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This article reports on the development of an atmospheric pressure filtering electrospray ionization (FESI) source – composed of a syringe, a filter, and the ESI source – for the determination of furazolidone, amoxicillin, nitrofurantoin, and nitrofural, common antibiotics. Spiked food samples were also analyzed; the analytes were placed in the filter head, and the flow rate of the extraction solution from the syringe pump was adjusted. Using a mixture of oleic acid and antibiotics, hydrophilic and hydrophobic filters were compared, demonstrating the advantage of FESI in reducing the background and noise for the mixture. The device simplifies not only the experimental procedure but also the sample pretreatment process. Additionally, the limits of detection of the antibiotics were determined to be 1 mg L−1 for furazolidone, amoxicillin, and nitrofurantoin and 2 mg L−1 for nitrofural. The linear regression coefficients (R2) of the antibiotic standard solutions were all ≥0.99. Furthermore, the spiked recovery rates of pork, chicken, and egg samples ranged from 73.3% to 107.5%, with relative standard deviations (RSDs) from 1.1% to 15.6%. This study uncovers the potential capabilities of ion trap mass spectrometry (ITMS) for the on-site detection of antibiotics and offers a new method for ensuring food safety. [ABSTRACT FROM AUTHOR]

Almond-based beverages are valued for their functionalities. However, cases of adulteration are found in the literature aiming to reduce costs. In this study, almond (LA) and peanut (LP)-based beverages were used as investigational controls in commercial products analyzed by gas chromatography and direct infusion electrospray ionization mass spectrometry (ESI-MS) combined with principal component analysis (PCA). Thus, characteristic fatty acids were identified in plant-based beverages. The ESI-MS method combined with PCA indicated individualities regarding the disposition of triacylglycerol (TAG) composition, as higher intensities of TAG were found as a lipid marker at m/z 919 [TAG+NH4]+ of ions formed by arachidic (20:0), 8/heptadecenoic (17:1n-9) and oleic (18:1n-9) fatty acids in LP. The technique demonstrated efficiency in the detection of fraud due to its sensitivity, identifying peanut content in three almond-based commercial beverages (4.4–11.58%). This study highlights the importance of robust analytical methods to the authenticity and quality of food products. [ABSTRACT FROM AUTHOR]

Worldwide, it is estimated that there are 1.8 to 2.7 million cases of envenoming caused by snakebites. Snake venom is a complex mixture of protein toxins, lipids, small molecules, and salts, with the proteins typically responsible for causing pathology in snakebite victims. For their chemical characterization and identification, analytical methods are required. Reversed-phase liquid chromatography coupled with electrospray ionization mass spectrometry (RP-LC-ESI-MS) is a widely used technique due to its ease of use, sensitivity, and ability to be directly coupled after LC separation. This method allows for the efficient separation of complex mixtures and sensitive detection of analytes. On the other hand, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is also sometimes used, and though it typically requires additional sample preparation steps, it offers desirable suitability for the analysis of larger biomolecules. In this study, seven medically important viperid snake venoms were separated into their respective venom toxins and measured by ESI-MS. In parallel, using nanofractionation analytics, post-column high-resolution fractionation was used to collect the eluting toxins for further processing for MALDI-MS analysis. Our comparative results showed that the deconvoluted snake venom toxin masses were observed with good sensitivity from both ESI-MS and MALDI-MS approaches and presented overlap in the toxin masses recovered (between 25% and 57%, depending on the venom analyzed). The mass range of the toxins detected in high abundance was between 4 and 28 kDa. In total, 39 masses were found in both the ESI-MS and/or MALDI-MS analyses, with most being between 5 and 9 kDa (46%), 13 and 15 kDa (38%), and 24 and 28 kDa (13%) in size. Next to the post-column MS analyses, additional coagulation bioassaying was performed to demonstrate the parallel post-column assessment of venom activity in the workflow. Most nanofractionated venoms exhibited anticoagulant activity, with three venoms additionally exhibiting toxins with clear procoagulant activity (Bothrops asper, Crotalus atrox, and Daboia russelii) observed post-column. The results of this study highlight the complementarity of ESI-MS and MALDI-MS approaches for characterizing snake venom toxins and provide a complementary overview of defined toxin masses found in a diversity of viper snake venoms. [ABSTRACT FROM AUTHOR]

The skin surface is an important sample source that the metabolomics community has only just begun to explore. Alterations in sebum, the lipid-rich mixture coating the skin surface, correlate with age, sex, ethnicity, diet, exercise, and disease state, making the skin surface an ideal sample source for future noninvasive biomarker exploration, disease diagnosis, and forensic investigation. The potential of sebum sampling has been realized primarily via electrospray ionization mass spectrometry (ESI-MS), an ideal approach to assess the skin surface lipidome. However, a better understanding of sebum collection and subsequent ESI-MS analysis is required before skin surface sampling can be implemented in routine analyses. Challenges include ambiguity in definitive lipid identification, inherent biological variability in sebum production, and methodological, technical variability in analyses. To overcome these obstacles, avoid common pitfalls, and achieve reproducible, robust outcomes, every portion of the workflow—from sample collection to data analysis—should be carefully considered with the specific application in mind. This review details current practices in sebum sampling, sample preparation, ESI-MS data acquisition, and data analysis, and it provides important considerations in acquiring meaningful lipidomic datasets from the skin surface. Forensic researchers investigating sebum as a means for suspect elimination in lieu of adequate fingerprint ridge detail or database matches, as well as clinical researchers interested in noninvasive biomarker exploration, disease diagnosis, and treatment monitoring, can use this review as a guide for developing methods of best-practice. [ABSTRACT FROM AUTHOR]

Herein, two atomically precise silver nanoclusters, Ag54 and Ag33, directed by inner anion templates (CrO42− and/or Cl−), are initially isolated as a mixed phase from identical reactants across a wide temperature range (20–80 °C). Interestingly, fine‐tuning the reaction temperature can realize pure phase synthesis of the two nanoclusters; that is, a metastable Ag54 is kinetically formed at a low temperature (20 °C), whereas such a system is steered towards a thermodynamically stable Ag33 at a relatively high temperature (80 °C). Electrospray ionization mass spectrometry illustrates that the stability of Ag33 is superior to that of Ag54, which is further supported by density functional theory calculations. Importantly, the difference in structural stability can influence the pathway of 1,4‐bis(pyrid‐4‐yl)benzene induced transformation reaction starting from Ag54 and Ag33. The former undergoes a dramatic breakage‐reorganization process to form an Ag31 dimer (Ag31), while the same product can be also achieved from the latter following a noninvasive ligand exchange process. Both the Ag54 and Ag33 have the potential for further remote laser ignition applications. This work not only demonstrates how temperature controls the isolation of a specific phase, but also sheds light on the structural transformation pathway of nanoclusters with different stability. [ABSTRACT FROM AUTHOR]

The reactivity of thioredoxin (Trx1) with the Au(I) drug auranofin (AF) and two therapeutic N-heterocyclic carbene (NHC)2-Au(I) complexes (bis [1-methyl-3-acridineimidazolin-2-ylidene]gold(I) tetrafluoroborate (Au3BC) and [1,3-diethyl-4,5-bis(4methoxyphenyl)imidazol-2-ylidene]gold(I) (Au4BC)) was investigated. Direct infusion (DI) electrospray ionization (ESI) mass spectrometry (MS) allowed information on the structure, stoichiometry, and kinetics of formation of Trx-Au adducts. The fragmentation of the formed adducts in the gas phase gave insights into the exact Au binding site within the protein, demonstrating the preference for Trx1 Cys32 or Cys35 of AF or the (NHC)2-Au(I) complex Au3BC, respectively. Reversed-phase HPLC suffered from the difficulty of elution of gold compounds, did not preserve the formed metal-protein adducts, and favored the loss of ligands (phosphine or NHC) from Au(I). These limitations were eliminated by capillary electrophoresis (CE) which enabled the separation of the gold compounds, Trx1, and the formed adducts. The ICP-MS/MS detection allowed the simultaneous quantitative monitoring of the gold and sulfur isotopes and the determination of the metallation extent of the protein. The hyphenation of the mentioned techniques was used for the analysis of Trx1-Au adducts for the first time. [ABSTRACT FROM AUTHOR]

In this article, a comparison of ionization techniques is provided and discussed. Conventional liquid chromatography with an electrospray ionization source shows higher robustness and repeatability in comparison with liquid chromatography coupled with a coordination ion spray (CIS-MS) source using silver nitrate as the dopant. However, the higher sensitivity and possibility to collect more data in untargeted applications mean CIS-MS is emerging as an instrument used in specific applications. During this research, the limit of detection (LOD) for GHRP-2 and GHRP-6 was established at 0.2 ng/mL, and the lower limit of quantification (LLOQ) was 0.5 ng/mL for CIS-MS. For conventional ESI-MS combined with solid-phase extraction on weak cation exchange columns, the limit of detection was found to be 1 ng/mL, and the lower limit of quantification was 2 ng/mL. [ABSTRACT FROM AUTHOR]

Investigations on binding strength differences of non-covalent protein complex components were performed by mass spectrometry. T4 fibritin foldon (T4Ff) is a well-studied miniprotein, which together with its biotinylated version served as model system to represent a compactly folded protein to which an Intrinsically Disordered Region (IDR) was attached. The apparent enthalpies of the gas phase dissociation reactions of the homo-trimeric foldon F-F-F and of the homo-trimeric triply biotinylated foldon bF-bF-bF have been determined to be rather similar (3.32 kJ/mol and 3.85 kJ/mol) but quite distinct from those of the singly and doubly biotinylated hetero-trimers F-F-bF and F-bF-bF (1.86 kJ/mol and 1.08 kJ/mol). Molecular dynamics simulations suggest that the ground states of the (biotinylated) T4Ff trimers are highly symmetric and well comparable to each other, indicating that the energy levels of all four (biotinylated) T4Ff trimer ground states are nearly indistinguishable. The experimentally determined differences and/or similarities in enthalpies of the complex dissociation reactions are explained by entropic spring effects, which are noticeable in the T4Ff hetero-trimers but not in the T4Ff homo-trimers. A lowering of the transition state energy levels of the T4Ff hetero-trimers seems likely because the biotin moieties, mimicking intrinsically disordered regions (IDRs), induced asymmetries in the transition states of the biotinylated T4Ff hetero-trimers. This transition state energy level lowering effect is absent in the T4Ff homo-trimer, as well as in the triply biotinylated T4Ff homo-trimer. In the latter, the IDR-associated entropic spring effects on complex stability cancel each other out. ITEM-FIVE enabled semi-quantitative determination of energy differences of complex dissociation reactions, whose differences were modulated by IDRs attached to compactly folded proteins. [ABSTRACT FROM AUTHOR]

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Domino reaction of benzo[d]thiazole‐2‐methylamine (S1) has been developed in the presence of MnCl2 ⋅ 4H2O, leading to tetrasubstituted pyrrole coordinated dinuclear Mn(II) complex 1 ([MnClP]2, P−=2,3,4,5‐tetrakis(benzo[d]thiazol‐2‐yl)pyrrol‐1‐ide). The reaction process has been studied by assigning a series of intermediates based on time‐dependent mass spectrometry, control experiments, crystallography, and density functional theory (DFT) theoretical calculation. A plausible mechanism involving an unprecedented divergent‐convergent domino sequence has been proposed. Compound S1 could be activated by MnCl2 ⋅ 4H2O via coordination, which divergently produces two intermediates imine II (1‐(benzo[d]thiazol‐2‐yl)‐N‐(benzo[d]thiazol‐2‐ylmethyl)methanimine) and alkene C (1,2‐bis(benzo[d]thiazol‐2‐yl)ethene) through oxidative self‐condensation and free radical coupling followed by elimination, respectively. They could then react with each other convergently via formal [3+2] cycloaddition to give deprotonated tetrasubstituted pyrrole coordinated intermediate [MnClP] after aromatization. Dimerization of [MnClP] produces the final product 1. Three C−C bonds and one C−N bond are formed through this six‐step domino sequence. The corresponding organic skeleton (HP: 2,2′,2′′,2′′′‐(1H‐pyrrole‐2,3,4,5‐tetrayl)tetrakis(benzo[d]thiazole)) has been obtained from 1 and shows a higher fluorescent quantum yield (52 %) than the reported 3,4‐diphenyl substituted analogue 2,2′‐(3,4‐diphenyl‐1H‐pyrrole‐2,5‐diyl)bis(benzo[d]thiazole) (DPB) (42 %). [ABSTRACT FROM AUTHOR]

Electrospray ionization mass spectrometry (ESI-MS) analysis is frequently associated with noncovalent adduct formation, both in positive and negative modes. Anion binding and sensing by mass spectrometry, notably more challenging compared to cation binding, will have major research potential with the development of appropriate sensors. Here, we demonstrated identification of stable bisquaternary dication adducts with trifluoroacetate (TFA−), Cl− and HSO4− in positive-mode ESI-MS analysis. The observed adducts were stable in MS/MS mode, leading to the formation of characteristic fragment ions containing a covalently bound anion, which requires bond reorganization. This phenomenon was confirmed by computational methods. Furthermore, given that anion detection and anion sensor chemistry have gained significant prominence in chemistry, we conducted an analysis of the fluorescent properties of bisquaternary ammonium compound as a potential anion sensor. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) represent crucial intermediates in the formation of insoluble metal oxides from soluble metal ions, however, the rapid hydrolysis‐condensation kinetics of MoVI or WVI makes the direct characterization of coexisted molecular species in a given medium extremely difficult. Silver nanoclusters have shown versatile capacity to encapsulate diverse POMs, which provides an alternative scene to appreciate landscape of POMs in atomic precision. Here, we report a thiacalix[4]arene protected silver nanocluster (Ag72b) that simultaneously encapsulates three kinds of molybdates (MoO42−, Mo6O228− and Mo7O258−) in situ transformed from classic Lindqvist Mo6O192−, providing more deep understanding on the structural diversity and condensation growth route of POMs in solution. Ag72b is the first silver nanocluster trapping so many kinds of molybdates, which in turn exert collective template effect to aggregate silver atoms into a nanocluster. The post‐reaction of Ag72b with AgOAc or PhCOOAg produces a discrete Ag24 nanocluster (Ag24a) or an Ag28 nanocluster based 1D chain structure (Ag28a), respectively. Moreover, the post‐synthesized Ag28a can be utilized as potential ignition material for further application. This work not only provides an important model for unlocking dynamic features of POMs at atom‐precise level but also pioneers a promising approach to synthesize silver nanoclusters from known to unknown. [ABSTRACT FROM AUTHOR]

The surprising formation of highly charged protein ions from aqueous ammonium bicarbonate solution is a fascinating phenomenon referred to as electrothermal supercharging (ETS). Although the precise mechanism involved is not clearly understood, previous studies predominantly suggest that ETS is due to native protein destabilization in the presence of bicarbonate anion inside the electrospray ionization droplets under high temperatures and spray voltages. To evaluate existing hypotheses surrounding the underlying mechanism of ETS, the effects of several additives on protein charging under ETS conditions were investigated. The changes in the protein charge state distributions were compared by measuring the ratios between the intensities of highest intensity charge states of native and unfolded protein envelopes and shifts in the lowest and highest observed charge states. This study demonstrated that source temperature plays a more important role in ETS compared to spray voltage, especially when using a nebulized microelectrospray ionization source. Moreover, the effect of amino acids on ETS were generally in good agreement with the extensive literature available on the stabilization or destabilization of proteins by these additives in bulk solution. Among the natural amino acids, protein supercharging was significantly reduced by proline and glycine; however, imidazole provided the highest degree of noncovalent complex stabilization against ETS, outperforming the amino acids. Overall, our study shows that the simple addition of stabilizing reagents such as proline and imidazole can reduce the extent of apparent protein unfolding and supercharging in ammonium bicarbonate solution and provide evidence against the roles of charge depletion and thermal unfolding during ETS. [ABSTRACT FROM AUTHOR]

Worldwide, it is estimated that there are 1.8 to 2.7 million cases of envenoming caused by snakebites. Snake venom is a complex mixture of protein toxins, lipids, small molecules, and salts, with the proteins typically responsible for causing pathology in snakebite victims. For their chemical characterization and identification, analytical methods are required. Reversed-phase liquid chromatography coupled with electrospray ionization mass spectrometry (RP-LC-ESI-MS) is a widely used technique due to its ease of use, sensitivity, and ability to be directly coupled after LC separation. This method allows for the efficient separation of complex mixtures and sensitive detection of analytes. On the other hand, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is also sometimes used, and though it typically requires additional sample preparation steps, it offers desirable suitability for the analysis of larger biomolecules. In this study, seven medically important viperid snake venoms were separated into their respective venom toxins and measured by ESI-MS. In parallel, using nanofractionation analytics, post-column high-resolution fractionation was used to collect the eluting toxins for further processing for MALDI-MS analysis. Our comparative results showed that the deconvoluted snake venom toxin masses were observed with good sensitivity from both ESI-MS and MALDI-MS approaches and presented overlap in the toxin masses recovered (between 25% and 57%, depending on the venom analyzed). The mass range of the toxins detected in high abundance was between 4 and 28 kDa. In total, 39 masses were found in both the ESI-MS and/or MALDI-MS analyses, with most being between 5 and 9 kDa (46%), 13 and 15 kDa (38%), and 24 and 28 kDa (13%) in size. Next to the post-column MS analyses, additional coagulation bioassaying was performed to demonstrate the parallel post-column assessment of venom activity in the workflow. Most nanofractionated venoms exhibited anticoagulant activity, with three venoms additionally exhibiting toxins with clear procoagulant activity (Bothrops asper, Crotalus atrox, and Daboia russelii) observed post-column. The results of this study highlight the complementarity of ESI-MS and MALDI-MS approaches for characterizing snake venom toxins and provide a complementary overview of defined toxin masses found in a diversity of viper snake venoms.

Modern medical research develops interest in sophisticated artificial nano‐ and microdevices for future treatment of human diseases related to biological dysfunctions. This covers the design of protocells capable of mimicking the structure and functionality of eukaryotic cells. The authors use artificial organelles based on trypsin‐loaded pH‐sensitive polymeric vesicles to provide macrophage‐like digestive functions under physiological conditions. Herein, an artificial cell is established where digestive artificial organelles (nanosize) are integrated into a protocell (microsize). With this method, mimicking crossing of different biological barriers, capture of model protein pathogens, and compartmentalized digestive function are possible. This allows the integration of different components (e.g., dextran as stabilizing block) and the diffusion of pathogens in simulated cytosolic environment under physiological conditions. An integrated characterization approach is carried out, with identifying electrospray ionization mass spectrometry as an excellent detection method for the degradation of a small peptide such as β‐amyloid. The degradation of model enzymes is measured by enzyme activity assays. This work is an important contribution to effective biomimicry with the design of cell‐like functions having potential for therapeutic action. [ABSTRACT FROM AUTHOR]

We analyzed ten pulses (the dried seeds of legumes), i.e., baby lima beans, black beans, black-eyed peas, butter beans, cranberry beans, garbanzo beans, green split peas, lentils, navy beans, and pinto beans, using three-dimensional liquid chromatography (3D-LC) with parallel second dimensions, LC × (LC + LC). We combined non-aqueous reversed-phase (NARP) chromatography as the first dimension separation, 1D, with argentation UHPLC for separation based on degree and location of unsaturation in the first second dimension, 2D(1), and multi-cycle NARP-UHPLC in the second second dimension, 2D(2). Pulses contained 1.9% to 2.7% lipids, except garbanzo beans, which contained 6.2% lipids. High-resolution, accurate-mass (HRAM) orbitrap mass spectrometry (MS) was used to perform lipidomic analysis of the 2D(2) and percent relative quantification, showing that the most abundant average triacylglycerol (TAG) molecular species across all pulses were PLL at 10.67% and PLLn at 10.45%. Common beans (Phaseolus vulgaris) were clustered together using principal component analysis (PCA), showing the highest levels of linolenic acid, C18:3, in molecular species such as PLnLn, LLnLn, and OLLn, with palmitic (P), C16:0, linoleic (L), 18:2, linolenic (Ln), 18:3, and oleic (O), 18:1, FAs. Calibration curves derived from interweaved sets of regioisomer standards allowed the absolute quantification of 1,2- and 1,3-regioisomers for a subset of TAGs. [ABSTRACT FROM AUTHOR]

Electrospray Ionization Mass Spectrometry (ESI‐MS) technique and density functional theory (DFT) calculations were combined to study the formation of the complexes of lanthanides (Ln = La, Ce, Nd, Sm, Eu, Yb) and actinides (UO22+, Th4+) with CyMe4‐BTBP (6,6′‐bis(5,5,8,8‐tetramethyl‐5,6,7,8‐tetrahydro‐benzo‐[1,2,4‐]triazin‐3‐yl)‐[2,2′]bipyridine) to understand the mechanisms during the extraction process. Mass spectrometry titrations showed the formation of the complexation in acetonitrile. For lanthanides, only 1:2 complexes ([Ln(L)2]3+, [Ln(L)2(CH3CN)]3+), [Ln(L)2(NO3)]2+) were found at low [Ln]/[L] concentration ratios, whereas the 1:1 complexes ([Ln(L)(NO3)2]+) were observed when the [Ln]/[L] concentration ratio reached 1.0. For uranyl complexes, 1:1 complex ([UO2L(NO3)]+) was the only species within the measuring range. Th4+ complexes had two compositions: 1:1 and 1:2, in which 1:2 species was the dominant complex. Collision‐induced dissociation (CID) was employed to characterize the fragmentation process. The fragmentation process was unfolded sequentially on both sides of CyMe4‐BTBP ligand with the loss of alkyl groups and cleavage of triazinyl rings. The CID results of CyMe4‐BTBP complexes revealed a slight difference depending on the metal center. The DFT calculations showed that the stable complexes formed in acetonitrile solution were consistent with the ESI‐MS results. [ABSTRACT FROM AUTHOR]

Anionic complex of antamanide with the nitrate anion has been proven by electrospray ionization mass spectrometry (ESI-MS) method. Further, applying quantum chemical DFT calculations, the most probable structure of this complex was derived. The nitrate anion is embedded in the molecule of antamanide and its oxygens atoms are bonded by seven bonds to the hydrogen atoms of the ligand. Finally, the interaction energy, E(int), of the antamanide-NO3− complex was calculated as E(int) = -175.9 kJ/mol. Highlights: Antamanide-NO3− complex has been proved using the ESI-MS method. The structures of this complex has been determined applying quantum chemical DFT calculations. The interaction energies of antamanide-NO3− complex has been calculated. [ABSTRACT FROM AUTHOR]

In this article, a comparison of ionization techniques is provided and discussed. Conventional liquid chromatography with an electrospray ionization source shows higher robustness and repeatability in comparison with liquid chromatography coupled with a coordination ion spray (CIS-MS) source using silver nitrate as the dopant. However, the higher sensitivity and possibility to collect more data in untargeted applications mean CIS-MS is emerging as an instrument used in specific applications. During this research, the limit of detection (LOD) for GHRP-2 and GHRP-6 was established at 0.2 ng/mL, and the lower limit of quantification (LLOQ) was 0.5 ng/mL for CIS-MS. For conventional ESI-MS combined with solid-phase extraction on weak cation exchange columns, the limit of detection was found to be 1 ng/mL, and the lower limit of quantification was 2 ng/mL.

Investigations on binding strength differences of non-covalent protein complex components were performed by mass spectrometry. T4 fibritin foldon (T4Ff) is a well-studied miniprotein, which together with its biotinylated version served as model system to represent a compactly folded protein to which an Intrinsically Disordered Region (IDR) was attached. The apparent enthalpies of the gas phase dissociation reactions of the homo-trimeric foldon F-F-F and of the homo-trimeric triply biotinylated foldon bF-bF-bF have been determined to be rather similar (3.32 kJ/mol and 3.85 kJ/mol) but quite distinct from those of the singly and doubly biotinylated hetero-trimers F-F-bF and F-bF-bF (1.86 kJ/mol and 1.08 kJ/mol). Molecular dynamics simulations suggest that the ground states of the (biotinylated) T4Ff trimers are highly symmetric and well comparable to each other, indicating that the energy levels of all four (biotinylated) T4Ff trimer ground states are nearly indistinguishable. The experimentally determined differences and/or similarities in enthalpies of the complex dissociation reactions are explained by entropic spring effects, which are noticeable in the T4Ff hetero-trimers but not in the T4Ff homo-trimers. A lowering of the transition state energy levels of the T4Ff hetero-trimers seems likely because the biotin moieties, mimicking intrinsically disordered regions (IDRs), induced asymmetries in the transition states of the biotinylated T4Ff hetero-trimers. This transition state energy level lowering effect is absent in the T4Ff homo-trimer, as well as in the triply biotinylated T4Ff homo-trimer. In the latter, the IDR-associated entropic spring effects on complex stability cancel each other out. ITEM-FIVE enabled semi-quantitative determination of energy differences of complex dissociation reactions, whose differences were modulated by IDRs attached to compactly folded proteins.

Human metallothioneins (MTs) are involved in binding the essential elements, Cu(I) and Zn(II), and the toxic element, Cd(II), in metal‐thiolate clusters using 20 reduced cysteines. The brain‐specific MT3 binds a mixture of Cu(I) and Zn(II) in vivo. Its metallation properties are critically important because of potential connections between Cu, Zn and neurodegenerative diseases. We report that the use of isotopically pure 63Cu(I) and 68Zn(II) greatly enhances the element resolution in the ESI‐mass spectral data revealing species with differing Cu:Zn ratios but the same total number of metals. Room temperature phosphorescence and circular dichroism spectral data measured in parallel with ESI‐mass spectral data identified the presence of specific Cu(I)‐thiolate clusters in the presence of Zn(II). A series of Cu(I)‐thiolate clusters form following Cu(I) addition to apo MT3: the two main clusters that form are a Cu6 cluster in the β domain followed by a Cu4 cluster in the α domain. 63Cu(I) addition to 68Zn7‐MT3 results in multiple species, including clustered Cu5Zn5‐MT3 and Cu9Zn3‐MT3. We assign the domain location of the metals for Cu5Zn5‐MT3 as a Cu5Zn1‐β cluster and a Zn4‐α cluster and for Cu9Zn3‐MT3 as a Cu6‐β cluster and a Cu3Zn3‐α cluster. While many reports of the average MT3 metal content exist, determining the exact Cu,Zn stoichiometry has proven very difficult even with native ESI‐MS. The work in this paper solves the ambiguity introduced by the overlap of the naturally abundant Cu(I) and Zn(II) isotopes. Contrary to other reports, there is no indication of a major fraction of Cu4‐β‐Znn‐α‐MT3 forming. [ABSTRACT FROM AUTHOR]

Different oxidative pathways of sulfur dioxide promoted by ZnO(NO3)2−, Zn(NO3)2− and Zn(NO2)(NO3)− are revealed by a joint investigation by mass spectrometry and theoretical calculations. The reactions are triggered by [Zn2+‐O−⋅]+ or by the low‐valence Zn+ through oxygen ion transfer or electron transfer to SO2, respectively. The NOx− ligands intervene in the oxidation only when sulfur dioxide is converted to SO3− or SO2−, leading to the formation of zinc sulfate and zinc sulfite coordinated to nitrate or nitrite anions. Kinetic analyses show that the reactions are fast and efficient, and theory discloses the elementary steps, namely oxygen ion transfer, oxygen atom transfer and electron transfer, occurring through similar energy landscapes for the three reactive anions. [ABSTRACT FROM AUTHOR]

Elicitation is used in agriculture as a method of crop protection or a means to enhance nutraceutically or pharmaceutically important metabolites with the help of chemical stimuli known as elicitors. In the present experiment elicitor potential of Salicylic acid has been exploited to induce metabolic changes in spinach plant. Salicylic acid of various concentrations (1–0.01 mg/ml) were applied on spinach leaves through foliar spray and observed for biochemical changes. A multifold increase in the amount of total phenolic and total flavonoid as well as enzyme activity of peroxidase, catalase and superoxide dismutase was observed in a dose dependent manner. An increase in the antioxidant activity was observed and was shown to be correlated with the phenolic compounds. Growth parameters measured in the form of total biomass and total chlorophyll were decreased by high concentrations. Metabolite profile of the control and treated leaves was generated through ESI-MS in the positive and negative ion modes. The results showed an increase in the ion intensity peak of phenolic acids, such as gentisic acid, hydroxycinnamic acid, coumaric acid, ferulic acid and caffeic acid as well as major flavonoids of spinach plant, like kaempferol, quercetin, isorhamnetin and patulitin glycosides. Ferulic and caeffic acids were quantified by HPLC and showed an increase in their amount after elicitor treatment.

Abstract This paper identifies the materials used to make a brocade belt belonging to the Qajar courtiers in Iran. This belt consists of two fabric types: red support and golden brocade. Accordingly, this paper examined the skin and tannin type, fiber types, dyeing agents, mordant, and metal wrapping of brocade yarns and metal buckle. Technical imaging, ESI–MS, FORS, FTIR and SEM–EDS were used to identify the materials. Multi-band imaging methods included Vis, UVL, IRR, and UVR, in which UVFC and IRFC images were obtained after processing. The results showed that cotton yarn was used in both fabrics. The red fabric yarns were dyed using cochineal and alum mordant. Also, the yellow brocade yarns were dyed using catechins-rich plants, and in this dyeing process, polyphenols and alum have been as mordant. Madder-dyed yarns are also found in parts of the belt. Examination of the metal wrapping of brocade yarns suggests using strips of copper-nickel alloy with a thin layer of gold-silver alloy. This secondary coating protects the copper-nickel strips and increases their golden luster. The leather analysis of the leather parts also indicated the using cattle/calfskin tanned with gallotannins. Belt buckle analysis also shows the use of brass alloy with a high percentage of zinc, leading to a golden sheen and the buckle desired strength. The results show the use of low-cost materials in the manufacture of clothing for the lower levels of the Qajar court.

Accurate and absolute quantification of peptides in complex mixtures using quantitative mass spectrometry (MS)-based methods requires foreground knowledge and isotopically labeled standards, thereby increasing analytical expenses, time consumption, and labor, thus limiting the number of peptides that can be accurately quantified. This originates from differential ionization efficiency between peptides and thus, understanding the physicochemical properties that influence the ionization and response in MS analysis is essential for developing less restrictive label-free quantitative methods. Here, we used equimolar peptide pool repository data to develop a deep learning model capable of identifying amino acids influencing the MS1 response. By using an encoder-decoder with an attention mechanism and correlating attention weights with amino acid physicochemical properties, we obtain insight on properties governing the peptide-level MS1 response within the datasets. While the problem cannot be described by one single set of amino acids and properties, distinct patterns were reproducibly obtained. Properties are grouped in three main categories related to peptide hydrophobicity, charge, and structural propensities. Moreover, our model can predict MS1 intensity output under defined conditions based solely on peptide sequence input. Using a refined training dataset, the model predicted log-transformed peptide MS1 intensities with an average error of 9.7 ± 0.5% based on 5-fold cross validation, and outperformed random forest and ridge regression models on both log-transformed and real scale data. This work demonstrates how deep learning can facilitate identification of physicochemical properties influencing peptide MS1 responses, but also illustrates how sequence-based response prediction and label-free peptide-level quantification may impact future workflows within quantitative proteomics.

Electrospray ionization mass spectrometry (ESI-MS) analysis is frequently associated with noncovalent adduct formation, both in positive and negative modes. Anion binding and sensing by mass spectrometry, notably more challenging compared to cation binding, will have major research potential with the development of appropriate sensors. Here, we demonstrated identification of stable bisquaternary dication adducts with trifluoroacetate (TFA−), Cl− and HSO4− in positive-mode ESI-MS analysis. The observed adducts were stable in MS/MS mode, leading to the formation of characteristic fragment ions containing a covalently bound anion, which requires bond reorganization. This phenomenon was confirmed by computational methods. Furthermore, given that anion detection and anion sensor chemistry have gained significant prominence in chemistry, we conducted an analysis of the fluorescent properties of bisquaternary ammonium compound as a potential anion sensor.

The members of the genus Pseudomonas can secrete a wide range of ribosomally encoded antagonistic peptides and proteins, ranging from small microcins to large tailocins. In this study, a drug-sensitive Pseudomonas aeruginosa strain isolated from a high-altitude virgin soil sample showed a broad range of antibacterial activity against Gram-positive and Gram-negative bacteria. The antimicrobial compound, purified by affinity chromatography, ultrafiltration, and high-performance liquid chromatography, showed a molecular weight (M + H)+ of 494.7667 daltons, as revealed by ESI-MS analysis. The MS-MS analysis divulged the compound as an antimicrobial pentapeptide with the sequence NH 2 -Thr-Leu-Ser-Ala-Cys-COOH (TLSAC) and was further verified by evaluating the antimicrobial activity of the chemically synthesized pentapeptide. The extracellularly released pentapeptide, which is relatively hydrophobic in nature, is encoded in a symporter protein, as appraised from the whole genome sequence analysis of strain PAST18. The influence of different environmental factors was examined to determine the stability of the antimicrobial peptide (AMP), which was also assessed for several other biological functions, including antibiofilm activity. Further, the antibacterial mechanism of the AMP was evaluated by a permeability assay. Overall, the characterised pentapeptide, as revealed in this study, may find use as a potential biocontrol agent in various commercial applications. • An antimicrobial peptide was isolated from Pseudomonas aeruginosa species. • The purified peptide was characterized by mass spectrometric analyses. • The characterized pentapeptide revealed a broad-spectrum antimicrobial activity. • The peptide was found to be stable at wide ranges of pH and temperature. • The peptide also exhibited antibiofilm activity. [ABSTRACT FROM AUTHOR]

Etidronic acid (1-Hydroxyethylidene-1,1-diphosphonic acid, HEDP, H4L) is a proposed decorporation agent for U(VI). This paper studied its complex formation with Eu(III), an inactive analog of trivalent actinides, over a wide pH range, at varying metal-to-ligand ratios (M:L) and total concentrations. Combining spectroscopic, spectrometric, and quantum chemical methods, five distinct Eu(III)−HEDP complexes were found, four of which were characterized. The readily soluble EuH2L+ and Eu(H2L)2− species with log β values of 23.7 ± 0.1 and 45.1 ± 0.9 are formed at acidic pH. At near-neutral pH, EuHL0s forms with a log β of ~23.6 and, additionally, a most probably polynuclear complex. The readily dissolved EuL− species with a log β of ~11.2 is formed at alkaline pH. A six-membered chelate ring is the key motif in all solution structures. The equilibrium between the Eu(III)–HEDP species is influenced by several parameters, i.e., pH, M:L, total Eu(III) and HEDP concentrations, and time. Overall, the present work sheds light on the very complex speciation in the HEDP–Eu(III) system and indicates that, for risk assessment of potential decorporation scenarios, side reactions of HEDP with trivalent actinides and lanthanides should also be taken into account. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) are critical for many cellular functions, and dysregulation of ROS involves the development of multiple types of tumors, including pancreatic cancer. However, ROS have been grouped into a single biochemical entity for a long time, and the specific roles of certain types of ROS in tumor cells (e.g. pancreatic ductal adenocarcinoma (PDAC)) have not been systematically investigated. In this work, a highly sensitive and accurate mass spectrometry‐based method was applied to study PDAC cells of humans and of genetically modified animals. The results show that the oncogenic KRAS mutation promotes the accumulation of hydrogen peroxide (H2O2) rather than superoxide or hydroxyl radicals in pancreatic cancer cells. We further identified that the enriched H2O2 modifies cellular metabolites and promotes the survival of pancreatic cancer cells. These findings highlight the specific roles of H2O2 in pancreatic cancer development, which may provide new directions for pancreatic cancer therapy. [ABSTRACT FROM AUTHOR]

In our research on sphingolipids from marine invertebrates, a mixture of phytoceramides was isolated from the sponge Monanchora clathrata (Western Australia). Total ceramide, ceramide molecular species (obtained by RP-HPLC, high-performance liquid chromatography on reversed-phase column) and their sphingoid/fatty acid components were analyzed by NMR (nuclear magnetic resonance) spectroscopy and mass spectrometry. Sixteen new (1b, 3a, 3c, 3d, 3f, 3g, 5c, 5d, 5f, 5g, 6b–g) and twelve known (2b, 2e, 2f, 3b, 3e, 4a–c, 4e, 4f, 5b, 5e) compounds were shown to contain phytosphingosine-type backbones i-t17:0 (1), n-t17:0 (2), i-t18:0 (3), n-t18:0 (4), i-t19:0 (5), or ai-t19:0 (6), N-acylated with saturated (2R)-2-hydroxy C21 (a), C22 (b), C23 (c), i-C23 (d), C24 (e), C25 (f), or C26 (g) acids. The used combination of the instrumental and chemical methods permitted the more detailed investigation of the sponge ceramides than previously reported. It was found that the cytotoxic effect of crambescidin 359 (alkaloid from M. clathrata) and cisplatin decreased after pre-incubation of MDA-MB-231 and HL-60 cells with the investigated phytoceramides. In an in vitro paraquat model of Parkinson's disease, the phytoceramides decreased the neurodegenerative effect and ROS (reactive oxygen species) formation induced by paraquat in neuroblastoma cells. In general, the preliminary treatment (for 24 or 48 h) of the cells with the phytoceramides of M. clathrata was necessary for their cytoprotective functions, otherwise the additive damaging effect of these sphingolipids and cytotoxic compounds (crambescidin 359, cisplatin or paraquat) was observed. [ABSTRACT FROM AUTHOR]

The molecular composition of lubricating oils has a strong impact on how automotive engines function, but the techniques used to monitor the quality parameters of these oils only inspect their gross physical–chemical properties such as viscosity, color, and bulk spectroscopy profiles; hence, bad‐quality, adulterated, or counterfeit oils are hard to detect. Herein, we investigated the ability of direct infusion electrospray ionization mass spectrometry (ESI‐MS) to provide simple, rapid but characteristic fingerprint profiles for such oils of the mineral and synthetic types. After a simple aqueous extraction, ESI‐MS analyses, particularly in the positive ion mode, did indeed show characteristic molecular markers with unique profiles, which were confirmed and more clearly visualized by partial least squares‐discriminant analysis (PLS‐DA). Nuclear magnetic resonance and Fourier transform infrared‐attenuated total reflection spectroscopy were also tested for the bulk samples but showed nearly identical spectra, thus failing to reveal their distinct molecular composition and to differentiate the oil samples. To simulate adulteration, mixtures of mineral and synthetic oils were also analyzed by ESI(+)‐MS, and additions as low as 1% of mineral oil to synthetic oil could be detected. The technique therefore offers a simple and fast but powerful tool to monitor the molecular composition of lubricant oils, particularly vias their more polar constituents. [ABSTRACT FROM AUTHOR]

A new protein wood adhesive was studied with Camellia oleifera protein. Formaldehyde and N-(2)-L-Ala-L-Gln (LAG) were used as the model compounds of amino resins and Camellia oleifera protein, aiming to provide scientific foundations for the improvement and applications of Camellia oleifera protein adhesive by the reaction of model compounds. The experimental results demonstrate that, under alkaline conditions, formaldehyde is easier to react with Camellia oleifera protein by quicker reaction and lower curing temperature. Under acid conditions, amino hydroxymethylated structure of aliphatic series from LAG is difficult to form stable reactive intermediates and further polycondensation. Hydroxymethylation of end acylamino and peptide bond amino from LAG is relatively weak. Under alkaline conditions, the free aliphatic amino and acylamino of LAG both can make hydroxymethylation reaction with formaldehyde. In the polycondensation, hydroxymethyl amide is the initial structure and the reactive intermediate is produced by E1cb reaction of hydroxymethyl amide. Methylene bridge bonds and methylene ether bonds are structures of the polycondensation products, which are competing reactions. The former is mainly formed by the reaction between alkaline reactive intermediate and amino of aliphatic series, and the latter is produced by the reaction of reactive intermediate and amino of hydroxymethyl aliphatic series with hydroxymethyl amide. [ABSTRACT FROM AUTHOR]

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper identifies the materials used to make a brocade belt belonging to the Qajar courtiers in Iran. This belt consists of two fabric types: red support and golden brocade. Accordingly, this paper examined the skin and tannin type, fiber types, dyeing agents, mordant, and metal wrapping of brocade yarns and metal buckle. Technical imaging, ESI–MS, FORS, FTIR and SEM–EDS were used to identify the materials. Multi-band imaging methods included Vis, UVL, IRR, and UVR, in which UVFC and IRFC images were obtained after processing. The results showed that cotton yarn was used in both fabrics. The red fabric yarns were dyed using cochineal and alum mordant. Also, the yellow brocade yarns were dyed using catechins-rich plants, and in this dyeing process, polyphenols and alum have been as mordant. Madder-dyed yarns are also found in parts of the belt. Examination of the metal wrapping of brocade yarns suggests using strips of copper-nickel alloy with a thin layer of gold-silver alloy. This secondary coating protects the copper-nickel strips and increases their golden luster. The leather analysis of the leather parts also indicated the using cattle/calfskin tanned with gallotannins. Belt buckle analysis also shows the use of brass alloy with a high percentage of zinc, leading to a golden sheen and the buckle desired strength. The results show the use of low-cost materials in the manufacture of clothing for the lower levels of the Qajar court. [ABSTRACT FROM AUTHOR]

From Camellia nitidissima Chi flowers four undescribed flavonoids, nitidissimol A, nitidissimol B, sexangularetin 3-O-(6''-trans-p-coumarolyglucopyranoside) and sexangularetin 3-O-(2''-trans-p-coumarolyglucopyranoside) (1–4), and two previously unreported phenolics, nitidissimol C, D (9, 10), were isolated first time along with ten known compounds, kaempferol 3-O-(6"-O-trans-p-coumaroyl)-β-D- glucopyranoside (5), kaempferol-3-O-rhamnoside (6), Quercetin-3'-O-β-D-glucoside (7), kaempferol-7-O-β-D-glucoside (8), erythro-guaiacylglycerol-O-4'-coniferyl ether (11), threo-guaiacylglycerol-O-4'-coniferyl ether (12), protocatechuic acid (13), 1,2-Diethoxybenzene (14), ethyl shikimate (15), 2,4,6-trihydroxybenzoic acid 4-O-allopyranoside (16). The structures of the isolated compounds were elucidated by spectroscopic analysis of 1 D- and 2 D-NMR and MS data. Moreover, all isolated compounds (1-16) were tested for the antibacterial activity against Xanthomonas oryzae pv. oryzae and their quorum sensing inhibitory activity in Pseudomonas aeruginosa PAO1. However, no one showed signifcant inhibition of X. oryzae pv. oryzae (MIC90 > 0.1 mg/mL), nor did they significantly inhibit the pyocyanin synthesis, which is controlled by quorum sensing in PAO1. [ABSTRACT FROM AUTHOR]

Copyright of ESPOCH Congresses: The Ecuadorian Journal of S.T.E.A.M. is the property of Knowledge E DMCC and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A short 10‐min ultra high performance liquid chromatography (UHPLC) method was used for separation and lipidomic analysis of triacylglycerols (TAGs) in 10 pulses: baby lima beans, black beans, black‐eyed peas, butter beans, cranberry beans, garbanzo beans, green split peas, lentils, navy beans, and pinto beans. The lipids extracted using chloroform/methanol averaged 1.9–2.7% across all pulses except garbanzo beans, which gave 6.2% lipids. TAGs were analyzed using dual parallel mass spectrometry (LC1MS2), areas were integrated using LipidSearch 4.2 software, and percent relative TAG compositions were calculated. Fatty acid response factors were calculated by comparison to calibrated GC‐FID, which were used to calculate response‐factor adjusted TAG compositions. Principal component analysis revealed that the pulses separated into three clusters, which were further highlighted using hierarchical cluster analysis. A subset of TAGs was quantified using calibration curves made from alternating sets of regioisomers in the non‐linear high concentration range (~2.5 nMol/ml to ~300 nMol/ml). A linear calibration curve for the sum of tocopherols detected by fluorescence was constructed with a coefficient of determination, r2, >0.99 for low concentrations (0.50–50 μg/ml), but tocopherols in pulses appeared to be inefficiently extracted. TAG regioisomers were quantified based on a Critical Ratio (CR), [AA]+/[AB]+, interpolated between the CRs of two pure regioisomer standards taken from alternating calibration standards. TAG mole percent relative compositions are reported for the first time for most pulses and the compositions are given with more detail and specificity than previously reported. [ABSTRACT FROM AUTHOR]

We analyzed ten pulses (the dried seeds of legumes), i.e., baby lima beans, black beans, black-eyed peas, butter beans, cranberry beans, garbanzo beans, green split peas, lentils, navy beans, and pinto beans, using three-dimensional liquid chromatography (3D-LC) with parallel second dimensions, LC × (LC + LC). We combined non-aqueous reversed-phase (NARP) chromatography as the first dimension separation, 1D, with argentation UHPLC for separation based on degree and location of unsaturation in the first second dimension, 2D(1), and multi-cycle NARP-UHPLC in the second second dimension, 2D(2). Pulses contained 1.9% to 2.7% lipids, except garbanzo beans, which contained 6.2% lipids. High-resolution, accurate-mass (HRAM) orbitrap mass spectrometry (MS) was used to perform lipidomic analysis of the 2D(2) and percent relative quantification, showing that the most abundant average triacylglycerol (TAG) molecular species across all pulses were PLL at 10.67% and PLLn at 10.45%. Common beans (Phaseolus vulgaris) were clustered together using principal component analysis (PCA), showing the highest levels of linolenic acid, C18:3, in molecular species such as PLnLn, LLnLn, and OLLn, with palmitic (P), C16:0, linoleic (L), 18:2, linolenic (Ln), 18:3, and oleic (O), 18:1, FAs. Calibration curves derived from interweaved sets of regioisomer standards allowed the absolute quantification of 1,2- and 1,3-regioisomers for a subset of TAGs.

The incidence of ultraviolet radiation has increased on the Earth's surface due to depletion of the stratospheric ozone layer which has several detrimental effects on living organisms including cyanobacteria. Mycosporine-like amino acids (MAAs) are eco-friendly natural sun screening biomolecules having prominent photoprotective potentials. Our study provides the identification and characterization of one of these MAAs from the cyanobacterium Scytonema sp. strain HKAR-16. The identification and characterization of MAA palythine (λmax = 320 nm; m/z = 245.1) from this strain was performed using ultraviolet-visible spectrophotometer, high-performance liquid chromatography (HPLC) associated with photodiode array (PDA) detector and electrospray ionization-mass spectrometry (ESI-MS) analyses. Further characterization was performed by Raman spectroscopy. To the best of our knowledge, this is the first report regarding the presence of MAA palythine in Scytonema sp. HKAR-16. Our results indicate that the cyanobacterium can protect itself by synthesizing MAA palythine in response to injurious UV radiation. This naturally occurring photoprotective compound may have the potential to replace synthetic photoprotectants that can be used by the humans.

Pepper is one of the most consumed spices in the world. Its main compound is capsaicin, a widely studied biomarker that has pharmacological activities due to its anti-inflammatory and analgesic capacity. Topical formulations such as patches based on capsaicin have been developed as an option in relieving pain and reducing swelling. In addition, capsaicin is used as an active ingredient in non-lethal weapon formulations such as pepper spray through the QuEChERS concept (Quick, Easy, Cheap, Effective, Robust, Safe) technique. Used for food analysis, it allows the direct analysis of the biomarker by TLC-ESI-MS, which are previously separated by HPTLC (High Performance Thin Layer Chromatography) using an internal standard for determination of Rf and confirmation of capsaicin in different matrices. [ABSTRACT FROM AUTHOR]

Electrospray ionization mass spectrometry was used to investigate the cation‐π interaction of Ag+ cation with [2.2]paracyclophane. It was found that cationic Ag.([2.2]paracyclophane)+ and Ag.([2.2]paracyclophane)2+ complex species are formed in the gas phase. Further, applying quantum mechanical calculations in the frame of the density functional theory, using B3LYP functional with Def2TZVP basis set, the most probable structures of the proved Ag+ ‐ [2.2]paracyclophane complexes were derived. In the Ag.([2.2]paracyclophane)+ complex, the cation Ag+ is bounded to three carbon atoms of one benzene ring of [2.2]paracyclophane ligand via cation‐π interaction. Quite analogously is bonded also second [2.2]paracyclophane molecule in Ag.([2.2]paracyclophane)2+ complex. The interaction energy, E(int), of Ag.([2.2]paracyclophane)+ complex was calculated to be −220.79 kJ/mol, E(int) of Ag.([2.2]paracyclophane)2+ complex is −362.67 kJ/mol. It is consistent with the formation of the considered Ag+ ‐ [2.2]paracyclophane complex species. [ABSTRACT FROM AUTHOR]

Metal ions can be analyzed by ESI‐MS with chelating agents. However, matrix effect and the marginal difference in atomic weight of the isotopes of some metal ions make the analysis of a metal ion mixture not feasible. In this paper, we present the use of IP‐HPLC in conjunction with a metal ion chelating agent to analyze the metal ion mixtures. Hydrophobic (±)‐trans‐1,2‐cyclohexylenedinitrilotetraacetic acid (CDTA) was used to chelate 16 metal ions. The chelates were then separated by IP‐HPLC followed by ESI‐MS analysis. For IP‐HPLC, different combinations of primary amines and their salts were employed as the ion‐pairing reagent in eluent on a high‐pH resistant C‐18 column under basic conditions. For ESI‐MS, Q‐Exactive Focus system was used. Among the metal ions, the results indicated that Al3+ showed the lowest LOD (3.88 × 10−3 μM) while Zn2+ showed the highest (0.227 μM). The sensitivity was close to that of ICP‐AES. The coefficients of determination (R2) were greater than 0.995 except for Sr2+ (R2 = 0.9899), indicating the high accuracy of the method. Finally, this method was used to analyze the black soybean samples from two different sources. Eight metal ions were successfully identified with simultaneous detection of sugars, organic acids, and nucleotides. [ABSTRACT FROM AUTHOR]

Two types of lung cells (epithelial cancer lung cells, A-549 and lung fibroblasts MRC-5) were exposed to the clinically established gold drug auranofin at concentrations close to the half-maximal inhibitory drug concentrations (IC50). Collected cells were subjected to speciation analysis using inductively coupled plasma mass spectrometry (ICP-MS). Auranofin showed better affinity toward proteins than DNA, RNA, and hydrophilic small molecular weight compounds. It can bind to proteins that vary in size (~20 kDa, ~75 kDa, and ≥200 kDa) and pI. However, the possibility of dimerization and protein–protein complex formation should also be taken into account. µRPLC/CZE-ESI-MS/MS studies on trypsinized proteins allowed the indication of 76 peptides for which signal intensity was influenced by auranofin presence in cells. Based on it, identity was proposed for 20 proteins. Except for thioredoxin reductase (TrxR), which is directly targeted by gold complex, the proteins were found to be transformed. Five indicated proteins: myosin, plectin, talin, two annexins, and kinase M3K5, are responsible for cell–cell, cell–protein interactions, and cell motility. A wound healing test confirmed their regulation by auranofin as cell migration decreased by 40% while the cell cycle was not interrupted. [ABSTRACT FROM AUTHOR]

An on‐line sample preconcentration technique based on transient trapping (tr‐trapping) in micellar electrokinetic chromatography (MEKC) was applied for steroid detection with UV (tr‐trapping‐UV) and electrospray ionization mass spectrometry detection (tr‐trapping‐ESI‐MS). ESI‐MS was used to improve the sensitivity in MEKC. The MEKC separation was carried out using volatile ammonium formate as a background solution to facilitate the coupling with ESI‐MS. The partial introduction of a sodium dodecyl sulfate (SDS) micellar solution before the introduction of a sample solution to the capillary provided the effective preconcentration of analytes. At the same time, the SDS micelle would not enter the ESI‐MS system, so its interference in ESI‐MS detection was suppressed under the optimal condition, then five steroids can be separated by the developed method. In tr‐trapping‐ESI‐MS, an acidic condition of pH 3.5 was employed to suppress the electroosmotic flow, which can avoid micellar solution migrating to the MS instrument. The developed method showed that the micellar solution requires a twofold slower time than the sample to migrate along the column, which can prohibit the cause of the problem with the MS instrument and interference signal of SDS in the steroid's detection. The tr‐trapping‐ESI‐MS protocol showed up to 540‐fold enhancements of the peak intensity and 50‐fold improvement of the limit of detection compared with capillary zone electrophoresis using androsterone as a model sample. [ABSTRACT FROM AUTHOR]

The Tl+ corannulene complexes have been proven by ESI-MS method. The structure of these complexes have been determined by DFT calculations. [Display omitted] • Thallium (I) − corannulene complexes have been proved using the ESI-MS method. • The structures of resulting complexes have been determined applying quantum chemical DFT calculations. • The interaction energies of thallium (I) − corannulene complexes have been calculated. The interaction of Tl+ cation with corannulene was investigated by using electrospray ionization mass spectrometry (ESI-MS). It was found that the thallium cation Tl+ forms with corannulene (C 20 H 10) two cationic complexes [Tl(C 20 H 10)]+ and [Tl(C 20 H 10) 2 ]+. Quantum chemical calculations proceed by density functional theory with two different functionals (B3LYP and M06-D3) provided the most probable structures of these complexes. In the energetically most favored conformation of [Tl(C 20 H 10)]+ complex, the Tl+ cation lies on the apex of pyramid which base is formed by the central pentagon of the convexly oriented corannulene molecule. In the [Tl(C 20 H 10) 2 ]+ complex the "central" cation Tl+ is situated between two molecules of the corannulene ligand. Both ligand molecules are convex to the Tl+ cation. The interaction energies, E (int), of the considered cation-π complexes [Tl(C 20 H 10)]+ and [Tl(C 20 H 10) 2 ]+ were calculated to be −121.75 and −176.98 kJ/mol, respectively. [ABSTRACT FROM AUTHOR]

• Antamanide complexes with halide anions have been proven using the ESI-MS method. • The structures of these complexes have been determined applying quantum mechanical DFT calculations. • The interaction energies of the complexes of antamanide with halide anions have been calculated. Anionic complexes of antamanide with chloride, bromide and iodide anions have been proven by the electrospray ionization mass spectrometry (ESI-MS) method. Further, the most probable structures of these complexes were derived through the application of quantum mechanical DFT calculations. The chloride and bromide anions are embedded in the molecule of antamanide while the iodide one lies on the apex of the pyramid, the base of which is formed by the three hydrogen atoms of the antamanide ligand. The interaction energies of the antamanide halide anion complexes decrease in the order Cl− > Br− > I−. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A dinuclear Cu(II) complex with oxazolidine ligand and two Schiff base complexes with the same ligand were synthesized by "one-pot" method and characterized. The self-assembly process of these complexes were monitored by ESI-MS. • This is the first report of oxazolidine complex/ tetrabutylammonium halide co-catalyst in for the cycloaddition of CO 2 and epoxides reaction. • The catalytic explore for the cycloaddition of CO 2 and different reaction substrates and preliminary kinetic studies shows that the reaction is a intramolecular Lewis acid-base catalytic mechanism. Catalytic chemical fixation of carbon dioxide to high value-added chemicals has attracted extensive attention and the discovery of new catalytic system has always been a research hotspot in carbon dioxide chemistry. Three complexes were synthesized by using 2-quinoline formaldehyde and tris-base precursor through Schiff base reaction and characterized. Compound Co[L 1 ] 2 Cl 2 ·2H 2 O (1) and compound Ni[L 1 ] 2 Cl 2 ·2H 2 O (2) are two mononuclear complex with derived schiff base ligand (L 1 = 2-(hydroxymethyl)-2-((quinolin-2-ylmethylene)amino)propane-1,3-diol), while compound Cu 2 [L 2 ] 2 Cl 2 ∙2CH 3 OH (3) is a dinuclear complex containing derived deprontonated ligand (L 2 = (2-(quinolin-2-yl)oxazolidine-4,4-diyl)dimethanol) The self-assembly process of these complexes were monitored by ESI-MS. The catalytic explore for the cycloaddition of CO 2 and different reaction substrates and preliminary kinetic studies shows that all complexes are active and the reaction is an intramolecular Lewis acid-base catalytic mechanism. This is the first report of oxazolidine complex/ tetrabutylammonium halide catalyst in for cycloaddition of epoxides and CO 2 reaction and the complex 3 is more active than the other two complexes, which provides new notions for the design and solicitation of Schiff base/oxazolidine catalysts. [ABSTRACT FROM AUTHOR]