exhibited the highest antioxidant activity compared to the purified fractions, commercial fucoidan, and ascorbic acid standard (p < 0.05). The molecular attributes of biologically active fucoidan-rich MWCO fraction was characterised by quadruple time of flight mass spectrometry and Fourier-transform infrared (FTIR) spectroscopy. The electrospray ionisation mass spectra of purified fucoidan revealed quadruply ([M+4H]4+) and triply ([M+3H]3+) charged fucoidan moieties at m/z 1376 and m/z 1824, respectively, and confirmed the molecular mass 5444 Da (~5.4 kDa) from multiply charged species. The FTIR analysis of both purified fucoidan and commercial fucoidan standard exhibited O-H, C-H, and S=O stretching which are represented by bands at 3400 cm-1, 2920 cm-1, and 1220-1230 cm-1, respectively. In conclusion, the fucoidan recovered from HAE followed by a three-step purification process was highly purified; however, purification reduced the antioxidant activity compared to the crude extract.

Effect of solution acidity on cytochrome c conformations of alternating current electrospray ionization mass spectrometry

AbstractThis paper reports notable observations regarding the ion charge states of thermally stable cytochrome c, generated using an alternating current (AC) electrospray ionization (ESI) device. An AC ESI sprayer entrains low‐mobility ions to accumulate at the meniscus cone tip prior to the ejection of detached aerosols to produce analyte ions. Therefore, as the solvent acidity varies, protein ions entrained in the AC cone tip are found to change conformation less significantly compared with those in the direct current (DC) cone. We acquired the AC ESI mass spectra of cytochrome c at pH range from 2 to 4. Unlike the DC ESI mass spectra showing clear conformation changes due to denaturing, the AC spectra indicated that only partial denaturing occurs even at extremely acidic pH 2. More native cytochrome c in lower charge states therefore remained. Moreover, with a solvent mixture of aqueous buffer and acetonitrile (70:30), partially denatured cytochrome c was still preserved at pH 2 by using AC ESI. Completely denatured proteins are observed at pH 2 by using DC ESI.

Rapid screening of high-priority N-nitrosamines in pharmaceutical, forensic, and environmental samples with paper spray ionization and filter cone spray ionization-mass spectrometry.

The burgeoning concern of N-nitrosamine (NAM) contamination found in various pharmaceutical compositions has increased the demand for rapid and reliable screening methods to better assess the breadth of the problem. These carcinogenic compounds are also found in food, water, and soil, and they have been used in poison-related homicides. A combination of complementary, ambient ionization methods, paper spray ionization (PSI) and filter cone spray ionization (FCSI)-mass spectrometry (MS), was characterized towards trace-level residue screening of select NAMs (e.g., N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine) directly from complex and problematic matrices of interest, including prescription and over-the-counter tablets, drinking water, soil, and consumable goods. Spectral data for analyte confirmation and detection limit studies were collected using a Thermo LCQ Fleet ion trap mass spectrometer. PSI-MS and FCSI-MS readily produced mass spectral data marked by their simplicity (e.g., predominantly protonated molecular ions observed) and congruence with traditional electrospray ionization mass spectra in under 2min. per sample. Both methods proved robust to the complex matrices tested, yielding ion signatures for target NAMs, as well as active pharmaceutical ingredients for analyzed tablets, flavorants inherent to food products, etc. Low part-per-million detection limits were observed but were shown dependent on sample composition. PSI-MS and FCSI-MS were successful in detecting trace-level NAMS in complex liquid- and solid-phase matrices with little to no prior preparation. This work suggests that these methodologies can provide a means for assessing problematic pharmaceutical adulterants/degradants for expedited quality control, as well as enhancing environmental stewardship efforts and forensic investigations.

A comparative performance evaluation of cephalosporin's drugs for fluoride recognition.

In this manuscript, readily available cephalosporin's drugs cefuroxime axetil (L1) cefpdoxime proxetil (L2), and cefditoren pivoxil (L3) possess dihydrothiazine ring as signaling unit, and -NH groups as the binding site were used for the sensing of fluoride (F-) ions. In the presence of F-, the drug selectively portrayed a naked-eye detectable color change from colorless. The binding constant of 1:1 stoichiometric complex of L1, L2, and L3 with F- was found to be 2.36 × 104M-1, 2.44 × 103M-1 and 1.02 × 104M-1 respectively. The lowest detection limit (LOD) of F- was found to be 11µM (209ppb) with drug L1 and L2. The binding mechanism of the drug with F- was studied by 1H and 19F nuclear magnetic resonance (NMR) spectral titration, electrospray ionization mass spectra (ESI-MS) analysis, and density functional theory (DFT) studies. The presence of F- was monitored in various spiked water and Colgate toothpaste samples. Overall, cephalosporin's drug demonstrates a promising potential for the detection of F- ions in the semi-aqueous phase.

Synthesis of 2-heteroylidene triterpenoids: complex formation with palladium and cytotoxic activity &lt;i&gt;in vitro &lt;/i&gt;

Triterpenoids with a pyridinylmethylidene substituent in the C2 position were prepared via the reaction of betulonic acid with pyridine-2-carbaldehyde, pyridine-3-carbaldehyde, pyridine-4-carbaldehyde or quinoline-2-carbaldehyde. The products were tested as ligands for palladium(II). Two ligands and one complex were prepared for the first time. The structures of new compounds were confirmed by 1D and 2D NMR spectra, as well as by electrospray ionization mass spectra. The E -isomerism of pyridinylmethylidene substituent in the C2 position of triterpenoid was proved. Cytotoxic activity of the complexes with respect to A549 (adenocarcinomic human alveolar basal epithelial cells) cell line was estimated.

Storing electrons from H2 for transfer to CO2, all at room temperature.

We present an Ir complex that extracts electrons from H2 at room temperature and stores them as a H2-derived energy carrier (H2EC) at room temperature. Furthermore, we demonstrate that this complex reduces CO2 to a metal-CO22- species at room temperature, and present the first electrospray ionisation mass spectrum for this compound.

Natural Antioxidants, Tyrosinase and Acetylcholinesterase Inhibitors from Cercis glabra Leaves.

Cercis glabra is a plant belonging to the legume family, whose flowers and barks are commonly used as food and traditional Chinese medicines. However, its leaves are usually disposed of as wastes. This research comprehensively investigated the bioactive constituents of C. glabra leaves, and two new phenolic, ceroffesters A-B (1-2) and thirteen known compounds (3-15) were isolated. Their structures were elucidated by spectroscopic methods such as nuclear magnetic resonance (1D NMR and 2D NMR), high-resolution electrospray ionization mass spectra (HR-ESI-MS), optical rotatory dispersion (ORD) and electronic circular dichroism (ECD). All of them were assessed for their antioxidant activities through ABTS, DPPH and PTIO methodologies, and evaluated for inhibitory activities against two enzymes (mushroom tyrosinase and acetylcholinesterase). As a result, compounds 3-6, 10 and 13 exhibited evident antioxidant activities. Meanwhile, compounds 5, 10 and 13 showed the most potent tyrosinase inhibitory activities, with IC50 of 0.64, 0.65 and 0.59 mM, and compared with the positive control of 0.63 mM (kojic acid). In the initial concentration of 1 mg/mL, compounds 3, 5 and 6 demonstrated moderate inhibitory activities against acetylcholinesterase with 85.27 ± 0.06%, 83.65 ± 0.48% and 82.21 ± 0.09%, respectively, compared with the positive control of 91.17 ± 0.23% (donepezil). These bioactive components could be promising antioxidants, tyrosinase and acetylcholinesterase inhibitors.

The Use of Polydialkylsiloxanes/Triflic Acid as Derivatization Agents in the Analysis of Sulfur-Containing Aromatics by “Soft”-Ionization Mass Spectrometry

Polycyclic aromatic sulfur-containing compounds are widely distributed in oil, especially in its low-volatile and heavy fractions (resins, asphaltenes), and this dictates the need for their determination when reliable methods for sulfur removing, cleaning and processing oil are developed. In these cases, "soft" ionization mass spectrometry methods, based on electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI), are particularly effective. However, aromatic sulfur-containing compounds have low polarity and cannot be readily ionized by these methods. To overcome the problem, their preliminary conversion into sulfonium salts by the action of alkyl iodides and a silver-containing agent is widely used. In the process of developing more economical derivatization methods, we found a rather unexpected possibility of implementing S-alkylation of organic sulfides with commercial polydialkylsiloxanes (alkyl = CH3 or C2H5) in the presence of triflic acid (CF3SO3H) as a superacid co-alkylating agent. For homologous dibenzothiophenes as a typical model representative of petroleum sulfur-containing aromatic compounds, ESI and MALDI mass spectra exhibited the signals of corresponding S-alkylsulfonium salts with a high signal-to-noise ratio. A rational mechanism for the described chemical transformation is proposed, including the indispensable activation by triflic acid and the cleavage of the Si-C bond. Specific collision-induced dissociation of corresponding S-alkylated sulfonium cations is considered. The applicability of the derivatization approach to the analysis of petroleum products by high-resolution mass spectrometry is demonstrated.

Monoterpenoid acylphloroglucinols from Hypericum hengshanense W. T. Wang with antiproliferative activities

Hypericum species (Hypericaceae) are a group of important plants with medicinal, edible, and ornamental values. A phytochemical study on the whole plants of H. hengshanense W. T. Wang, a species endemic to China, led to the isolation and elucidation of 25 monoterpenoid acylphloroglucinols (MAPs). Among them, 10 are undescribed compounds, namely hyphengshanols A–D, (+)-empetrilatinol A, (−)-empetrilatinol B, (−)-hyperjovinol A, (9S,2′S)-dauphinol F, and (8R,2′S)-empetrikathiforin. In addition, the absolute configurations of other six compounds were firstly determined in the current study. The structures were established by ultraviolet (UV), high resolution electrospray ionization mass spectrum (HR-ESI-MS), and nuclear magnetic resonance spectroscopy (NMR) data. The absolute configurations were determined by experimental and calculated electronic circular dichroism (ECD) data analyses. Cytotoxicity assays on five human cell lines HL-60, A549, SMMC-7721, MDA-MB-231, and SW480 revealed that 16 compounds exhibited broad-spectrum antiproliferative activities with IC50 ranging from 7.54 to 45.70 μM.

Efficient removal of rhodamine B and methylene blue from water using polyurethane based porous material

AbstractHere the thermally catalyzed azide‐alkyne click reaction was invoked for synthesis of functional triazole. The formed triazole was invoked to engineer polyurethane as water immiscible material. The synthesized functional triazole and polyurethane were well characterized using spectroscopic techniques—nuclear magnetic resonance (NMR), electrospray ionization mass spectrum (ESI MS), and attenuated total reflectance Fourier transform infrared (ATR‐FTIR) accordingly. The N2 adsorption–desorption isotherms confirmed the material to be mesoporous in nature with a surface area of 12.89 m2/g, pore volume of 0.085 cc/g, and pore radius of 7.14 nm. The characterized triazole material can be crucial with properties related to antifungal responses and UV absorption. The polyurethane material showed adsorption of amphiphilic dye—rhodamine (RH B) and methylene blue (MB). It was selective to release of rhodamine B (RH B) quite efficiently. The recycling of polyurethane reported up to cycle four revealed efficient adsorption‐release.

A New 1,3-Benzodioxole Compound from Hypecoum erectum and Its Antioxidant Activity.

The purpose of this study was to identify the chemical components in aerial parts of Hypecoum erectum. A new 1,3-benzodioxole derivative, identified as Hypecoumic acid (1), was isolated, together with the three known compounds: protopine (2), coptisine (3), and cryptopine (4). Their structures were identified based on extensive spectroscopic experiments, including nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectra (HR-ESI-MS), as well as comparison with those reported in the literature. Meanwhile, the in vitro antioxidative activity of all compounds was determined using a DPPH-scavenging assay, and compound 1 (IC50 = 86.3 ± 0.2 μM) was shown to have moderate antioxidative activity.

Terpenoids from the Seeds of Toona sinensis and Their Ability to Attenuate High Glucose-Induced Oxidative Stress and Inflammation in Rat Glomerular Mesangial Cells.

Toona sinensis (A. Juss.) Roem is an edible medicinal plant that belongs to the genus Toona within the Meliaceae family. It has been confirmed to display a wide variety of biological activities. During our continuous search for active constituents from the seeds of T. sinensis, two new acyclic diterpenoids (1–2), together with five known limonoid-type triterpenoids (3–7), five known apotirucallane-type triterpenoids (8–12), and three known cycloartane-type triterpenoids (13–15), were isolated and characterized. Their structures were identified based on extensive spectroscopic experiments, including nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectra (HR-ESI-MS), and electronic circular dichroism (ECD), as well as the comparison with those reported in the literature. We compared these findings to those reported in the literature. Compounds 5, 8, and 13–14 were isolated from the genus Toona, and compounds 11 and 15 were obtained from T. sinensis for the first time. The antidiabetic nephropathy effects of isolated compounds against high glucose-induced oxidative stress and inflammation in rat glomerular mesangial cells (GMCs) were assessed in vitro. The results showed that new compounds 1 and 2 could significantly increase the levels of Nrf-2/HO-1 and reduce the levels of NF-κB, TNF-α, and IL-6 at concentrations of 30 μM. These results suggest that compounds 1 and 2 might prevent the occurrence and development of diabetic nephropathy (DN) and facilitate the research and development of new antioxidant and anti-inflammatory drugs suitable for the prevention and treatment of DN.

Fragmentation of Protonated Histamine and Histidine by Electrospray Ionization In-Source Collision-Induced Dissociation

Electrospray ionization (ESI) generally produces intact gas-phase ions without extensive fragmentation; however, for histamine and histidine, ESI provides fragment ions through in-source collision-induced dissociation (CID). In this study, we investigated the fragmentation of these compounds both experimentally and using density functional theory calculations. We found that histamine undergoes protonation with subsequent NH3 loss by ESI in-source CID. The corresponding fragmentation mainly produces bicyclo and spiro compounds. In contrast, the ESI in-source CID of protonated histidine preferentially results in H2O loss rather than NH3 loss. However, the corresponding fragment ion is not observed in the ESI mass spectrum of histidine, because it undergoes further CO loss within 100 ps. Consequently, protonated histidine produces a fragment ion arising from a 46 Da loss, which corresponds to the masses of H2O and CO, by ESI in-source CID. The fragment ion yields of histamine and histidine produced by ESI in-source CID are then estimated from the dissociation rate constant and internal energy of the analyte ion, respectively. The dissociation rate constant and internal energy of the analyte ion were determined by double-hybrid density functional theory calculations and the survival yield method using benzylpyridinium thermometer ions, respectively. Because intense fragment ion signals are present in the ESI mass spectrum, the analysis of the fragment ions produced by ESI in-source CID facilitates the identification of metabolites originating from aromatic amino acids, such as histamine.

Comparative Analysis of Binary Similarity Measures for Compound Identification in MassSpectrometry-Based Metabolomics.

Compound identification is a critical step in untargeted metabolomics. Its most important procedure is to calculate the similarity between experimental mass spectra and either predicted mass spectra or mass spectra in a mass spectral library. Unlike the continuous similarity measures, there is no study to assess the performance of binary similarity measures in compound identification, even though the well-known Jaccard similarity measure has been widely used without proper evaluation. The objective of this study is thus to evaluate the performance of binary similarity measures for compound identification in untargeted metabolomics. Fifteen binary similarity measures, including the well-known Jaccard, Dice, Sokal–Sneath, Cosine, and Simpson measures, were selected to assess their performance in compound identification. using both electron ionization (EI) and electrospray ionization (ESI) mass spectra. Our theoretical evaluations show that the accuracy of the compound identification was exactly the same between the Jaccard, Dice, 3W-Jaccard, Sokal–Sneath, and Kulczynski measures, between the Cosine and Hellinger measures, and between the McConnaughey and Driver–Kroeber measures, which were practically confirmed using mass spectra libraries. From the mass spectrum-based evaluation, we observed that the best performing similarity measures were the McConnaughey and Driver–Kroeber measures for EI mass spectra and the Cosine and Hellinger measures for ESI mass spectra. The most robust similarity measure was the Fager–McGowan measure, the second-best performing similarity measure in both EI and ESI mass spectra.

Characterization of human tear proteome reveals differentially abundance proteins in thyroid-associated ophthalmopathy.

BackgroundThyroid-associated ophthalmopathy (TAO) is a common orbital inflammatory disease, but the abnormal expression of proteins in tears of TAO patients has not been systematically studied. The purpose of this study is to compare and analyze the total tear protein profile of TAO patients and to provide protein cues for TAO pathogenesis.MethodsTear samples were isolated from 30 TAO patients with obvious ocular surface damage and 30 healthy control subjects. Tear samples from 30 individuals were mixed and divided into three sample pools. Easy nano-scale LC-MS/MS based on labeling-free quantitative technology was utilized to profile tear proteome.ResultsHere, electrospray ionization mass spectra and SDS-PAGE results confirmed the good parallelisms among samples. A total of 313 proteins were obtained from six tear pools, among them, 103 differential abundance proteins (DAPs) were identified, including 99 up-regulated DAPs (including APOA1, HV103, IGH, and Transferrin variant) and four down-regulated DAPs (including FABA, VCC1, NUCB2, and E-cadherin) in the TAO group compared with the control group. GO analysis showed that up-regulated DAPs were mainly enriched in lipid metabolism and platelet molecular function, and down-regulated DAPs were involved in binding, cell junction, and cellular process. KEGG results indicated that DAPs were involved in 117 kinds of signal transduction pathways, among which the immune-related pathway of complement and coagulation cascades had the greatest relevance.ConclusionIn conclusion, label-free LC-MS/MS is an effective strategy for profiling tear proteins component. Our study provides proteins and pathways altered in TAO and provides protein cues for further study on the precise mechanism of TAO pathogenesis.

New acylglycosides from the roots of Rheum palmatum L.

A phytochemical investigation of the EtOH extract of the roots of Rheum palmatum L. was performed, leading to the isolation of 3 new acylglycosides ( 1 – 3 ) and 19 previously reported compounds, including 4 cinnamoyl glucosides ( 4 – 7 ) and 15 anthraquinones ( 8 – 22 ). Their structures were elucidated using nuclear magnetic resonance, infrared, ultraviolet and high-resolution electrospray ionization mass spectra and X-ray diffraction data. The biological activities of compounds 2 , 4 – 9 , and 11 – 13 , including their lymphocyte activation gene 3 (LAG3)/major histocompatibility complex class II (MHC II) and LAG3/fibrinogen-like protein 1 (FGL1) binding inhibition activities, were evaluated. Among the isolates, compound 7 exhibited clear inhibitory activity against the LAG3/FGL1 interaction with an IC 50 of 7.89 μ M, meanwhile compound 6 inhibited the LAG3/MHC II interaction with an IC 50 of 6.00 μ M. • Three undescribed acylglycosides were isolated from roots of Rheum palmatum L. • The absolute configuration of 1 was confirmed by single crystal X-ray diffraction. • This is the first report of the crystal structure of a cinnamoyl glucoside. • Their activities against the interaction of LAG3 with MHC II or FGL1 were evaluated.

Biotechnological potential of a new strain of Cylindrotheca fusiformis producing fatty acids and fucoxanthin

A new strain of benthic diatom Cylindrotheca fusiformis producing fucoxanthin (Fx) and polyunsaturated fatty acids (PUFAs) proved to be promising for biotechnology. Identification of Fx was carried out from the analysis of the ultraviolet and visible (UV-VIS) absorption spectra, electrospray ionization mass spectra (ESI MS) and proton magnetic resonance spectra (1H NMR). The specific growth rate of the culture was 0.52 1/day, and the maximum productivity 1.56 g/(L × day). The accumulation rates of eicosapentaenoic and arachidonic acids in the stationary growth phase were 4.5 and 3.2 mg/(L × day), respectively, and that of Fx was 6 mg/(L × day). The accumulation of PUFAs in the biomass reached 4.68% of dry weight. The Fx content in the biomass reached 21.4 mg/g. The strain settles to the photobioreactor bottom in the absence of mixing, which property simplifies the biomass harvesting.

Oxidation of sodium cholate catalyzed by Au NPs and chiral selective binding of R- and S-binaphthyl derivatives

Au NPs generated in situ by photochemical reduction method were used as catalysts for the oxidation of sodium cholate. The circular dichroism of the oxidation product of sodium cholate exhibits a positive Cotton effect at 335 nm and an intense negative Cotton effect at 281 nm. Electrospray ionization (ESI) mass spectra and nuclear magnetic resonance (NMR) spectra were performed to characterize the chemical composition of the oxidation product of sodium cholate, revealing that two of the hydroxyl groups were selectively oxidized to oxo groups and the oxidation product is 12-hydroxy-3,7-diketo-cholanic acid (3,7-DKCA). The chiral recognition abilities of the aggregates of 3,7-DKCA were investigated by using planar chiral molecules R- and S-binaphthyl compounds. Compared with sodium cholate, the aggregates of 3,7-DKCA displayed higher chiral selective host–guest binding to the model molecules and the chiral recognition mechanism was clarified.

Natural tyrosinase inhibitors from Betula platyphylla barks

Abstract During the process of searching for tyrosinase inhibitors from natural medicines, one new monoterpene rhamnoside (1) and 13 known compounds (2–14) were isolated from the ethanolic extract of Betula platyphylla barks by repeated column chromatography. These structures were identified by comprehensive spectroscopic data analysis such as high-resolution electrospray ionization mass spectra (HR-ESI-MS), nuclear magnetic resonance (NMR), optical rotatory dispersion (ORD) and acid hydrolysis. In vitro assay revealed that compounds 6, 7 and 14 showed obvious inhibitory activity against tyrosinase.

Isolation and characterization of antioxidative monoterpenes from Cynanchum atratum roots.

One novel monoterpene rhamnoside (1) and 7 known monoterpenes (2-8) were isolated from the ethanol extract of Cynanchum atratum for the first time. Their structures were identified by comprehensive spectroscopic data analysis such as nuclear magnetic resonance, high-resolution electrospray ionization mass spectra, optical rotatory dispersion, and acid hydrolysis. In the subsequent antioxidant assay, compound 8 exhibited obvious 2,2-diphenyl-2-picrylhydrazyl hydrate radical scavenging activity.