Ion Signal Research Articles

To 200,000 m/z and Beyond: Native Electron Capture Charge Reduction Mass Spectrometry Deconvolves Heterogeneous Signals in Large Biopharmaceutical Analytes.

Great progress has been made in the detection of large biomolecular analytes by native mass spectrometry; however, characterizing highly heterogeneous samples remains challenging due to the presence of many overlapping signals from complex ion distributions. Electron-capture charge reduction (ECCR), in which a protein cation captures free electrons without apparent dissociation, can separate overlapping signals by shifting the ions to lower charge states. The concomitant shift to higher m/z also facilitates the exploration of instrument upper m/z limits if large complexes are used. Here we perform native ECCR on the bacterial chaperonin GroEL and megadalton scale adeno-associated virus (AAV) capsid assemblies on a Q Exactive UHMR mass spectrometer. Charge reduction of AAV8 capsids by up to 90% pushes signals well above 100,000 m/z and enables charge state resolution and mean mass determination of these highly heterogeneous samples, even for capsids loaded with genetic cargo. With minor instrument modifications, the UHMR instrument can detect charge-reduced ion signals beyond 200,000 m/z. This work demonstrates the utility of ECCR for deconvolving heterogeneous signals in native mass spectrometry and presents the highest m/z signals ever recorded on an Orbitrap instrument, opening up the use of Orbitrap native mass spectrometry for heavier analytes than ever before.

Differential expression of ion channel coding genes in the endometrium of women experiencing recurrent implantation failures

Our study probed the differences in ion channel gene expression in the endometrium of women with Recurrent Implantation Failure (RIF) compared to fertile women. We analyzed the relative expression of genes coding for T-type Ca2+, ENaC, CFTR, and KCNQ1 channels in endometrial samples from 20 RIF-affected and 10 control women, aged 22–35, via microarray analysis and quantitative real-time PCR. Additionally, we examined DNA methylation in the regulatory region of KCNQ1 using ChIP real-time PCR. The bioinformatics component of our research included Gene Ontology analysis, protein–protein interaction networks, and signaling pathway mapping to identify key biological processes and pathways implicated in RIF. This led to the discovery of significant alterations in the expression of ion channel genes in RIF women’s endometrium, most notably an overexpression of CFTR and reduced expression of SCNN1A, SCNN1B, SCNN1G, CACNA1H, and KCNQ1. A higher DNA methylation level of KCNQ1’s regulatory region was also observed in RIF patients. Gene-set enrichment analysis highlighted a significant presence of genes involved with ion transport and membrane potential regulation, particularly in sodium and calcium channel complexes, which are vital for cation movement across cell membranes. Genes were also enriched in broader ion channel and transmembrane transporter complexes, underscoring their potential extensive role in cellular ion homeostasis and signaling. These findings suggest a potential involvement of ion channels in the pathology of implantation failure, offering new insights into the mechanisms behind RIF and possible therapeutic targets.

Effects of potassium-mediated electrical communication inhibition on nitrogen removal in microbial fuel cells

Potassium ion signaling mediates microbial communication in electroactive biofilms within microbial fuel cells (MFCs), but its role in nitrogen removal remains unclear. This study investigated the impact of inhibiting potassium signaling on nitrogen removal in MFCs using tetraethylammonium chloride (TEA) as an inhibitor. Results demonstrated that 5 mM and 10 mM TEA reduced the maximum power generation of MFCs from 77.95 mW/cm2 to 57.18 mW/cm2 and 48.23 mW/cm2, respectively. Correspondingly, total nitrogen (TN) removal efficiency was decreased from 46.57 ± 1.01% to 35.93 ± 0.63% and 38.97 ± 0.74%, respectively. This decline was attributed to inhibited potassium ion signaling, which compromised the electrochemical performance of the MFC and hindered the nitrogen removal process. The relative abundance of exoelectrogen Geobactor decreased from 15.37% to 5.17% and 8.05%, while the relative abundance of cathodic nitrifying bacteria Nitrosomonas decreased from 17.87% to 4.92% and 3.63% under 5 mM and 10 mM TEA. These findings underscore the crucial role of potassium ion signaling in enhancing the bioelectrochemical nitrogen removal process in MFCs.

Sprayable biomimetic double mask with rapid autophasing and hierarchical programming for scarless wound healing.

Current sprayable hydrogel masks lack the stepwise protection, cleansing, and nourishment of extensive wounds, leading to delayed healing with scarring. Here, we develop a sprayable biomimetic double wound mask (BDM) with rapid autophasing and hierarchical programming for scarless wound healing. The BDMs comprise hydrophobic poly (lactide-co-propylene glycol-co-lactide) dimethacrylate (PLD) as top layer and hydrophilic gelatin methacrylate (GelMA) hydrogel as bottom layer, enabling swift autophasing into bilayered structure. After photocrosslinking, BDMs rapidly solidify with strong interfacial bonding, robust tissue adhesion, and excellent joint adaptiveness. Upon implementation, the bottom GelMA layer could immediately release calcium ion for rapid hemostasis, while the top PLD layer could maintain a moist, breathable, and sterile environment. These traits synergistically suppress the inflammatory tumor necrosis factor-α pathway while coordinating the cyclic guanosine monophosphate/protein kinase G-Wnt/calcium ion signaling pathways to nourish angiogenesis. Collectively, our BDMs with self-regulated construction of bilayered structure could hierarchically program the healing progression with transformative potential for scarless wound healing.

Measurements of Atmospheric HO2 Radicals Using Br-CIMS with Elimination of Potential Interferences from Ambient Peroxynitric Acid.

As a promising direct measurement method of atmospheric hydroperoxyl radicals (HO2), bromide chemical ionization mass spectrometry (Br-CIMS) has been first demonstrated by Sanchez et al. (Atmos. Meas. Tech. 2016, 9, 3851-3861). However, field application of this method is currently still sparse, and there is still a gap between measured HO2 concentrations and calculated ones derived from the atmospheric equilibrium between HO2 and peroxynitric acid (HO2NO2). In this work, we constructed an improved Br-CIMS with optimizations of custom-built front-end devices, chamber pressures, and instrumental voltages to achieve a 3σ detection limit of 0.5 ppt at an integration time of 60 s and a sensitivity of 1-3 cps ppt-1 under a total reagent ion signal of 0.2 MHz for HO2 detection. HO2NO2, a product from atmospheric reactions between HO2 and NO2, can also be detected by Br-CIMS, whose interference on the HO2 measurement was found but nearly eliminated by regulating key CIMS voltages to minimize the decomposition of (BrHO2NO2)- ions in the MS. In addition, a 2 week field campaign was carried out in urban Shanghai, demonstrating that the interference of HO2 from ambient HO2NO2 was less than 10% of the true HO2 signal under our optimized CIMS voltage setting. Our study suggests that Br-CIMS is a reliable technique for atmospheric HO2 measurements.

Advances in Millimeter-Wave Treatment and Its Biological Effects Development.

This comprehensive review critically examines the current state of research on the biological effects of millimeter-wave (MMW) therapy and its potential implications for disease treatment. By investigating both the thermal and non-thermal impacts of MMWs, we elucidate cellular-level alterations, including changes in ion channels and signaling pathways. Our analysis encompasses MMW's therapeutic prospects in oncology, such as inducing apoptosis, managing pain, and modulating immunity through cytokine regulation and immune cell activation. By employing a rigorous methodology involving an extensive database search and stringent inclusion criteria, we emphasize the need for standardized protocols to enhance the reliability of future research. Although MMWs exhibit promising therapeutic potential, our findings highlight the urgent need for further elucidation of non-thermal mechanisms and rigorous safety assessments, considering the intricate nature of MMW interactions and inconsistent study outcomes. This review underscores the importance of focused research on the biological mechanisms of MMWs and the identification of optimal frequencies to fully harness their therapeutic capabilities. However, we acknowledge the challenges of variable study quality and the necessity for advanced quality control measures to ensure the reproducibility and comparability of future investigations. In conclusion, while MMW therapy holds promise as a novel therapeutic modality, further research is imperative to unravel its complex biological effects, establish safety profiles, and optimize treatment protocols before widespread clinical application.

Development of an Ion Mobility Spectrometer Based on a Pulsed Photoelectric Effect Ionization Source.

Ion mobility spectrometry (IMS) is a compact and sensitive trace gas analysis instrument that ionizes the sample into ions for detection. Typically, an ion gate is used to cut the continuous ion beam into ion packets for separation and detection. However, commonly used ion gates suffer from complex structures or low ion transmission rates, making the gateless IMS a viable alternative. In this study, an IMS based on a pulsed photoelectric effect ionization source was designed. The photoelectrons were generated by irradiating a photoelectric material with a back-illuminated pulsed xenon lamp. This allows for low-energy photoelectron generation and the production of simple reactant ions (O2-(H2O)n) and thus negative product ions. The photoelectron current generated by this ionization source was analyzed, which can reach an intensity of a few microamperes and can be converted into an ion signal exceeding 10 nA. The introduction of the pulsed photoelectric effect ionization source makes it possible to generate separate ion packets and complete ion injection when a constant electric field is maintained in the ionization region. And with an assisted pulsed electric field in the ionization region, the resolving power of the system can be effectively improved to 1.85 times that of the constant electric field. The IMS developed in this study was used for the detection of common volatile hazardous chemicals, yielding effective results. The detection limit for phenol was below 1 ppb, and the dynamic response range exceeded 1 order of magnitude, which implies the potential applications of this IMS to detect substances with high electron affinity, such as explosives detection in public safety.

Evaluation of femtosecond-LA-ICP-TOFMS for multi-elemental mapping at cellular resolution of human-tissue from cancer patients

The characterization of the multi-elemental distributions within a thin tissue section of a liver metastasis from colorectal cancer patient after oxaliplatin-based chemotherapy, is critically evaluated using Ultraviolet Femtosecond Laser Ablation Inductively Coupled Plasma-Time of Flight Mass Spectrometry (UV-fs-LA-ICP-TOFMS). Different femtosecond laser ablation conditions, in terms of spot size and energy per pulse, were investigated to achieve proper ablation of the formalin-fixed paraffin-embedded tumor sections, while also trying to minimize the ablation of the glass substrate. Moreover, histological images of the tissues before and after the ablation processes were combined with UV-fs-LA-ICP-TOFMS elemental mapping to achieve multi-elemental spatial distributions at cellular level. For instance, spatial distributions of endogenous 31P, 56Fe, 63Cu and 64Zn analytes were determined within the thin tissue section. Furthermore, spatial distribution of elements such as 24Mg, 28Si, and 40Ca were employed to study glass substrate ablation during tissue analysis. Additional analytes, which might be partially associated to compounds employed on hematoxylin and eosin tissue staining processes, such as 23Na, 27Al, 32S, 39K, 79Br and 127I, were also detected. Finally, the accumulation of the oxaliplatin-based chemotherapy products in the stroma was confirmed from the spatial distribution of 196Pt ion signals within the tissue.

Assessment of the molecular mechanism in fish using eugenol as anesthesia based on network pharmacology.

Eugenol is a commonly used fish anesthetic, but its mechanism of action is not fully understood. This study employed network pharmacology, molecular docking, and molecular dynamics simulation to explore the anesthetic targets of eugenol in fish. Initially, 63 potential targets for eugenol anesthesia were identified using databases such as SwissTarget, TargetNet, GeneCards, OMIM, and TTD. The DAVID database was utilized to analyze the GO functions and KEGG pathways of these targets, revealing 384 GO enrichment terms and 43 KEGG pathways. These terms involved neuroactive ligand-receptor interaction, calcium signaling pathway, and synaptic transmission. Subsequently, AutodockTools software facilitated molecular docking with targets in the KEGG pathway for "neuroactive ligand-receptor interaction." The results showed that eugenol had a strong affinity with these proteins. Concurrently, molecular dynamics simulations were conducted on the proteins with the top four lowest binding energies (Cnr1, Oprk1, Nr3c1, and Chrm5a) in the presence of eugenol. The eugenol-protein complexes remained stable and equilibrated within the dynamic environment. The results indicated that eugenol-anesthesia might affect membrane receptors, neurotransmitters, and ion signaling. This study elucidates the anesthetic mechanism of eugenol, enriches the primary data on fish anesthesia, and offers new analytical tools for understanding the action mechanisms of fishery drugs.

Ion Signaling in Cell Motility and Development in Dictyostelium discoideum.

Cell-to-cell communication is fundamental to the organization and functionality of multicellular organisms. Intercellular signals orchestrate a variety of cellular responses, including gene expression and protein function changes, and contribute to the integrated functions of individual tissues. Dictyostelium discoideum is a model organism for cell-to-cell interactions mediated by chemical signals and multicellular formation mechanisms. Upon starvation, D. discoideum cells exhibit coordinated cell aggregation via cyclic adenosine 3',5'-monophosphate (cAMP) gradients and chemotaxis, which facilitates the unicellular-to-multicellular transition. During this process, the calcium signaling synchronizes with the cAMP signaling. The resulting multicellular body exhibits organized collective migration and ultimately forms a fruiting body. Various signaling molecules, such as ion signals, regulate the spatiotemporal differentiation patterns within multicellular bodies. Understanding cell-to-cell and ion signaling in Dictyostelium provides insight into general multicellular formation and differentiation processes. Exploring cell-to-cell and ion signaling enhances our understanding of the fundamental biological processes related to cell communication, coordination, and differentiation, with wide-ranging implications for developmental biology, evolutionary biology, biomedical research, and synthetic biology. In this review, I discuss the role of ion signaling in cell motility and development in D. discoideum.

Discovery of Positive Allosteric Modulators of α 7 nAChR by an Ensemble-based Virtual Screening Method, Molecular Dynamics Simulation, and in vitro Biological Activity Testing

The [Formula: see text]7 nicotinic acetylcholine receptor (nAChR) is a neurotransmitter receptor and a promising therapeutic target for neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. In this study, we used deep learning-based classification modeling, molecular docking, and intracellular calcium signal detection experiments to identify positive allosteric modulators (PAMs) of the [Formula: see text]7 nAChR from natural tobacco products. First, we used a classification prediction model based on the direct message-passing neural network (D-MPNN) and molecular docking to predict potential [Formula: see text]7 PAMs. Subsequently, absorption, distribution, metabolism, excretion, and toxicity (ADMET) predictions were performed to determine its pharmacological properties and minimal toxic side effects, leading to the selection of three natural compounds for in vitro activity validation. Calcium signaling assay experiments revealed that diosmetin can enhance nicotine-induced calcium ion signaling. 100 ns molecular dynamics (MD) simulations indicated that diosmetin can form a dense and stable complex with [Formula: see text]7 nAChR. This study provides valuable insights for the design of more effective and selective ligands for the [Formula: see text]7 nAChR.

Matrices to enhance the ion yield of OLED molecules in ToF-SIMS: An interesting alchemist solution

Since the early days of time of flight secondary ion mass spectrometry (ToF-SIMS), increasing the ion signal has been crucial. It is even more crucial when performing tandem mass spectrometry experiments. To achieve this goal, many developments have been made over the years, which are divided into two categories: instrumental development and sample modification. The latter involves sample metallization, matrix deposition, or changing the temperature of the measurement. In this study, the possibility of using matrices to enhance the signals of organic light emitting device (OLED) molecules was explored. Seven molecules commonly used in OLEDs were separately deposited on Si wafers: Alq3, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile, Ir(mppy)3, N,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)benzidine, 2,2′,7,7′-tetra(N,N-ditolyl)-amino-spiro-bifluor (STTB), and tris(4-carbazoyl-9-ylphenyl)amine. Using the same solvent, three different matrices with different thicknesses, common in matrix assisted light desorption ionization time of flight mass spectrometry, α-cyano-4-hydroxycinnamic acid, 2,5-dihydrobenzoic acid (DHB), and dihydrochloride N-(1-Naphthyl)ethylenediamine, were sprayed on these surfaces. Spectra were acquired for all compounds and spraying conditions in static ToF-SIMS experiments for Alq3 chemical imaging and depth profiling were performed. This allowed the investigation of the fragmentation pattern of the chosen matrices in ToF-SIMS and, thus, obtained a reference for these molecules. The results show that matrices can enhance the signal of fragments of the studied molecules, for example, the signal of STTB is increased with DHB spraying. Samples sprayed only with the solvent were also prepared to verify the impact of the matrices on the signal. Spraying with the solvent alone can enhance the signal even more than the matrices up to four times in the case of Alq3. This result opens new possibilities in the field of matrix-enhanced ToF-SIMS in terms of applications and matrix choices.

Nano-vibration exciter: Hypoxia-inducible factor 1 signaling pathway-mediated extracellular vesicles as bioactive glass substitutes for bone regeneration

Bioactive glasses (BG) play a vital role in angiogenesis and osteogenesis through releasing functional ions. However, the rapid ion release in the early stage will cause excessive accumulation of metal ions, which in turn leads to obvious cytotoxicity, long-term inflammation, and bone repair failure. Inspired by the vibration exciter, small extracellular vesicles (sEVs) obtained by treating mesenchymal stem cells with copper-doped bioactive glass (CuBG-sEVs), is prepared as a nano-vibration exciter. The nano-vibration exciter can convert the ion signals of CuBG into biochemical factor signals through hypoxia-inducible factor 1 (HIF-1) signaling pathway and its activated autophagy, so as to better exert the osteogenic activity of BG. The results showed that CuBG extracts could significantly improve the enrichment of key miRNAs and increase the yield of CuBG-sEVs by activating HIF-1 signaling pathway and its activated autophagy. Cell experiments showed that CuBG-sEVs are favor to cell recruitment, vascularization and osteogenesis as the enrichment of key miRNAs. The animal experiments results showed that CuBG-sEVs stimulated angiogenesis mediated by CD31 and promoted bone regeneration by activating signaling pathways related to osteogenesis. These findings underscored the significant potential of sEVs as alternative strategies to better roles of BG.

In-Situ Gas Permeation-Driven Ionic Current Rectification of Heterogeneously Charged Nanopore Arrays.

Ionic diodes provide ionic current rectification (ICR), which is useful for micro-/nanofluidic devices for ionic current-mediated applications. However, the modulation of ICR is not fully developed, and current challenges include limited active control and localized modulation for further multiplexing of micro-/nanofluidic ionic diodes. Herein, a microfluidic device integrated with particle-assembly-based ionic diodes (PAIDs) and a gas-flow channel above them is presented. Exploiting in-situ gas permeation through a polymeric film, precise control over the physiochemical conditions of the nanopores within the PAIDs, leading to the modulation of ICR is demonstrated. The investigation not only characterizes the rectification properties of the PAIDs but also unveils their capacitor-like behavior and the ability to actively modulate ICR using various gas flows. Furthermore, the reversible modulation of ICR through dynamic switching of gas-dissolved solutions, enabling ion-signal amplification is showcased. This pioneering approach of in situ gas-permeation offers programmable manipulation of ion transport along PAIDs, thereby positioning ionic diodes as versatile nanofluidic components. Looking ahead, the development of multiplexed PAIDs in an addressable manner on a chip holds promise for practical applications across diverse fields, including ion signaling, ion-based logic, chemical reactors, and (bio)chemical sensing.

Assessing the matrix effects on MALDI-MS in the positive and negative ion mode detection for protein-protected metal nanoclusters

Protein-protected metal nanoclusters (MNCs) represent a new class of highly photoluminescent nanomaterials that have wide applications. Suitable reaction conditions combining protein and metal precursors can produce a vast range of different NC sizes (i.e. different number of metal atoms). The average number of metal atoms per protein can be determined by mass spectrometry (MS). MS coupled with matrix-assisted laser desorption ionization (MALDI) presents a number of advantages such as detection with high sensitivity of nanoclusters with high molecular weights. Although many protein-protected MNCs have been characterized by MALDI-MS, a large dispersion in the number of metal atoms has been reported mainly due to sample preparation. In this work, we optimized the protocols for negative and positive ion detection mode as a general MALDI-MS sample preparation method for protein-protected MNCs (bovine serum albumin and lysozyme and with gold and silver). Negative and positive ion mode detection was compared, showing that negative ion mode detection in MALDI-MS can also be used with acidic matrices. Obvious matrix effects on ion signals and peak positions by MALDI-MS were observed. The average metal numbers of MNCs embedded in proteins are different depending on the MALDI matrix. The matrix effects give a warning for more serious consideration on MALDI-MS measurement and spectra analysis of MNCs.

Time-Resolved Ion Mobility Spectrometry with a Stop Flow Confined Volume Reaction Region.

An ion source concept is described where the sample flow is stopped in a confined volume of an ion mobility spectrometer creating time-dependent patterns of ion patterns of signal intensities for ions from mixtures of volatile organic compounds and improved signal-to-noise rate compared to conventional unidirectional drift gas flow. Hydrated protons from a corona discharge were introduced continuously into the confined volume with the sample in air at ambient pressure, and product ions were extracted continuously using an electric field for subsequent mobility analysis. Ion signal intensities for protonated monomers and proton bound dimers were measured and computationally extracted using mobilities from mobility spectra and exhibited distinct times of appearance over 30 s or more after sample injection. Models, and experimental findings with a ternary mixture, suggest that the separation of vapors as ions over time was consistent with differences in the reaction rate for reactions between primary ions from hydrated protons and constituents and from cross-reactions that follow the initial step of ionization. The findings suggest that the concept of stopped flow, introduced here for the first time, may provide a method for the temporal separation of atmospheric pressure ions. This separation relies on ion kinetics and does not require chromatographic technology.

Photoreduced Ag+/sodium alginate supramolecular hydrogel as a sensitive SERS membrane substrate for rapid detection of uranyl ions

BackgroundIn the fields of environmental monitoring and nuclear emergency, in order to obtain the relevant information of uranyl-induced environmental pollution and nuclear accident, it is necessary to establish a rapid quantitative analytical technique for uranyl ions. As a new promising technique, surface-enhanced Raman scattering (SERS) is hopeful to achieve this goal. However, uranyl ions are easily desorbed from SERS substrates under acidic conditions, and the structures of SERS substrates will be destroyed in the strong acidic aqueous solutions. Besides, the quantitative detection ability of SERS for uranyl ions needs to be promoted. Hence, it is necessary to develop new SERS substrates for accurate quantitative detection of trace uranyl in environmental water samples, especially in acidic solutions. ResultsIn this work, we prepared silver ions/sodium alginate supramolecular hydrogel membrane (Ag+/SA SMH membrane), and the Ag+ ions from the membrane were transformed into Ag/Ag2O complex nanoparticles under laser irradiation. The Raman signal of uranyl was strongly enhanced under the synergistic interaction of electromagnetic enhancement derived from the Ag nanoparticles and charge transfer enhancement between uranyl and Ag2O. Utilizing the peak of SA (550 cm−1) as an internal standard, a quantitative detection with a LOD of 6.7 × 10−9 mol L−1 was achieved due to a good linear relation of uranyl concentrations from 1.0 × 10−8 mol L−1 to 2 × 10−6 mol L−1. Furthermore, foreign metal ions hardly affected the SERS detection of uranyl, and the substrate could determine trace uranyl in natural water samples. Particularly, the acidity had no obvious effect on SERS signals of uranyl ions. Therefore, in addition to the detection of uranyl ions in natural water samples, the proposed strategy could also detect uranyl ions in strong acidic solutions. Significance and noveltyA simple one-step method was used to prepare an Ag+/SA SMH membrane for rapid quantitative detection of uranyl ions for the first time. The proposed substrate successfully detected uranyl ions under acidic conditions by immobilizing uranyl ion in hydrogel structure. In comparison with the previous studies, a more accurate quantitative analysis for uranyl ions was achieved by using an internal standard, and the proposed strategy could determine trace uranyl in either natural water samples or strong acidic solutions.

Bioinspired Heterocoordination in Adaptable Cobalt Metal-Organic Framework for DNA Epigenetic Modification Detection.

Metal-organic frameworks (MOFs) show unique advantages in simulating the dynamics and fidelity of natural coordination. Inspired by zinc finger protein, a second linker was introduced to affect the homogeneous MOF system and thus facilitate the emergence of diverse functionalities. Under the systematic identification of 12 MOF species (i.e., metal ions, linkers) and 6 second linkers (trigger), a dissipative system consisting of Co-BDC-NO2 and o-phenylenediamine (oPD) was screened out, which can rapidly and in situ generate a high photothermal complex (η = 36.9%). Meanwhile, both the carboxylation of epigenetic modifications and metal ion (Fe3+, Ni2+, Cu2+, Zn2+, Co2+ and Mn2+) screening were utilized to improve the local coordination environment so that the adaptable Co-MOF growth on the DNA strand was realized. Thus, epigenetic modification information on DNA was converted to an amplified metal ion signal, and then oPD was further introduced to generate bimodal dissipative signals by which a simple, high-sensitivity detection strategy of 5-hydroxymethylcytosine (LOD = 0.02%) and 5-formylcytosine (LOD = 0.025‰) was developed. The strategy provides one low-cost method (< 0.01 $/sample) for quantifying global epigenetic modifications, which greatly promotes epigenetic modification-based early disease diagnosis. This work also proposes a general heterocoordination design concept for molecular recognition and signal transduction, opening a new MOF-based sensing paradigm.

Alignment of ND3 molecules in dc-electric fields.

The control of movement and orientation of gas-phase molecules has become the focus of many research areas in molecular physics. Here, ND3 molecules are polarized in a segmented, curved electrostatic guide and adiabatically aligned inside a rotatable mass spectrometer (MS). Alignment is probed by photoionization using a linearly polarized laser. Rotation of the polarization at fixed MS orientation has the same effect as the rotation of the MS at fixed polarization, proving that the molecular alignment adiabatically follows the MS axis. Polarization-dependent ion signals reveal state-specific populations and allow for a quantification of the aligned sample in the space-fixed reference frame.

Probing Metal Ion Adduction in the ESI Charged Residue Mechanism via Gas-Phase Ion/Ion Chemistry.

The final stages of the charged residue mechanism/model (CRM) for ion generation via electrospray ionization (ESI) involves the binding of excess charge onto analyte species. Ions of both polarities can bind to the analyte with an excess of ions of the same polarity as the droplet. For large biomolecule/biocomplex ions, which are commonly the species of interest in native mass spectrometry (MS), the binding of acids and salts onto the analyte can lead to extensive broadening of ion signals due to adduction. Therefore, heating step(s) to facilitate desolvation and salt adduct removal are commonplace. In this work, we describe an approach to study the final stages of CRM using gas-phase ion/ion reactions to generate analyte ion/salt clusters of well-defined composition, followed by gas-phase collision-induced dissociation (CID). While there are many variables that can be studied systematically via this approach, the work described herein is focused on salt clusters of the form [Na10X11]-, where X = acetate (Ac-), chloride (Cl-), or nitrate (NO3-), in reaction with a common charge state of ubiquitin as well as several model peptides. Experiments in which equimolar quantities of each salt (i.e., NaAc, NaCl, and NaNO3) are subjected to ESI with ubiquitin (Ubi) and gas-phase ion/ion reaction studies involving [Na10X11]- and [Ubi + 6H]6+ show similar trends, in terms of the extent of sodium ion incorporation into the protein ions. Ion/ion reaction studies using model peptides show that the acetate-containing salt transfers significantly more Na+ ions into the peptide ions. Exchange of Na+ for H+ is shown to occur at the C-terminus and at up to all of the amide linkages using [Na10X11]-, whereas only the C-terminus engages in Na+/H+ exchange with [Na10Cl11]- and [Na10(NO3)11]-. In the latter cases, an additional Na+ is taken up as the excess positive charge, presumably due to solvation of the charge by multiple sites (e.g., carbonyl oxygens and basic sites).