Electrospray Research Articles

REVIEW ON SIZE EXCLUSION CHROMATOGRAPHY COUPLED WITH MASS SPECTROSCOPY

The hyphenated technique was created by integrating the differentiating technique with directly spectroscopic technology to facilitate detection. It is discussed how SEC and electrospray ionization mass spectrometry (ESI-MS) can be combined, emphasizing the advantages this has for characterizing polymers. The capacity of SEC-ESI-MS to gather polymer structural information as well as to confirm polymer homologous transitions is first described. It's significant that the broad applicability of SEC-ESI-MS is underlined, for instance by its usage in the analysis of precise molecular weight distribution of polymers, the calculation of radical rate of polymerization coefficients, and the thorough exploration of radical photoinitiation systems. Thus, this momentous tutorial review intends to highlight the high potential of SEC-ESI-MS to emerge as a formidable and well-liked analytical method in polymer chemistry and to illustrate the capability of SEC-ESI-MS for the analysis of complicated polymers. The article addresses recent advancements in the uses of a variety of hyphenated techniques, such as the GC-MS method, LC-MS analysis, LC-FTIR, LC-NMR, CE-MS, and others.

Altering Lipid A Precursor Ion Types in the Gas Phase for In-Depth Structural Elucidation via Tandem Mass Spectrometry.

Lipid A, a well-known saccharolipid, acts as the inner lipid-glycan anchor of lipopolysaccharides in Gram-negative bacterial cell membranes and functions as an endotoxin. Its structure is composed of two glucosamines with β(1 → 6) linkages and various fatty acyl and phosphate groups. The lipid A structure can be used for the identification of bacterial species, but its complexity poses significant structural characterization challenges. In this work, we present a comprehensive strategy combining condensed-phase sample preparation, electrospray ionization, and gas-phase ion/ion reactions with tandem mass spectrometry for detailed lipid A structural elucidation. We use proton transfer reactions, charge-inversion reactions, and sequential ion/ion reactions for magnesium transfer to generate targeted lipid A ions. The strategy, established with a synthetic monophosphoryl lipid A (MPLA) and known MPLA and diphosphorylated lipid A (DPLA) from Escherichia coli F583, demonstrated that [MPLA - 2H]2-, [MPLA - H]-, and [MPLA - H + Mg]+ precursor ions offer complementary information for MPLA, while [DPLA - H]-, [DPLA + H]+, and [DPLA - H + Mg]+ precursor ions provide analogous information for DPLA analysis. We validated the strategy using known lipid A species and also successfully applied this strategy to profile unknown MPLA and DPLA in the same E. coli strain.

Chemical Diversity of UK-Grown Tea Explored Using Metabolomics and Machine Learning

Background/Objectives: Dartmoor Estate Tea plantation in Devon, UK, is renowned for its unique microclimate and varied soil conditions, which contribute to the distinctive flavours and chemical profiles of tea. The chemical diversity of fresh leaf samples from various garden locations was explored within the plantation. Methods: Fresh leaf, which differed by location, cultivar, time of day, and variety, was analysed using Flow Infusion Electrospray Ionisation Mass Spectrometry (FIE-MS). Results: Random forest classification revealed no significant differences between Georgian N2 cultivar garden locations. However, a significant degree of variability was observed within four tri-clonal variants (Tocklai Variety) with TV9 exhibiting greater similarity to the Georgian N2 cultivar compared to TV8 and TV11, while TV11 was found to be most like TV1. The intraclass variability in leaf composition was similar between the varieties. We explored the metabolic changes over the day in one variant (Camellia assamica Masters), yielding a model with a significant R2 value of 0.617 (p < 0.01, 3000 permutations). Starch and sucrose metabolism was found to be significant where the abundance of these chemical features increased throughout the day and then began to decrease at night. Conclusions: This research highlights the complex interplay of cultivars, geographical location, and temporal factors on the chemical composition of tea. It provides insightful data on the metabolic pathways influencing tea cultivation and production and underscores the importance of these variables in determining the final chemical profile and organoleptic characteristics of tea products.

Isolation and Identification of Mercury-Dissolved Organic Matter Complexes in Mercury-Humic Acid Suspensions.

The complexation with dissolved organic matter (DOM) is a pivotal factor influencing transformations, transport, and bioavailability of mercury (Hg) in aquatic environments. However, identifying these complexes poses a significant challenge because of their low concentrations and the presence of coexisting ions. In this study, mercury-dissolved organic matter (Hg-DOM) complexes were isolated through solid-phase extraction (SPE) from Hg-humic acid suspensions, and complexes were putatively identified using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Dissolved organic carbon (DOC) and total Hg analysis before and after SPE showed an increase in DOC:Hg ratio. The DOC:Hg ratio was lower in extracts from cartridges with silica structure bonded with hydrocarbon chains (C18) than priority pollutant (PPL) cartridges at circumneutral pH, indicating that C18 was more effective at extracting DOM complexed Hg. These results were confirmed with FTICR-MS analysis, where two Hg-DOM complexes were putatively identified from PPL extracts as opposed to eight from C18 (Winnow score > 75%). In addition, C8H13HgN2O2S, a molecular formula with a m/z ratio of 403.04, was identified across three separate extractions using a C18 cartridge, suggesting that the complexes were preserved during extraction and, presumably, electrospray ionization. The results highlight the effectiveness of the methodology developed in this study-SPE coupled with FTICR-MS for isolating and identifying Hg-DOM complexes. This approach allows for the exploration of the elemental and structural composition of Hg-DOM complexes, which affects Hg speciation, bioavailability, and transformations in aquatic ecosystems. A methodology was developed to identify Hg-DOM complexes at low concentrations to gain insight into mercury bioavailability, transformations, and transport in the environment.

Method Validation for Estimation of Imidacloprid and its Metabolites in Maize and Soil by LCMS-MS.

Validation of Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method was performed for estimation of imidacloprid (IM) and its metabolites in maize leaves, immature kernels, mature kernels, stalk, and soil using liquid chromatograph tandem mass spectrometry, coupled with electrospray ionization. The extraction in different matrices of maize and soil was performed using acetonitrile +0.1% formic acid followed by clean-up with primary secondary amine sorbent and anhydrous magnesium sulfate. The method was validated in terms of selectivity, linearity, limit of detection, limit of quantification, matrix effect, ion ratios, quality control, robustness, accuracy, and precision. The validation of all parameters was done in accordance with European Commission's Directorate-General for Health and Food Safety (DG SANTE) guidelines. A linear relationship with high correlation coefficients R2 > 0.99 was obtained for solvents and different matrices viz., maize leaves, immature kernels, mature kernels, stalk, and soil. The recovery and relative standard deviations were ˃78% and ˂5.4%, respectively. This method permits a simple, sensitive, accurate, cost-effective, precise, and rapid extraction of IM and its metabolites from maize leaves, immature kernels, mature kernels, stalks, and soil. This can help the residue analysts to address effective residue estimation, regular monitoring of residues and can also aid in the regulatory and food safety concerns about the usage of IM in maize.

Feasibility of IR-MALDESI Mass Spectrometry Imaging of PFAS.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a class of emerging contaminants that have been in use industrially since the 1940s. Their long-term and extensive commercial use has led to their ubiquitous presence in the environment. The ability to measure the bioconcentration and distribution of PFAS in the tissue of aquatic organisms helps elucidate the persistence of PFAS as well as environmental impacts. Traditional analysis by LC-MS/MS can measure total PFAS concentrations within an organism but cannot provide comprehensive spatial information regarding PFAS concentrations within the organism. In the current study, we used infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) to determine the limit of detection (LOD) of several PFAS utilizing a commercial standard mix spotted on mouse liver tissue. The traditional ice matrix and an alternative matrix, 1,8-bis (tetramethylguanidino)naphthalene (TMGN), were explored when determining the limits of detection for various PFAS by IR-MALDESI. The ice matrix alone resulted in a higher response than the combination of TMGN and ice. The resulting LOD for perfluorooctane sulfonic acid (PFOS) on a per voxel basis was 0.16 fmol/voxel. For comparison, zebrafish that were exposed to perfluorooctanoic acid (PFOA), PFOS, and perfluorohexanesulfonic acid (PFHxS) at different concentrations were homogenized, and PFAS were extracted by solid-liquid extraction, purified by solid phase extraction, and analyzed by LC-MS/MS to determine the level of bioaccumulation in the zebrafish. PFOS resulted in the highest level of bioaccumulation (731.9 μg/kg, or 234.2 fg/voxel). A zebrafish that had been exposed to a PFAS mixture of PFOA (250 ng/L), PFOS (250 ng/L), and PFHxS (125 ng/L) was cryosectioned and analyzed by IR-MALDESI. Images could not be generated as the accumulation of PFAS in the sectioned tissue was below detection limit of the technique.

Chemical Fingerprinting and Multivariate Analysis of Different Grades of Farfarae Flos Using HPLC and UPLC-ESI-Q/TOF-MS/MS.

Farfarae Flos is widely used as a traditional herbal medicine. Currently, its size has been the primary grading criterion used in market circulation. Whether this empirical criterion can accurately reflect the quality of the medicinal material has not been systematically studied. This study aimed to evaluate the quality of Farfarae Flos from different regions based on their grades. Ultra-high performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-Q/TOF-MS/MS) were applied to study the chemical constituents of Farfarae Flos; high performance liquid chromatography (HPLC) was used to quantify the content of Farfarae Flos samples. Meanwhile, fingerprint analysis and chemometric methods, including principal component analysis (PCA) and analysis of variance (ANOVA), were used to evaluate the quality differences among 33 batches of Farfarae Flos samples of different grades. A total of 95 individual components were identified in Farfarae Flos. Fingerprint analysis revealed 23 common peaks, with fingerprint similarity among the 33 batches ranging from 0.838 to 0.995. PCA divided the 33 batches of Farfarae Flos into three categories based on their grades. ANOVA indicated significant differences in five of the 14 main active components across different grades of Farfarae Flos, with two components showing extremely significant differences. HPLC content determination showed that the content of 11 main active components was positively correlated with the grades of Farfarae Flos. This method is straightforward, efficient, and reliable, offering a valuable reference for establishing quality grading standards and ensuring the quality control of Farfarae Flos.

Atomically Precise Cu12 Nanoclusters with Thermally Activated Delayed Fluorescence Properties.

Ligand-stabilized metal nanoclusters with atomic precision are considered to be promising materials in the field of light-emitting and harvesting. Among these, nanoclusters with thermally activated delayed fluorescence (TADF) properties are highly sought after. While several gold and silver nanoclusters with TADF properties have been reported in recent years, research on copper counterparts has significantly lagged behind. In this study, we present the synthesis, total structure determination, and photoluminescent properties of a copper cluster with TADF properties. The cluster, with the molecular formula (PPh4)[Cu12(NO3)6(AdmS)6] (PPh4 is tetraphenylphosphine tetraphenylboron, and AdmSH is adamantanethiol), was obtained in a single reaction in the presence of air and fully characterized using electrospray ionization mass spectroscopy (ESI-MS), X-ray photoelectron spectroscopy, nuclear magnetic resonance, and ultraviolet-visible spectroscopy (UV-vis). The molecular structure of the cluster, as determined by X-ray crystallographic analysis, reveals the stabilization of a Cu12 core (layer-by-layer growth mode of Cu3@Cu6@Cu3) with 6 NO3- and 6 AdmS- ligands acting as stabilizing ligands. Interestingly, the cluster exhibits photoluminescence in both crystalline and solution states and displays typical TADF characteristics within the temperature range of 163-243 K. This study not only presents a pioneering example of copper nanoclusters with TADF properties but also highlights the promising future of copper clusters in material science.

Development and Validation of a Robust LC-MS/MS Method for Quantitation of a Novel Kinase Inhibitor, Ritlecitinib, in Rat Plasma: Application in Pharmacokinetic Study

Background Ritlecitinib (RIT) is a novel kinase inhibitor with promising therapeutic applications in the treatment of autoimmune disease alopecia areata. Accurate quantification of RIT in biological matrices is essential for pharmacokinetic studies and drug development. Objectives This study aims to develop and validate a sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantitation of RIT in rat plasma and to apply this method in a pharmacokinetic study. Materials and Methods A sensitive and selective LC-MS/MS method was developed in a AB Sciex QTRAP 5500 coupled with Shimadzu Prominence LC-20AD UFLC (ultra-fast liquid chromatography) System using an C18 column (Xselect HSS T3 2.5 µm, 2.1x150 mm) with a mobile phase consisting of 0.1% formic acid in high-performance liquid chromatography (HPLC) grade water and 0.1% formic acid in acetonitrile (70:30, v:v). RIT ( m/z 286.1 ↓ 105.7) and [ 13 C4]-ritlecitinib (internal standard, IS) ( m/z 290.1 ↓ 109.7) were detected in a positive mode by electrospray ionization (ESI) using multiple reaction monitoring (MRM) and extracted from rat plasma samples through protein precipitation We validated the method according to United States Food and Drug Administration (U.S. FDA) guidelines, assessing parameters such as linearity, accuracy, precision, selectivity, sensitivity, recovery and stability. The validated method was then applied to a pharmacokinetic study in rats following the administration of RIT. Results On rat plasma, the LC-MS/MS method has shown exceptional linearity across the concentration range of 5–100 ng/mL. The FDA’s approved standards of ±15% matched the accuracy and precision measurements. The matrix effect was negligible, and the mean recovery was about 93%, indicating that RIT was fully extracted from plasma. Different experimental conditions found RIT to be stable. RIT is quickly absorbed, with a peak plasma concentration (Cmax) of 43.82 ng/mL occurring 0.5–0.75 hours after the dose. It then drops in concentration in a way that is biexponential, with a half-life at the end of 1.5 hours. Conclusion A highly sensitive and specific LC-MS/MS method for quantitation of RIT in rat plasma was successfully developed and validated. The method was effectively applied to a pharmacokinetic study, providing critical data on the absorption and elimination characteristics of RIT in rats. This established approach may support additional preclinical pharmacokinetic investigations of RIT.

An electrospray-active N-heterocyclic carbene ligand for real-time analysis of organometallic reactions.

A charge-tagged N-heterocyclic carbene (NHC) has been synthesized and its utility in allowing the dynamic behaviour of metal complexes to be monitored in real time using electrospray ionization mass spectrometry demonstrated. This compound was used to prepare different metal-NHC complexes, and the kinetic behaviour of complex formation and ligand exchange was monitored in real time through the use of pressurized sample infusion electrospray mass spectrometry (PSI-ESI-MS).

Generation of glucosylantimycins by heterologous expression of a promiscuous glycosyltransferase in a deepsea-derived Streptomyces.

Antimycins are a class of depsipeptide compounds that exhibit diverse bioactivities. However, their potential clinical applications are hampered by high cell toxicities. Glycosylation usually has profound impacts on the physicochemical properties, bioactivities and toxicities of natural products. In this study, we overexpressed an artificial glycosyltransferase (GT) gene sbmGT1 in deepsea-derived Streptomyces albus ZH66, leading to the discovery of three new antimycin derivatives glucosylantimycins A, B and C (1-3). Their structures were determined by a combination of spectroscopic methods, including high resolution electrospray ionisation mass spectrometry (HRESIMS) and nuclear magnetic resonance (NMR) analysis. The glycosylation remarkably improved the water solubility but simultaneously reduced the cytotoxicities of antimycins towards human cervix epidermoid carcinoma (HeLa) and human hepatic carcinoma (HepG2) cell lines.

Оцінка безпечності дієтичної добавки “Rheumacаre Ultra”, оптимізація дієтологічних умов для функціонування суглобів

In Ukraine, among chronic diseases, pathology of the musculoskeletal system is one of the most frequent problems, and about 3.5 million people have problems with the musculoskeletal system and its various complications, which require continuous therapy throughout life. Aim. Generalization of the results of a comprehensive sanitary and hygienic assessment of the safety for consumers of a dietary supplement created to support the normal functioning of joints; data analysis of electronic publishers Scopus, Web of Science, PubMed, other foreign and domestic sources of scientific information on the research topic. Materials and Methods. The dietary supplement "Rheumacare Ultra" has been tested for the content of heavy metals and pesticides for compliance with the State Sanitary Rules and Regulations of Ukraine. The microbiological safety of the dietary supplement was controlled by the content of mesophilic aerobic and facultative anaerobic microorganisms. The method of ultra-high-performance high-speed mass spectrometric liquid chromatography with electron spray ionization (UPLC-MC/MC, Waters, USA) and the gas chromatography method were used to determine the content of pesticide residues; the content of lead, cadmium, mercury was determined by the atomic emission method (instrument ‒ atomic emission spectrometer "SHIMADSU ICPE ‒ 9820"). Results. Based on expert assessment of documentation, analysis of data sources of scientific information, results of sanitarychemical, radiological and sanitary-microbiological studies, it was established that dietary supplement "Rheumacare Ultra" ("Rheumacare Ultra") is safe for the health of consumers and can be used for purpose: to promote the normalization of metabolism, optimization of the chemical composition of the diet, creation of optimal dietary conditions to support the normal functioning of the musculoskeletal system, in particular ‒ joints; to purposefully affect the growth of the level of adaptation capabilities of the human body in conditions of constantly increasing harmful effects of the environment. Conclusions. Assessing the safety of traditional Ayurvedic recipes is a difficult task due to the multicomponent composition of organic-mineral complexes and the lack of complete information on the chemical structure of biologically active components of endemic plants and their impact on human health. Keywords: dietary supplements, sanitary and hygienic assessment, musculoskeletal system, joints.

Easy and Fast Detection of Hypochlorite by a Bithiophene-Based Fluorescent Turn-on Sensor and its Applications to Test Strips, Real Water Samples, and Smartphone-Assisted Platform.

We report a bithiophene-based fluorescence probe BDT (2,2'-(((1 E, 1'E)-[2,2'-bithiophene]-5,5'-diylbis(methaneylylidene))bis(azaneylylidene))bis(4-(tert-butyl)phenol)) for recognizing ClO-. BDT selectively responded to ClO-, leading to a blue fluorescence enhancement in a mixture of DMF/HEPES buffer (9:1, v/v). Importantly, BDT showed an ultrafast response (within 1 s) to ClO- among the fluorescent turn-on chemosensors based on bithiophene. BDT recognized ClO- through cleavage reaction with a low detection limit of 2.16 µM, and it had the ability to sense ClO- across a pH range of 3-11. The recognition mechanism for ClO- was investigated by 1H nuclear magnetic resonance (NMR) titration, electrospray ionization mass spectrometry (ESI-MS), and density functional theory (DFT) calculations. In addition, BDT could be used to detect ClO- using test strips as a convenient tool, allowing real-time monitoring rapidly. Practically, BDT exhibited reliable recoveries for quantifying ClO- using a smartphone application with a spike-and-recovery method in real water samples such as drinking, tap, mineral, and river water.

Rapid Determination of Organic and Inorganic Selenium in Poultry Tissues by Internal Extractive Electrospray Ionization Mass Spectrometry.

An online reactive internal extraction electrospray ionization (iEESI) method was developed for the rapid determination of organic and inorganic speciation information for selenium in poultry tissue samples without complex sample pretreatment. The addition of citric acid as a reducing agent to the internal extraction solvent of methanol/acetic acid (99:1, V/V) for iEESI resulted in the reduction of selenate in the sample to selenite, accompanied by the production of malic acid as an oxidation product. The quantitative analysis of selenate was conducted by using malic acid. By addition of o-phenylenediamine (OPD) to the extractant, inorganic selenium including selenite and selenite reduced from selenate was immediately extracted and converted into 1,3-dihydro-2,1,3-benzoselenadiazole after an in situ reaction. The methanol in the reagent extracted organic selenium compounds from the samples, enabling a rapid quantitative analysis of organic and inorganic selenium in chicken tissue. The concentrations of selenomethionine (SeMet), l-selenocystine (SeCys(2)), selenite, and selenate in different tissue samples were examined, showing strong linearity in the range of 1.00-100.00 μg/kg with the limit of detection (LOD) ranging from 0.36 to 0.84 μg/kg. The results were validated by two conventional methods with an accuracy of 84.2-107.6%. The quantitative analysis of three chicken visceral samples revealed that the highest concentration of organic selenium was present in chicken livers, while the highest concentration of inorganic selenium was observed in gizzards. The findings may provide a reliable method for studying selenium metabolism pathways in organisms.

Visualizing the spatial distribution of Alprazolam in the mouse brain following nasal administration using desorption electrospray ionization mass spectrometry imaging.

Alprazolam (Alp), a triazolobenzodiazepine, is widely prescribed for the treatment of sleep disorders, anxiety, and panic disorder. While oral administration remains the standard route, its slow onset of action has prompted interest in intranasal delivery as an alternative, offers the potential for direct drug delivery to the brain. This study aims to develop a fast-acting intranasal formulation of Alp (Alp-nd). Safety evaluations were conducted using mucociliary toxicity tests in bullfrogs and ciliary toxicity tests in rats, demonstrating that Alp-nd was safe and did not cause damage to the nasal mucosa. The righting reflex test was employed to assess the dose-response effect of Alp-nd on sleep in mice, revealing a 95 % effective dose (ED95) of 1.81 mg/kg, which is lower than that observed with intragastric administration (Alp-ig). A comparison of the pharmacodynamics, plasma pharmacokinetics, and brain distribution between intranasal and intragastric administration was performed. Sleep phase analysis revealed that Alp-nd significantly shortened sleep latency and prolonged sleep duration compared to Alp-ig. LC-MS/MS analysis indicated that Alp plasma concentrations were significantly higher at 5 and 10 min post-dosing with Alp-nd compared to Alp-ig. Furthermore, desorption electrospray ionization-time of flight mass spectrometry imaging (DESI-MSI) demonstrated that Alp-nd significantly increased Alp content in the olfactory bulb within 2-5 min, and in the cortex, thalamus and hypothalamus within 2-30 min, and in the pineal gland within 5-30 min. These results suggest that the Alp-nd shortens sleep latency via the nose-to-brain pathway and extends sleep duration by increasing Alp concentrations in sleep-related brain regions.

The Addition of Tomato and Spinach Powder to Semolina Pasta: A Study of the Impact of the Production Process and Cooking on Phenolic Compounds

Pasta is a staple food with daily recommended consumption; thus, it can be an excellent vehicle for delivering bioactive compounds like phenols. However, the high-temperature drying process in pasta production, combined with cooking in boiling water, can significantly reduce the concentration of phenolic compounds. This study aimed to enhance the phenolic content of traditional semolina pasta by incorporating tomato and spinach powder into the recipe. High-performance liquid chromatography–electrospray ionization triple quadrupole mass spectrometry (HPLC-ESI-QqQ-MS) was employed to analyse the free and bound phenolic content in the raw materials, as well as in both dried uncooked and cooked pasta. The addition of tomato and spinach powders, known for their high content in bioactive compounds, increased the overall phenolic content of the final enriched pasta by three and two times, respectively, compared to the semolina and whole-wheat semolina pasta. These findings suggest that pasta enriched with tomato and spinach could serve as a functional food with a greater nutritional profile and health benefits through the enhanced delivery of phenolic compounds.

Temperature Induced Unfolding and Compaction of Cytochrome c in the Same Aqueous Solutions.

Most conventional methods used to measure protein melting temperatures reflect changes in structure between different conformational states and are typically fit to a two-state model. Population abundances of distinct conformations were measured using variable-temperature electrospray ionization ion mobility mass spectrometry to investigate the thermally induced unfolding of the model protein cytochrome c. Nineteen conformers formed at high temperature have elongated structures, consistent with unfolded forms of this protein. However, one conformer that is more compact than the native state of the protein is also formed from this same solution upon heating. The abundance of this compact conformer increases with temperatures up to 90 °C. Rapid mixing and collision-induced gas-phase unfolding experiments demonstrate that formation of this compact conformer is not an artifact of rapid refolding during the ESI process or structural rearrangement in the gas-phase, and therefore the compact conformer must be formed in bulk solution at higher temperatures. The main folded conformer at 90 °C has a cross section that is ∼30 Å2 larger than that at 27 °C. Results from collision-induced unfolding experiments indicate that they have different gas-phase stabilities that are not directly related to differences in their initial internal energies upon transitioning into the gas phase and therefore have different structures. These results demonstrate the advantage of mass and ion mobility measurements for investigating protein conformational landscapes and provide the first evidence for formation of both unfolded and more compact conformations of a protein from the same solution upon heating.

Dissociation of Macromolecules in Laser-Heated Droplets Monitored by CD-MS.

Charge detection mass spectrometry (CD-MS) is used to monitor the dissociation of large (300 kDa to 20 MDa) protein complexes in droplets heated with a 10.6 μm CO2 laser. In this approach, electrospray ionization (ESI) is used to produce charged droplets containing macromolecular complexes. As the droplets travel from the ESI capillary tip to the entrance of the CD-MS instrument, they pass through a variable-power laser field, where they are rapidly heated and dissociate to produce fragments. The approach is illustrated for three model systems: glutamate dehydrogenase (GDH), a 334 kDa hexameric protein complex, which dissociates into protein monomers, dimers, and tetramers; the ∼3 MDa T = 3, and ∼4 MDa T = 4 hepatitis B virus VLPs (virus-like particles) that produce a distribution of protein dimer clusters; and the ∼20 MDa T = 7 human papillomavirus VLP, which dissociates primarily into small capsid protein clusters that are not well-resolved by CD-MS. The fragments produced by in-droplet activation provide information that is useful for characterizing the structures of the intact antecedent complexes. A discussion of the advantages and current limitations of this approach is presented.

Nontargeted Screening Nitrogen-Containing Organic Compounds in Frost and Wet Deposition in Rural Northeast China.

Nitrogen-containing organic compounds (NOCs) in frost serve as a critical pathway for atmospheric nitrogen deposition, significantly impacting the biogeochemical cycles of nitrogen. However, the molecular characteristics of NOCs in frost and their deposition fluxes are scarcely studied. In this work, frost samples, collected in rural Northeast China in the winter of 2023, were analyzed using nontargeted ultrahigh performance liquid chromatography-orbitrap mass spectrometry (UHPLC-Orbitrap MS) to reveal their content in nitrogen-containing organic compounds (NOCs) and explore their wet deposition fluxes. The average number of assigned molecular formulas were lager on hazy days compared to nonhazy days for both water-soluble (WSOM) and water-insoluble organic matter (WISOM) in frost (3114 vs. 1934 for WSOM and 3042 vs. 2224 for WISOM in electrospray ionization (ESI-); 6921 vs. 5954 for WSOM and 6629 vs. 5547 in ESI+). Specifically, the number proportions of CHON were 35.6-49.9% (724-1517) and 47-51.1% (2686-3388) in the ESI- and ESI+ modes, respectively. Nitrophenol (C6H5NO3) and methyl nitrophenol (C7H7NO4) were the most abundant NOCs, with wet deposition fluxes (at maximum average concentrations) of 22.2 and 21.2 μg m-2·h-1, respectively. On hazy days, the deposition fluxes of nitrophenol compounds reached up to 1.73 times that of nonhazy days, indicating significant ambient nitrogen deposition during the haze episode. This deposition flux positively correlated with PM2.5 concentration, implying the important role of atmospheric particulates in influencing NOC deposition through frost. These findings highlight the susceptibility of frost to capturing NOCs from the atmosphere, potentially impacting nitrogen cycling in ecosystems.

Phytochemical Profiling by UHPLC-ESI-MS/MS, In Vitro Antioxidant, In Vivo Antidiabetic, and Pro-Sexual Effects of Salvia balansae Noë Ex Coss. Flower Extract in Diabetic Male Rats.

Our study assessed the phytochemical composition and the effects of Salvia balansae flower aqueous extract (FAE) on sexual dysfunction in diabetic rats. Total phenolic and flavonoid content, quantification of phytochemicals by ultrahigh performance liquid chromatography (UHPLC)-electrospray ionization (ESI)-tandem mass spectrometry (MS/MS) method, and in vitro antioxidant capacity of FAE extract were elucidated. For the in vivo study, diabetes was induced by one intraperitoneal injection of streptozotocin (STZ) (40mg/kg), and treated diabetic rats were given FAE at 200mg/kg. Rats were subjected to a sexual incentive motivation test (SIM) and a mating behavior test, and then serum testosterone levels and sperm quality were analyzed. Our study indicates that FAE contained a large amount of phenolic compounds and flavonoids, and 13 constituents were quantified; cynaroside (3.8mg analyte/g extract) was the main compound, followed by rosmarinic acid (3.145mg analyte/g extract), thus confirming its high antioxidant capacity. FAE treatment significantly reduced blood glucose levels, improved sexual motivation and copulatory behavior, increased testosterone levels, and enhanced sperm quality in diabetic-treated rats compared to diabetic untreated rats. The present work demonstrates the therapeutic potential of S. balansae flowers in enhancing reproductive function in diabetic rats, potentially through its antioxidant, antihyperglycemic, and aphrodisiac properties.