Direct Observation of Anionic Yields from the Liquid-Vapor Interface by Electron Irradiation.

Dissociative electron attachment (DEA) is widely believed to play a high-profile role in ionizing radiation damages of bioorganic molecules, and its fundamentals are mainly learned from the gas-phase studies. However, the DEA process in aqueous solution is still in debate. Here we provide experimental evidence about the DEA processes of liquid methanol by using electron-impact-time-delayed mass spectrometry. In contrast to the gas- and solid-phase DEAs, methoxide ion CH3O- is the predominant product from the liquid interface. Furthermore, this anion can be produced with both the primary low-energy electrons and the inelastically scattered and secondary low-energy electrons. On the contrary, the primary low-energy electrons in the liquid bulk are more likely to be solvated, rather than directly participating in the DEA process. Our study provides new insights into radiation chemistry, particularly of bioorganic relevance.

[Analysis of differential metabolites of spikes of Prunella vulgaris at different stages based on UPLC-MS/MS].

Prunella vulgaris, aptly named for its withering at the summer solstice, displays significant variation in quality arising from differing harvest time. However, research on the chemical composition changes of its spikes at various stages is limited, and the specific metabolites remain unclear. In order to elucidate the metabolites and metabolic pathways of the spikes of P. vulgaris, the current study deployed ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) and targeted metabolomics to characterize the compound variability in the spikes of P. vulgaris across different periods. Multivariate statistical techniques such as principal component analysis(PCA) and orthogonal partial least squares-discriminant analysis(OPLS-DA) were used to identify the differences in metabolites, and relevant metabolic pathways were analyzed. A total of 602 metabolites were identified by metabolomics, of which organic acids and their derivatives were the most abundant, followed by flavonoids. Multiple differential metabolites, including p-hydroxybenzoic acids and gallic acids were identified based on variable importance in projection(VIP)>1 and P<0.05. The results of enrichment analysis suggested that isoflavonoids biosynthesis, aminobenzoate degradation, benzoate degradation, anthocyanins biosynthesis, metabolic pathways, microbial metabolism in different environments, secondary plant metabolite biosynthesis, tryptophan metabolism, and phenylpropanoid synthesis were the main metabolic pathways. These results intend to elucidate the dynamic changes of differential metabolites of P. vulgaris and provide a theoretical basis for further study of the harvesting mechanism of spikes of P. vulgaris.

Plant-Derived Caffeic Acid and Its Derivatives: An Overview of Their NMR Data and Biosynthetic Pathways.

In recent years, caffeic acid and its derivatives have received increasing attention due to their obvious physiological activities and wide distribution in nature. In this paper, to clarify the status of research on plant-derived caffeic acid and its derivatives, nuclear magnetic resonance spectroscopy data and possible biosynthetic pathways of these compounds were collected from scientific databases (SciFinder, PubMed and China Knowledge). According to different types of substituents, 17 caffeic acid and its derivatives can be divided into the following classes: caffeoyl ester derivatives, caffeyltartaric acid, caffeic acid amide derivatives, caffeoyl shikimic acid, caffeoyl quinic acid, caffeoyl danshens and caffeoyl glycoside. Generalization of their 13C-NMR and 1H-NMR data revealed that acylation with caffeic acid to form esters involves acylation shifts, which increase the chemical shift values of the corresponding carbons and decrease the chemical shift values of the corresponding carbons of caffeoyl. Once the hydroxyl group is ester, the hydrogen signal connected to the same carbon shifts to the low field (1.1~1.6). The biosynthetic pathways were summarized, and it was found that caffeic acid and its derivatives are first synthesized in plants through the shikimic acid pathway, in which phenylalanine is deaminated to cinnamic acid and then transformed into caffeic acid and its derivatives. The purpose of this review is to provide a reference for further research on the rapid structural identification and biofabrication of caffeic acid and its derivatives.

Effect and mechanism of Prunella vulgaris L. extract on alleviating lipopolysaccharide-induced acute mastitis in protecting the blood-milk barrier and reducing inflammation.

ETHNOPHARMACOLOGICAL RELEVANCE: According to ancient literature, Prunella vulgaris L. (P vulgaris) alleviates mastitis and has been used in China for many years; however, there are no relevant reports that confirm this or the mechanism of its efficacy. AIM OF THE STUDY: To explore the anti-acute mastitis effect and potential mechanism of P vulgaris extract. MATERIALS AND METHODS: First, the active ingredients and targets of P vulgaris against mastitis were predicted using network pharmacology. Next, the relevant active ingredients were enriched using macroporous resins and verified using UV and UPLC-Q-TOF-MS/MS. Lastly, a mouse model of acute mastitis was established by injecting lipopolysaccharides into the mammary gland and administering P vulgaris extract by oral gavage. The pathological changes in mammary tissue were observed by HE staining. Serum and tissue inflammatory factors were measured by ELISA method. MPO activity in mammary tissue was measured using colorimetry and MPO expression was detected by immunohistochemistry. The expression of tight junction proteins (ZO-1, claudin-3, and occludin) in mammary tissue was detected by immunofluorescence and Western blot. iNOS and COX-2 in mammary tissue were detected by Western blot. MAPK pathway and NF-κB pathway related proteins were also detected by Western blot. RESULTS: Network pharmacology predicted that phenolic acids and flavonoids in P vulgaris had anti-mastitis effects. The contents of total flavonoids and total phenolic acids in P vulgaris extract were 64.5% and 29.4%, respectively. UPLC-Q-TOF-MS/MS confirmed that P vulgaris extract contained phenolic acids and flavonoids. The results of animal experiments showed that P vulgaris extract reduced lipopolysaccharide-induced inflammatory edema, inflammatory cell infiltration, and interstitial congestion of mammary tissue. It also reduced the levels of serum and tissue inflammatory factors TNF-α, IL-6, and IL-1ß, and inhibited the activation of MPO. Furthermore, it downregulated the expression of MAPK and NF-κB pathway-related proteins. The expressions of ZO-1, occludin, and claudin-3 in mammary gland tissues were upregulated. CONCLUSIONS: P vulgaris extract can maintain the integrity of mammary connective tissue and reduce its inflammatory response to prevent acute mastitis. Its mechanism probably involves regulating NF-κB and MAPK pathways.

Evaporative cooling and reaction of carbon dioxide clusters by low-energy electron attachment.

Anionic carbonate CO3- has been found in interstellar space and the Martian atmosphere, but its production mechanism is in debate so far. To mimic the irradiation-induced reactions on icy micrograins in the Martian atmosphere and the icy shell of interstellar dust, here we report a laboratory investigation on the dissociative electron attachments to the molecular clusters of CO2. We find that anionic species (CO2)n-1O- and (CO2)n- (n = 2, 3, 4) are produced in the concerted reaction and further stabilized by the evaporative cooling after the electron attachment. We further propose a dynamics model to elucidate their competitive productions: the (CO2)n- yields survive substantially in the molecular evaporative cooling at the lower electron attachment energy, while the reactions leading to (CO2)n-1O- are favored at the higher attachment energy. This work provides new insights into physicochemical processes in CO2-rich atmospheres and interstellar space.

Recent advances in medicinal and edible homologous plant polysaccharides: Preparation, structure and prevention and treatment of diabetes.

Medicinal and edible homologs (MEHs) can be used in medicine and food. The National Health Commission announced that a total of 103 kinds of medicinal and edible homologous plants (MEHPs) would be available by were available in 2023. Diabetes mellitus (DM) has become the third most common chronic metabolic disease that seriously threatens human health worldwide. Polysaccharides, the main component isolated from MEHPs, have significant antidiabetic effects with few side effects. Based on a literature search, this paper summarizes the preparation methods, structural characterization, and antidiabetic functions and mechanisms of MEHPs polysaccharides (MEHPPs). Specifically, MEHPPs mainly regulate PI3K/Akt, AMPK, cAMP/PKA, Nrf2/Keap1, NF-κB, MAPK and other signaling pathways to promote insulin secretion and release, improve glycolipid metabolism, inhibit the inflammatory response, decrease oxidative stress and regulate intestinal flora. Among them, 16 kinds of MEHPPs were found to have obvious anti-diabetic effects. This article reviews the prevention and treatment of diabetes and its complications by MEHPPs and provides a basis for the development of safe and effective MEHPP-derived health products and new drugs to prevent and treat diabetes.

Direct production of molecular oxygen from carbon dioxide and helium ion collisions.

The prebiotic mechanism to produce molecular oxygen (O2) in carbon dioxide (CO2)-rich planetary atmospheres is of great importance in understanding astrochemical reactions and is potentially relevant to the origin of life on Earth. Here, we demonstrate that, aside from the direct productions of O2 by photodissociation and dissociative electron attachment, the low-energy ion-molecule reaction between cationic helium in solar winds and molecular CO2 is a noticeable mechanism. Branching ratios of the reaction channels are determined, and their absolute cross-sections are estimated accordingly. The present findings represent a further, indispensable step towards fully understanding the origins of atmospheric O2.

Dissociation dynamics of anionic carbon monoxide in dark states.

A resonant system consisting of an excess electron and a closed-shell atom or molecule, as a temporary negative ion, is usually in doublet-spin states that are analogous to bright states of photoexcitation of the neutral. However, anionic higher-spin states, noted as dark states, are scarcely accessed. Here, we report the dissociation dynamics of CO- in dark quartet resonant states that are formed by electron attachments to electronically excited CO (a3Π). Among the dissociations to O-(2P) + C(3P), O-(2P) + C(1D), and O-(2P) + C(1S), the latter two are spin-forbidden in the quartet-spin resonant states of CO-, while the first process is preferred in 4Σ- and 4Π states. The present finding sheds new light on anionic dark states.

Dissociation Dynamics of Anionic Nitrogen Dioxide in the Low-Lying Resonant States.

Experimental studies of the dynamics near the molecular dissociation threshold are frequently frustrated, due to the small cross sections and the demand for identification of close-lying electronic states or nuclear motions with multiple degrees of freedom. Using the high-resolution anion velocity map imaging technique, here we report a dynamics study of the dissociations of anionic nitrogen dioxide in low-lying resonant states formed by electron attachment [e- + NO2 (X2A1) → NO2- → NO (X2Π) + O- (2P)]. The long-term puzzling issues about the near-threshold dissociations of NO2- are settled. We suggest that three low-lying resonant states (1B1, 3B1, and 3B2) of NO2- contribute to the production of O- at attachment energies of <5 eV. Furthermore, B1 and B2 symmetries of the resonant states lead to different anisotropies of the O- angular distribution. At the relatively high electron attachment energies, a prompt fragmentation in the molecular bent conformation competes with an indirect dissociation in the straightened conformation.

Dipsacoside B Inhibits the Migration and Proliferation of VSMCs and Blunts Neointimal Formation by Upregulating PTEN Expression.

BACKGROUND: To investigate the effect and potential molecular mechanisms of Dipsacoside B (DB), an herb monomer extracted from Dipsacusasper or Lonicera macranthoides, on the migration and proliferation of vascular smooth muscle cells (VSMCs) and balloon-induced neointimal formation. METHODS: In vivo, rat abdominal aorta balloon injury model was utilized to investigate the effect of DB on the neointimal formation. In vitro, cultured VSMCs were used to investigate the effect of DB on Angiotensin-II (Ang-II)-induced migration and proliferation of VSMCs. Western blot and immunofluorescence were used to measure PTEN expression. RESULTS: As compared to vehicle control balloon-injury group, DB treatment significantly inhibited the neointimal formation together up-regulated the expression of phosphatase and tension homolog deleted on chromosome 10 (PTEN). Cell proliferations (MTT and Edu incorporation) assays and wound migration measurement further revealed that treatment with DB significantly blunted Ang-II-induced proliferation and migration potential of VSMCs. Western blot analysis exhibited that DB upregulated the expression of PTEN in vivo and in vitro. CONCLUSIONS: DB treatment suppresses the proliferation and migration of VSMCs and reduces neointimal formation by the mechanisms involving regulating the phenotype switch of VSMCs via upregulating PTEN expression.

An in vivo and in vitro assessment of the anti-breast cancer activity of crude extract and fractions from Prunella vulgaris L.

Prunella vulgaris L.(P. vulgaris) is a perennial herb belonging to the Labiate family and widely distributed in China, Japan, Korea and Europe. Medical monographs and previous studies have shown that P. vulgaris has significant anti-breast cancer activity, and its use in breast treatment has a long history. However, systematically reports about the material basis and mechanism of P. vulgaris on anti-breast cancer activity are limited. In the present study, we first screened the best active fraction from the crude extract (PVE) and ethanol eluted fractions of P. vulgaris by using MDA-MB-231, MCF-7, 4T1 cell models in vitro and a 4T1-BALB/c transplanted tumour mouse breast cancer model in vivo. Furthermore, the anti-breast cancer mechanism of the best active fraction was investigated. The results demonstrated that PVE and ethanol fractions exhibited anti-breast cancer activity, especially with the 50% ethanol eluted fraction (PV50), which effectively regulated the 4T1 cell cycle, inhibited tumour cell proliferation, and promoted cancer cell apoptosis. In case of in vivo assays, PV50 inhibited tumour growth and lung metastasis, as well as inducing cell apoptosis by promoting damage of nuclear DNA and increasing expression of cleaved caspase-3. In addition, the chemical compositions of PV50 were analyzed by HPLC and UPLC-MS/MS, which were identified as flavonoids, moderately polar triterpenes, and a small amount of phenolic acid. The PV50 could be applied as natural sources against breast cancer in the pharmaceutical industry. These findings provide a basis for understanding the mechanism of the anti-breast cancer activity of P. vulgaris.

Integrative transcriptomic, proteomic and metabolomic analysis reveals the dynamic regulation of secondary metabolism upon development of Prunella vulgaris L.

Prunella vulgaris L. (P. vulgaris, Labiatae) is a perennial medicinal and edible plant widely used in China, Korea, Japan and Europe. The reddish brown spica of P. vulgaris (Prunellae Spica), which is collected in summer, has been commonly used in traditional medicine and food industry, while it is also used with whole grass in Europe and Taiwan. To clarify the regulatory pathways and mechanism of quality formation in P. vulgaris, targeted metabolomic, transcriptomic, and proteomic analyses of Prunellae Spica samples from five consecutive developmental stages were carried out. The results showed that terpenoids were mainly synthesized in the maturity stage of Prunellae Spica, with the key enzymes and coding genes in downstream pathways being mainly expressed during ripening, while related enzymes in the upstream pathway showed the opposite pattern. Flavonoids mainly accumulated before ripening, with highly expressed pathway enzymes and coding genes. The accumulation of phenylpropanoids was relatively active throughout the development process. Rosmarinic acid (RA) and its synthetic intermediate products mainly accumulated via more active pathway enzymes and coding genes before ripening. The regulatory factors and metabolites related to RA synthesis were mainly enriched in phenylpropanoid biosynthesis, plant hormone signal transduction, plant pathogen interaction, oxidative phosphorylation, and endoplasmic reticulum protein processing pathways.

Dissociation Dynamics of Anionic Carbon Dioxide in the Shape Resonant State 2Πu.

Dissociative electron attachments via the lowest shape resonant state 2Πu of CO2-, e- + CO2 → O- + CO, are investigated with our high-resolution anion velocity map imaging apparatus. The production efficiency curve of O- obtained in this work is consistent with those reported previously. The forward-backward asymmetric distribution superimposed on the isotopic background is observed in the time-sliced velocity image of O- yield, implying that the dissociation of CO2-(2Πu) proceeds through a combinational motion of bond stretching and bending. Thereby, the coproduct CO is proposed to be in the rovibrational states. The long-standing arguments about the dissociation dynamics of CO2-(2Πu) are settled.

Collision-Energy Dependent Stereodynamics of Dissociative Charge Exchange Reaction between Ar+ and CO.

Long-distance charge-dipole attraction between atomic ion and randomly oriented polar molecule potentially makes the molecular orientation, which profoundly influences the products' kinetics of collisional reaction. Using the three-dimensional ion velocity map imaging technique, here we report a collision-energy dependent stereodynamics of dissociative charge exchange reaction Ar+ + CO → Ar + O + C+ in a range of 7.46-9.97 eV. At the lowest collision energy, the most C+ products are forward-scattered and are along the collision axis and are attributed to three different dissociation channels including the predominant one experiencing the rotating intermediate ArC+. At the high collision energies, the remarkably diffusive distribution of C+ arises from the prompt dissociation of the rebounded CO+. The different dynamic processes arising from the nearly collinear collision are elaborated explicitly on the basis of the data analyses using the Doppler kinetics models.

Superposition-state N2 + produced in the intermolecular charge transfer from low-energy Ar+ to N2.

Molecular electronic or vibrational states can be superimposed temporarily in an extremely short laser pulse, and the superposition-state transients formed therein receive much attention, owing to the extensive interest in molecular fundamentals and the potential applications in quantum information processing. Using the crossed-beam ion velocity map imaging technique, we disentangle two distinctly different pathways leading to the forward-scattered N2 + yields in the large impact-parameter charge transfer from low-energy Ar+ to N2. Besides the ground-state (X2Σg +) N2 + produced in the energy-resonant charge transfer, a few slower N2 + ions are proposed to be in the superpositions of the X2Σg +-A2Πu and A2Πu-B2Σu + states on the basis of the accidental degeneracy or energetic closeness of the vibrational states around the X2Σg +-A2Πu and A2Πu-B2Σu + crossings in the non-Franck-Condon region. This finding potentially shows a brand-new way to prepare the superposition-state molecular ion.

Ion-Molecule Charge Exchange Reactions between Ar+ and trans-/cis-Dichloroethylene.

We report an ion velocity imaging study of the charge exchange reactions between Ar+ ion and trans-/cis-dichloroethylene in the collision energy range of 2.1-9.5 eV, and we find that the energy-resonant charge transfer plays a dominant role in the large impact-parameter reaction. The parent yields C2H2Cl2+ in the high-lying excited states are directly produced in the charge exchange reactions, while they prefer spontaneous fragmentations in photoionization. This significant difference indicates that the present charge exchange reactions are much slower than the photoelectron detachment. The structural relaxations of the target molecule are allowed in multiple dimensions of freedom during the charge transfer, which should be frequently observed for the charge exchange reactions with large molecules.

Stereodynamics Observed in the Reactive Collisions of Low-Energy Ar+ with Randomly Oriented O2.

Stereodynamics of the collisional reaction between mutually aligned or oriented reactants has been a striking topic of chemical dynamics for decades. However, the stereodynamic aspects are scarcely revealed for the low-energy collision with a randomly oriented target. Here in the dissociative charge-exchange reaction between randomly oriented O2 and low-energy Ar+, we, using the three-dimensional ion velocity map imaging technique, clearly observe a linear alignment and a nearly isotropic distribution of the O+ yields along the collision axis. These observations are rationalized with the Doppler kinetic models in which the O2 bond is assumed to be parallel or unparallel to the collision axis of the large impact parameter collision. The linearly aligned O+, as the predominant yield, is produced in the parallel collision, while a rotating O2+, as the intermediate in the unparallel collision, leads to the isotropic distribution of O+.

Comparative proteomic analysis of Prunella vulgaris L. spica ripening.

Prunella vulgaris L., better known as 'self-heal', has been extensively used in the traditional system of medicines. To reveal the regulatory mechanism of its development, TMT-based quantitative proteome analysis was performed in the Prunella vulgaris L. spica before and during ripening (Group A and Group B, respectively). This analysis resulted in the identification of 7655 proteins, of which 1910 showed differential abundance between the two groups. Pronounced changes in the proteomic profile included the following: 1) Stress-responsive proteins involved in protecting cells and promoting fruit ripening and seed development were highly abundant during ripening. 2) The degradation of chlorophyll, inhibition of chlorophyll biosynthesis and increased abundance of transketolase occurred simultaneously in the spica of Prunella vulgaris L., resulting in the spica changing color from green to brownish red. 3) The abundance of protein species related to phenylpropanoid biosynthesis mainly increased during ripening, while flavonoid and terpenoid backbone biosynthesis mostly occurred before ripening. SIGNIFICANCE: This study establishes a link between protein profiles and mature phenotypes, which will help to improve our understanding of the molecular mechanisms involved in the maturation of Prunella vulgaris L. at the proteome level and reveal the scientific connotation for the best time to harvest Prunella vulgaris L. This work provides a scientific basis for the production of high-quality medicinal Prunella vulgaris L., as well as a typical demonstration of molecular research used for the harvest period of traditional Chinese medicine. BIOLOGICAL SIGNIFICANCE: This work provided a comprehensive overview on the functional protein profile changes of Prunella vulgaris L. spica at different growing stages, as well as the scientific rationale of Prunella vulgaris L. harvested in summer after brownish red, thus laid an intriguing stepping stone for elucidating the molecular mechanisms of quality development.

Direct observation of long-lived cyanide anions in superexcited states.

The cyanide anion (CN-) has been identified in cometary coma, interstellar medium, planetary atmosphere and circumstellar envelopes, but its origin and abundance are still disputed. An isolated CN- is stabilized in the vibrational states up to ν = 17 of the electronic ground-state 1Σ+, but it is not thought to survive in the electronic or vibrational states above the electron autodetachment threshold, namely, in superexcited states. Here we report the direct observation of long-lived CN- yields of the dissociative electron attachment to cyanogen bromide (BrCN), and confirm that some of the CN- yields are distributed in the superexcited vibrational states ν ≥ 18 (1Σ+) or the superexcited electronic states 3Σ+ and 3Π. The triplet state can be accessed directly in the impulsive dissociation of BrCN- or by an intersystem transition from the superexcited vibrational states of CN-. The exceptional stability of CN- in the superexcited states profoundly influences its abundance and is potentially related to the production of other compounds in interstellar space.

Probing the Potential Energy Surfaces of BrCN- by Dissociative Electron Attachment.

State coupling certainly determines the topologic features of the molecular potential energy surface (PES) and potentially diversifies chemical reaction pathways. Here we report the new PESs of BrCN- in the low-lying electronic states that are distinctly different from the previous predictions in the short Br-CN bond region but validated by the high-resolution ion velocity imaging measurements of low-energy dissociative electron attachment (DEA) to BrCN. Besides the vibrating CN- ions produced in the fast Br-CN bond stretching motions, we confirm that the ro-vibrating CN- ions with a nearly isotropic angular distribution are produced by receiving a torque in the combinational motion of Br-CN bond bending and stretching. The latter process is closely related to the potential well of BrCN- at the first excited state A2Π3/2 that arises from the Π-Σ state couplings. Our findings not only suggest that the PESs of other anionic cyanogen halides are in dire need of reexamination but also show that ion velocity imaging of the DEA process is a powerful experimental method for evaluating the theoretical PESs of molecular anions.