Shale pore structures and irregularities are significant for gas adsorption and interstifial flow. High complexity and nonuniformity, wide pore scales, and multiple morphology hinder the thorough ...characterization of multi-scale pore structure and heterogeneity in shales. In this work, the geochemistry, pore structure and fractal characteristics of the Upper Cretaceous Nenjiang shale in the Songliao Basin of NE China were investigated, combining geochemistry experiments, physical property analysis, FE-SEM and nano-CT image observation, CO2/N2 gas adsorption, mercury intrusion porosimetry, and methane methane sorption analysis. The results show that the Nenjiang shales are low-mature (Ro of 0.55%–0.93%) and rich in organic matters (OMs) and clays. The size diameters of shale pores are generally distributed in sizes of 0.3–0.8, 1.4–4.5, 80–600 nm and 10–80 μm. Shale pores have strong heterogeneity and complexity, good connectivity and openness, mainly with inkbottle- and slit-shapes. Total pore volume (PV) is positive correlate with specific surface area (SSA), porosity and permeability, but negative correlate with the average pore size. The development of micro-, meso-, and macro-pores were dominated by the contents of OM, clays, and quartz, respectively. Positive correlations were found among fractal dimension, contents of OMs and clays, total PV, SSA, and methane adsorption capacity, which would provides better understanding on reservoir assessment and shale gas storage capacity.
•Pore structures and fractal dimensions of clay-rich lacustrine shale were studied.•Inkbottle- and slit-shaped pores are dominated in pore system with good connectivity.•OM, clays, and quartz respectively control micro-, meso-, and macro-pore growth.•The correlations among fractal features, pore structures and components were analyzed.•Shales with higher fractal dimensions have greater methane adsorption capacity.
Link weights have the equally important position as links in complex networks, and they are closely associated with each other for the emergence of communities. How to assign link weights to make a ...clear distinction between internal links of communities and external links connecting communities is of vital importance for community detection. Edge centralities provide a powerful approach for distinguishing internal links from external ones. Here, we first use edge centralities such as betweenness, information centrality and edge clustering coefficient to weight links of networks respectively to transform unweighted networks into weighted ones, and then a weighted function that both considers links and link weights is adopted on the weighted networks for community detection. We evaluate the performance of our approach on random networks as well as real-world networks. Better results are achieved on weighted networks with stronger weights of internal links of communities, and the results on unweighted networks outperform that of weighted networks with weaker weights of internal links of communities. The availability of our findings is also well-supported by the study of Granovetter that the weak links maintain the global integrity of the network while the strong links maintain the communities. Especially in the Karate club network, all the nodes are correctly classified when we weight links by edge betweenness. The results also give us a more comprehensive understanding on the correlation between links and link weights for community detection.
•Links and link weights are closely associated for the emergence of communities.•Edge centralities can distinguish internal links of communities and external ones.•Results on weighted networks with greater internal link weights outperform others.
In the clades of animals that diverged from the bony fish, a group of Mas-related G-protein-coupled receptors (MRGPRs) evolved that have an active role in itch and allergic signals
. As an MRGPR, ...MRGPRX2 is known to sense basic secretagogues (agents that promote secretion) and is involved in itch signals and eliciting pseudoallergic reactions
. MRGPRX2 has been targeted by drug development efforts to prevent the side effects induced by certain drugs or to treat allergic diseases. Here we report a set of cryo-electron microscopy structures of the MRGPRX2-G
trimer in complex with polycationic compound 48/80 or with inflammatory peptides. The structures of the MRGPRX2-G
complex exhibited shallow, solvent-exposed ligand-binding pockets. We identified key common structural features of MRGPRX2 and describe a consensus motif for peptidic allergens. Beneath the ligand-binding pocket, the unusual kink formation at transmembrane domain 6 (TM6) and the replacement of the general toggle switch from Trp
to Gly
(superscript annotations as per Ballesteros-Weinstein nomenclature) suggest a distinct activation process. We characterized the interfaces of MRGPRX2 and the G
trimer, and mapped the residues associated with key single-nucleotide polymorphisms on both the ligand and G-protein interfaces of MRGPRX2. Collectively, our results provide a structural basis for the sensing of cationic allergens by MRGPRX2, potentially facilitating the rational design of therapies to prevent unwanted pseudoallergic reactions.
At present, the diagnosis of sepsis associated-acute kidney injury (SA-AKI) mainly relies on monitoring urine volume or serum creatinine (SCr) levels. Due to decreased renal blood supply and the use ...of diuretics, the diagnosis is intrusive and non-specific. Early identification of the clinical process of SA-AKI and effective management can restore renal function as soon as possible and improve outcomes. This paper discusses the epidemiology, diagnostic limitations, pathophysiological mechanism, treatment and prognosis of SA-AKI. Approximately 30% of patients with sepsis were found to develop acute kidney injury (AKI), and 50% of patients with AKI in the intensive care unit (ICU) were found to have sepsis. Once a diagnosis of SA-AKI is made, close monitoring and timely organ support therapy should be combined to prevent further kidney injury. SA-AKI can be reversed early in the first week after admission, and the prognosis is good. The main mechanisms of organ injury in sepsis are reduced perfusion of bilatera
The G-protein-coupled bile acid receptor (GPBAR) conveys the cross-membrane signalling of a vast variety of bile acids and is a signalling hub in the liver-bile acid-microbiota-metabolism axis
. Here ...we report the cryo-electron microscopy structures of GPBAR-G
complexes stabilized by either the high-affinity P395
or the semisynthesized bile acid derivative INT-777
at 3 Å resolution. These structures revealed a large oval pocket that contains several polar groups positioned to accommodate the amphipathic cholic core of bile acids, a fingerprint of key residues to recognize diverse bile acids in the orthosteric site, a putative second bile acid-binding site with allosteric properties and structural features that contribute to bias properties. Moreover, GPBAR undertakes an atypical mode of activation and G protein coupling that features a different set of key residues connecting the ligand-binding pocket to the G
-coupling site, and a specific interaction motif that is localized in intracellular loop 3. Overall, our study not only reveals unique structural features of GPBAR that are involved in bile acid recognition and allosteric effects, but also suggests the presence of distinct connecting mechanisms between the ligand-binding pocket and the G-protein-binding site in the G-protein-coupled receptor superfamily.
We apply perturbative QCD to investigate the near threshold heavy quarkonium photoproduction at large momentum transfer. From an explicit calculation, we show that the conventional power counting ...method will be modified and the three quark Fock state with nonzero orbital angular momentum dominates the near threshold production. It carries a power behavior of 1/(−t)5 for the differential cross section. We further comment on the impact of our results on the interpretation of the experiment measurement in terms of the gluonic gravitational form factors of the proton.
Bimetallic catalysts based on nonprecious transition metals have attracted increasing attention because of their unique synergistic effects in catalytic reactions, but the understanding of the nature ...of synergistic effects and their roles in a specific hydrogenation reaction remains lacking. Herein, a series of bimetallic Cu x Co y /Al2O3 (x/y = 5:1, 2:1, 1:1, 1:2, 1:5) nanocomposite catalysts were fabricated via the successive calcination and reductive activation process of layered double hydroxide precursors. Their catalytic performance in the selective hydrogenation of bioderived ethyl levulinate to 1,4-pentanediol (1,4-PeD) depended sensitively on the chemical composition of bimetallic CuCo catalysts. The optimal bimetallic Cu2Co1/Al2O3 catalyst exhibited markedly improved catalytic activity and selectivity compared to monometallic Cu/Al2O3, as confirmed by its lower apparent activation energy barrier of 65.1 kJ mol–1 of the rate-determining step and its high selectivity of 93% to 1,4-PeD. Detailed characterization analyses and intrinsic catalytic studies revealed that the presence of CoO x species in the bimetallic Cu x Co y /Al2O3 catalysts enhanced the metallic Cu dispersion and H2 activation ability. More importantly, the strong electronic interaction at the interface of Cu and adjacent CoO x species modified the chemical states of Cu species to create proper surface Cu0/Cu+ distributions and, particularly, provided synergic catalysis sites of Cu and electron-deficient CoO x species, which was primarily responsible for the excellent catalytic performance of bimetallic CuCo catalysts. The bimetallic CuCo catalysts exhibited good stability in both batch and fixed-bed continuous flow reactions. Furthermore, present CuCo nanocomposite catalyst could be applied to the highly selective hydrogenation of other carboxylic esters and lactones to synthesize valuable C4, C5, and C6 diols.
Arrestins recognize different receptor phosphorylation patterns and convert this information to selective arrestin functions to expand the functional diversity of the G protein-coupled receptor ...(GPCR) superfamilies. However, the principles governing arrestin-phospho-receptor interactions, as well as the contribution of each single phospho-interaction to selective arrestin structural and functional states, are undefined. Here, we determined the crystal structures of arrestin2 in complex with four different phosphopeptides derived from the vasopressin receptor-2 (V2R) C-tail. A comparison of these four crystal structures with previously solved Arrestin2 structures demonstrated that a single phospho-interaction change results in measurable conformational changes at remote sites in the complex. This conformational bias introduced by specific phosphorylation patterns was further inspected by FRET and
H NMR spectrum analysis facilitated via genetic code expansion. Moreover, an interdependent phospho-binding mechanism of phospho-receptor-arrestin interactions between different phospho-interaction sites was unexpectedly revealed. Taken together, our results provide evidence showing that phospho-interaction changes at different arrestin sites can elicit changes in affinity and structural states at remote sites, which correlate with selective arrestin functions.
Single-atom metal-nitrogen-carbon (M-N-C) catalysts have sparked intensive interests, however, the development of an atomically dispersed metal-phosphorus-carbon (M-P-C) catalyst has not been ...achieved, although molecular metal-phosphine complexes have found tremendous applications in homogeneous catalysis. Herein, we successfully construct graphitic phosphorus species coordinated single-atom Fe on P-doped carbon, which display outstanding catalytic performance and reaction generality in the heterogeneous hydrogenation of N-heterocycles, functionalized nitroarenes, and reductive amination reactions, while the corresponding atomically dispersed Fe atoms embedded on N-doped carbon are almost inactive under the same reaction conditions. Furthermore, we find that the catalytic activity of graphitic phosphorus coordinated single-atom Fe sharply decreased when Fe atoms were transformed to Fe clusters/nanoparticles by post-impregnation Fe species. This work can be of fundamental interest for the design of single-atom catalysts by utilizing P atoms as coordination sites as well as of practical use for the application of M-P-C catalysts in heterogeneous catalysis.
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