Search

We investigated the influence of signal transducer and activator of transcription-3 (STAT3) on the spinal cord tissue grafts of rat fetuses with spina bifida aperta. In particular, we hoped to identify whether transfection of the STAT3 overexpression plasmid increases the survival of spinal cord transplantation in order to improve therapeutic efficacy. The fetal rat model of spina bifida aperta was established using retinoic acid and treated with a microsurgical injection of bone marrow mesenchymal stem cells (BMSCs). The animals were divided into either the blank control group, negative control group or the experimental group. The optical density (OD) value of BMSCs viability was determined using the Cell Counting Kit-8 (CCK-8). The expression of STAT3, phosphorylated STAT3 (pSTAT3), neural markers and apoptosis-related factors were evaluated using real-time PCR and Western blot. The OD value in the experimental group was highest at eight hours after transplantation using CCK-8. The expression of pSTAT3, glial fibrillary acidic protein, neuron-specific enolase, neurofilament and nestin in the experimental group was significantly higher compared to the blank control group and negative control group (P

CO2 hydrogenation into valuable chemical products has attracted intensive research interest in recent years, with product selectivity control remaining an important topic that requires fine tuning of the catalytic structure and mechanistic understanding. Herein we report our study of anionic phosphorus-regulated indium oxide In2O3 (P-In2O3) nanocatalyst materials for CO2 hydrogenation and achieve nearly full-range selectivity control between methanol and CO products by means of tuning the P content. In situ DRIFTS experiments and XPS characterization reveal the importance of P anion regulation in controlling the CO2 hydrogenation pathways, with an increase in the P content resulting in a decrease in the reducibility of In2O3 that alters CO2 adsorption configuration by blocking and weakening oxygen vacancy (OV) sites for methanol generation and in the meantime creates new sites predominantly active for CO generation. This study demonstrates excellent control of the product selectivity property by regulating the catalyst composition with P anions and provides mechanistic discussions, which offers a new, effective strategy in CO2 hydrogenation catalyst research.

Formaldehyde is an essential building block for hundreds of chemicals and a promising liquid organic hydrogen carrier (LOHC), yet its indirect energy-intensive synthesis process prohibits it from playing a more significant role. Here we report a direct CO reduction to formaldehyde (CORTF) process that utilizes hydrogen underpotential deposition to overcome the thermodynamic barrier and the scaling relationship restriction. This is the first time that this reaction has been realized under ambient conditions. Using molybdenum phosphide as a catalyst, formaldehyde was produced with nearly a 100% faradaic efficiency in aqueous KOH solution, with its formation rate being one order of magnitude higher compared with the state-of-the-art thermal catalysis approach. Simultaneous tuning of the current density and reaction temperature led to a more selective and productive formaldehyde synthesis, indicating the electrochemical and thermal duality of this reaction. DFT calculations revealed that the desorption of the *H2CO intermediate likely served as the rate-limiting step, and the participation of H2O made the reaction thermodynamically favorable. Furthermore, a full-cell reaction set-up was demonstrated with CO hydrogenation to HCHO achieved without any energy input, which fully realized the spontaneous potential of the reaction. Our study shows the feasibility of combining thermal and electrochemical approaches for realizing the thermodynamics and for scaling relationship-confined reactions, which could serve as a new strategy in future reaction design.

Proximity to graphene has an extraordinary effect on the dynamics of entangled chains, as evidenced by strong slowing of thermally stimulated fluctuations at the surface of a thin supported film of polystyrene (PS) when a single layer of graphene is placed between the supporting substrate and the PS film. This slowing is due to a layer of highly viscous polymer next to the substrate being thicker for graphene (75 nm or 7.5Rg) than for silicon (13 nm or 1.3Rg). Molecular dynamics simulations of unentangled PS chain melts on silicon and on multiple layers of graphene show that the work of adhesion with graphene is roughly 4 times larger than that with silicon. In addition, PS chains adjacent to silicon readily form loops, with phenyl rings pointing predominantly toward the substrate. Chains adjacent to graphene more readily form trains, with the phenyl rings predominantly parallel to the graphene.

Methanol synthesis via CO2 hydrogenation has attracted intensive research efforts, but is challenged with development of active and selective catalyst materials that would allow the reaction occurs under milder conditions and being economically more viable. Herein we report the use of bifunctional active sites and their synergy in promoting CO2 hydrogenation kinetics and selectivity. A series of Cu-In-Zr-O mixed oxide nanomaterials containing Cu and defective In2O3 active sites were synthesized and studied for the catalytic properties. Significantly higher CO2 conversion and methanol selectivity were achieved using the Cu-In-Zr-O compared to its non-copper counterpart In-Zr-O, revealing synergy between the two active sites. Insights into the mechanism and functionality of the two actives in CO2 hydrogenation catalysis were obtained with in situ DRIFTS study. A formate-methoxy-methanol pathway and the possible rate-limiting steps were discovered. The excellent selectivity property of the Cu-In-Zr-O was attributed to strong adsorption of CO2 to defective In2O3, which creates a large energy barrier that suppresses CO2 dissociation into CO. The promotion in CO2 hydrogenation kinetics was attributed to cooperation between the bifunctional active sites, with Cu sites adsorb and provide active hydrogen atoms that hydrogenate adsorbed CO2 at adjacent defective In2O3 sites. The findings confirmed synergy between bifunctional sites in CO2 hydrogenation catalysis and provided a new concept in development of active and selective catalyst materials.

Carbon monoxide preferential oxidation (PROX) in an H2-rich stream represents one promising H2 purification technology but requires the development of active and selective catalysts to make the technology viable. We conducted density functional theory simulations of CO PROX catalysis on model Pt alloy systems to establish correlations between the catalyst parameters and the catalytic properties, which validated EA,COOR and EA,HOR as descriptors for CO oxidation and H2 oxidation kinetics, ΔEA as a descriptor for CO PROX selectivity, and ed as a catalyst parameter descriptor for the activation energy barriers. We discovered an interesting compromising relationship between the CO PROX activity and selectivity properties. Pt-Ni and Pt-Mn nanoparticle catalysts were selected for synthesis on the basis of the computational data and tested for their properties, which matched well with the DFT calculations and verified the effectiveness of the computational findings. The use of computation-guided methods and the ...

The synthesis of hierarchical lamellar zeolites with a controlled meso-/microporous morphology and acidity is an expanding area of research interest for a wide range of applications. Here, we report a one-step synthesis of a hierarchical meso-/microporous lamellar MFI–Sn/Al zeolite (i.e., containing both Lewis acidic Sn- and Al-sites and a Bronsted acidic Al–O(H)–Si site) and its catalytic application for the conversion of glucose into 5-(ethoxymethyl)furfural (EMF). The MFI–Sn/Al zeolite was prepared with the assistance of a diquaternary ammonium ([C22H45–N+(CH3)2–C6H12–N+(CH3)2–C6H13]Br2−, C22-6-6) template in a composition of 100SiO2/5C22-6-6/18.5Na2O/xAl2O3/ySnO2/2957H2O (x = 0.5, 1, and 2; y = 1 and 2, respectively). The MFI–Sn/Al zeolites innovatively feature dual meso-/microporosity and dual Lewis and Bronsted acidity, which enabled a three-step reaction cascade for EMF synthesis from glucose in ethanol solvent. The reaction proceeded via the isomerization of glucose to fructose over Lewis acidic Sn sites and the dehydration of fructose to 5-hydroxymethylfurfural (HMF) and then the etherification of HMF and ethanol to EMF over the Bronsted acidic Al–O(H)–Si sites. The co-existence of multiple acidities in a single zeolite catalyst enabled one-pot cascade reactions for carbohydrate upgrading. The dual meso-/microporosity in the MFI–Sn/Al zeolites facilitated mass transport in processing of bulky biomass molecules. The balance of both types of acidity and meso-/microporosity realized an EMF yield as high as 44% from the glucose reactant.

Formaldehyde is an essential building block for hundreds of chemicals and a promising liquid organic hydrogen carrier (LOHC), yet its indirect energy-intensive synthesis process prohibits it from playing more significant role. Here we report a direct CO reduction to formaldehyde (CORTF) process that hybridizes thermal and electro-catalysis and utilizes hydrogen underpotential deposition property to overcome thermodynamic barrier and scaling relationship restriction. Using molybdenum phosphide as catalyst, formaldehyde can be produced with nearly 100% Faradaic efficiency in aqueous KOH solution, with its formation rate being one order of magnitude higher compared with state-of-the-art thermal catalysis approach. Simultaneous tuning of current density and reaction temperature leads to more selective and productive formaldehyde synthesis, confirming the effectiveness of “hybrid” approach. DFT calculations reveal that desorption of *H2CO intermediate likely serves as rate-limiting step, and the participation of H2O turns the reaction into thermodynamically favorable. Furthermore, a full-cell reaction set-up was demonstrated with CO hydrogenation to HCHO being achieved without any energy input, which shows the spontaneous potential of the reaction. Our study shows the advantage of hybridizing thermal and electro-catalysis in realizing thermodynamics and scaling relation confined reaction, which could serve as a new strategy in future reaction design.

A reliable clean water supply is now one important and challenging issue for the human society. With the facts that only 0.4% of the water on earth is readily drinkable and 98% of the water is saltwater, water desalination for clean water production has become a key strategic solution to satisfy the increasing global water demand. Over the years, different saltwater desalination technologies were researched and developed, including reverse osmosis membrane desalination (RO), electrodialysis (ED), capacitive desalination (CDI) and multi-effect distillation (MED). However, some inherent technical issues, like high operation cost, large capital cost and/or low desalination capacity, associate with these existing technologies that lead to a high clean water production cost and limit their applications. Thus, there is a need of new water desalination technology that can purify saltwater with low cost and high efficiency. In this work we report a new water-soluble nickel phthalocyanine tetrasulfonic acid tetrasodium salt (NiPcTATS)-based redox flow desalination battery (RFDB) for safe, effective and efficient water-salt separation. The fabricated RFDB cell exhibited a high desalination rate at 3.4 gNaCl/(molNiPcTATS∙hr) even with a low 0.5 V cell voltage and required as low as 11.5 kJ/mol salt in energy consumption. The cell showed excellent reversibility and durability for long-term operation, benefiting from the fast-redox kinetics and chemical stability of the redox couple. With no consumption of the redox couple and energy recovery during the salination process, this new method provides a continuous desalination capability with unlimited salt removal capacity. We also demonstrated the use of simple solar panel for effectively driving the RFDB cell, proving it a promising and practical technology for clean water production in remote places like islands and ships.

Understanding the growth pathway of faceted alloy nanoparticles at the atomic level is crucial to morphology control and property tuning. Yet, it remains a challenge due to complexity of the growth process and technical limits of modern characterization tools. We report a combinational use of multiple cutting-edge in situ techniques to study the growth process of octahedral Pt3Ni nanoparticles, which reveal the particle growth and facet formation mechanisms. Our studies confirm the formation of octahedral Pt3Ni initiates from Pt nuclei generation, which is followed by continuous Pt reduction that simultaneously catalyzes Ni reduction, resulting in mixed alloy formation with moderate elemental segregation. Carbon monoxide molecules serve as a facet formation modulator and induce Ni segregation to the surface, which inhibits the (111) facet growth and causes the particle shape to evolve from a spherical cluster to an octahedron as the (001) facet continues to grow., Understanding the growth pathway of faceted alloy nanoparticles at the atomic level is crucial to morphology control and property tuning, but remains a challenge. Here, the authors reveal the particle growth and facet formation mechanisms of octahedral Pt3Ni nanoparticles using multiple cutting-edge in situ techniques.

Active sites play an essential role in heterogeneous catalysis and largely determine the reaction properties. Yet identification and study of the active sites remain challenging owing to their dynamic behaviors during catalysis process and issues with current characterization techniques. This article provides a short review of research progresses in active sites of metal and metal oxide catalysts, which covers the past achievements, current research status, and perspectives in this research field. In particular, the concepts and theories of active sites are introduced. Major experimental and computational approaches that are used in active site study are summarized, with their applications and limitations being discussed. An outlook of future research direction in both experimental and computational catalysis research is provided.

Liquid–liquid equilibrium data for three ternary systems which contain glycerol and its etherification (tert-butylation) products including mono-tert-butyl ethers of glycerol (ME), di-tert-butyl ethers of glycerol (DE) and tri-tert-butyl ether of glycerol (TE) in the temperature range of 343.2–373.2 K under 101.3 kPa were obtained by phase equilibrium experiments. Reliability of the experimental data was verified by Othmer–Tobias equation. The non-random two liquid (NRTL) model was employed to describe the equilibrium compositions, and corresponding binary interaction parameters were estimated by data regression. The modeling results agreed well with measured data. In addition, three UNIFAC based methods were also adapted to model liquid–liquid equilibrium behavior for these systems; however, the predicted results emerged obvious deviation from experimental results.

An enzymatic approach to label peptide N-termini with isotope-coded affinity tags is presented. This method exploits the high activity of trypsin for peptide synthesis in organic solvents. A cosubstrate containing a stable isotope-coded Arg residue and a biotin tag was synthesized. When the cosubstrate was incubated with tryptic peptides and trypsin in ethanol solution, the stable isotope-coded affinity tag was specifically coupled onto the N-termini of peptides via the formation of new peptide bonds. The labeled peptides were specifically enriched by avidin affinity chromatography and then were submitted to liquid chromatography-tandem mass spectrometry (LC/MS/MS) for quantification. This enrichment step effectively reduced the interference by unlabeled peptides. The excellent performance of this approach was demonstrated by labeling standard peptides as well as a mouse liver digest. In addition to one amino acid residue, a few dipeptide tags were also introduced to the N-termini of peptides successfully by this enzymatic approach. It was found that the identifications for samples labeled with these tags were highly complementary. Coupling a short sequence tag onto peptides could be an effective approach to improve the coverage for proteome analysis.

A novel copolymer of chitosan-g-poly(p-dioxanone) (CGP) was synthesized in bulk by ring-opening polymerization of p-dioxanone (PDO) initiated by the hydroxyl group or amino group of chitosan using SnOct2 as catalyst. The chemical structure was determined by 1H NMR. It was found that the feed ratio of chitosan to PDO had a great effect on the degree of polymerization (DP) and the substitution (DS) of PDO. The thermal stability and crystallization behavior of graft copolymer CGP were closely related to the values of DP and DS. When the resulting copolymer was used as Ibuprofen carrier, the release rate of Ibuprofen decreased compared with that of pure chitosan carrier. The drug release behavior was also influenced by the structure of graft copolymers.

Protein allylation and fluorophore targeting: Arginine residues of the yeast nuclear ribonucleoprotein Npl3 were extensively modified by Hmt1-catalyzed allylation reaction with allyl-SAM as the allyl group donor. The allylated protein was further treated with tetrazole compounds under UV irradiation, leading to formation of protein-attached fluorescent products.

A new biodegradable copolymer of chitosan and poly(p-dioxanone) (PPDO) was prepared through a protection-graft-deprotection procedure using N-phthaloyl-chitosan as an intermediate. PPDO terminated with the isocyanate group was allowed to react with hydroxyl groups of the N-phthaloyl-protected chitosan, and then the phthaloyl group was cleaved to give the free amino groups. The length of PPDO graft chains can be controlled easily by using the prepolymers of PPDO with different molecular weights. The resulting products were thoroughly characterized with FT-IR, (1)H NMR, TG, DSC, SEM, and WAXD. The copolymers were used as drug carriers for sinomenine (7,8-didehydro-4-hydroxy-3,7-dimethoxy-17-methyl-9alpha,13alpha,14alpha-morphinan-6-one) and these exhibited a significant controlled drug-releasing behavior whether in artificial gastric juice or in neutral phosphate buffer solution.