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"Liu, Pan"
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Zeolite-confined subnanometric PtSn mimicking mortise-and-tenon joinery for catalytic propane dehydrogenation
Heterogeneous catalysts are often composite materials synthesized via several steps of chemical transformation, and thus the atomic structure in composite is a black-box. Herein with machine-learning-based atomic simulation we explore millions of structures for MFI zeolite encapsulated PtSn catalyst, demonstrating that the machine-learning enhanced large-scale potential energy surface scan offers a unique route to connect the thermodynamics and kinetics within catalysts’ preparation procedure. The functionalities of the two stages in catalyst preparation are now clarified, namely, the oxidative clustering and the reductive transformation, which form separated Sn
4
O
4
and PtSn alloy clusters in MFI. These confined clusters have high thermal stability at the intersection voids of MFI because of the formation of “Mortise-and-tenon Joinery”. Among, the PtSn clusters with high Pt:Sn ratios (>1:1) are active for propane dehydrogenation to propene, ∼10
3
in turnover-of-frequency greater than conventional Pt
3
Sn metal. Key recipes to optimize zeolite-confined metal catalysts are predicted.
The atomic structure of heterogeneous catalysts is usually a blackbox. Here the authors demonstrate large-scale machine learning atomic simulations help to resolve the catalyst structure and reaction mechanism of encapsulated PtSnO
x
clusters in zeolite that feature a mortise-and-tenon joinery structure and the superior activity towards propane dehydrogenation.
Journal Article
طلاق على الطريقة الصينية /
تقدم هذه الرواية صورة عن قرب للسياسة المحلية التي هي المحرك لكل شيء في الصين» هكذا كتبت نيويورك تايمز عن رواية \"طلاق على الطريقة الصينية\"، فيما وصفة الرواية حسب kirkus reviews بأنها : «حكاية بارعة تجعلك تضحك حتى وأنت مبتئس، إنها ببساطة هجاء خفي ماكر». بينما يقر المترجم الأمريكي الشهير هاوارد جولدبلات بأن ليو كتب «قصة بارعة ستجعلك تضحك وتبكي. كلماته بسيطة لكنها ستظل باقية في ذاكرتك لفترة طويلة بعد أن تنتهي من قراءتها». \"طلاق على الطريقة الصينية\"، رواية ساخرة ولاذعة وتهكمية. أثارت ضجة كبيرة في الصين حين صدروها، وترجمت إلى 34 لغة، كما تحولت إلى فيلم سينمائي، أثار بدوره هو الآخر ضجة كبيرة سببها الطابع السياسي الذي يحمله النص الأصلي.
BOOK
Shear-induced assembly of a transient yet highly stretchable hydrogel based on pseudopolyrotaxanes
Dissipative self-assembly is common in biological systems, where it serves to maintain a far-from-equilibrium functional state through fuel consumption. Synthetic dissipative systems have been prepared that can mimic some of the properties of biological systems, but they often show poor mechanical performance. Here, we report a shear-induced transient hydrogel that is highly stretchable. The system is constructed by adding Cu(
ii
) into the aqueous solution of a pseudopolyrotaxane, which is itself formed by threading molecular tubes on polyethylene glycol chains. Vigorous shaking transforms the solution into a gel, which gradually relaxes back to the sol state over time. This cycle can be repeated at least five times. A mechanism is proposed that relies on a shear-induced transition from intrachain to interchain coordination and subsequent thermal relaxation. The far-from-equilibrium hydrogel is highly stretchable, which is probably due to ‘frictional’ sliding of the molecular tubes on the polyethylene glycol chains. On shaking, the hydrogel undergoes fast self-healing.
Synthetic dissipative systems, formed by out-of-equilibrium self-assembly processes, can mimic some of the properties of biological systems, but often show poor mechanical performance. Now, a shear-induced transient hydrogel has been prepared that is also highly stretchable. The system is based on coordination interactions between Cu(
ii
) centres and the pendant carboxylate groups of a pseudopolyrotaxane.
Journal Article
Advances in photobiomodulation for cognitive improvement by near-infrared derived multiple strategies
Cognitive function is an important ability of the brain, but cognitive dysfunction can easily develop once the brain is injured in various neuropathological conditions or diseases. Photobiomodulation therapy is a type of noninvasive physical therapy that is gradually emerging in the field of neuroscience. Transcranial photobiomodulation has been commonly used to regulate neural activity in the superficial cortex. To stimulate deeper brain activity, advanced photobiomodulation techniques in conjunction with photosensitive nanoparticles have been developed. This review addresses the mechanisms of photobiomodulation on neurons and neural networks and discusses the advantages, disadvantages and potential applications of photobiomodulation alone or in combination with photosensitive nanoparticles. Photobiomodulation and its associated strategies may provide new breakthrough treatments for cognitive improvement.
Journal Article
The non-structural protein of SFTSV activates NLRP1 and CARD8 inflammasome through disrupting the DPP9-mediated ternary complex
Inflammasomes function as immune-signaling platforms that were assembled following detection of pathogens. NLRP1 and CARD8 are related inflammasomes that use their C-terminal (CT) fragments containing a caspase recruitment domain (CARD) and the UPA domain to initiate the inflammasome. At rest, dipeptidyl peptidases 8 and 9 (DPP8/9) inhibit inflammatory CT by interacting with the function-to-find domain (FIIND) of NLRP1/CARD8 and forming an inhibitory NLRP1/CARD8-DPP9 ternary complex consisting of DPP9, full-length NLRP1/CARD8, and NLRP1/CARD8 CT. However, the specific triggers of NLRP1 and CARD8 have not yet been fully identified. Here, we report that a tick-borne bunyavirus SFTSV infection activates the NLRP1 inflammasome in primary keratinocytes and the CARD8 inflammasome in macrophages in a similar manner by targeting the ternary inhibitory complex, respectively. Mechanistically, SFTSV NSs interact with NLRP1 and CARD8 via their FIIND domains, suggesting that DPP8/9 are likely to compete for binding; on the other hand, NSs promote the degradation of DPP8 and DPP9. Both contribute to more efficient destabilization of the DPP8/9 ternary complex and release the activated CT. Moreover, CARD8 deletion promotes SFTSV replication. In conclusion, we found a novel mechanism of viral protein activation of NLRP1 and CARD8 by disrupting the DPP9-binding checkpoint.
Journal Article
Regulation of stem-like cancer cells by glutamine through β-catenin pathway mediated by redox signaling
Background
Cancer stem cells (CSCs) are thought to play an important role in tumor recurrence and drug resistance, and present a major challenge in cancer therapy. The tumor microenvironment such as growth factors, nutrients and oxygen affect CSC generation and proliferation by providing the necessary energy sources and growth signals. The side population (SP) analysis has been used to detect the stem-like cancer cell populations based on their high expression of ABCG2 that exports Hoechst-33342 and certain cytotoxic drugs from the cells. The purpose of this research is to investigate the effect of a main nutrient molecule, glutamine, on SP cells and the possible underlying mechanism(s).
Methods
Biochemical assays and flow cytometric analysis were used to evaluate the effect of glutamine on stem-like side population cells in vitro. Molecular analyses including RNAi interfering, qRT-PCR, and immunoblotting were employed to investigate the molecular signaling in response to glutamine deprivation and its influence on tumor formation capacity in vivo.
Results
We show that glutamine supports the maintenance of the stem cell phenotype by promoting glutathione synthesis and thus maintaining redox balance for SP cells. A deprivation of glutamine in the culture medium significantly reduced the proportion of SP cells. L-asparaginase, an enzyme that catalyzes the hydrolysis of asparagine and glutamine to aspartic acid and glutamate, respectively, mimics the effect of glutamine withdrawal and also diminished the proportion of SP cells. Mechanistically, glutamine deprivation increases intracellular ROS levels, leading to down-regulation of the β-catenin pathway.
Conclusion
Glutamine plays a significant role in maintaining the stemness of cancer cells by a redox-mediated mechanism mediated by β-catenin. Inhibition of glutamine metabolism or deprivation of glutamine by L-asparaginase may be a new strategy to eliminate CSCs and overcome drug resistance.
Journal Article
Efficient hydrogen production on MoNi4 electrocatalysts with fast water dissociation kinetics
Various platinum-free electrocatalysts have been explored for hydrogen evolution reaction in acidic solutions. However, in economical water-alkali electrolysers, sluggish water dissociation kinetics (Volmer step) on platinum-free electrocatalysts results in poor hydrogen-production activities. Here we report a MoNi
4
electrocatalyst supported by MoO
2
cuboids on nickel foam (MoNi
4
/MoO
2
@Ni), which is constructed by controlling the outward diffusion of nickel atoms on annealing precursor NiMoO
4
cuboids on nickel foam. Experimental and theoretical results confirm that a rapid Tafel-step-decided hydrogen evolution proceeds on MoNi
4
electrocatalyst. As a result, the MoNi
4
electrocatalyst exhibits zero onset overpotential, an overpotential of 15 mV at 10 mA cm
−2
and a low Tafel slope of 30 mV per decade in 1 M potassium hydroxide electrolyte, which are comparable to the results for platinum and superior to those for state-of-the-art platinum-free electrocatalysts. Benefiting from its scalable preparation and stability, the MoNi
4
electrocatalyst is promising for practical water-alkali electrolysers.
In water-alkali electrolyzers, sluggish water dissociation kinetics on platinum-free electrocatalysts result in poor hydrogen-production activities. Here the authors report a MoNi
4
electrocatalyst which reduces the kinetic energy barrier of water dissociation, leading to improved hydrogen-production performance.
Journal Article
Environmentally stable interface of layered oxide cathodes for sodium-ion batteries
Sodium-ion batteries are strategically pivotal to achieving large-scale energy storage. Layered oxides, especially manganese-based oxides, are the most popular cathodes due to their high reversible capacity and use of earth-abundant elements. However, less noticed is the fact that the interface of layered cathodes always suffers from atmospheric and electrochemical corrosion, leading to severely diminished electrochemical properties. Herein, we demonstrate an environmentally stable interface via the superficial concentration of titanium, which not only overcomes the above limitations, but also presents unique surface chemical/electrochemical properties. The results show that the atomic-scale interface is composed of spinel-like titanium (III) oxides, enhancing the structural/electrochemical stability and electronic/ionic conductivity. Consequently, the interface-engineered electrode shows excellent cycling performance among all layered manganese-based cathodes, as well as high-energy density. Our findings highlight the significance of a stable interface and, moreover, open opportunities for the design of well-tailored cathode materials for sodium storage.
The interface of layered cathodes for sodium ion batteries is subject to atmospheric and electrochemical corrosions. Here, the authors demonstrate an environmentally stable interface via titanium enriched surface reconstruction in a layered manganese-based oxide.
Journal Article
A supramolecular system that strictly follows the binding mechanism of conformational selection
Induced fit and conformational selection are two dominant binding mechanisms in biology. Although induced fit has been widely accepted by supramolecular chemists, conformational selection is rarely studied with synthetic systems. In the present research, we report a macrocyclic host whose binding mechanism is unambiguously assigned to conformational selection. The kinetic and thermodynamic aspects of this system are studied in great detail. It reveals that the kinetic equation commonly used for conformational selection is strictly followed here. In addition, two mathematical models are developed to determine the association constants of the same guest to the two host conformations. A “conformational selectivity factor” is defined to quantify the fidelity of conformational selection. Many details about the kinetic and thermodynamic aspects of conformational selection are revealed by this synthetic system. The conclusion and the mathematical models reported here should be helpful in understanding complex molecular recognition in both biological and synthetic systems.
Conformational selection is one of the two dominant binding mechanisms in biology, but has rarely been studied in synthetic systems. Here, the authors report a supramolecular system that strictly follows the binding mechanism of conformational selection.
Journal Article