Mass Spectrometry Research Articles

Immunoglobulins G from Patients with Systemic Sclerosis Modify the Molecular Signatures of Endothelial Cells

ObjectiveAntinuclear antibodies (ANA) are powerful biomarkers in systemic sclerosis (SSc). Functional antibodies (FA) might be implicated in vasculopathy, in which endothelial cells (EC) are key players. We aimed to explore...

Two eIF4E paralogs occupy separate germ granule mRNPs that mediate mRNA repression and translational activation.

We studied translation factor eIF4E paralogs that regulate germline mRNAs. Translational control of mRNAs is essential for germ cell differentiation and embryogenesis. Messenger ribonucleoprotein (mRNP) complexes assemble on mRNAs in the nucleus, as they exit via perinuclear germ granules, and in the cytoplasm. Bound mRNP proteins including eIF4Es exert both positive and negative post-transcriptional regulation. In C. elegans, germ granules are surprisingly dynamic mRNP condensates that remodel during development. Two eIF4E paralogs (IFE-1 and IFE-3), their cognate eIF4E-Interacting Proteins (4EIPs), and polyadenylated mRNAs are present in germ granules. Affinity purification of IFE-1 and IFE-3 mRNPs allowed mass spectrometry and mRNA-Seq to identify other proteins and the mRNAs that populate stable eIF4E complexes. We find translationally repressed mRNAs (e.g. pos-1, mex-3, spn-4, etc.) enriched with IFE-3, but excluded from IFE-1. Identified mRNAs overlap substantially with mRNAs previously described to be IFE-1-dependent for translation. The findings suggest that oocytes and embryos utilize the two eIF4Es for opposite purposes on critically regulated germline mRNAs. Sublocalization within adult perinuclear germ granules suggests an architecture in which Vasa/GLH-1, PGL-1 and the IFEs are stratified, which may facilitate sequential remodeling of mRNPs leaving the nucleus. Biochemical composition of isolated mRNPs indicates opposing yet cooperative roles for the two eIF4Es. We propose that the IFEs accompany controlled mRNAs in the repressed or activated state during transit to the cytoplasm. Copurification of IFE-1 with IFE-3 suggests they may interact to move repressed mRNAs to ribosomes.

Full Window Data-Independent Acquisition Method for Deeper Top-Down Proteomics.

Top-down proteomics (TDP) is emerging as a vital tool for the comprehensive characterization of proteoforms. However, as its core technology, top-down mass spectrometry (TDMS) still faces significant analytical challenges. While data-independent acquisition (DIA) has revolutionized bottom-up proteomics and metabolomics, they are rarely employed in TDP. The unique feature of protein ions in an electrospray mass spectrum as well as the data complexity require the development of new DIA strategies. This study introduces a machine learning-assisted Full Window DIA (FW-DIA) method that eliminates precursor ion isolation, making it compatible with a wide range of commercial mass spectrometers. Moreover, FW-DIA leverages all precursor protein ions to generate high-quality tandem mass spectra, enhancing signal intensities by ∼50-fold and protein sequence coverage by 3-fold in a modular protein analysis. The method was successfully applied to the analysis of a five-protein mixture under native conditions and Escherichia coli ribosomal proteoform characterization.

Plasma metabolomics of Mycoplasma synoviae infection in SPF White Leghorn hens by liquid chromatography-tandem mass spectrometry

Mycoplasma synoviae (M. synoviae) is a major bacterial pathogen that causes serious economic losses in the global poultry industry. Systemic changes in specific pathogen free White Leghorn egg-laying hens after M. synoviae infection were investigated using intra-tracheally inoculated animals. Samples were collected 10 days post-infection (dpi) (204-day-old) and 52 dpi (246-day-old). Infection caused air sac lesion, footpad swelling and oviduct atrophy. The qPCR and in situ hybridization showed that bacteria colonized the trachea and oviduct, and that bacterial loads in the magnum and uterus were significantly higher than in the infundibulum and isthmus. Histopathological examination revealed increased tracheal mucosal thickening accompanied by inflammatory cell infiltration, and that tubular glands of the uterus were edematous or dissolved. Infection also induced decreased egg production and eggshell strength, and eggshell apex abnormalities appeared at 14 dpi. Plasma metabolomics of hens analyzed by liquid chromatography-tandem mass spectrometry showed 168 and 128 differentially-expressed metabolites (DEM) at 10 and 52 dpi, respectively. Pathway analysis revealed that DEM at 10 dpi were enriched in five distinctive pathways: regulation of the actin cytoskeleton, neuroactive ligand-receptor interaction, sphingolipid metabolism, gap junctions, and necroptosis. In contrast, DEM at 52 dpi were enriched in fifteen pathways involved in steroid hormone biosynthesis, ferroptosis, the calcium signaling pathway, apelin signaling pathway, progesterone-mediated oocyte maturation, and oocyte meiosis. Combined metabolic analysis demonstrated that changes in ethylsalicylate, nicotinamide, (3-Methoxy-4-hydroxyphenyl) ethylene glycol sulfate, sphingosine-1-phosphate (d18:1), carnitine C24:6, and 15(R)-prostaglandin E1 correlated the best with M. synoviae infection. This study provides new insights into understanding pathogen mechanisms and signposts novel treatments for M. synoviae infection in poultry.

Engineering Yarrowia lipolytica for Enhanced Gastrodin Production via High-Throughput Screening and Transcriptomics-Guided Optimization.

Gastrodin, the principal bioactive component of the renowned herb Gastrodia elata, is extensively utilized in medicinal drugs and nutraceuticals. This study seeks to enhance microbial production of gastrodin through high-throughput screening (HTS) and transcriptomics-guided optimization. Initially, atmospheric pressure and room temperature plasma (ARTP)-mediated mutagenesis were employed to develop a library of mutant strains. Furthermore, a transcription factor-based biosensor and a high-throughput solid-phase extraction mass spectrometry (HP-SPE-MS) were evaluated to establish an HTS method for gastrodin. Consequently, mutant strain MT8 was isolated, producing 9.8 g/L of gastrodin in YPD medium, which represents a 55.6% increase compared to the control strain. Next, key genes identified via transcriptomics were overexpressed in strain MT8, with the overexpression of gene YALI2E01737g, a gene involved in the synthesis of aromatic amino acids, significantly enhancing gastrodin production to reach 10.1 g/L. In addition, fermentation process optimization further improved gastrodin titer up to 13.1 g/L in shaking flasks. This study demonstrated the utility of HTS techniques to enhance gastrodin production and paved the way for its future industrial application.

Cultivation technology optimization and identification of secondary metabolites from elm oyster mushroom Hypsizygus ulmarius (Bull.) Redhead (Agaricomycetes) through GC-MS metabolomic profiling from India

ABSTRACT Hypsizygus ulmarius, a novel oyster mushroom species, offers potential scope due to its low-cost production, high biological efficiency, and notable nutritional, medicinal, and therapeutic properties. The present study standardized commercial cultivation technology for H. ulmarius in the Trans-Gangetic Plains of India. The mycelium grew well on potato dextrose agar and carrot extract broth at pH 8.0 and temperature 25 C. Wheat straw supplemented with the cotton seed hull at the rate of 10.0% dose, spawned with pearl millet grain spawn at the rate of 5.0% spawn dose, gave the highest mushroom yield (953.66 g/0.4 kg dry substrate) with biological efficiency (238.41%). The first flush sporocarps were freeze-dried for physicochemical characterization, revealing 16 strong peaks and 8 functional groups via Fourier transform infrared (FTIR) analysis. Particle size averaged 45.97 µm of mushroom powder, and scanning electron microscopy (SEM) analysis showed diverse surface textures. Gas chromatography–mass spectrometry metabolic profiling identified 20 key secondary metabolites each from hexane and methanolic extracts, with therapeutic uses that are valuable for pharmaceutical, nutraceutical, and food industry applications.

Reducing laboratory delays in blood culture pathogen identification: a quality improvement project

Sepsis is a medical emergency caused by bacteria in the bloodstream and a dysregulated immune response. It is important to identify the bacteria rapidly so that the patient receives effective...

Deep tissue sensing of chiral molecules using polarization-enhanced photoacoustics.

Chiral molecule sensing is typically performed using techniques like chromatography, electrophoresis, enzymatic assays, mass spectrometry, and chiroptical methods. While polarimetry allows for in vivo sensing up to 1 mm depth using ultraviolet-visible light, it is limited by dominant light scattering beyond this depth. We propose that photoacoustic sensing in the near-infrared II (NIR-II) window can enable deep tissue sensing as acoustic waves scatter less than light. To achieve this, we developed a photoacoustic polarization-enhanced optical rotation sensing (PAPEORS) system, capable of estimating optical rotation from photoacoustic signals and correlating it with chiral molecular concentration for depths up to 3.5 mm. Experiments were conducted using aqueous glucose solutions, naproxen, serum-based glucose samples, and ex vivo chicken tissue. PAPEORS achieved a detection limit of 80 mg/dl while using circularly polarized light with serum samples, demonstrating the potential for deep-tissue chiral molecular sensing. PAPEORS holds promise for in vivo sensing and easy miniaturization using single wavelength.

Natural human tRNAAla anticodon variants mistranslate the genetic code.

Transfer RNAs (tRNAs) play an essential role in protein synthesis by linking the nucleic acid sequences of gene products to the amino acid sequences of proteins. There are > 400 functional tRNA genes in humans, and adding to this diversity, there are many single nucleotide polymorphisms in tRNAs across our population, including anticodon variants that mistranslate the genetic code. In human genomes, we identified three rare alanine tRNA (tRNAAla) variants with non-synonymous anticodon mutations: tRNAAlaCGC G35T, tRNAAlaUGC G35A, and tRNAAlaAGC C36T. Since alanyl-tRNA synthetase (AlaRS) does not recognize the anticodon, we hypothesized that these tRNAAla variants will mis-incorporate Ala at glutamate (Glu), valine (Val), and threonine (Thr) codons, respectively. We found that expressing the naturally occurring tRNAAla variants in human cells led to defects in protein production without a substantial impact on cell growth. Using mass spectrometry, we confirmed and estimated Ala mis-incorporation levels at Glu (0.7%), Val (5%) and Thr (0.1%) codons. Although Ala mis-incorporation was higher at Val codons, cells mis-incorporating Ala at Glu codons had the most severe defect in protein production. The data demonstrate the ability of natural human tRNAAla variants to generate mistranslation leading to defects in protein production that depend on the nature of the amino acid replacement.

Rapid, non-invasive breath analysis for enhancing detection of silicosis using mass spectrometry and interpretable machine learning

Occupational lung diseases, such as silicosis, are a significant global health concern, especially with increasing exposure to engineered stone dust. Early detection of silicosis is helpful for preventing disease progression, but existing diagnostic methods, including x-rays, computed tomography scans, and spirometry, often detect the disease only at late stages. This study investigates a rapid, non-invasive diagnostic approach using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) to analyze volatile organic compounds (VOCs) in exhaled breath from 31 silicosis patients and 60 healthy controls. Six different interpretable machine learning (ML) models with Shapley additive explanations (SHAP) were applied to classify these samples and determine VOC features that contribute the most significantly to model accuracy. The extreme gradient boosting classifier demonstrated the highest performance, achieving an area under the receiver-operator characteristic curve of 0.933 with the top ten SHAP features. Them/z442 feature, potentially corresponding to leukotriene-E3, emerged as a significant predictor for silicosis. The VOC sampling and measurement process takes less than five minutes per sample, highlighting its potential suitability for large-scale population screening. Moreover, the ML models are interpretable through SHAP, providing insights into the features contributing to the model's predictions. This study suggests that APCI-MS breath analysis could enable early and non-invasive diagnosis of silicosis, helping to improve disease outcomes.

Underreporting of synthetic cathinone poisoning with clinical immunoassays: an experimental and observational study.

There is an increasing global concern about the use of synthetic cathinones (SCs). Detecting these drugs in human urine samples can be difficult, particularly in emergency settings. Cross-reactivity has been described for several immunoassays. We evaluated the analytical interference caused by common SCs in MDMA and amphetamine assays that use the EMIT Atellica CH (Siemens Healthineers) with both clinical and in-vitro experimental data. Drug-free urine samples were spiked with various concentrations (5 to 100 µg/mL) of 2-methylmethcathinone (MMC), 3-MMC, 4-MMC, 3-chloromethcathinone (CMC), methylone and alpha-PHP and tested using EMIT assays. The percentage of false positive results was determined in urine samples from patients above 18 years of age admitted to the ICU or emergency department who underwent routine toxicology screening and urine immunoassays over a four-year period. Confirmatory analyses of SC were performed by mass spectrometry techniques. False-positive results occurred for the MDMA assay with methylone (10 µg/mL) and 3-CMC (100 µg/mL) and for the amphetamine test with 2-MMC (50 µg/mL). We studied 2,033 urine samples from 1,812 patients (mean age 39 years, 61.8% men), of which 49 tested positive for amphetamine and 76 for MDMA. SCs were responsible for a false positive rate of 16.3% for the amphetamine tests and 17.1% for the MDMA tests. Most of the false-positive tests occurred among young male patients (mean age 38 years, 92.8% men). This study demonstrates that SC intoxication may be underreported in immunoassay toxicology testing and should always be confirmed by specific mass spectrometry methods.

Novel activity assay for botulotoxin A1 detection using functionalized chips and matrix-assisted laser desorption/ionization mass spectrometry

ABSTRACT Background Botulinum neurotoxins (BoNTs) are a group of neurotoxins produced by Clostridium bacteria. Their effect on neuro-muscular connections through cleaving proteins of the SNARE complex results in blocking acetylcholine signal transduction. The FDA-approved mouse bioassay, which involves exposing live mice to potentially contaminated food, is the most widely used method. However, this assay is costly, time-consuming, and raises ethical concerns. Therefore, there is a need for alternative assays that can enzymatically measure the activity of BoNTs. Research design and methods We present an approach that combines the EndoPep-MS assay with protein affinity chips fabricated using ion soft-landing technology. Toxic activity is indirectly assessed by monitoring the N- and C-terminal fragments of the substrate peptide. This new method employs a protein array with affinity molecules targeting either the BoNT/A1 or the substrate peptide. Both variants enable in-situ reaction and detection of substrate peptides via MALDI-ToF MS on the protein chip. Results This method demonstrated successful detection of active BoNT/A1 in both buffer and complex matrices, achieving a detection limit of 0.5 ng/mL. Conclusions This study reports the in-situ detection of botulotoxin A1 using functionalized MALDI chips. The advantages of the MALDI chip technology include speed, robustness, cost-effectiveness, and possible automatization.

Pneumatically Assisted Microfluidic Probe for Enhanced Mass Spectrometry Imaging Performance.

A pneumatically assisted microfluidic probe (MFP) with two microfluidic channels has been developed for nanospray desorption electrospray ionization mass spectrometry imaging (nano-DESI MSI) of biological samples. This design simplifies the experimental setup, making it independent of the vacuum suction at the mass spectrometer inlet. The implementation of pneumatically assisted solvent flow through the probe enables stable, high solvent flow rates required to maintain a consistent liquid bridge during high-throughput MSI experiments. This approach addresses challenges associated with using MFP nano-DESI probes on mass spectrometers that have limited vacuum suction and the operation of MFPs with small microfluidic channels. We demonstrate the robustness of the pneumatically assisted MFP with 30 μm channels, which cannot be used for high-throughput MSI experiments without pneumatic assistance, by successfully imaging five mouse brain tissue sections without interruptions.

Investigation of Surface-Induced Dissociation Processes via Molecular Dynamics Simulations of Wall Collisions of Large Droplets Produced by Electrospray Ionization.

Electrospray ionization is one of the most utilized ionization techniques in atmospheric pressure mass spectrometry. Recent experimentally reported results are in disagreement with fundamentals revolving around ESI droplet sizes and their lifetimes. Specifically, much larger droplet sizes and longer lifetimes have been experimentally observed to exist in typical ESI ion sources. Experiments involving a custom scan mode on a triple quadrupole system have shown that high-mass fragments of large ESI droplets can be observed in mass spectra. Initial hypotheses rationalizing these results were focused on the creation of droplet fragments by collision-induced dissociation (CID). The collision energy accumulated by CID is most likely too small to lead to the observed mass spectra. In response, surface-induced dissociation (SID) was proposed as an additional mechanism to provide large amounts of collision energy to the droplets. The present work thus investigates the possible fragmentation pathways and dynamics of droplet fragments resulting from aspirated ESI droplets upon surface collisions through classical molecular dynamics simulations. Different types of collisions are simulated, where the impact of the simulated droplet fragments is either frontal or angled. The resulting fragmentation dynamics are thoroughly analyzed, showing the possibility for charged fragments to be liberated through SID events. A second, much larger droplet fragment is employed to illustrate the altered collision dynamics found for such larger aggregates, where no charged clusters are released through the surface collision. Since approximated force fields have to be used to model the interactions between the particles observed in the simulation, a sensitivity study is carried out regarding the critical parameters governing such processes. Further modifications of the MD system have to be carried out, including more realistic walls and much larger ESI droplets, to clarify the possibility of charged fragment releases from larger droplet fragments through SID.

Affinity selection-mass spectrometry with linearizable macrocyclic peptide libraries.

Despite their potential, the preparation of large synthetic macrocyclic libraries for ligand discovery and development has been limited. Here, we produce 100-million-membered macrocyclic libraries containing natural and nonnatural amino acids. Near-quantitative intramolecular disulfide formation is facilitated by rapid oxidation with iodine in solution. After use in affinity selection, treatment with dithiothreitol enables near-quantitative reduction, rendering linear peptide analogs for standard tandem mass spectrometry. We use these libraries to discover macrocyclic binders to cadherin-2 and anti-hemagglutinin antibody clone 12ca5. Structure-activity relationship studies of an initial cadherin-binding peptide [CBP; apparent dissociation constant (Kd) = 53 nanomolar] reveal residues responsible for driving affinity (hotspots) and mutation-tolerant residues (coldspots). Two original macrocyclic libraries are prepared in which these hotspots and coldspots are derivatized with nonnatural amino acids. Following discovery and validation, high-affinity ligands are discovered from the coldspot library, with NCBP-4 demonstrating improved affinity (Kd = 29 nanomolar). Overall, we expect that this work will improve the use of macrocyclic libraries in therapeutic peptide development.

Blood lead levels in children 5-7-years from the Republic of Georgia-a feasibility study on lead surveillance using volumetric absorptive microsampling.

For years, children in the Republic of Georgia, have experienced elevated blood lead levels (BLLs). From September 2023 to April 2024, the National Center for Disease Control and Public Health in Georgia piloted a national surveillance program for lead in children in two western regions of the country, using volumetric absorptive microsampling (VAMS) to measure BLLs. To monitor BLLs and assess predictors of elevated BLLs in children aged 5-7 years from two regions in the Republic of Georgia. We also aimed to demonstrate the feasibility of VAMS for BLL surveillance. Children aged 5-7 years were randomly selected from the regions of Adjara and Imereti, Georgia; and 1,635 children participated. A trained phlebotomist collected two capillary blood samples from the children's fingertips using 30 μL VAMS devices. The samples were analyzed using inductive coupled plasma tandem mass spectrometry. Guardians completed a questionnaire detailing demographics, household, and lifestyle characteristics. We employed multivariable logistic regression models to identify predictors of BLLs ≥3.5 or ≥10.0 μg/dL in Georgia. Approximately, 39.8%, 20%, and 4% of the participants had BLLs ≥3.5, ≥5.0, and ≥10.0 μg/dL, respectively. In both regions, male sex and unpainted housing predicted BLLs ≥3.5 μg/dL, but not BLLs ≥10.0 μg/dL. In Imereti, urban living additionally predicted BLLs ≥3.5 μg/dL, while small household size and metal toys (metal vs. plastic toys: Odds Ratio [OR]=3.58, 95% confidence interval [CI]: 1.66-7.72) were associated with BLLs ≥10.0 μg/dL. In Adjara, age, housing type, use of certain spices (yes vs. no: OR=1.47, 95% CI: 1.11-1.94), and household lead bullet production (yes vs. no: OR=6.66, 95% CI: 1.41-31.6) predicted BLLs ≥3.5 μg/dL, but not BLLs ≥10.0 μg/dL. Our findings confirm that lead exposure remains a significant public health issue in two regions of the Republic of Georgia, despite a national decrease in BLLs over the past five years. To our knowledge, this research marks the first large-scale application of VAMS technology for national BLL surveillance, offering significant advantages as a less invasive lead testing method-accurate and suitable for settings with limited resources to handle, store, and transport venous blood samples. https://doi.org/10.1289/EHP15788.

Morning Salivary Cortisone Versus Serum Cortisol in the Overnight Dexamethasone Suppression Test (ODNST): Evaluation in a Clinical Setting.

Saliva hormone measurement is increasingly being applied in everyday clinical practice. In relation to salivary cortisone measurement, there is a particular advantage, with minimal chance of cross-reaction with prescribed glucocorticoids and greater convenience. We evaluated the utility of salivary cortisone measurement in patients undergoing an overnight dexamethasone suppression test (ONDST). Individuals undergoing an ONDST had parallel measurement of serum cortisol and salivary cortisone at 0900 following midnight dexamethasone (1 mg). Salivary cortisone was measured by electrospray positive liquid chromatography tandem mass spectrometry. The threshold for adequate suppression of salivary cortisone was< 2.7nmol/L; serum cortisol was< 50nmol/L. Results for 34 individuals which included 21% men (mean age 49.4 years) and 79% women (mean age 56.7 years) were analysed. Serum cortisol did not suppress in 22/34 cases. Salivary cortisone did not suppress in two of the cases where cortisol did suppress. We found a strong correlation between 0900 salivary cortisone and serum cortisol after 1 mg ONDST (r2 = 0.65, p = 0.009). When performance of post-dexamethasone salivary cortisone (< 2.7nmol/L) alone in relation to suppression of serum cortisol (< 50nmol/L) was analysed all but 2 individuals were correctly classified. They had values for post dexamethasone salivary cortisone/serum cortisol of respectively 5.9/23 nmol/L (presented with unexplained fatigue, case 25) and 7/32 nmol/L (investigated for cyclical Cushing's Syndrome that was excluded, case 29). Agreement was 94.1%, kappa 0.87, p < 0.0001. The sensitivity of salivary cortisone for potential Cushing's syndrome as indicated by the post-dexamethasone 0900 serum cortisol was 100% (all cases of potential cortisol excess (0900 cortisol > 50nmol/L) were picked up) and specificity of 84.6% with a positive predictive value of 90.5% of salivary cortisone (using serum cortisol as the standard) and negative predictive value of 100% in relation to ruling out cortisol excess. We have provided further evidence that ONDST salivary cortisone has potential to be the first-line test for suspected Cushing's syndrome, not requiring venepuncture or attendance at hospital, with 100% sensitivity and reasonable specificity. Application of the salivary cortisone test has the potential for significant savings of money and time in this and other contexts.

Pharmacokinetics and Bioavailability of Single-Dose Intramuscular and Intravenous Administration of Thiafentanil in Goats (Capra hircus).

Thiafentanil is a popular opioid agonist used for wildlife chemical immobilisation. Its effects are quickly and completely reversed by the antagonist naltrexone. Successful wildlife immobilisations using thiafentanil have been documented in a variety of wildlife species globally. The aim of this study was to describe the single-dose intramuscular (IM) and intravenous (IV) pharmacokinetics of thiafentanil in goats at a dose of 90 μg/kg using a single cross-over study. The IM dose was administered in the left Vastus lateralis. Plasma samples were collected up to 120 min after thiafentanil administration from two female and eight male adult goats. Samples were analysed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Pharmacokinetic parameters from one and two-compartment models were estimated via a Bayesian approach. The two-compartment model was preferred overall. The estimated bioavailability was 0.677 (90% Crl: 0.542-0.888), absorption rate constant (ka) was 0.058 1/min (90% Crl: 0.045-0.115) and clearance was 29.0 mL/min/kg (90% Crl: 23.7-36.3) from this model. This study provides key pharmacokinetic data on thiafentanil, supporting a two-compartment model and offering insights into its absorption, bioavailability, and clearance when used for wildlife immobilisation.

Signatures of Charged Droplets from ESI: A Statistical Analysis of Non-summed Mass Spectra Compared to APCI.

Electrospray ionization (ESI) is the most widely used technique for the ionization of liquid samples, for example, from liquid chromatography (LC) coupled to mass spectrometry. Recent experiments demonstrate the penetration of charged droplets or at least large clusters into the high-vacuum region of different ESI mass spectrometers. Using a Bruker micrOTOF equipped with a standard Bruker Apollo ESI source, we demonstrated that time-of-flight (TOF) MS can detect signatures of these droplets by analyzing the statistics of individual TOF spectra, resulting from a single orthogonal acceleration (oa) stage pulse. A custom experimental setup allows additional online monitoring of the ion current in the oa-stage by coupling an oscilloscope to an auxiliary secondary electron multiplier (SEM). The results obtained with ESI are compared to mass spectra recorded under similar conditions using atmospheric pressure chemical ionization (APCI). Our findings reveal that the observation of droplet signatures is unique to the ESI process, with their frequency and intensity strongly determined by the ion source settings. We also report that the majority of the individual spectra obtained do not contain ion signals. The observed intensity in the summed spectra stems from a few very intense spectra, which result from single droplet fragment bursts. In contrast, APCI provides an almost continuous and stable ion current, without intense signal bursts characteristic for ESI. Additional optical monitoring strongly suggests that these signatures are not a result of spray instability, but are common even for undisturbed, continuous spray operation. The variation of ion source parameters shows that specific capillary voltages, nebulizer pressures, and dry gas flows lead to an increase in the frequency of droplet occurrence. Since these parameters are fundamental and frequently altered in analytical measurements, the results reported in this contribution underscore the significance of understanding droplet dynamics in ESI-MS and provide insights regarding droplets affecting the ESI signal intensity recorded in analytical runs.

Association Between Multiple Plasma Toxic Metal and Metalloid Exposures and Hypertension in Elderly Chinese Adults.

Although environmental exposure to toxic metals and metalloids is linked with the risk of cardiovascular diseases, the evidence is limited in the elderly. We evaluated the associations between 12 plasma metal levels including aluminum (Al), titanium (Ti), strontium (Sr), lead (Pb), vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), cuprum (Cu), zinc (Zn), arsenic (As), and selenium (Se) with prevalence of hypertension in the elderly Chinese population. In this study, stratified cluster sampling was conducted among elderly residents in three communities in Gansu province from June to July 2023, with a total of 330 participants included. The concentrations of metals in whole plasma were measured using inductively coupled plasma mass spectrometry (ICP-MS). Logistic regression and restricted cubic spline analyses were used to evaluate the dose-response relationship between plasma metal levels and hypertension, with all metal concentrations log-transformed. We applied quantile g-computation (QG-comp) and Bayesian kernel machine regression (BKMR) models to examine the associations of both individual metals and metal mixtures with hypertension. After multivariable adjustments, the odds ratios (ORs) and 95% confidence intervals (CIs) for hypertension associated with the highest quartile of metal concentrations compared to the lowest quartile were as follows: 4.20 (1.36, 12.98) for Sr, 3.95 (1.30, 12.03) for V, 3.43 (1.09, 10.78) for Cr, 3.28 (1.16, 9.28) for Cu, 3.28 (1.13, 9.52) for Zn, and 2.87 (0.94, 8.74) for As.Using BKMR and restricted cubic spline analysis, we found that exposure to metal mixtures was positively associated with an increased risk of hypertension, with Ni, Cr, As, and V being the primary contributing factors. In addition, Zn, Ni, and Sr were significantly and positively correlated with hypertension, while plasma titanium levels were negatively associated with hypertension development. These results suggest a complex interaction between various metals and the risk of hypertension in the elderly.Exposure to metal mixtures was positively associated with hypertension risk in elderly Chinese adults, with Ni, Cr, As, and V as key contributors. In addition, Zn, Ni, and Sr are significantly associated with an increased risk of hypertension, while Ti was positively associated with its development.