Mass Spectra Research Articles

On the instrument-dependent appearance of ion dissociation events in atom probe tomography mass spectra

The successful application of atom probe tomography (APT) relies on the accurate interpretation of the mass spectrum (i.e.m/z histogram) from a sample. Some materials yield mass spectra that are amenable to a straightforward peak assignment/ranging, however, there are many materials that produce mass spectra with features that defy simple interpretation. One such example is Ga2O3 which yields mass spectra containing several broad and difficult to interpret features. Herein, we study the GaO2+→ O1++ Ga1+ dissociation and we explain how this dissociation process gives rise to broad and previously unassigned features in the mass spectrum. Trajectory simulations are performed for the dissociation reaction utilizing realistic electrostatic models and compared to experiments using commercially available straight flight and reflectron based local electrode (LE) APT instruments. It is shown that the appearance of these features is strongly dependent on the specific design of the time-of-flight (ToF) mass analyzer. We explore how various experimental parameters can affect the appearance of the dissociation process in the one-dimensional (1D) mass spectrum and in the two-dimensional (2D) correlation histogram. While the focus of this work is on a particular dissociation process related to Ga2O3, the understanding gained in the course of these simulations and experiments should be applicable to the interpretation of dissociation processes in other materials.

Synergistic extraction of zinc from spent acid using P507-P204: A novel approach for efficient separation

A novel system for the synergistic extraction of zinc from spent acid using a mixture of 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507) and Di-2-ethylhexyl phosphoric acid (P204) as extractant is proposed. The optimum extraction parameters of P507-P204 are investigated, and the results exhibit that 84.80% of zinc is extracted at a solution pH control of 1, the V(P507):V(P204) of 4:1, the P507-P204 concentration of 30% (v/v), and the phase ratio (O/A) of 2:1. Furthermore, the zinc can be effectively stripped from its extracted complex by sulfuric acid. The synergistic extraction mechanism of P507-P204 is identified by slope analysis, FT-IR, mass spectrum, and 31P-NMR. In addition, the mechanism of synergistic extraction of zinc by P507-P204 is cation exchange and releases two hydrogen ions during zinc extraction. In a word, the establishment of this synergistic system realizes the effective separation of zinc from spent acid and has potential industrial application value.

Construction of a two-dimensional magnetic solid phase extraction microfluidic chip/tandem mass spectrometry platform for the determination of cytarabine in plasma

A novel concept of two-dimensional magnetic solid phase extraction microfluidic chip (2D-MSPE-chip) was proposed, in which two or even more different separation mechanisms of solid phase extraction units were designed and constructed on microfluidic chips in series. The synthesized Fe3O4-UiO-66-C18 was used in the first dimension to retain protein and phospholipid through hydrophobic effect and ZrOP coordination, which could almost eliminate the interference of the matrix effect on the mass spectrum. The second dimensional material utilized Fe3O4-UiO-66-NH2 to enable cytarabine enrichment via π-π and hydrogen bonding. The parameters of 2D MSPE-Chip/tandem MS method such as desorption solvent (5 % acetic acid acetonitrile), loading solvent (20 % acetonitrile), and flow rate for extraction and desorption (10 μL/min) were select. The LOD of the established method for cytarabine in plasma was 0.13 ng/mL, and the linear range was between 2.0 ng/mL and 1000 ng/mL with correlation coefficient (R2 = 0.9991). The matrix effect was −5.0 %. The recovery rate of real samples ranged from 95.5 % to 104.8 %, with RSD ≤ 5.2 %. The chip design was simple and efficient and could be reused, thereby decreasing analysis expenses. It held considerable potential for application in rapid clinical diagnostics and precision medicine.

Knowledge-based In Silico Fragmentation and Annotation of Mass Spectra for Natural Products with MassKG

Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is a potent analytical technique utilized for identifying natural products from complex sources. However, due to the structural diversity, annotating LC-MS/MS data of natural products efficiently remains challenging, hindering the discovery process of novel active structures. Here, we introduce MassKG, an algorithm that combines a knowledge-based fragmentation strategy and a deep learning-based molecule generation model to aid in rapid dereplication and the discovery of novel NP structures. Specifically, MassKG has compiled 407,720 known NP structures and, based on this, generated 266,353 new structures using chemical language models for the discovery of potential novel compounds. Furthermore, MassKG demonstrates exceptional performance in spectra annotation compared to state-of-the-art algorithms. To enhance usability, MassKG has been implemented as a web server for annotating tandem mass spectral data (MS/MS, MS2) with a user-friendly interface, automatic reporting, and fragment tree visualization. Lastly, the interpretive capability of MassKG is comprehensively validated through composition analysis and MS annotation of Panax notoginseng, Ginkgo Biloba, Codonopsis pilosula, and Astragalus membranaceus. MassKG is now accessible at https://xomics.com.cn/masskg.

Enantioselective complexation of protonated tyrosine by a chiral crown-ether: the nature of the Hydrogen bonds makes the difference.

The complexes formed between (18-crown-6)-tetracarboxylic acid, denoted as 18C6TA, and the two enantiomers of protonated tyrosine, L- and D-Tyr, are studied in a cryogenic ion trap by combining mass spectrometry, laser spectroscopy, and DFT calculations. Both UV and IR photodissociation spectra indicate the formation of multiple isomers for each complex, some of them interconverting upon IR irradiation. Conformer-selective vibrational spectroscopy reveals that all structures involve an internally hydrogen-bonded folded structure of the crown ether. The complexes formed with L-Tyr involve two NH…O interactions with the ether oxygen atoms,and two hydrogen bonds to the crown ether carboxylic function, one from the NH group and the other from the COOH group of tyrosine. TheD-Tyr complexesshow more conformational mobility: two out of the three lowest energy conformers observed are tripodal, with three NH…O interactions between the amino acid ammonium and the crown ether oxygens. An additional conformer shows only one NH…O interaction, but has two interactions involving one of the cavity COOH moieties, one with the NH and one with the phenol OH. The increased calculated stability of the complex made from (-) 18C6TA and L-Tyr parallels its higher abundance in the mass spectrum of an isotopically labelled racemic mixture.

Potential Prognostic Protein Biomarkers in Tears From Noninfectious Uveitis Patients Under Biologic Treatment as a Prelude to Personalized Medicine.

Adalimumab (ADA) is a systemic biological treatment option approved for the treatment of noninfectious uveitis (NIU); however, up to 40% of patients do not respond to the drug, either in a primary or secondary manner. Here, we evaluated the proteomic profile of patients with NIU who fail to ADA to identify proteins implicated in intraocular inflammation, as well as potential biomarkers for treatment response and novel therapeutic targets. Cross-sectional observational study of patients with NIU under ADA treatment for six or more months. Tears were collected with microcapillary tubes and protein analyzed by data-independent acquisition/sequential window acquisition of all theoretical mass spectra. Differentially expressed proteins (DEPs) were defined based on the fold change between their expression in nonresponders (NR) and responders (R). Protein network and gene ontology analysis were performed. The χ2 test for trend and receiver operating characteristic (ROC) curves were used to evaluate potential biomarkers of treatment response. Twenty-nine DEPs, 14 upregulated and 15 downregulated, were detected in NR. These proteins were mainly related to enhanced neutrophil effector functions and redox imbalance. ROC analysis identified defensin-1,3 (DEF-1,3), biotinidase, and ATP-binding cassette transporter A1 as potential biomarkers for treatment response. This is the first study on a clinical cohort of patients with noninfectious uveitis that identifies tear proteins related to neutrophil hyperactivation as drivers of the persistent intraocular inflammation observed in NR to ADA and provides evidence that targeting interleukin 6, Janus kinases, or the complement cascade could be potential alternative therapeutic strategies in these patients. Our results indicate the potential of high-throughput proteomics to provide insights into the underlying pathological mechanisms of persistent intraocular inflammation observed in patients who do not adequately respond to anti-TNF treatment and the value of tear proteomics as a tool for personalized medicine.

Laser-Assisted Field Evaporation of Chromia with Deep Ultraviolet Laser Light.

In this work, samples of chromia (Cr2O3) scale have been prepared for atom probe tomography and field evaporated with deep ultraviolet laser light (258 nm wavelength). The investigated range of laser energies spans more than three orders of magnitude between 0.03 and 90 pJ. Furthermore, the effects of detection rate and temperature were investigated. Simultaneous voltage and laser pulses were employed on additional needle specimens to reduce the standing voltage and minimize background noise during the measurement. Smooth evaporation with minimal mass spectrum peak tails was maintained over the whole range of measurement parameters. High laser energies result in significant underestimation of the oxygen content. Only laser energies below 1 pJ resulted in measured values near the expected oxygen content of 60 at%, the closest being about 58 at%.

From historical drugs to present perils: UHPLC-QqQ-MS/MS determination of methaqualone and its designer analogs (NPS) with comprehensive fragmentation pathways study (QTOF)

Methaqualone, introduced in the 1960s as a sedative-hypnotic alternative to barbiturates, was withdrawn from the market due to its side effects and growing recreational use. Despite this, interest in methaqualone and its analogs remains high, raising concerns about potential abuse in the future. An ultra-high-performance liquid chromatography method coupled with triple quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS) was developed to determine nine methaqualone-related compounds simultaneously. Biological samples were prepared using liquid–liquid extraction with ethyl acetate at pH9; quantification was performed in blood using multiple reaction monitoring (MRM) mode. Methaqualone-d7 served as an internal standard. The limit of quantification (LOQ) ranged from 0.1 to 0.2 ng/mL, with precision and accuracy within 20%. Recovery ranged from 84.2% to 113.7%. The developed method allowed chromatographic separation of all compounds tested, including two structural isomers: methylmethaqualone and etaqualone. The mass spectra acquired from quadrupole time-of-flight mass spectrometer allowed for the elucidation of comprehensive fragmentation study of methaqualone derivatives. The described situation poses a significant problem from the analytical point of view, as well as interpretation and forensic toxicological expertise. The developed method will contribute to increased analytical capabilities and enhanced detection of compounds from the methaqualone group that may appear on the illicit market.

Abstract 4118993: β1 Adrenergic Receptor Autoantibodies Promote Heart Failure Though Activation of Prostaglandin E2 Receptor EP1/Phosphodiesterase 4B Pathway

Background: β1 adrenergic receptor (β1-AR) autoantibodies (β1-AA) can cause heart failure (HF) through activating of β1-AR; However, β-AR antagonists cannot completely reverse the cardiac injury induced by β1-AA and improve the survival rate of patients with β1-AA-positive HF. However, the β1-AR-independent mechanisms of heart failure induced by β1-AA are unclear. Methods: Proteomics of mice hearts was used to identify the specific changed proteins induced by β1-AA. The expression of phosphodiesterase 4B (PDE4B) was detected by western blot in neonatal mice mouse cardiomyocytes (NMCMs) and heart tissues. The binding proteins with β1-AA were enriched by immunoprecipitation (IP) and identified by mass spectrum. The interaction between β1-AA and prostaglandin E2 Receptor EP1 was detected by co-IP and surface plasmon resonance. The cardiac function and cardiac remodeling of PDE4B transgenic (TG) mice and EP1 knockout (KO) mice. Results: Firstly, PDE4B was changed the most proteins induced by β1-AA compared to β1 adrenergic receptor dobutamine. Moreover, the decrease of PDE4B induced by β1-AA cannot be reversed by metoprolol in vivo and in vitro. Secondly, the cAMP/PKA pathway and cardiac injury/dysfunction induced by β1-AA were inhibited after activation of PDE4B or PDE4B-TG in vivo and in vitro. Thirdly, β1-AA can bind with EP1 and activate Gq/IP3 pathway. The activation effect was abolished by EP1 antagonist. Lastly, blocked EP1 or EP1-KO will reverse the decreased PDE4B and cardiac injury/dysfunction induced by β1-AA. Conclusions: Our work reveals that β1-AA can activate of EP1/PDE4B pathway to result in heart failure.

Mixing effects on spectroscopy and partonic observables of heavy mesons with logarithmic confining potential in a light-front quark model

Using the variational principle, we systematically investigate the mass spectra and wave functions of both 1S and 2S state heavy pseudoscalar (P) and vector (V) mesons within the light-front quark model. This approach incorporates a Coulomb plus logarithmic confinement potential to accurately describe the constituent quark and antiquark dynamics. Additionally, spin hyperfine interactions are introduced perturbatively to compute the masses of pseudoscalar and vector mesons. The present analyses of the 1S and 2S states require the consideration of mixing between them to account for empirical constraints. These constraints include the mass gap ΔMP>ΔMV, where ΔMP(V)=MP(V)2S−MP(V)1S and the hierarchy of the decay constants f1S>f2S. We find the optimal value of the mixing angle to be θ=18°, significantly enhancing the consistency between our spectroscopic predictions and the experimental data compiled by the Particle Data Group. Furthermore, based on the predicted mass, the newly observed resonance BJ(5840) could be assigned as a 21S0 state in the B meson family. The study also reports various pertinent observables, including twist-two distribution amplitudes, electromagnetic form factors, charge radii, ξ moments, and transition form factors that are found to be consistent with both available lattice simulations and experimental data. In addition, our predicted branching ratios for the channels of B+→τ+ντ as well as rare decays of B0 and Bs0 appear in accordance with experimental data. Published by the American Physical Society 2024

On the Thermomechanics of Hadrons and Their Mass Spectrum

A little-known thermomechanical relation between entropy and action, originally discovered by Boltzmann in the classical domain, was later reconsidered by de Broglie in relation to the wave–particle duality in the free propagation of single particles. In this paper, we present a version adapted to the phenomenological description of the hadronization process. The substantial difference with respect to the original de Broglie scheme is represented by the universality of the temperature at which the process occurs; this, in fact, coincides with the Hagedorn temperature. The main results are as follows: (1) a clear connection between the universality of the temperature and the existence of a confinement radius of the color forces; (2) a lower bound on the hadronic mass, represented by the universal temperature, in agreement with experimental data; and (3) a scale invariance, which allows the reproduction of the well-known hadronic mass spectrum solution of the statistical bootstrap model. The approach therefore presents a heuristic interest connected to the study of the strong interaction.

A database on pharmaceuticals in the environment: What do stakeholders need?

Pharmaceutical pollution has raised concerns about how these contaminants affect ecosystems. Data to assess the environmental risk of pharmaceuticals exist but are dispersed and not always publicly accessible. To address this issue, the European Commission recently proposed to develop a data source for human medicinal products, involving relevant stakeholders, including healthcare and industry representatives. The aim of our study was to define the user requirements for such a database on pharmaceuticals in the environment (PiE). We reached out to over 100 professionals that work on PiE, asking what data should be incorporated in the database and what features it should have. The results show that most stakeholders are affected by data gaps, mainly related to ecotoxicity, monitoring, transformation products, metabolites and removal rates in wastewater treatment plants. Interest in the mechanism of action of active pharmaceutical ingredients was specifically expressed by the pharma sector, including stakeholders related to the authorisation, production and use of medicines. Researchers and stakeholders dealing with environmental and water quality have greater interest for mass spectrum data, modelled environmental concentrations and data on transformation products and metabolites. While showing that the key actors working on PiE strongly endorse the development of an accessible and transparent database, we provide recommendations for creating such a data repository on pharmaceuticals.

Are Hydroxyl Radicals Spontaneously Generated in Unactivated Water Droplets?

AbstractSpontaneous ionization/breakup of water at the surface of aqueous droplets has been reported with evidence ranging from formation of hydrogen peroxide and hydroxyl radicals, indicated by ions at m/z 36 attributed to OH⋅‐H3O+ or (H2O‐OH2)+⋅ as well as oxidation products of radical scavengers in mass spectra of water droplets formed by pneumatic nebulization. Here, aqueous droplets are formed both by nanoelectrospray, which produces highly charged nanodrops with initial diameters ~100 nm, and a vibrating mesh nebulizer, which produces 2–20 μm droplets that are initially less highly charged. The lifetimes of these droplets range from 10s of μs to 560 ms and the surface‐to‐volume ratios span ~100‐fold range. No ions at m/z 36 are detected with pure water, nor are significant oxidation products for the two radical scavengers that were previously reported to be formed in high abundance. These and other results indicate that prior conclusions about spontaneous hydroxyl radical formation in unactivated water droplets are not supported by the evidence and that water appears to be stable at droplet surfaces over a wide range of droplet size, charge and lifetime.

How CO2 gas accelerates water nucleation at low temperature.

We conducted homogeneous nucleation experiments for dilute binary H2O-CO2 mixtures in Ar-N2 carrier gas with different CO2/H2O ratios at temperatures of 57 and 75K and total pressures of ∼40 and 70Pa, respectively. Direct experimental information on the number and type of molecules in the clusters and on the cluster number concentration is obtained by mass spectrometric detection of nucleating clusters that form in the uniform region of Laval expansions. Only homo-molecular water clusters are observed in the mass spectra. However, as the CO2/H2O ratio increases, a significant increase in the nucleation rate is observed. A simple kinetic model suggests that this acceleration of nucleation is due to the formation of short-lived, transient hetero-molecular H2O-CO2 dimers. Comparison with homogeneous binary nucleation of toluene-CO2 and unary nucleation of H2O shows that nucleation becomes more efficient in systems with stronger intermolecular interactions and a larger number of degrees of freedom. Such studies at the molecular level will improve our understanding of homogeneous nucleation mechanisms in atmospheric and industrial processes.

Results from a multi-laboratory ocean metaproteomic intercomparison: effects of LC-MS acquisition and data analysis procedures

Abstract. Metaproteomics is an increasingly popular methodology that provides information regarding the metabolic functions of specific microbial taxa and has potential for contributing to ocean ecology and biogeochemical studies. A blinded multi-laboratory intercomparison was conducted to assess comparability and reproducibility of taxonomic and functional results and their sensitivity to methodological variables. Euphotic zone samples from the Bermuda Atlantic Time-series Study (BATS) in the North Atlantic Ocean collected by in situ pumps and the autonomous underwater vehicle (AUV) Clio were distributed with a paired metagenome, and one-dimensional (1D) liquid chromatographic data-dependent acquisition mass spectrometry analysis was stipulated. Analysis of mass spectra from seven laboratories through a common bioinformatic pipeline identified a shared set of 1056 proteins from 1395 shared peptide constituents. Quantitative analyses showed good reproducibility: pairwise regressions of spectral counts between laboratories yielded R2 values averaged 0.62±0.11, and a Sørensen similarity analysis of the top 1000 proteins revealed 70 %–80 % similarity between laboratory groups. Taxonomic and functional assignments showed good coherence between technical replicates and different laboratories. A bioinformatic intercomparison study, involving 10 laboratories using eight software packages, successfully identified thousands of peptides within the complex metaproteomic datasets, demonstrating the utility of these software tools for ocean metaproteomic research. Lessons learned and potential improvements in methods were described. Future efforts could examine reproducibility in deeper metaproteomes, examine accuracy in targeted absolute quantitation analyses, and develop standards for data output formats to improve data interoperability. Together, these results demonstrate the reproducibility of metaproteomic analyses and their suitability for microbial oceanography research, including integration into global-scale ocean surveys and ocean biogeochemical models.

The development of a novel, green, efficient, and eco-friendly GC-MS/MS analytical method for the reliable and rapid determination of dl-PCBs, and PCDD/Fs using hydrogen as a carrier gas and a modified ion source

The polychlorinated dibenzo–p–dioxins/furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) are worldwide contaminants, and they tend to accumulate in wide variety of matrices. Therefore, due to the highest accumulation rate and recalcitrancy, their precise quantification makes significant concern about their toxicological effects on both humans and organisms. The objective of the study is that using hydrogen carrier gas instead of helium in gas chromatography with triple quadrupole (GC-MS/MS) systems could contribute to improvements on the analysis of dl-PCBs and PCDD/Fs in environmental matrices. The study evaluates the performance of the analysis time under the desired chromatographic resolution criteria for PCDD/Fs analysis, monitoring the plausible mass spectrum/fragmentation ratio changes, and finally the quantification limits of the targeted most toxic persistent organic compound congeners. The main advantage of using H2 carrier gas is that the analysis time was drastically reduced (∼2.5 times) along with improved resolution due to an increase in peak widths in ∼0.6–0.7 factor. This study emphasized that the resolution was remarkably affected by the hexa congeners of PCDD/Fs; nearly baseline separation was observed. However, the sensitivity was slightly reduced (∼6–7 fold), which affected the calibration starting concentrations (0.8–3.2 pg/μl). The acquired mass spectra indicated that the lower fragment enhancement was noticeable, particularly on higher chlorinated ones (hexa, hepta, and octa congeners). The calculated ortho-effect values (1–58) in this study are consistent with the previous results in the literature (1–66 and 1–83) and supports the conclusion about the observations of lower fragment enhancement. Despite non-detection of hydrogenation, there is a significant difference in the quant/qual ion ratios in the studied compounds between helium and hydrogen carrier gas. The finalized methodology was examined, and the performance of the hydroinert® ion source was assessed over a three-month analysis period with a real sample analysis (RSD ≤17.8 %). The results indicate that hydrogen is a potential and reliable GC-MS/MS carrier gas in dl-PCBs and PCDD/Fs for environmental matrices.

Enhanced Payload Localization in Antibody-Drug Conjugates Using a Middle-Down Mass Spectrometry Approach with Proton Transfer Charge Reduction.

Antibody-drug conjugates (ADCs) represent a novel class of immunoconjugates with growing therapeutic relevance, since they combine the efficacy of cytotoxic drugs with the specificity of antibodies. However, by design, ADCs introduce structural features into the monoclonal antibody scaffold that complicate their analysis. Payload attachment to cysteine or lysine residues can often result in product heterogeneity, regarding both the number of attached drug molecules and their conjugation site, necessitating the use of state-of-the-art MS instrumentation to elucidate their complexity. In middle-down mass spectrometry (MD MS), the gas-phase sequencing of ∼25 kDa ADC subunits with different ion activation techniques generally produces rich fragmentation mass spectra; however, spectral congestion can cause some fragment ions to go undetected, including those that can pinpoint the exact location of payload conjugation sites. Proton transfer charge reduction (PTCR) can substantially simplify fragment ion spectra, thereby unveiling the presence of product ions whose signals were previously suppressed. Herein, we present an MD MS strategy relying on the use of PTCR to investigate a cysteine-based ADC mimic with a variable drug-to-antibody ratio, targeting the unambiguous localization of payload conjugation sites. Unlike traditional tandem MS experiments (MS2), which could not provide a complete map of conjugation sites, a single PTCR-based experiment (MS3) proved to be sufficient to achieve this goal across all variably modified ADC subunits, including isomeric ones. Combining the results obtained from orthogonal ion activation techniques followed by PTCR further strengthened the confidence in the assignments.

Simulation of Space Charge Effects in Fourier Transform Quadrupole Ion Traps (FT-QITs).

We present ion dynamics simulations regarding the effect of space charge on the performance of Fourier transform quadrupole ion traps (FT-QITs) with special attention to signal stability, mass resolving power, and sensitivity. Ion trajectory simulations within an idealized QIT geometry are performed by applying a dedicated application (QITSim) using an in-house developed open simulation framework (IDSimF). Image current detection transients are generated by the application and are subsequently transformed into frequency spectra of ion secular motion. Such frequency spectra are the basis for the calculation of mass spectra in FT-QIT instruments. The simulation results are used to assess the extent of space charge induced effects regarding the analytical performance of FT-QIT systems. The simulation results for two Cl+ and seven Xe+ isotope ions exhibit diverse space charge induced phenomena. Most prominently, complete isotope signal fusion, quantitative individual signal suppression, and severe signal distortions are observed even at low absolute numbers of trapped ions. Furthermore, significant shifts of the secular oscillation frequencies occur, even when the signal shape appears to be mostly unaffected and when the frequency separation for trapped ions with different masses is large. This significantly limits the applicability of FT-QIT systems for high resolution mass spectrometry. An increase of the RF amplitude of the trapping field as well as increasing the extent of ion excitation partly mitigate these adverse space charge effects; nevertheless, the usable operational range of the simulated FT-QIT system for analytical applications remains rather narrow.

A magnetic epitope-imprinted microsphere used for selective separation and rapid detection of SHV-type β-lactamases in bacteria: a novel strategy of antimicrobial resistance detection

BackgroundThe production of β-lactamases is the most prevalent resistance mechanism for β-lactam antibiotics in Gram-negative bacteria. Presently, over 4900 β-lactamases have been discovered, and they are categorized into hundreds of families. In each enzyme family, amino acid substitutions result in subtle changes to enzyme hydrolysis profiles; in contrast, certain conserved sequences retained by all of the family members can serve as important markers for enzyme family identification.ResultsThe SHV family was chosen as the study object. First, a unique 10-mer peptide was identified as SHV family's epitope by an approach of protein fingerprint analysis. Then, an SHV-specific magnetic epitope-imprinted gel polymer (MEI-GP) was prepared by an epitope surface imprinting technique, and its sorption behavior and recognition mechanism for template epitope and SHV were both elaborated. Finally, the MEI-GP was successfully applied to selectively extract SHV from bacteria, and the extracted SHV was submitted to MALDI-TOF MS for specific determination. By following this strategy, other β-lactamase families can also be specifically detected. According to the molecular weight displayed in mass spectra, the kind of β-lactamase and its associated hydrolysis profile on β-lactams can be easily identified. Based on this, an initial drug option scheme can be quickly formulated for antimicrobial therapy. From protein extraction to medication guidance reporting, the mean time to detection (MTTD) was less than 2 h, which is much faster than conventional phenotype-based methods (at least 16–20 h) and gene-based techniques (usually about 8 h).ConclusionsThis enzyme-specific detection strategy combined the specificity of epitope imprinting with the sensitivity of mass spectrometry, enabling β-lactamase to be selectively extracted from bacteria and clearly presented in mass spectra. Compared with other drug resistance detection methods, this technique has good specificity, high sensitivity (≤ 15 mg of bacteria), a short MTTD (less than 2 h), and simple operation, and therefore has a broad application prospect in clinical medicine.Graphical

Interpretation of recently discovered single bottom baryons in the relativistic flux tube model

Following recent experimental progress in the study of bottom baryons, we systematically calculate the mass spectra of Λb, Ξb, Σb, Ξb′, and Ωb baryons with a quark-diquark picture in the framework of a relativistic flux tube model with spin-dependent interactions in the j-j coupling scheme. Furthermore, we calculate the strong decay width of bottom baryons decaying into a bottom baryon and a light pseudoscalar meson. Good agreement is found between the calculated masses and the experimentally available masses of singly bottom baryons. By analyzing both mass spectra and strong decay widths, we interpret Σb(6097) as a 1P(3/2−) state and Ξb(6100) as a 1P(1/2−) state of the Ξb baryon. The Ξb(6227) is identified to be an orbital excitation 1P of the Ξb′ baryon with JP=3/2−. Further, we determine Ξb(6327) and Ξb(6333) as a 1P(3/2−) state and 1P(5/2−) state, respectively, of Ξb′ baryon. From the obtained mass spectra, we construct the Regge trajectories in the (J,M2) plane, which are found to be essentially linear, parallel, and equidistant. Our predictions for higher orbital and radial excited states can help experimentalists identify missing excited states of singly bottom baryons. Published by the American Physical Society 2024