[Network Meta-analysis of Chinese patent medicines combined with antibiotics in treatment of pelvic inflammatory diseases].

To evaluate the efficacy and safety of different Chinese patent medicines in the treatment of pelvic inflammatory disease(PID) using network Meta-analysis. The databases of CNKI, Wanfang, VIP, SinoMed, PubMed, Cochrane Library, EMbase, and Web of Science were searched, and from the time of database construction to July 16, 2023, the randomized controlled trial(RCT) of Chinese patent medicines combined with antibiotics in the treatment of PID included in these databases was collected. The quality of the included literature was evaluated using the Cochrane risk of bias tool, and data was analyzed using RevMan 5.4 and Stata 16 software. Forty-six RCTs were finally included, including Kangfu Xiaoyan Suppositories, Fuke Qianjin Tablets/Capsules, Kangfuyan Capsules, Fuyanxiao Capsules, Huahong Tablets/Capsules, Fuyanshu Capsules, Fuyue Tablets, Jingangteng Capsules, and Fuyan Kangfu Capsules. Network Meta-analysis showed that,(1) in terms of clinical effective rate, the optimal intervention was Kangfu Xiaoyan Suppositories combined with antibiotics.(2) In terms of lowering hypersensitive C-reactive protein(hs-CRP), the optimal intervention was Huahong Tablets/Capsules combined with antibiotics.(3) In terms of lowering tumor necrosis factor-α(TNF-α), the optimal intervention was Fuyue Tablets combined with antibiotics.(4) In terms of lowering recurrence rate, the optimal intervention was Fuyanshu Capsules combined with antibiotics.(5) In terms of safety, the intervention with the least adverse reactions was Kangfuyan Capsules combined with antibiotics. The results show that Chinese patent medicines combined with antibiotics in the treatment of PID can improve the comprehensive efficacy, reduce the patient's hs-CRP and TNF-α, and have a low recurrence rate, as well as safe and reliable efficacy. In clinical treatment, Kangfu Xiaoyan Suppositories or Kangfuyan Capsules combined with antibiotics can be preferred. Due to the limitations of the sample size and the quality of the literature, more large-sample and high-quality studies are needed to validate the conclusions.

Functional Analysis and Tissue-Specific Expression of Calcitonin and CGRP with RAMP-Modulated Receptors CTR and CLR in Chickens.

Calcitonin (CT) and calcitonin gene-related peptide (CGRP) are critical regulators of calcium balance and have extensive implications for vertebrate physiological processes. This study explores the CT and CGRP signaling systems in chickens through cloning and characterization of the chicken calcitonin receptor (CTR) and calcitonin receptor-like receptor (CLR), together with three receptor activity-modifying proteins (RAMPs). We illuminated the functional roles for chickens between the receptors examined alone and in RAMP-associated complexes using luciferase reporter assays. Chicken CTRs and CLRs stimulated the cAMP/PKA and MAPK/ERK signaling pathways, signifying their functional receptor status, with CT showing appreciable ligand activity at nanomolar concentrations across receptor combinations. Notably, it is revealed that chicken CLR can act as a functional receptor for CT without or with RAMPs. Furthermore, we uncovered a tissue-specific expression profile for CT, CGRP, CTR, CLR, and RAMPs in chickens, indicating the different physiological roles across various tissues. In conclusion, our data establish a clear molecular basis to reveal information on CT, CGRP, CTR, CLR, and RAMPs in chickens and contribute to understanding the conserved or divergent functions of this family in vertebrates.

SSTR2 Mediates the Inhibitory Effect of SST/CST on Lipolysis in Chicken Adipose Tissue.

Somatostatin shows an anti-lipolytic effect in both chickens and ducks. However, its molecular mediator remains to be identified. Here, we report that somatostatin type 2 receptor (SSTR2) is expressed at a high level in chicken adipose tissue. In cultured chicken adipose tissue, the inhibition of glucagon-stimulated lipolysis by somatostatin was blocked by an SSTR2 antagonist (CYN-154086), supporting an SSTR2-mediated anti-lipolytic effect. Furthermore, a significant pro-proliferative effect was detected in SST28-treated immortalized chicken preadipocytes (ICP-1), and this cell proliferative effect may be mediated through the MAPK/ERK signaling pathway activated by SSTR2. In summary, our results demonstrate that SSTR2 may regulate adipose tissue development by affecting the number and volume of adipocytes in chickens.

Effect of miR-27b on the proliferation and apoptosis of diffuse large b-cell lymphoma cells by targeting the regulation of MET/PI3K/AKT pathway.

BACKGROUND: This study aimed to explore the regulation of miR-27b expression on MET/PI3K/AKT pathway, and to explain its effect on biological functions of DLBCL cells. METHODS: The expressions of miR-27b and MET gene in DLBCL cells and normal human B cell lines were determined by qRT-PCR. miR-27b expression in DLBCL cell line Toledo was over-expressed with the cell transfection method. The proliferation of DLBCL cells was determined by MTT. And the invasiveness of DLBCL cells was determined by Transwell. The level of apoptosis in DLBCL cells was determined by ELISA. miR-27b targeting of MET was verified by dual- luciferase reporter assay. The activation of MET/PI3K/AKT pathway and the expression of downstream related proteins were determined by Western blot. RESULTS: The results showed that miR-27b was poorly expressed in DLBCL cell lines compared with normal human B cell lines, and was associated with its high proliferation, high invasiveness and low apoptosis level. High miR-27b expression can reduce the proliferation and increase the apoptosis level in DLBCL cells. By examining the effect of miR-27b over-expression on the MET/PI3K/AKT pathway, it was found that miR-27b can inhibit the proliferation and invasiveness and promote the apoptosis of DLBCL cells by targeting the inhibition of MET expression and the activation of PI3K/AKT pathway. CONCLUSION: miR-27b can inhibit the proliferation and invasiveness of DLBCL cells and promote the apoptosis of the cells by targeting MET/PI3K/AKT pathway.

Characterization of the chicken melanocortin 5 receptor and its potential role in regulating hepatic glucolipid metabolism.

Melanocortin receptors (MC1R-MC5R) and their accessory proteins (MRAPs) are involved in a variety of physiological processes, including pigmentation, lipolysis, adrenal steroidogenesis, and immunology. However, the physiological roles of MC5R are rarely characterized in vertebrates, particularly in birds. In this work, we cloned the full-length cDNA of chicken MC5R and identified its core promoter region. Functional studies revealed that cMC5R was more sensitive to ACTH/α-MSH than ß-MSH/γ-MSH, and was coupled to the cAMP/PKA signaling pathway. We demonstrated that MRAP2 decreased MC5R sensitivity to α-MSH, whereas MRAP1 did not have a similar effect, and that both MRAPs significantly reduced MC5R expression on the cell membrane surface. Transcriptome and qPCR data showed that both MRAP1 and MC5R were highly expressed in chicken liver. Additionally, we observed that ACTH might increase hepatic glucose production and decrease lipogenesis in primary hepatocytes, and dose-dependently downregulated the expression levels of ELOVL6 and THRSPA genes. These findings indicated that ACTH may act directly on hepatocytes to regulate glucolipid metabolism, which will help to understand the function of MC5R in avian.

Characterization of CRH-Binding Protein (CRHBP) in Chickens: Molecular Cloning, Tissue Distribution and Investigation of Its Role as a Negative Feedback Regulator within the Hypothalamus-Pituitary-Adrenal Axis.

Corticotropin (ACTH) is a pituitary hormone playing important roles in stress response within the hypothalamus-pituitary-adrenal (HPA) axis. The biosynthesis and secretion of ACTH are controlled by multiple factors, including corticotropin-releasing hormone (CRH). As a key hypothalamus-derived regulator, CRH binds to corticotropin-releasing hormone receptor 1 (CRHR1) in the anterior pituitary gland to regulate ACTH synthesis and release. Thus, CRH-binding protein (CRHBP), which binds CRH with high affinity to inhibit CRH-induced ACTH secretion from pituitary cells, draws wide attention. In contrast to the extensive investigation of CRHBP in mammals and other lower vertebrates, the gene structure, tissue expression and physiological functions of CRHBP in birds remain largely unknown. In the present study, using chicken (c-) as our animal model, we examined the gene structure, tissue expression and functionality of CRHBP. Our results showed that: (1) cCRHBP cDNA encodes a 345 amino acid precursor, which shares high sequence identity with that of mammals, reptiles, frogs and fish; (2) cCRHBP is abundantly expressed in the brain (cerebrum and hypothalamus), pituitary and ovary; (3) cCRHBP inhibits the signaling of cCRHRs induced by cCRH, thus reducing the cCRH-induced ACTH secretion from cultured chick pituitary cells; (4) stress mediators (e.g., glucocorticoids) and stress significantly upregulate CRHBP mRNA expression in chickens, supporting its role as a negative feedback regulator in the HPA axis. The present study enriches our understanding of the conserved roles of CRHBP across vertebrates. In addition, chicken is an important poultry animal with multiple economic traits which are tightly controlled by the HPA axis. The characterization of the chicken CRHBP gene helps to reveal the molecular basis of the chicken HPA axis and is thus beneficial to the poultry industry.

Non-linear association between composite dietary antioxidant index and depression.

Background: Growing evidence has shown that the antioxidant diet is a protective factor against depression. However, the relationship between the Composite Dietary Antioxidant Index (CDAI), an important measure of antioxidant diet, and depression has received little attention. Therefore, we investigated the relationship between CDAI and depression through a cross-sectional analysis of the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2018. Methods: The association between CDAI and depression was investigated using a weighted multiple logistic regression model with subgroup analysis. Non-linear correlations were explored using fitted smoothing curves. And we used a recursive method to figure out the turning point and build a weighted two-piece linear regression model. Results: In the multivariate logistic regression model with full adjustment for confounding variables, the ORs (95% CI) for the association between CDAI and depression were 0.83 (0.78, 0.88). Moreover, a non-linear association was found, with 0.16 being the inflection point. Before the inflection point, each unit increase in CDAI was associated with a 30% decrease in the risk of depression. After the inflection point, the risk of depression was found to be reduced by 11% for each unit increase. None of the interactions in all subgroup analyses were statistically significant. Conclusions: Our study highlighted a negative non-linear association between CDAI and depression in a nationally representative sample of US adults. Further clinical and basic research is needed to explore their association better.

The severity of depression is associated with pelvic inflammatory diseases: A cross-sectional study of the United States National Health and Nutrition Examinations from 2013 to 2018.

Purpose: As depression in patients with pelvic inflammatory diseases (PID) has received increasing attention in recent years, this study aims to investigate the relationship between depression severity and risk factors for pelvic inflammatory disease, and to provide new perspectives in the treatment of PID. Patients and methods: Multivariate regression was used to evaluate the association between pelvic inflammatory disease and the severity of depression. Females who participated in the United States National Health and Nutrition Examination Survey (NHANES) from 2013 to 2018 were included. In addition, risk factors for PID and depression were also included in the analysis as adjustment factors. Results: The risk of developing PID was associated with depressive status (odds ratio, OR 1.10, 95% confidence interval, CI 1.08-1.12), especially in people with severe depression (odds ratio, OR 6.34, 95% confidence interval, CI 3.72-10.79). Subgroup analysis showed differences in the risk of PID among people with different characteristics. Conclusion: This study showed that there may be a potential positive association between depressive status and the prevalence of PID in the United States adult female population. Depression should be actively looked for in all patients with PID and treated appropriately.

Effect and Related Mechanism of Platelet-Rich Plasma on the Osteogenic Differentiation of Human Adipose-Derived Stem Cells.

Objective: Human adipose-derived stem cells (hADSCs) are ideal seed cells for the regeneration of alveolar bone defects. Platelet-rich plasma (PRP), which is rich in growth factors, promotes tissue repair. The purpose of the present study was to investigate whether PRP promotes the osteogenic differentiation of hADSCs and to perform high-throughput sequencing to explore the possible mechanism. Methods: hADSCs were divided into the three following groups: CON group, OM group, and PRP group. Osteogenesis was detected by Alizarin Red staining on day 14. Total RNA was extracted from the OM and PRP groups for high-throughput sequencing. The target genes of the differentially expressed osteogenic-related miRNAs were predicted, and combined miRNA/mRNA analysis was then performed. The mRNA and protein expression levels of hsa-miR-212-5p, type 1 cannabinoid receptor (CNR1), alkaline phosphatase (ALP), Runx2, osteocalcin (OCN), and collagen 1 A1 (COL1A1) in the OM and PRP groups were detected by qRT-PCR and Western blot analyses. The binding between hsa-miR-212-5p and CNR1 was detected by a dual-luciferase reporter assay. Results: Both the OM and PRP groups exhibited enhanced proliferation of hADSCs, and the differences at 48 h and 72 h were statistically significant (P < 0.05). The PRP group had significantly more calcium nodules than the CON group (P < 0.05). Through high-throughput sequencing analysis, differential miRNA and mRNA expression profiles were obtained. During hADSC osteogenesis, the expression of hsa-miR-212-5p was downregulated, and the expression of CNR1 was upregulated. hsa-miR-212-5p was found to bind directly to the 3' UTR of CNR1. Conclusions: The present findings indicated that downregulation of hsa-miR-212-5p and upregulation of CNR1 may be involved in the process by which PRP promotes the osteogenic differentiation of hADSCs.

Electrospun Microfibers Modulate Intracellular Amino Acids in Liver Cells via Integrin ß1.

Although numerous recent studies have shown the importance of polymeric microfibrous extracellular matrices (ECMs) in maintaining cell behaviors and functions, the mechanistic nexus between ECMs and intracellular activities is largely unknown. Nevertheless, this knowledge will be critical in understanding and treating diseases with ECM remodeling. Therefore, we present our findings that ECM microstructures could regulate intracellular amino acid levels in liver cells mechanistically through integrin ß1. Amino acids were studied because they are the fundamental blocks for protein synthesis and metabolism, two vital functions of liver cells. Two ECM conditions, flat and microfibrous, were prepared and studied. In addition to characterizing cell growth, albumin production, urea synthesis, and cytochrome p450 activity, we found that the microfibrous ECM generally upregulated the intracellular amino acid levels. Further explorations showed that cells on the flat substrate expressed more integrin ß1 than cells on the microfibers. Moreover, after partially blocking integrin ß1 in cells on the flat substrate, the intracellular amino acid levels were restored, strongly supporting integrin ß1 as the linking mechanism. This is the first study to report that a non-biological polymer matrix could regulate intracellular amino acid patterns through integrin. The results will help with future therapy development for liver diseases with ECM changes (e.g., fibrosis).

Potent PDE4 inhibitor activates AMPK and Sirt1 to induce mitochondrial biogenesis.

AMP-activated protein kinase (AMPK) is an evolutionarily conserved energy sensor. Activation of AMPK leads to a number of metabolic benefits, including improved mitochondrial function in skeletal muscle and lowering of serum glucose levels in type-2 diabetes models. However, direct activation of AMPK leads to cardiac enlargement, and an alternative strategy that activates AMPK without affecting the heart is needed. Inhibition of phosphodiesterase 4 (PDE4), which is poorly expressed in the human heart, activates AMPK in other tissues. In a screen to identify novel PDE4 inhibitors, we discovered compound CBU91, which is 5-10 fold more potent than rolipram, the best characterized PDE4 inhibitor. CBU91, like rolipram, is able to activate AMPK and Sirt1 and increase mitochondrial function in myotubes. These findings suggest that activation of AMPK in myotubes is a general property of PDE4 inhibition and that PDE4 inhibition may activate AMPK in metabolically relevant tissues without affecting the heart.

3D-Printed, Modular, and Parallelized Microfluidic System with Customizable Scaffold Integration to Investigate the Roles of Basement Membrane Topography on Endothelial Cells.

Because dysfunctions of endothelial cells are involved in many pathologies, in vitro endothelial cell models for pathophysiological and pharmaceutical studies have been a valuable research tool. Although numerous microfluidic-based endothelial models have been reported, they had the cells cultured on a flat surface without considering the possible three-dimensional (3D) structure of the native extracellular matrix (ECM). Endothelial cells rest on the basement membrane in vivo, which contains an aligned microfibrous topography. To better understand and model the cells, it is necessary to know if and how the fibrous topography can affect endothelial functions. With conventional fully integrated microfluidic apparatus, it is difficult to include additional topographies in a microchannel. Therefore, we developed a modular microfluidic system by 3D-printing and electrospinning, which enabled easy integration and switching of desired ECM topographies. Also, with standardized designs, the system allowed for high flow rates up to 4000 µL/min, which encompassed the full shear stress range for endothelial studies. We found that the aligned fibrous topography on the ECM altered arginine metabolism in endothelial cells and thus increased nitric oxide production. There has not been an endothelial model like this, and the new knowledge generated thereby lays a groundwork for future endothelial research and modeling.

Recyclable deep eutectic solvent coupling sodium hydroxide post-treatment for boosting woody/herbaceous biomass conversion at mild condition.

A novel recyclable deep eutectic solvent (DES) consisting of p-toluene sulfonic acid (p-TsOH) and choline chloride (ChCl) was developed for efficient woody poplar sawdust (PL) and herbaceous miscanthus (MC) conversion at mild condition. The extraction of leftover lignin on the surface of DES pretreated residues using NaOH solution at room temperature greatly improved the enzymatic hydrolysis efficiency. Near complete cellulose conversion of PL and MC residues were obtained with a degree of delignification and xylan removal over 90% at 100 °C within 40 min. The strong correlations between xylan (R2 = 0.95) and lignin (R2 = 0.82) removal with cellulose conversion were observed in MC as well as positive correlations (R2 > 0.77) in PL. The results demonstrated that the DES system coupling NaOH post-treatment was a promising method to achieve an economically feasible biomass conversion process, which was effective for both woody PL residues and herbaceous MC.

Microfibrous Extracellular Matrix Changes the Liver Hepatocyte Energy Metabolism via Integrins.

Cell line-based liver models are critical tools for liver-related studies. However, the conventional monolayer culture of hepatocytes, the most widely used in vitro model, does not have the extracellular matrix (ECM), which contributes to the three-dimensional (3D) arrangement of the hepatocytes in the liver. As a result, the metabolic properties of the hepatocytes in the monolayer tissue culture may not accurately reflect those of the hepatocytes in the liver. Here, we developed a modular platform for 3D hepatocyte cultures on fibrous ECMs produced by electrospinning, a technique that can turn a polymer solution to the micro/nanofibers and has been widely used to produce scaffolds for 3D cell cultures. Metabolomics quantitation by liquid chromatography-mass spectrometry (LC-MS) indicated that Huh7 hepatocytes grown in microfibers electrospun from silk fibroin exhibited reduced glycolysis and tricarboxylic acid (TCA) cycle, as compared to the cells cultured as a monolayer. Further mechanistic studies suggested that integrins were correlated to the ECM's effects. This is the first time to report how an ECM scaffold could affect the fundamental metabolism of the hepatocytes via integrins.

Novel Gene Signature Reveals Prognostic Model in Acute Myeloid Leukemia.

BACKGROUND: Acute myeloid leukemia (AML) is a clonal malignant disease with poor prognosis and a low overall survival rate. Although many studies on the treatment and detection of AML have been conducted, the molecular mechanism of AML development and progression has not been fully elucidated. The present study was designed to pursuit the molecular mechanism of AML using a comprehensive bioinformatics analysis, and build an applicable model to predict the survival probability of AML patients in clinical use. METHODS: To simplify the complicated regulatory networks, we performed the gene co-expression and PPI network based on WGCNA and STRING database using modularization design. Two machine learning methods, A least absolute shrinkage and selector operation (LASSO) algorithm and support vector machine-recursive feature elimination (SVM-RFE), were used to filter the common hub genes by five-fold cross-validation. The candidate hub genes were used to build the predictive model of AML by the cox-proportional hazards analysis, and validated in The Cancer Genome Atlas (TCGA) cohort and ohsu cohort, which were reliable in the experimental verification by qRT-PCR and western blotting in mRNA and protein levels. RESULTS: Three hub genes, FLT3, CD177 and TTPAL were used to build a clinically applicable model to predict the survival probability of AML patients and divided them into high and low groups. To compare the survival ability of the model with the classical clinical features, we generated the nomogram. The model displayed the most risk points contrast to other clinical characteristics, which was compatible with the data of cox multivariate regression. CONCLUSION: This study reveal the novel molecular mechanism of AML, and construct a clinical model significantly related to AML patient prognosis. We showed the integrated roles of critical pathways, hub genes associated, which provide potential targets and new research ideas for the treatment and early detection of AML.

Improved activity of Ho-modified Mn/Ti catalysts for the selective catalytic reduction of NO with NH3.

A series of Ho-modified Mn/Ti catalysts with various content of Ho were prepared by impregnation method, and the low-temperature catalytic performance was tested. Techniques of BET, SEM, XRD, H2-TPR, and XPS were carried out to research the effects of Ho modification on the physicochemical properties of Mn/Ti catalysts. Results showed that appropriate Ho addition could reduce the starting temperature of Mn/TiO2 catalyst to 100 °C. 0.2HoMn/Ti exhibiting a wider temperature range of 140~220 °C with nearing 100% NOx conversion. It was found that the 0.2HoMn/TiO2 catalyst possessed a better dispersion of active component, enhanced redox capacity, a higher concentration of Mn4+ species, and a larger amount of Oß content on the catalyst surface, which are all likely predominant factors related to the excellent SCR activity. Additionally, Ho improved the Lewis acid sites and enhanced the adsorption and activation ability of NH3, as well as the NO to NO2 oxidation ability. The selective catalytic reduction with ammonia (NH3-SCR) deNOx mechanism over HoMn/Ti catalysts obeyed both the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms under low-temperature reaction conditions.

Isomeric Differentiation and Acidic Metabolite Identification by Piperidine-Based Tagging, LC-MS/MS, and Understanding of the Dissociation Chemistries.

We demonstrate a method for facile differentiation of acidic, isomeric metabolites by attaching high proton affinity, piperidine-based chemical tags to each carboxylic acid group. These tags attach with high efficiency to the analytes, increase the signal, and result in the formation of multiply-charged cations. We illustrate the present approach with citrate and isocitrate, which are isomeric metabolites each containing three carboxylic acid groups. We observe a 20-fold increase in signal-to-noise for citrate and an 8-fold increase for isocitrate as compared to detection of the untagged analytes in negative mode. Collision-induced dissociation of the triply tagged, triply charged analytes results in distinct tandem mass spectra. The phenylene spacer groups limit proton mobility and enable access to structurally informative C-C bond cleavage reactions. Modeling of the gas-phase structures and dissociation chemistry of these triply charged analyte ions highlights the importance of hydroxyl proton mobilization in this low proton mobility environment. Tandem mass spectrometric analyses of deuterated congeners and MS3 spectra are consistent with the proposed fragment ion structures and mechanisms of formation. Direct evidence that these chemistries are more generally applicable is provided by subsequent analyses of doubly tagged, doubly charged malate ions. Future work will focus on applying these methods to identify new metabolites and development of general rules for structural determination of tagged metabolites with multiple charges.

On-Surface Activation of Trimethylsilyl-Terminated Alkynes on Coinage Metal Surfaces.

The controlled attachment of protecting groups combined with the ability to selectively abstract them is central to organic synthesis. The trimethylsilyl (TMS) functional group is a popular protecting group in solution. However, insights on its activation behavior under ultra-high vacuum (UHV) and surface-confined conditions are scarce. Here we investigate a series of TMS-protected alkyne precursors via scanning tunneling microscopy (STM) regarding their compatibility with organic molecular beam epitaxy (OMBE) and their potential deprotection on various coinage metal surfaces. After in-situ evaporation on the substrates held in UHV at room temperature, we find that all molecules arrived and adsorbed as intact units forming ordered supramolecular aggregates stabilized by non-covalent interactions. Thus, TMS-functionalized alkyne precursors with weights up to 1100 atomic mass units are stable against OMBE evaporation in UHV. Furthermore, the TMS activation through thermal annealing is investigated with STM and X-ray photoelectron spectroscopy (XPS). We observe that deprotection starts to occur between 400 K and 500 K on the copper and gold surfaces, respectively. In contrast, on silver surfaces, the TMS-alkyne bond remains stable up to temperatures where molecular desorption sets in (≈600 K). Hence, TMS functional groups can be utilized as leaving groups on copper and gold surfaces while they serve as protecting groups on silver surfaces.

Fragmentation of Multi-charged Derivatized Lysine Using Nanospray CID Tandem Mass Spectrometry.

We demonstrate increasing the charge state of small molecules using derivatized lysine as our model system. Lysine is chemically tagged with three tertiary amines which enables efficient production of highly charged analytes. A +3 charge state is obtained from direct infusion nanoelectrospray conditions. Collisional activation of the +3 derivatized lysine yielded structurally informative product ions corresponding to cleavages across the analyte backbone and within the proton affinity tags. This suggests a role for multi-charging of metabolites in both targeted MRM analyses and untargeted analyses to help identify novel metabolites. Density functional calculations aid peak assignment and rationalization of structure-property relationships. Graphical Abstract.