Tandem Mass Spectrometry Research Articles

Enhancement of per- and Polyfluoroalkyl Substances (PFAS) quantification on surface waters from marinas in the douro river, Portugal

PFAS, known as "forever" compounds, are prevalent in various environments, including soils and aquatic systems, due to extensive usage. Surface waters in several European countries, especially marinas and ports with high boat traffic, require further study as potential contamination sources. Reliable methods for the extraction and quantification of these emergent compounds are essential. This study aimed to improve an existent solid phase extraction method to analyse marinas and ports’ surface waters with variable salinities (2, 9 and 17 PSU). The objectives were to: 1) optimise the solid phase extraction method, considering matrix salinity effects and cross-contaminations, 2) validate the extraction and quantification method of 18 EPA 537.1 PFAS in estuarine surface waters, using the Ultra-High Performance Liquid Chromatography – Quadrupole Time – Of – Flight – Tandem Mass spectrometry, and 3) apply the optimised method for PFAS quantification in three Portuguese marinas. All ICH criteria were successfully validated considering 9 PSU. Limits of quantification ranged from 117.80 ng/L to 385 ng/L, except for PFHpA (645.85 ng/L). PFAS levels (PFOA, HFPO-DA, PFBS, PFHxS and PFOS) were relatively low, reaching a maximum of 0.32 ng/L only for the PFOA. In Freixo marina, total average concentrations were slightly higher (∑PFAS = 1.02 ng/L) when compared to the ones found in Cais da Ribeira Port (∑PFAS = 0.94 ng/L) and Afurada marina (∑PFAS = 0.81 ng/L). PFOS concentrations are below the limit values set by the Environmental Quality Standards (36000 ng/L of PFOS for inland surface water, respectively), similar to other Portuguese river studies. This study enabled the development of a precise and reliable extraction and quantification method to quantify PFAS in estuarine surface waters, particularly from marinas. This method can be readily applied to analyse PFAS in other estuarine samples.

Analytical Methods for the Determination of Pharmaceuticals and Personal Care Products in Solid and Liquid Environmental Matrices: A Review.

Among the various compounds regarded as emerging contaminants (ECs), pharmaceuticals and personal care products (PPCPs) are of particular concern. Their continuous release into the environment has a negative global impact on human life. This review summarizes the sources, occurrence, persistence, consequences of exposure, and toxicity of PPCPs, and evaluates the various analytical methods used in the identification and quantification of PPCPs in a variety of solid and liquid environmental matrices. The current techniques of choice for the analysis of PPCPs are state-of-the-art liquid chromatography coupled to mass spectrometry (LC-MS) or tandem mass spectrometry (LC-MS2). However, the complexity of the environmental matrices and the trace levels of micropollutants necessitate the use of advanced sample treatments before these instrumental analyses. Solid-phase extraction (SPE) with different sorbents is now the predominant method used for the extraction of PPCPs from environmental samples. This review also addresses the ongoing analytical method challenges, including sample clean-up and matrix effects, focusing on the occurrence, sample preparation, and analytical methods presently available for the determination of environmental residues of PPCPs. Continuous development of innovative analytical methods is essential for overcoming existing limitations and ensuring the consistency and diversity of analytical methods used in investigations of environmental multi-class compounds.

A trapped ion mobility enabled Fourier transform ion cyclotron resonance mass spectrometer for infrared ion spectroscopy at FELIX

We report the installation of a new infrared ion spectroscopy platform at the free-electron laser facility FELIX, based on a Bruker SolariX Fourier Transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with a trapped ion mobility spectrometry (TIMS) stage. The instrument allows one to record infrared multiple-photon dissociation (IRMPD) spectra for mass and mobility selected ions, produced by a range of ion sources. We describe two strategies to achieve consistent overlap between the laser beam and the ion packet. Removing the original ECD cathode significantly enhanced the IR transmission and the overlap with the ion cloud, resulting in improved IRMPD yield per pulse. Enhancement of the photodissociation yield is observed when multiple pulses are used, as there is negligible collisional deactivation in the ultra-high vacuum trapping region of the ICR cell. We compare IRMPD spectra recorded on the new platform with IRMPD spectra of the same species recorded on one of our 3D-quadrupole ion trap platforms. We demonstrate the instrument’s performance using a sample containing a mixture of two trisaccharides. Mobility selection allows us to record individual IR spectra for the two isomeric species. This multi-modal platform, encompassing liquid chromatography, ion mobility spectrometry, ultra-high resolution (tandem) mass spectrometry, infrared ion spectroscopy (and soon also mass spectrometry imaging), is available to users at the FELIX facility.

Simultaneous determination of quaternary phosphonium compounds and phosphine oxides in environmental water and solid samples by ultrahigh performance liquid chromatography–tandem mass spectrometry

Quaternary phosphonium compounds (QPCs) and phosphine oxides (POs) are emerging contaminants that are attracting increasing attention. In the present study, a method for the quantification of QPCs and POs in multiple environmental media was developed using ultrahigh performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS). Analytes were extracted from water samples using solid phase extraction, and for the solid samples, ultrasonic extraction was employed. Compared with analytical methods established by previous studies, the approach developed in this study is more suitable for the quantitative analysis of compounds along with high sensitivity. The method quantification limit reached 0.12–2.55 ng⋅L–1 in water samples and 0.004–0.10 ng⋅g–1 in solid samples. The recoveries of target analytes spiked at low, medium and high concentrations in water and solid samples were in the range of 56.4–120 %, with relative standard deviations below 20 % (n = 6). Furthermore, the validated method succeeded in applying to analyse of eight QPCs and four POs in real environmental samples. At least five QPCs and two POs were detected in each environmental medium. This quantitative method would assist in further investigations on the occurrence, migration and the source of QPCs and POs.

Organic suspension droplet solid-phase dispersive liquid–liquid microextraction ultra-high performance liquid chromatography tandem mass spectrometry determination of antibiotic residues in water samples

A method was developed for the simultaneous detection of 38 antibiotic residues, which included 8 sulfonamides, 14 fluoroquinolones, 9 macrolides, and 7 anthelminthics, in drinking water, tap water, and environmental water. The method involved organic suspension droplet solid-phase dispersive liquid–liquid microextraction, followed by ultra-high performance liquid chromatography tandem mass spectrometry for the analysis of the water samples. Hypersil GOLD C18 chromatography column (100 × 2.1 mm, 1.9 μm) be used for separation of target analytes that were eluted by a gradient mobile phase composition of 0.2 % formic acid–water as mobile phase A and acetonitrile as mobile phase B at a flow rate of 0.2 mL min−1. Using 0.2 mL of octanoic acid as the extractant and 0.3 mL of acetonitrile as the dispersant. Under optimal conditions, the standard curve exhibits a good linear relationship within the range of 1–50 μg L−1. The spiked recovery rate of the method ranges from 63 % to 96 %, with a relative standard deviation of 0.6 % to 7.3 % (n = 6). The detection limit of the method is between 0.1 and 0.2 μg L−1. This method is characterized by its simplicity, speed, and high sensitivity, which sets the groundwork for investigating the exposure levels and environmental behavior of antibiotics.

Dissipation kinetics and decontamination of chlorantraniliprole and thiamethoxam residues in curry leaves

ABSTRACT Herein, using liquid chromatography – tandem mass spectrometry, we validated a modified QuEChERS method to analyse thiamethoxam and chlorantraniliprole residues in curry leaves. These insecticides are part of a pest management module against the major curry leaf insect pests, psyllid and leaf roller. Based on the SANTE guideline, the method exhibited satisfactory recovery and precision. For both insecticides, the R2 value was 0.99. Furthermore, the determined limit of detection and limit of quantification were 0.008 and 0.025 mg/kg, respectively. The field persistence of both insecticides was longer, and below quantification limit was achieved within 30 and 40 days for chlorantraniliprole and 35 and 40 days for thiamethoxam. Residue degradation followed first-order kinetics, with longer half-lives of 5.08 and 5.28 days for chlorantraniliprole and 3.50 and 3.96 days for thiamethoxam at single (x) and double (2×) doses, respectively. For both insecticides, the hazard index (HI), calculated based on the highest residue on the day of insecticide treatment in the field study, was less than 1 at x and 2× doses, indicating an acceptable level of risk. Seasoning or quick frying of curry leaves in oil reduced maximum of thiamethoxam and chlorantraniliprole residues followed by treatment with NaCl (2%)/tamarind water (2%)/lemon water (2%) solutions. Analysis of 85 farm-gate samples revealed detectable residues of thiamethoxam in 25 samples (0.03–0.49 mg kg−1) and chlorantraniliprole in 1 sample (0.18 mg kg−1). The HI for the maximum quantity of insecticide residues detected in monitoring study was <1. Therefore, the research backs the idea of ensuring safe harvested produce, considering the field persistence of chlorantraniliprole and thiamethoxam in curry leaf and simple decontamination methods to satisfy consumer need for clean food commodity, if properly adopted.

Rapid UHPLC-MS/MS measurement of pregnanediol 3-glucuronide in spot urine samples for detecting ovulation.

Biochemical confirmation of ovulation typically involves measuring serum progesterone levels during the mid-luteal phase. Alternatively, this information could be obtained by monitoring urinary excretion of conjugated metabolites of ovarian steroids such as pregnanediol 3-glucuronide (PDG) using immunoassay techniques that have methodological limitations. The aim of the present study was to develop a mass spectrometry (MS)-based method for the rapid and accurate measurement of urinary PDG levels in spot urine samples. A "dilute and shoot" ultra-high-performance liquid cromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed for measuring PDG urinary concentration with a 6-min analysis time. The method underwent validation in accordance with ISO 17025 documentation for quantitative methods, proving an efficient separation of PDG from other structurally similar glucuro-conjugated steroid metabolites and ensuring a sufficient sensitivity for detecting the target analyte at concentrations as low as 0.01 μg/mL. The validation protocol yielded satisfactory results in terms of accuracy, repeatability, intermediate precision, and combined uncertainty. Additionally, the stability of both the samples and calibration curves was also conducted. The application to real urine samples confirmed the method's capability to measure PDG levels throughout an entire menstrual cycle and detecting ovulation. The rapidity of the analytical platform would therefore enable high throughput analysis, which is advantageous for large cohort clinical studies.

Histidine-rich glycoprotein modulates neutrophils and thrombolysis-associated hemorrhagic transformation

Intravenous thrombolysis using recombinant tissue plasminogen activator (tPA) remains the primary treatment for patients with acute ischemic stroke (AIS). However, the mechanism of tPA-related hemorrhagic transformation (HT) remains poorly understood. Elevation of histidine-rich glycoprotein (HRG) expression was detected by nano-liquid chromatography tandem mass spectrometry at 1 h following tPA infusion as compared to baseline prior to tPA infusion (discovery cohort, n = 10), which was subsequently confirmed in a validation cohort (n = 157) by ELISA. Surprisingly, no elevation of HRG was detected in individuals who subsequently developed HT. During in vitro experiments, HRG reduced neutrophil NETosis, inflammatory cytokine production, and migration across the blood–brain barrier induced by tPA. In a photothrombotic murine AIS model, HRG administration ameliorated HT with delayed thrombolysis, by inhibiting neutrophil immune infiltration and downregulating pro-inflammatory signaling pathways. Neutrophil depletion or NETosis inhibition also alleviated HT, whereas HRG siRNA treatment exacerbated HT. In conclusion, fluctuations in HRG levels may reflect tPA therapy and its associated HT. The inhibitory effect of HRG on neutrophils may counteract tPA-induced immune abnormalities and HT in patients with AIS.

Prevalence of Drugs of Abuse and Cognitive Enhancer Consumption Monitored in Grab Samples and Composite Wastewater via Orbitrap Mass Spectrometry Analysis.

Wastewater (WW)-based epidemiology is an approach for the objective surveillance of the consumption of (illicit) drugs in populations. The aims of this study were to monitor drugs of abuse, cognitive enhancers, and their metabolites as biomarkers in influent WW. Data obtained from different sampling points and mean daily loads were compared with previously published data. The prevalence of analytes was monitored in WW grab samples collected monthly over 22 months at two sampling points and 24 h composite WW samples collected over 2 weeks at a WW treatment plant in the same city. Quantification was performed using a previously validated and published method based on solid-phase extraction followed by liquid chromatography coupled with high-resolution tandem mass spectrometry. Grab samples allowed for frequent detection of ritalinic acid and sporadic detection of drugs of abuse. The daily mean loads calculated for 24 h WW composite samples were in accordance with data published in an international study. Furthermore, loads of amphetamine and methamphetamine increased compared with those observed in a previously published study from 2014. This study showed frequent quantification of ritalinic acid in the grab samples, while drugs of abuse were commonly quantified in the composite WW samples. Daily mean loads were in accordance with trends reported for Germany.

Evaluation of the binding interactions between Plasmodium falciparum Kelch-13 mutant recombinant proteins with artemisinin.

Malaria, an ancient mosquito-borne illness caused by Plasmodium parasites, is mostly treated with Artemisinin Combination Therapy (ACT). However, Single Nucleotide Polymorphisms (SNPs) mutations in the P. falciparum Kelch 13 (PfK13) protein have been associated with artemisinin resistance (ART-R). Therefore, this study aims to generate PfK13 recombinant proteins incorporating of two specific SNPs mutations, PfK13-V494I and PfK13-N537I, and subsequently analyze their binding interactions with artemisinin (ART). The recombinant proteins of PfK13 mutations and the Wild Type (WT) variant were expressed utilizing a standard protein expression protocol with modifications and subsequently purified via IMAC and confirmed with SDS-PAGE analysis and Orbitrap tandem mass spectrometry. The binding interactions between PfK13-V494I and PfK13-N537I propeller domain proteins ART were assessed through Isothermal Titration Calorimetry (ITC) and subsequently validated using fluorescence spectrometry. The protein concentrations obtained were 0.3 mg/ml for PfK13-WT, 0.18 mg/ml for PfK13-V494I, and 0.28 mg/ml for PfK13-N537I. Results obtained for binding interaction revealed an increased fluorescence intensity in the mutants PfK13-N537I (83 a.u.) and PfK13-V494I (143 a.u.) compared to PfK13-WT (33 a.u.), indicating increased exposure of surface proteins because of the looser binding between PfK13 protein mutants with ART. This shows that the PfK13 mutations may induce alterations in the binding interaction with ART, potentially leading to reduced effectiveness of ART and ultimately contributing to ART-R. However, this study only elucidated one facet of the contributing factors that could serve as potential indicators for ART-R and further investigation should be pursued in the future to comprehensively explore this complex mechanism of ART-R.

Establishment of a UPLC-MS method for quantitative analysis of tryptophan-kynurenine metabolism in IBS-D model rats

Background and Aims Abnormalities in tryptophan (TRP) metabolism induce abdominal pain and intestinal motility disorders. The study of TRP metabolism in diarrhea-predominant-irritable bowel syndrome (IBS-D) is important for the prevention, diagnosis, and treatment of this disease. In this study, a rapid and reliable ultra performance liquid chromatography-mass spectrometry (UPLC-MS) method was established to quantify tryptophan-kynurenine (TRP-Kyn) metabolism in the colon of a rat model with IBS-D. Methods The proteins were precipitated by methanol, chromatographically separated on a Welch Ultimate® Polar RP column with a gradient elution for 12 min, and detected by high-resolution tandem mass spectrometry. Pure water were used as an alternative mechanism for standard calibration, and the stable structural analog 2-Cl-Phe was used as an internal standard. Results Within a certain range, the r of TRP, kynurenine (Kyn) and quinolinic acid (QA), kynurenic acid (KA) are greater than 0.99, were found to be accurate and precise. The metabolism of TRP was significantly up-regulated along the Kyn pathway in the IBS-D model rats and normalized after treatment with pivacurium bromide. Conclusion This study investigates the mechanisms of IBS-D gastrointestinal dysfunction from the perspective of colonic TRP metabolism, and also provides new directions for the diagnosis and therapeutic approach of this disease.

Phosphatidylethanol is a promising tool for screening alcohol consumption during pregnancy.

Prenatal alcohol exposure (PAE) is one of the leading causes of preventable developmental disabilities. A lack of objective screening methods results in an under-recognition of the phenomenon. Phosphatidylethanol (PEth) is a specific ethanol biomarker that reveals alcohol intake up to several weeks after alcohol use. So far, PEth has mostly been a tool for detecting moderate and heavy drinking. With lower PEth cut-offs, revealing even minor prenatal alcohol consumption is possible. We aimed to find out if a sensitive method for PEth analysis would give additional information about PAE and to assess the cut-off value for a positive alcohol result in prenatal screening. The study was an observational study of 3000 anonymous blood samples collected from the Helsinki University Hospital Diagnostic Center between June and September 2023. The Finnish Red Cross Blood Service received the samples originally for blood group typing and antibody screening as part of the prenatal blood screening program. We developed a sensitive PEth 16:0/18:1 analysis method using ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) equipment after liquid-liquid extraction of PEth from whole blood. The lower limit of quantification was 1 ng/mL. PEth was ≥2 ng/mL in 5.2% of the cases, ≥8 ng/mL in 2.0%, and ≥20 ng/mL in 1.0%. The detection time of PEth can be several weeks, especially with low PEth concentrations and after heavy alcohol consumption. It remained unknown whether the positive PEth tests resulted from drinking deliberately during pregnancy or before pregnancy recognition. We suggest adding PEth 16:0/18:1 to a routine prenatal blood screening program with a cut-off of 2 ng/mL-and in positive cases, clinical evaluation and retesting in 2-4 weeks. In clinical settings, information on gestational week and alcohol consumption before pregnancy is relevant and needs to be considered when interpreting low PEth concentrations.

Tandem MS Elucidation of the Late-Stage Degradation Mechanism of Nitroplasticizer.

Understanding the degradation behavior of nitroplasticizer (NP) and the subsequent production of nitro-organics is crucial for both environmental monitoring and material development. A nontargeted approach via LC-QTOF-MS was employed to thoroughly study the degradation mechanism of NP in its late aging stage. Both positive and negative modes of ESI were performed to increase the compound coverage. To shed light on the fragmentation behavior of NP degradants (e.g., compounds containing a high density of NO2 moieties and oxygen sites) in the positive mode, which is rarely reported, the high-resolution tandem MS information on precursor ions at m/z 251(+), 254(+), 266(+), and 270(+) and a pair of isomeric ions at m/z 284(+) was investigated to extract their common diagnostic ions and dissociation channels, including the neutral loss of 2,2-dinitropropanol, nitro-nitrite rearrangement, homolytic cleavage of NO2, and simple inductive cleavage. Additionally, leveraging the sensitivity for nitroaromatics in the negative polarity, negative ions m/z 182(-) and 233(-) are identified as dinitroaniline and dinitronaphthol, respectively, which confirm the secondary hydrolysis pathway of the antioxidant (e.g., N-phenyl-2-naphthylamine) postulated in our previous work. In addition to earlier findings, the detection of these eight degradants further supports the evidence of increased acid concentration and aging temperatures in the late-stage NP environment, which contribute to intricate degradation behaviors in different aging environments.

Knockdown of Gonadotropin-Releasing Hormone II Receptor Impairs Ovulation Rate, Corpus Luteum Development, and Progesterone Production in Gilts.

Reproduction is classically controlled by gonadotropin-releasing hormone (GnRH-I) and its receptor (GnRHR-I) within the brain. In pigs, a second form (GnRH-II) and its specific receptor (GnRHR-II) are also produced, with greater abundance in peripheral vs. central reproductive tissues. The binding of GnRH-II to GnRHR-II has been implicated in the autocrine/paracrine regulation of gonadal steroidogenesis rather than gonadotropin secretion. Blood samples were collected from transgenic gilts, with the ubiquitous knockdown of GnRHR-II (GnRHR-II KD; n = 8) and littermate controls (n = 7) at the onset of estrus (follicular) and 10 days later (luteal); serum concentrations of 16 steroid hormones were quantified by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Upon euthanasia, ovarian weight (OWT), ovulation rate (OR), and the weight of each excised Corpus luteum (CLWT) were recorded; HPLC-MS/MS was performed on CL homogenates. During the luteal phase, serum progesterone concentration was reduced by 18% in GnRHR-II KD versus control gilts (p = 0.0329). Age and weight at puberty, estrous cycle length, and OWT were similar between lines (p > 0.05). Interestingly, OR was reduced (p = 0.0123), and total CLWT tended to be reduced (p = 0.0958) in GnRHR-II KD compared with control females. Luteal cells in CL sections from GnRHR-II KD gilts were hypotrophic (p < 0.0001). Therefore, GnRH-II and its receptor may help regulate OR, CL development, and progesterone production in gilts.

Proteomic profiling of Arabidopsis nuclei reveals distinct protein accumulation kinetics upon heat stress

Heat stress (HS) impacts the nuclear proteome and, subsequently, protein activities in different nuclear compartments. In Arabidopsis thaliana, a short exposure to 37 °C leads to loss of the standard tripartite architecture of the nucleolus, the most prominent nuclear substructure, and, consequently, affects the assembly of ribosomes. Here, we report a quantitative label-free LC‒MS/MS (Liquid Chromatography coupled to tandem Mass Spectrometry) analysis to determine the nuclear proteome of Arabidopsis at 22 °C, HS (37 °C for 4 and 24 h), and a recovery phase. This analysis identified ten distinct groups of proteins based on relative abundance changes in the nucleus before, during and after HS: Early, Late, Transient, Early Persistent, Late Persistent, Recovery, Early-Like, Late-Like, Transient-Like and Continuous Groups (EG, LG, TG, EPG, LPG, RG, ELG, LLG, TLG and CG, respectively). Interestingly, the RNA polymerase I subunit NRPA3 and other main nucleolar proteins, including NUCLEOLIN 1 and FIBRILLARIN 1 and 2, were detected in RG and CG, suggesting that plants require increased nucleolar activity and likely ribosome assembly to restore protein synthesis after HS.

Differential proteomic expression in non-functional pituitary neuroendocrine tumours and pituitary glands.

Pituitary neuroendocrine tumours (PitNETs) are common accounting for 10 to 25 % of all intracranial tumours. This project describes the feasibility of developing a novel membrane-based biomarker that could be used for fluorescent guided surgery. The aim was to catalogue the differential expression of membrane proteins between non-functional PitNETs and pituitary glands. Ten pituitary gland tissue specimens were obtained from the National Institute of Health (NIH) NeuroBio-Bank and twenty non-functional PitNETs were obtained from the Northwestern University Nervous System Tumour Bank. Mass spectrometry analysis using an Orbitrap Fusion Lumos Tribrid Mass Spectrometer linked to a Dionex Ultimate 3000 UPLC system was undertaken. Data Dependent Acquisition Mass Spectrometry and Data Independent Acquisition Mass Spectrometry was then completed. Pathway enrichment analysis was performed using clusterProfiler v4.6.0. Functional enrichment analysis was conducted using Gene Ontology terms and Reactome pathways. Differential expression analysis between the two groups revealed a total of 2110 significant differently expressed proteins (DEPs), with 1387 of these also having a Log2 fold change either greater than 1, or less than -1. Of the 2110 DEPs, 925 were upregulated in tumours compared to control, while 1185 were downregulated. We have demonstrated a proteomic comparison between non-functional PitNETs and normal pituitary glands. These results demonstrate differences consistent with contemporary literature but shows that NOTCH3 and PTPRJ are up-regulated in non-functional PitNETs compared to pituitary glands.

Unraveling the complexity of glycosphingolipidome: the key role of mass spectrometry in the structural analysis of glycosphingolipids.

Glycosphingolipids (GSL) are a highly heterogeneous class of lipids representing the majority of the sphingolipid category. GSL are fundamental constituents of cellular membranes that have key roles in various biological processes, such as cellular signaling, recognition, and adhesion. Understanding the structural complexity of GSL is pivotal for unraveling their functional significance in a biological context, specifically their crucial role in the pathophysiology of various diseases. Mass spectrometry (MS) has emerged as a versatile and indispensable tool for the structural elucidation of GSL enabling a deeper understanding of their complex molecular structures and their key roles in cellular dynamics and patholophysiology. Here, we provide a thorough overview of MS techniques tailored for the analysis of GSL, emphasizing their utility in probing GSL intricate structures to advance our understanding of the functional relevance of GSL in health and disease. The application of tandem MS using diverse fragmentation techniques, including novel ion activation methodologies, in studying glycan sequences, linkage positions, and fatty acid composition is extensively discussed. Finally, we address current challenges, such as the detection of low-abundance species and the interpretation of complex spectra, and offer insights into potential solutions and future directions by improving MS instrumentation for enhanced sensitivity and resolution, developing novel ionization techniques, or integrating MS with other analytical approaches for comprehensive GSL characterization.

Comparative Cross-Kingdom DDA- and DIA-PASEF Proteomic Profiling Reveals Novel Determinants of Fungal Virulence and a Putative Druggable Target.

Accurate and reliable detection of fungal pathogens presents an important hurdle to manage infections, especially considering that fungal pathogens, including the globally important human pathogen, Cryptococcus neoformans, have adapted diverse mechanisms to survive the hostile host environment and moderate virulence determinant production during coinfections. These pathogen adaptations present an opportunity for improvements (e.g., technological and computational) to better understand the interplay between a host and a pathogen during disease to uncover new strategies to overcome infection. In this study, we performed comparative proteomic profiling of an in vitro coinfection model across a range of fungal and bacterial burden loads in macrophages. Comparing data-dependent acquisition and data-independent acquisition enabled with parallel accumulation serial fragmentation technology, we quantified changes in dual-perspective proteome remodeling. We report enhanced and novel detection of pathogen proteins with data-independent acquisition-parallel accumulation serial fragmentation (DIA-PASEF), especially for fungal proteins during single and dual infection of macrophages. Further characterization of a fungal protein detected only with DIA-PASEF uncovered a novel determinant of fungal virulence, including altered capsule and melanin production, thermotolerance, and macrophage infectivity, supporting proteomics advances for the discovery of a novel putative druggable target to suppress C. neoformans pathogenicity.

Evaluation of in vitro Skin Permeation of Clascoterone From Clascoterone Topical Cream, 1% (w/w).

Winlevi® (clascoterone) topical cream (1%, w/w) was approved by the U.S. FDA for the treatment of acne vulgaris in patients 12years of age and older. The active ingredient, clascoterone, is not stable in physiological solutions and can hydrolyze to cortexolone at body temperature. Instability of clascoterone poses a significant challenge in accurately assessing the rate and extent of clascoterone permeation in vitro. Therefore, the purpose of this study was to develop an in vitro skin permeation test (IVPT) method, and a robust analytical method, that can minimize hydrolyzation of clascoterone during the study for quantification of clascoterone. Two IVPT methods, using either vertical diffusion cells or flow-through cells, were developed and compared to evaluate in vitro permeation of clascoterone from Winlevi. A liquid chromatography with tandem mass spectrometry (LC-MS/MS) method was developed to monitor the level of clascoterone and cortexolone in the IVPT samples. The analytical method features a 2-min high-throughput analysis with good linearity, selectivity, and showed a lower limit of quantitation (LLOQ) of 0.5ng/mL for both clascoterone and cortexolone. The in vitro skin permeation of clascoterone and cortexolone was observed as early as 2h in both IVPT methods. A substantive amount of clascoterone was found to hydrolyze to cortexolone when using the vertical static diffusion cells with aliquot sampling. Conversely, degradation of clascoterone was significantly minimized when using the flow-through diffusion cells with fractional sampling. The data enhanced our understanding of in vitro permeation of clascoterone following topical application of the Winlevi topical cream, 1% and underscores the importance of IVPT method development and optimization during product development.

Interrogating the Presence of RNA Phosphorothioate in Nature by a Highly Selective and Sensitive Fluorescence Method.

In nature, DNA phosphorothioate (PT) is found in the genomic materials of some prokaryotes. In contrast, whether there is natural RNA PT is still a question under debate. A groundbreaking study reported the discovery of RNA PT in cellular RNA samples from both prokaryotes and eukaryotes at contents of >100 PT per million nucleotides (PPM-nt) according to liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis. However, this finding was challenged by a later work showing that other RNA modifications, such as 2'-O-methylation, could give almost the same LC-MS/MS signal patterns as RNA PT. As the LC-MS/MS technique led to contradicting conclusions, another independent method is thus needed to interrogate the presence of RNA PT in nature. In this work, we have developed a highly selective and sensitive fluorescence method for RNA PT quantification based on a new RNA PT-specific conversion reaction. It can detect as low as 2.8 PPM-nt in RNA without interference from RNA thiobases or protein cysteines. We measured the total RNA samples from some bacteria and human cells using this method. None of these samples gave any RNA PT signal above the detection limit (2.8 PPM-nt), suggesting that the widespread presence of natural RNA PT at the 100 PPM-nt level or above is highly unlikely. Nevertheless, due to the limited number of cell species tested in this work, the possible existence of natural RNA PT cannot be excluded. The fluorescence method reported here is simple and low-cost; therefore, it should be an ideal assay for broadly screening various types of cells to search for the clue of RNA PT in nature.