Showing papers on "Electrospray ionization published in 2019"
TL;DR: This review attempts to present various developed techniques for the determination of the composition of noble metal NCs by ESI-MS and introduces advanced applications that use it to further understand the reaction mechanism, complexation behavior, and structure of nobleMetal NCs.
Abstract: Electrospray ionization mass spectrometry (ESI-MS) is an analytical technique that measures the mass of a sample through "soft" ionization. Recent years have witnessed a rapid growth of its application in noble-metal nanocluster (NC) analysis. ESI-MS is able to provide the mass of a noble-metal NC analyte for the analysis of their composition (n, m, q values in a general formula [Mn Lm ]q ), which is crucial in understanding their properties. This review attempts to present various developed techniques for the determination of the composition of noble metal NCs by ESI-MS. Additionally, advanced applications that use ESI-MS to further understand the reaction mechanism, complexation behavior, and structure of noble metal NCs are introduced. From the comprehensive applications of ESI-MS on noble-metal NCs, more possibilities in nanochemistry can be opened up by this powerful technique.
110 citations
TL;DR: In this review, the recent advances in single-cell analysis by mass spectrometry are summarized and the strategies of different ionization modes to achieve single- cell analysis are classified and discussed in detail.
Abstract: Cells are the most basic structural units that play vital roles in the functioning of living organisms. Analysis of the chemical composition and content of a single cell plays a vital role in ensuring precise investigations of cellular metabolism, and is a crucial aspect of lipidomic and proteomic studies. In addition, structural knowledge provides a better understanding of cell behavior as well as the cellular and subcellular mechanisms. However, single-cell analysis can be very challenging due to the very small size of each cell as well as the large variety and extremely low concentrations of substances found in individual cells. On account of its high sensitivity and selectivity, mass spectrometry holds great promise as an effective technique for single-cell analysis. Numerous mass spectrometric techniques have been developed to elucidate the molecular profiles at the cellular level, including electrospray ionization mass spectrometry (ESI-MS), secondary ion mass spectrometry (SIMS), laser-based mass spectrometry and inductively coupled plasma mass spectrometry (ICP-MS). In this review, the recent advances in single-cell analysis by mass spectrometry are summarized. The strategies of different ionization modes to achieve single-cell analysis are classified and discussed in detail.
88 citations
TL;DR: Improved spectral resolution was obtained using narrow-bore emitters and an analytically derived equation, and Kd values were simultaneously obtained for at least six ligands to a single druggable protein target from one spectrum for the first time.
Abstract: Electrospray ionization (ESI) mass spectrometry (MS) is a crucial method for rapidly determining the interactions between small molecules and proteins with ultrahigh sensitivity. However, nonvolatile molecules and salts that are often necessary to stabilize the native structures of protein–ligand complexes can readily adduct to protein ions, broaden spectral peaks, and lower signal-to-noise ratios in native MS. ESI emitters with narrow tip diameters (∼250 nm) were used to significantly reduce the extent of adduction of salt and nonvolatile molecules to protein complexes to more accurately measure ligand–protein binding constants than by use of conventional larger-bore emitters under these conditions. As a result of decreased salt adduction, peaks corresponding to protein–ligand complexes that differ in relative molecular weight by as low as 0.06% can be readily resolved. For low-molecular-weight anion ligands formed from sodium salts, anion-bound and unbound protein ions that differ in relative mass by 0....
73 citations
TL;DR: Method validation demonstrated that FIA-ESI-HRMS (MSX and FTMS) is applicable for quantification of FC and CE in samples used in basic science as well as clinical studies such as cultured cells, tissue homogenates, and serum.
Abstract: The quantification of free cholesterol (FC) and cholesteryl ester (CE) in mammalian samples is of great interest for basic science and clinical lipidomics. Here, we evaluated the feasibility of direct flow injection analysis (FIA) coupled to electrospray ionization high-resolution mass spectrometry (ESI-HRMS) to quantify FC and CE in lipid extracts from human serum, cultured cells, and mouse liver. Despite poor ionization efficiency of FC, the limit of quantitation was sufficient for precise and accurate quantification of FC by multiplexed HRMS (MSX) analysis without using a derivatization step. However, it was demonstrated that, upon full scan Fourier transform MS (FTMS) quantification, CE species show substantial differences in their analytical responses depending on number of double bonds, length of the acyl chain, infused lipid concentration, and other lipid components. A major determinant for these response differences is their susceptibility to in-source fragmentation. In particular, introduction of double bonds lowers the degree of in-source fragmentation. Therefore, CE species-specific response factors need to be applied for CE quantification by FTMS to achieve accurate concentrations. Method validation demonstrated that FIA-ESI-HRMS (MSX and FTMS) is applicable for quantification of FC and CE in samples used in basic science as well as clinical studies such as cultured cells, tissue homogenates, and serum.
70 citations
TL;DR: The short analysis time and 96-well plate format of the assay makes it suitable for high-throughput targeted UHPLC-ESI-MS/MS metabolomic analysis in large-scale clinical and epidemiological population studies.
Abstract: A targeted ultrahigh-performance liquid chromatography tandem mass spectrometry with electrospray ionization (UHPLC-ESI-MS/MS) method has been developed for the quantification of tryptophan and its downstream metabolites from the kynurenine and serotonin pathways. The assay coverage also includes markers of gut health and inflammation, including citrulline and neopterin. The method was designed in 96-well plate format for application in multiday, multiplate clinical and epidemiology population studies. A chromatographic cycle time of 7 min enables the analysis of two 96-well plates in 24 h. To protect chromatographic column lifespan, samples underwent a two-step extraction, using solvent protein precipitation followed by delipidation via solid-phase extraction (SPE). Analytical validation reported accuracy of each analyte <20% for the lowest limit of quantification and <15% for all other quality control (QC) levels. The analytical precision for each analyte was 2.1-12.9%. To test the applicability of the method to multiplate and multiday preparations, a serum pool underwent periodic repeat analysis during a run consisting of 18 plates. The % CV (coefficient of variation) values obtained for each analyte were <15%. Additional biological testing applied the assay to samples collected from healthy control participants and two groups diagnosed with inflammatory bowel disease (IBD) (one group treated with the anti-inflammatory 5-aminosalicylic acid (5-ASA) and one group untreated), with results showing significant differences in the concentrations of picolinic acid, kynurenine, and xanthurenic acid. The short analysis time and 96-well plate format of the assay makes it suitable for high-throughput targeted UHPLC-ESI-MS/MS metabolomic analysis in large-scale clinical and epidemiological population studies.
67 citations
TL;DR: The fragmentation patterns of 19 AAs were examined using high-resolution electrospray ionization MS/MS (HR-ESI-MS/MS) with collision-induced dissociation (CID) to resolve and identify Isobaric fragmentation products from protonated Met and Trp for the first time.
Abstract: Fragmentation reactions of protonated α-amino acids (AAs) were studied previously using tandem mass spectrometry (MS/MS) of unit mass resolution. Isobaric fragmentation products and minor fragmentation products could have been overlooked or misannotated. In the present study, we examined the fragmentation patterns of 19 AAs using high-resolution electrospray ionization MS/MS (HR-ESI-MS/MS) with collision-induced dissociation (CID). Isobaric fragmentation products from protonated Met and Trp were resolved and identified for the first time. Previously unreported fragmentation products from protonated Met, Cys, Gln, Arg, and Lys were observed. Additionally, the chemical identity of a fragmentation product from protonated Trp that was incorrectly annotated in previous investigations was corrected. All previously unreported fragmentation products and reactions were verified by pseudo MS3 experiments and/or MS/MS analyses of deuterated AAs. Clearer pictures of the fragmentation reactions for Met, Cys, Trp, Gln, Arg and Lys were obtained in the present study.
58 citations
TL;DR: H3L displayed high selectivity and sensitivity for detecting Cr3+, Cu2+, Fe3+ and Al3+ ions in DMF/H2O (v/v = 1/1) solution and the bonding modes and bonding ratios of H3L and metal ions were explored.
54 citations
TL;DR: It is suggested that organic molecules with a high modified aromaticity index, low O/C ratio, and low polarity showed stronger light absorption and that the contribution of CHON may be stronger.
Abstract: Water-soluble organic compounds (WSOC) and methanol-soluble organic compounds (MSOC) in smoke particles emitted from residential coal combustion were characterized by ultrahigh-resolution mass spec...
53 citations
TL;DR: Among the fifty compounds identified, non‐phenol metabolites, such as benzyl primeveroside and roseoside, as well as a lignan polyphenol (5′), are reported for the first time as constituents of the Stevia leaf.
52 citations
TL;DR: It is demonstrated that MALDI-2 increased the signal intensities for 7 out of the 10 drug compounds analyzed by up to 2 orders of magnitude compared to conventional MalDI analysis, enabling the distributions of drug compounds in both human cartilage and dog liver tissue to be visualized using MAL DI-2, whereas little-to-no signal was obtained using conventional MAlDI.
Abstract: Visualizing the distributions of drugs and their metabolites is one of the key emerging application areas of matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) within pharmaceutical research. The success of a given MALDI-MSI experiment is ultimately determined by the ionization efficiency of the compounds of interest, which in many cases are too low to enable detection at relevant concentrations. In this work we have taken steps to address this challenge via the first application of laser-postionisation coupled with MALDI (so-called MALDI-2) to the analysis and imaging of pharmaceutical compounds. We demonstrate that MALDI-2 increased the signal intensities for 7 out of the 10 drug compounds analyzed by up to 2 orders of magnitude compared to conventional MALDI analysis. This gain in sensitivity enabled the distributions of drug compounds in both human cartilage and dog liver tissue to be visualized using MALDI-2, whereas little-to-no signal from tissue was obtained using conventional MALDI. This work demonstrates the vast potential of MALDI-2-MSI in pharmaceutical research and drug development and provides a valuable tool to broaden the application areas of MSI. Finally, in an effort to understand the ionization mechanism, we provide the first evidence that the preferential formation of [M + H]+ ions with MALDI-2 has no obvious correlation with the gas-phase proton affinity values of the analyte molecules, suggesting, as with MALDI, the occurrence of complex and yet to be elucidated ionization phenomena.
52 citations
TL;DR: Overall, this study supports the view that solution-like protein structures can be retained because of kinetic trapping on the time scale of typical ESI-IMS experiments.
Abstract: Experiments and molecular dynamics (MD) simulations in the literature indicate that gaseous proteins generated by electrospray ionization (ESI) can retain native-like structures. However, the exact...
TL;DR: In this article, the authors summarized the progress of chemical derivatization-assisted liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) methods in the period of 2014-2018.
Abstract: Chemical derivatization-based liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) technique is an effective analytical tool for trace small-molecular weight compounds analysis present in complex samples. Chemical derivatization technique can improve the detection sensitivity, selectivity, chromatographic separation and identification capability of LC-ESI-MS analysis. In this review, we summarized the progress of chemical derivatization-assisted LC-MS methods in the period of 2014–2018, according to the functional groups of analytes, such as carboxyls, amines, carbonyls, thiols, hydroxyls, phosphates, modified nucleic acids, conjugated dienes and carbon-carbon double bonds. We mainly focused on the reaction principles of representative derivatization reagents with some application cases highlighting the impact of chemical derivatization-assisted LC-MS technique, which would be helpful for the designing and synthesis of new derivatization reagents for the analysis of small-molecular weight compounds in complex samples.
TL;DR: This review summarizes the most important features of tandem mass spectra generated by collision-induced dissociation fragmentation and presents didactic examples for the unexperienced users.
Abstract: Tandem mass spectrometry is an important tool for structure elucidation of natural and synthetic organic products. Fragmentation of odd electron ions (OE⁺) generated by electron ionization (EI) was extensively studied in the last few decades, however there are only a few systematic reviews available concerning the fragmentation of even-electron ions (EE⁺/EE-) produced by the currently most common ionization techniques, electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). This review summarizes the most important features of tandem mass spectra generated by collision-induced dissociation fragmentation and presents didactic examples for the unexperienced users.
TL;DR: Electrospray ionization (ESI) combined with ion mobility spectrometry (IMS) and mass spectromaetry (MS) techniques is used to examine the Biginelli reaction in an ensemble of ions generated from droplets.
Abstract: Electrospray ionization (ESI) combined with ion mobility spectrometry (IMS) and mass spectrometry (MS) techniques is used to examine the Biginelli reaction in an ensemble of ions generated from droplets. We find evidence for rapid dihydropyrimidinone formation from condensation of ethyl acetoacetate, benzaldehyde, and urea on the very short timescales associated with the electrospray process (∼10 μs to ∼1.0 ms). Control bulk-solution reactions show no product formation even after several days. This implies that the in-droplet reaction rate is enhanced by an astonishing factor. Examination of the reaction conditions and characterization of the intermediates en route to product shows evidence for variations in the reaction mechanism. IMS separation shows that the Knoevenagel condensation intermediate from benzaldehyde and ethyl acetoacetate exists as both the cis- and trans-isomer, in a ∼5 to 1 ratio. We suggest that the dramatic acceleration arises because of increased reagent confinement as electrosprayed droplets shrink. The ability of IMS-MS to resolve intermediates (including isomers) provides a new means of understanding reaction pathways.
TL;DR: Recent computational and experimental studies that have shed light on many of the mysteries in ESI have been discussed, and it appears that the framework outlined here covers most of the experimentally relevant conditions.
Abstract: Electrospray ionization (ESI) is an essential technique for transferring proteins from solution into the gas phase for mass spectrometry and ion mobility spectrometry. The mechanisms whereby [M + zH]z+ protein ions are released from charged nanodroplets during ESI have been controversial for many years. Here we discuss recent computational and experimental studies that have shed light on many of the mysteries in this area. Four types of protein ESI experiments can be distinguished, each of which appears to be associated with a specific mechanism. (i) Native ESI proceeds according to the charged residue model (CRM) that entails droplet evaporation to dryness, generating compact protein ions in low charge states. (ii) Native ESI supercharging is also a CRM process, but the dried-out proteins accumulate additional charge because supercharging agents such as sulfolane interfere with the ejection of small ions (Na+, NH4+, etc.) from the shrinking droplets. (iii) Denaturing ESI follows the chain ejection model (CEM), where protein ions are gradually expelled from the droplet surface. H+ equilibration between the droplets and the protruding chains culminates in highly charged gaseous proteins, analogous to the collision-induced dissociation of multi-protein complexes. (iv) Denatured ESI supercharging also generates protein ions via the CEM. Supercharging agents stabilize protonated sites on the protein tail via charge–dipole interactions, causing the chain to acquire additional charge. There will likely be scenarios that fall outside of these four models, but it appears that the framework outlined here covers most of the experimentally relevant conditions.
TL;DR: An assessment of non-separative methods based on mass spectrometry used to analyse volatile organic compounds in the field of bioanalysis is performed and can be considered a key issue for future clinical applications, as they allow real-time sample analysis, without patient suffering.
TL;DR: The results show that small emitter tips are advantageous in native mass spectrometry by eliminating effects of thermal destabilization of proteins in droplets inside of themass spectrometer, eliminating the effects of non-specific protein dimerization and aggregation that can occur in larger droplets that contain more than one protein molecule, and significantly reducing salt adduction.
Abstract: The location of gaseous ion formation in electrospray ionization under native mass spectrometry conditions was investigated using theta emitters with tip diameters between 317 nm and 4.4 μm to produce droplets with lifetimes between 1 and 50 μs. Mass spectra of β-lactoglobulin do not depend on instrument source temperatures between 160 and 300 °C with the smallest tips. A high charge-state distribution is observed for larger tips that produce droplets with lifetimes ≥10 μs and this distribution increases at higher source temperatures. These and other results show that gaseous protein ions originating from the smallest droplets are formed outside of the mass spectrometer whereas the majority of protein ions formed from the larger droplets are formed inside of the mass spectrometer where thermal heating of the droplet and concomitant protein unfolding inside of the droplet occurs. These results show that small emitter tips are advantageous in native mass spectrometry by eliminating effects of thermal destabilization of proteins in droplets inside of the mass spectrometer, eliminating the effects of non-specific protein dimerization and aggregation that can occur in larger droplets that contain more than one protein molecule, and significantly reducing salt adduction.
TL;DR: Three approaches to combat issues for direct "dilute and shoot" mass spectral analysis of petroleum samples are described, each of which relies on chromatographic fractionation to help reduce selective ionization discrimination and target either specific chemical functionalities or specific structural motifs known to be related to ionization efficiency.
Abstract: Direct "dilute and shoot" mass spectral analysis of complex naturally-occurring mixtures has become the "standard" analysis in environmental and petrochemical science, as well as in many other areas of research. Despite recent advances in ionization methods, that approach still suffers several limitations for the comprehensive characterization of compositionally complex matrices. Foremost, the selective ionization of highly acidic (negative electrospray ionization ((-) ESI)) and/or basic (positive electrospray ionization ((+) ESI)) species limits the detection of weakly acidic/basic species, and similar issues (matrix effects) complicate atmospheric pressure photo-ionization (APPI)/atmospheric pressure chemical ionization (APCI) analyses. Furthermore, given the wide range of chemical functionalities and structural motifs in these compositionally complex mixtures, aggregation can similarly limit the observed species to a small (10-20%) mass fraction of the whole sample. Finally, irrespective of the ionization method, the mass analyzer must be capable of resolving tens-of-thousands of mass spectral peaks and provide the mass accuracy (typically 50-300 ppb mass measurement error) required for elemental composition assignment, and thus is generally limited to high-field Fourier transform ion cyclotron mass spectrometry (FT-ICR MS). Here, we describe three approaches to combat the above issues for (+) ESI, (-) ESI, and (+) APPI FT-ICR MS analysis of petroleum samples. Each approach relies on chromatographic fractionation to help reduce selective ionization discrimination and target either specific chemical functionalities (pyridinic and pyrrolic species (nitrogen) or carboxylic acids (oxygen)) or specific structural motifs (single aromatic core (island) or multi-core aromatics (archipelago)) known to be related to ionization efficiency. Each fractionation method yields a 2-10-fold increase in the compositional coverage, exposes species that are undetectable using direct "dilute and shoot" analysis, and provides coarse selectivity in chemical functionalities that can both increase the assignment confidence and optimize ionization conditions to maximize compositional coverage.
TL;DR: The presented methodology provided mutual separation of various AAs, allowing chiral analysis of multiple AAs simultaneously which may be challenging with previous enantioselective IMS approaches, opening up possibilities for easy and fast analysis of AA enantiomers.
Abstract: A novel analytical method based on hybrid trapped ion mobility spectrometry-time-of-flight mass spectrometry (TIMS-TOFMS) has been developed to achieve fast enantiomeric separation of amino acids (AAs). Resolution of chiral AAs was achieved by forming diastereomers through derivatization with the chiral agent (+)-1-(9-fluorenyl)ethyl chloroformate (FLEC), avoiding the use of reference compounds. Electrospray ionization (ESI) in positive mode yielded sodiated FLEC-AAs ions of which the diastereomers could be separated by TIMS. The effect of other alkali metal ions (such as Li and K) on the enantioselectivity was studied, but chiral discrimination was only observed for Na. TIMS conditions, including voltage ramp, ramp time, and accumulation time were optimized for each AA, and collision cross sections (CCSs) were determined for all diastereomers. The migration order of the DL enantiomers was found to be dependent on the structure of the AA. The resulting TIMS resolution (K0/ΔK0) for the FLEC-AA diastereomer...
TL;DR: The observation of taurine and theanine suggests that the method should be generally applicable to other native amino acids than the proteinogenic amino acids selected for the development of this method.
Abstract: In this project, we aimed at analyzing native (or free) amino acids with supercritical fluid chromatography coupled to mass spectrometric detection, with modern instruments and methods, and maintaining as simple a mobile phase as possible to ensure applicability of the method. The purpose was twofold: (i) a generic method allowing for satisfactory elution of a wide range of amino acids (acidic, basic, or neutral residue) and (ii) resolution of the enantiomeric pairs. The Chiralpak ZWIX (+) and (−) stationary phases were selected as they are well-known for the enantioresolution of amino acids in liquid chromatographic modes. A wide range elution gradient, starting with a large concentration of carbon dioxide (90%) and finishing at 100% solvent (methanol containing 70 mM ammonium formate and 7% water) allowed the elution of 18 native proteinogenic amino acids out of 19 injected. In these conditions, enantioselectivity was achieved for 16 of them. The basic amino acids (arginine, histidine, and lysine) were the most difficult to elute in these conditions, resulting in rather poor peak shapes. Cysteine was never observed in any of the conditions tested. Sample application was attempted with two food supplements, tablets containing a mixture of 17 proteinogenic amino acids and capsules containing taurine and theanine that were not present in the standards used for the method development. The sample preparation method was very simple, involving dissolution of the tablets and capsules in acidified water, filtration, and dilution with methanol. Mass spectrometric detection (electrospray ionization with single-quadrupole mass detection) allowed for unambiguous identification of most amino acids, except for the leucine and isoleucine isomers that were not separated by the generic gradient. The observation of taurine and theanine also suggests that the method should be generally applicable to other native amino acids than the proteinogenic amino acids selected for the development of this method. As peak shapes and signal-to-noise ratios could still be improved, further developments are wanted to upgrade this method. Due to the wide gradient (10 to 100% co-solvent in carbon dioxide), the method cannot truly be called either supercritical fluid chromatography (SFC) or enhanced-fluidity liquid chromatography (EFLC), but should be related to “unified chromatography” (UC), joining SFC and HPLC.
TL;DR: Results demonstrated that no significant changes of total FAs and TAGs contents were observed after microwave pretreatment, while FFA contents increased and PLs contents significantly increased up to 40 folds.
TL;DR: The results of the phytochemical characterization obtained herein demonstrates the great potential of applying integrated identification strategies to HRMS data obtained from complementary LC- and GC-q-TOF-MS(/MS) platforms, as powerful identification tools for improving the authors' understanding on thePhytochemical composition of natural extracts intended to be used in functional foods or in traditional medicine preparations.
TL;DR: In this article, two benzimidazole/benzothiazole based azomethines, (E)-2-(1H-benzo[d]imidaxol-2-yl)-4-(4-(diethylamino)-2-hydroxybenzylideneamino)phenol (HBZA) and (E)−2-(benzo [d]thiazol- 2-yl)
Abstract: Two benzimidazole/benzothiazole based azomethines, (E)-2-(1H-benzo[d]imidazol-2-yl)-4-(4-(diethylamino)-2-hydroxybenzylideneamino)phenol (HBZA) and (E)–2-(benzo[d]thiazol–2-yl)–4-(4-(diethylamino)–2-hydroxybenzylideneamino)phenol (HBTA) were designed and synthesised. Investigations of solvatochromic behaviour of these fluorophores in solvents of varying polarities showed large Stokes shift of 134–210 nm. Time resolved Laser induced fluorescence measurements revealed the excited state dynamics of the fluorophores. Molecules were also found to be emissive in aggregated state as seen from the aggregation induced emission studies. Appreciable absorption and emission spectral changes upon co-ordination of HBZA with Al3+/Zn2+ and HBTA with Al3+, as well as good sensitivity and selectivity, indicated their capability of detecting the two analytes. The binding stoichiometry was determined using electrospray ionization mass spectrometry (ESI-MS) and the binding mechanism was studied using density functional theory.
TL;DR: The optimization and validation of a highly selective and sensitive analytical method using solid phase extraction and liquid chromatography tandem mass spectrometry (SPE LC-MS/MS) for the determination of some frequently prescribed pharmaceuticals in urban wastewater received and treated by Sharjah sewage treatment plant (STP).
Abstract: The present work describes the optimization and validation of a highly selective and sensitive analytical method using solid phase extraction and liquid chromatography tandem mass spectrometry (SPE LC-MS/MS) for the determination of some frequently prescribed pharmaceuticals in urban wastewater received and treated by Sharjah sewage treatment plant (STP). The extraction efficiency of different SPE cartridges was tested and the simultaneous extraction of pharmaceuticals was successfully accomplished using hydrophilic-lipophilic-balanced reversed phase Waters® Oasis HLB cartridge (200 mg/ 6 mL) at pH 3. The analytes were separated on an Aquity BEH C18 column (1.7 µm, 2.1 mm × 150 mm) using gradient elution and mass spectrometric analysis were performed in multiple reactions monitoring (MRM) selecting two precursor ions to produce ion transition for each pharmaceutical using positive electrospray ionization (+ESI) mode. The correlation coefficient values in the linear calibration plot for each target compound exceeded 0.99 and the recovery percentages of the investigated pharmaceuticals were more than 84%. Limit of detection (LOD) varied between 0.1–1.5 ng/L and limit of quantification (LOQ) was 0.3–5 ng/L for all analytes. The precision of the method was calculated as the relative standard deviation (RSD%) of replicate measurements and was found to be in the ranges of 2.2% to 7.7% and 2.2% to 8.6% for inter and intra-day analysis, respectively. All of the obtained validation parameters satisfied the requirements and guidelines of analytical method validation.
TL;DR: Imidazole-modified G-quadruplex DNA binds transition metals Cu, Zn, Ni, Ni and Co and generates a stimuli-responsive peroxidase mimic.
Abstract: Four imidazoles, serving as metalloprotein-inspired ligands for complexing a range of transition metal cations, were incorporated into tetramolecular G-quadruplex DNA structures. Modified quadruplexes were found to complex Cu(II), Ni(II), Zn(II) and Co(II) in a 1 : 1 ratio with unprecedented strong thermal stabilizations of up to ΔT1/2 = +51 °C. Furthermore, addition of Cu(II) was found to lead to extraordinarily fast G-quadruplex association rates with kon values being ∼100 times higher compared to unmodified G-quadruplexes. This is ascribed to a template effect of Cu(II), preorganizing the four single strands via coordination, followed by rapid formation of hydrogen-bonded G-quartets. Native electrospray ionization mass spectrometry (ESI), coupled with trapped ion-mobility spectrometry (timsTOF), supports the proposed 1 : 1 G-quadruplex-metal complexes and could further disclose their ability to bind the iron–porphyrin complex hemin in a 1 : 1 stoichiometry. DNA sequence design allowed us to equip this G-quadruplex-hemin complex, known to function as a horseradish peroxidase mimic, with a metal-dependent trigger. A competitive screen of transition metals revealed a high selectivity for Cu(II), even in mixtures of several divalent metal cations. Once formed, the Cu(II)-carrying DNAzyme was shown to be preserved in the presence of EDTA, attributed to its remarkable kinetic stability. Stimuli-responsive G-quadruplexes promise application in DNAzymes with switchable activity, adaptive sensors and dynamic DNA origami constructs.
TL;DR: Overall, particle organics composition is far more complex than previously shown, while separation through better chromatographic techniques helps to understand formation processes of atmospheric particle constituents.
Abstract: A 2D-liquid chromatographic fractionation method was combined with direct infusion electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry to better resolve the high com...
TL;DR: The results herein presented demonstrated that the direct coupling of SPME fibers with ESI-MS-based systems allowed for the simple and ultra-sensitive determination of analytes from raw samples such as human urine.
TL;DR: YGIYPR as mentioned in this paper was identified as Tyr-Gly-Ile-Tyr-Pro-Arg by high-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometer.
Abstract: To prepare immunomodulation peptides from rice protein hydrolysates (RPHs), trypsin was employed for enzymatic hydrolysis, and the immunomodulating activities of RPHs were studied using mouse peritoneal macrophage proliferation assay. The peptide fractions with the highest activity were further purified using macroporous adsorption resin, strong cation-exchange chromatography, gel filtration chromatography and reversed-phase high-performance liquid chromatography. The peptide sequence was identified as Tyr-Gly-Ile-Tyr-Pro-Arg (YGIYPR) by high-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometer. Evaluating its immunomodulatory activity showed that YGIYPR enhanced the proliferation of macrophage RAW 264.7 cells in the range of 12.5–100 μg/mL, and even a minimum dose achieved good proliferation. The results demonstrated that the RPHs prepared by trypsin could serve as a source of immunomodulating peptides and the immunomodulatory peptide YGIYPR is a p...
TL;DR: Characterization of each sequence-defined chain (size-exclusion chromatography (SEC), high-resolution electrospray ionization mass spectrometry (ESI-MS), and NMR spectroscopy), confirms the precision nature of the macromolecules.
Abstract: An advanced light-induced avenue to monodisperse sequence-defined linear macromolecules via a unique photochemical protocol is presented that does not require any protection-group chemistry. Starting from a symmetrical core unit, precision macromolecules with molecular weights up to 6257.10 g mol−1 are obtained via a two-monomer system: a monomer unit carrying a pyrene functionalized visible light responsive tetrazole and a photo-caged UV responsive diene, enabling an iterative approach for chain growth; and a monomer unit equipped with a carboxylic acid and a fumarate. Both light-induced chain growth reactions are carried out in a λ-orthogonal fashion, exciting the respective photosensitive group selectively and thus avoiding protecting chemistry. Characterization of each sequence-defined chain (size-exclusion chromatography (SEC), high-resolution electrospray ionization mass spectrometry (ESI-MS), and NMR spectroscopy), confirms the precision nature of the macromolecules.
TL;DR: Investigation on the marine-sourced fungus Penicillium sp.
Abstract: The marine-sourced fungus Penicillium sp. ZZ380 was previously reported to have the ability to produce a series of new pyrrospirone alkaloids. Further investigation on this strain resulted in the isolation and identification of novel penicipyrroether A and pyrrospirone J. Each of them represents the first example of its structural type, with a unique 6/5/6/5 polycyclic fusion that is different from the 6/5/6/6 fused ring system for the reported pyrrospirones. Their structures were elucidated by extensive nuclear magnetic resonance (NMR) and high resolution electrospray ionization mass spectroscopy (HRESIMS) spectroscopic analyses, electronic circular dichroism (ECD) and 13C NMR calculations and X-ray single crystal diffraction. Penicipyrroether A showed potent antiproliferative activity against human glioma U87MG and U251 cells with half maximal inhibitory concentration (IC50) values of 1.64–5.50 μM and antibacterial inhibitory activity with minimum inhibitory concentration (MIC) values of 1.7 μg/mL against methicillin-resistant Staphylococcus aureus and 3.0 μg/mL against Escherichia coli.