Nuclear quantum effects at aqueous metal interfaces captured by molecular dynamics simulations

In this review, we summarize the recent development in modeling nuclear quantum effects at aqueous metal interfaces. First, we review the nuclear quantum effects on the water-metal interface at ultra-high vacuum. Then, we illustrate the nuclear quantum effects at the potential of zero charge conditions. At last, we give some outlook for the perspective work in modeling the nuclear quantum effects at electrochemical interfaces and some practical simulation strategies

Shallow and deep trap states of solvated electrons in methanol and their formation, electronic excitation, and relaxation dynamics

We present condensed-phase first-principles molecular dynamics simulations to elucidate the presence of different electron trapping sites in liquid methanol and their roles in the formation, electronic transitions, and relaxation of solvated electrons (emet−) in methanol. Excess electrons injected into liquid methanol are most likely trapped by methyl groups, but rapidly diffuse to more stable trapping sites with dangling OH bonds. After localization at the sites with one free OH bond (1OH trapping sites), reorientation of other methanol molecules increases the OH coordination number and the trap depth, and ultimately four OH bonds become coordinated with the excess electrons under thermal conditions. The simulation identified four distinct trapping states with different OH coordination numbers. The simulation results also revealed that electronic transitions of emet− are primarily due to charge transfer between electron trapping sites (cavities) formed by OH and methyl groups, and that these transitions differ from hydrogenic electronic transitions involving aqueous solvated electrons (eaq−). Such charge transfer also explains the alkyl-chain-length dependence of the photoabsorption peak wavelength and the excited-state lifetime of solvated electrons in primary alcohols

In situ spectroelectrochemical probing of CO redox landscape on copper single-crystal surfaces

Electrochemical reduction of CO$_{(2)}$to value-added chemicals and fuels is a promising strategy to sustain pressing renewable energy demands and to address climate change issues. Direct observation of reaction intermediates during the CO$_{(2)}$reduction reaction will contribute to mechanistic understandings and thus promote the design of catalysts with the desired activity, selectivity, and stability. Herein, we combined in situ electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy and ab initio molecular dynamics calculations to investigate the CORR process on Cu single-crystal surfaces in various electrolytes. Competing redox pathways and coexistent intermediates of CO adsorption (*CO$_{atop}$and *CO$_{bridge}$), dimerization (protonated dimer *HOCCOH and its dehydrated *CCO), oxidation (*CO$_{2}$$^{−}$and *CO$_{3}$$^{2−}$), and hydrogenation (*CHO), as well as Cu-O$_{ad}$/Cu-OH$_{ad}$species at Cu-electrolyte interfaces, were simultaneously identified using in situ spectroscopy and further confirmed with isotope-labeling experiments. With AIMD simulations, we report accurate vibrational frequency assignments of these intermediates based on the calculated vibrational density of states and reveal the corresponding species in the electrochemical CO redox landscape on Cu surfaces. Our findings provide direct insights into key intermediates during the CO$_{(2)}$RR and offer a full-spectroscopic tool (40–4,000 cm$^{−1}$) for future mechanistic studies

In-situ nanospectroscopic imaging of plasmon-induced two-dimensional [4+4]-cycloaddition polymerization on Au(111)

From Springer Nature via Jisc Publications RouterHistory: received 2021-01-14, accepted 2021-06-16, registration 2021-07-13, pub-electronic 2021-07-27, online 2021-07-27, collection 2021-12Publication status: PublishedFunder: EC | EU Framework Programme for Research and Innovation H2020 | H2020 Priority Excellent Science | H2020 European Research Council (H2020 Excellent Science - European Research Council); doi: https://doi.org/10.13039/100010663; Grant(s): 741431-2DNanoSpecFunder: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (Swiss National Science Foundation); doi: https://doi.org/10.13039/501100001711; Grant(s): URPP-LightChECFunder: EC | Horizon 2020 Framework Programme (EU Framework Programme for Research and Innovation H2020); doi: https://doi.org/10.13039/100010661; Grant(s): 841653-2DvdWHsFunder: the Swiss National Supercomputing Centre (CSCS) under Project ID uzh1 and s965Abstract: Plasmon-induced chemical reactions (PICRs) have recently become promising approaches for highly efficient light-chemical energy conversion. However, an in-depth understanding of their mechanisms at the nanoscale still remains challenging. Here, we present an in-situ investigation by tip-enhanced Raman spectroscopy (TERS) imaging of the plasmon-induced [4+4]-cycloaddition polymerization within anthracene-based monomer monolayers physisorbed on Au(111), and complement the experimental results with density functional theory (DFT) calculations. This two-dimensional (2D) polymerization can be flexibly triggered and manipulated by the hot carriers, and be monitored simultaneously by TERS in real time and space. TERS imaging provides direct evidence for covalent bond formation with ca. 3.7 nm spatial resolution under ambient conditions. Combined with DFT calculations, the TERS results demonstrate that the lateral polymerization on Au(111) occurs by a hot electron tunneling mechanism, and crosslinks form via a self-stimulating growth mechanism. We show that TERS is promising to be plasmon-induced nanolithography for organic 2D materials

Dynamics and control of active sites in hierarchically nanostructured cobalt phosphide/chalcogenide-based electrocatalysts for water splitting

The rational design of efficient electrocatalysts for industrial water splitting is essential to generate sustainable hydrogen fuel. However, a comprehensive understanding of the complex catalytic mechanisms under harsh reaction conditions remains a major challenge. We apply a self-templated strategy to introduce hierarchically nanostructured “all-surface” Fe-doped cobalt phosphide nanoboxes (Co@CoFe–P NBs) as alternative electrocatalysts for industrial-scale applications. Operando Raman spectroscopy and X-ray absorption spectroscopy (XAS) experiments were carried out to track the dynamics of their structural reconstruction and the real catalytically active intermediates during water splitting. Our operando analyses reveal that partial Fe substitution in cobalt phosphides promotes a structural reconstruction into P–Co–O–Fe–P configurations with low-valence metal centers (M0/M+) during the hydrogen evolution reaction (HER). Results from density functional theory (DFT) demonstrate that these in situ reconstructed configurations significantly enhance the HER performance by lowering the energy barrier for water dissociation and by facilitating the adsorption/desorption of HER intermediates (H*). The competitive activity in the oxygen evolution reaction (OER) arises from the transformation of the reconstructed P–Co–O–Fe–P configurations into oxygen-bridged, high-valence CoIV–O–FeIV moieties as true active intermediates. In sharp contrast, the formation of such CoIII/IV–O–FeIII/IV moieties in Co–FeOOH is hindered under the same conditions, which outlines the key advantages of phosphide-based electrocatalysts. Ex situ studies of the as-synthesized reference cobalt sulfides (Co–S), Fe doped cobalt selenides (Co@CoFe–Se), and Fe doped cobalt tellurides (Co@CoFe–Te) further corroborate the observed structural transformations. These insights are vital to systematically exploit the intrinsic catalytic mechanisms of non-oxide, low-cost, and robust overall water splitting electrocatalysts for future energy conversion and storage

Evaluating Prophylactic Effect of Bovine Colostrum on Intestinal Barrier Function in Zonulin Transgenic Mice : A Transcriptomic Study

The intestinal barrier comprises a single layer of epithelial cells tightly joined to form a physical barrier. Disruption or compromise of the intestinal barrier can lead to the inadvertent activation of immune cells, potentially causing an increased risk of chronic inflammation in various tissues. Recent research has suggested that specific dietary components may influence the function of the intestinal barrier, potentially offering a means to prevent or mitigate inflammatory disorders. However, the precise mechanism underlying these effects remains unclear. Bovine colostrum (BC), the first milk from cows after calving, is a natural source of nutrients with immunomodulatory, anti-inflammatory, and gut-barrier fortifying properties. This novel study sought to investigate the transcriptome in BC-treated Zonulin transgenic mice (Ztm), characterized by dysbiotic microbiota, intestinal hyperpermeability, and mild hyperactivity, applying RNA sequencing. Seventy-five tissue samples from the duodenum, colon, and brain of Ztm and wild-type (WT) mice were dissected, processed, and RNA sequenced. The expression profiles were analyzed and integrated to identify differentially expressed genes (DEGs) and differentially expressed transcripts (DETs). These were then further examined using bioinformatics tools. RNA-seq analysis identified 1298 DEGs and 20,952 DETs in the paired (Ztm treatment vs. Ztm control) and reference (WT controls) groups. Of these, 733 DEGs and 10,476 DETs were upregulated, while 565 DEGs and 6097 DETs were downregulated. BC-treated Ztm female mice showed significant upregulation of cingulin (Cgn) and claudin 12 (Cldn12) duodenum and protein interactions, as well as molecular pathways and interactions pertaining to tight junctions, while BC-treated Ztm males displayed an upregulation of transcripts like occludin (Ocln) and Rho/Rac guanine nucleotide exchange factor 2 (Arhgf2) and cellular structures and interfaces, protein-protein interactions, and organization and response mechanisms. This comprehensive analysis reveals the influence of BC treatment on tight junctions (TJs) and Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) signaling pathway gene expressions. The present study is the first to analyze intestinal and brain samples from BC-treated Ztm mice applying high-throughput RNA sequencing. This study revealed molecular interaction in intestinal barrier function and identified hub genes and their functional pathways and biological processes in response to BC treatment in Ztm mice. Further research is needed to validate these findings and explore their implications for dietary interventions aimed at improving intestinal barrier integrity and function. The MGH Institutional Animal Care and Use Committee authorized the animal study (2013N000013).Peer reviewe

Prophylactic Effect of Bovine Colostrum on Intestinal Microbiota and Behavior in Wild-Type and Zonulin Transgenic Mice

Funding Information: This research was partly supported by the Spector Family Foundation to M.F.; the MGH ECOR Feasibility Grant to A.M.R.; European Commission, award number 825033 “GEMMA project” funded on Horizon 2020 program (call H2020-SC1-BHC -03-2018) to A.F.; the Fulbright Foundation, the Leifur Eiríksson Foundation, University of Iceland Research Fund, and the Nutricia Research Foundation to B.A.; the Uehara Memorial Foundation Overseas Postdoctoral Fellowships and the Ito Foundation for the Promotion of Medical Science Travel Grants for Overseas Exchange to T.K. Publisher Copyright: © 2022 by the authors.The microbiota–gut–brain axis (MGBA) involves bidirectional communication between intestinal microbiota and the gastrointestinal (GI) tract, central nervous system (CNS), neuroendocrine/neuroimmune systems, hypothalamic–pituitary–adrenal (HPA) axis, and enteric nervous system (ENS). The intestinal microbiota can influence host physiology and pathology. Dysbiosis involves the loss of beneficial microbial input or signal, diversity, and expansion of pathobionts, which can lead to loss of barrier function and increased intestinal permeability (IP). Colostrum, the first milk from mammals after birth, is a natural source of nutrients and is rich in oligosaccharides, immunoglobulins, growth factors, and anti-microbial components. The aim of this study was to investigate if bovine colostrum (BC) administration might modulate intestinal microbiota and, in turn, behavior in two mouse models, wild-type (WT) and Zonulin transgenic (Ztm)—the latter of which is characterized by dysbiotic microbiota, increased intestinal permeability, and mild hyperactivity—and to compare with control mice. Bioinformatics analysis of the microbiome showed that consumption of BC was associated with increased taxonomy abundance (p = 0.001) and diversity (p = 0.004) of potentially beneficial species in WT mice and shifted dysbiotic microbial community towards eubiosis in Ztm mice (p = 0.001). BC induced an anxiolytic effect in WT female mice compared with WT female control mice (p = 0.0003), and it reduced anxiogenic behavior in Ztm female mice compared with WT female control mice (p = 0.001), as well as in Ztm male mice compared with WT BC male mice (p = 0.03). As evidenced in MGBA interactions, BC supplementation may well be applied for prophylactic approaches in the future. Further research is needed to explore human interdependencies between intestinal microbiota, including eubiosis and pathobionts, and neuroinflammation, and the potential value of BC for human use. The MGH Institutional Animal Care and Use Committee authorized the animal study (2013N000013).Peer reviewe

Aquaporin-9 Contributes to the Maturation Process and Inflammatory Cytokine Secretion of Murine Dendritic Cells

Dendritic cells (DCs) are the most potent antigen-presenting cells able to trigger the adaptive immune response to specific antigens. When non-self-antigens are captured, DCs switch from an “immature” to a “mature” state to fulfill their function. Among the several surface proteins involved in DCs maturation, the role of aquaporins (AQPs) is still poorly understood. Here we investigated the expression profile of Aqps in murine bone marrow derived dendritic cells (BMDCs). Among the Aqps analyzed, Aqp9 was the most expressed by DCs. Its expression level was significantly upregulated 6 h following LPS exposure. Chemical inhibition of Aqp9 led to a decreased inflammatory cytokines secretion. BMDCs from AQP9-KO mice release lower amount of inflammatory cytokines and chemokines and increased release of IL-10. Despite the reduced release of inflammatory cytokines, Aqp9-KO mice were not protected from DSS induced colitis. All together, our data indicate that AQP9 blockade can be an efficient strategy to reduce DCs inflammatory response but it is not sufficient to protect from acute inflammatory insults such as DSS induced colitis