Mechanocatalytic Synthesis of Ammonia by Titanium Dioxide with Bridge-Oxygen Vacancies: Investigating Mechanism from the Experimental and First-Principle Approach.

Mechanochemical ammonia (NH3) synthesis is an emerging mild approach derived from nitrogen (N2) gas and hydrogen (H) source. The gas-liquid phase mechanochemical process utilizes water (H2O), rather than conventional hydrogen (H2) gas, as H sources, thus avoiding carbon dioxide (CO2) emission during H2 production. However, ammonia yield is relatively low to meet practical demand due to huge energy barriers of N2 activation and H2O dissociation. Here, six transition metal oxides (TMO) such as titanium dioxide (TiO2), iron(III) oxide (Fe2O3), copper(II) oxide (CuO), niobium(V) oxide(Nb2O5), zinc oxide (ZnO), and copper(I) oxide (Cu2O) are investigated as catalysts in mechanochemical N2 fixation. Among them, TiO2 shows the best mechanocatalytic effect and the optimum reaction rate constant is 3.6-fold higher than the TMO-free process. The theoretical calculations show that N2 molecules prefer to side-on chemisorb on the mechano-induced bridge-oxygen vacancies in the (101) crystal plane of TiO2 catalyst, while H2O molecules can dissociate on the same sites more easily to provide free H atoms, enabling an alternative-way hydrogeneration process of activated N2 molecules to release NH3 eventually. This work highlights the cost-effective TiO2 mechanocatalyst for ammonia synthesis under mild conditions and proposes a defect-engineering-induced mechanocatalytic mechanism to promote N2 activation and H2O dissociation.

Biocatalytic Thionation of Epoxides for Enantioselective Synthesis of Thiiranes.

Expanding the enzymatic toolbox for the green synthesis of valuable molecules is still of high interest in synthetic chemistry and the pharmaceutical industry. Chiral thiiranes are valuable sulfur-containing heterocyclic compounds, but relevant methods for their enantioselective synthesis are limited. Herein, we report a biocatalytic thionation strategy for the enantioselective synthesis of thiiranes, which was developed based on the halohydrin dehalogenase (HHDH)-catalyzed enantioselective ring-opening reaction of epoxides with thiocyanate and a subsequent nonenzymatic rearrangement process. A novel HHDH was identified and engineered for enantioselective biocatalytic thionation of various aryl- and alkyl-substituted epoxides on a preparative scale, affording the corresponding thiiranes in up to 43 % isolated yield and 98 % ee. Large-scale synthesis and useful transformations of chiral thiiranes were also performed to demonstrate the utility and scalability of the biocatalytic thionation strategy.

Development and validation of a nomogram to predict B-cell primary thyroid malignant lymphoma-specific survival: A population-based analysis.

B cell primary thyroid malignant lymphoma (BC-PTML) accounts for 95% of all cases of PTML. However, development of effective treatment and management strategies for BC-PTML is challenging owing to the rarity of this disease. This study assessed data from 1,152 patients in the Surveillance, Epidemiology, and End Results (SEER) database who were diagnosed with BC-PTML during 2000-2015. Patients were randomly divided into a training group (n=806) and a test group (n=346) at a ratio of 7:3 using the hold-out method. Kaplan-Meier analysis and log-rank tests were used to calculate the survival rate of patients. Subsequently, a stepwise Cox regression model was established to screen the prognostic factors of patients with BC-PTML, and these variables were used to construct a nomogram to predict 5-, 10-, and 15-year BC-PTML cancer-specific survival (CSS). The discrimination and calibration of the new model were evaluated using the concordance index (C-index) and calibration curves, and the accuracy and benefits of the model were assessed through comparison with the traditional Ann Arbor staging system using decision curve analysis (DCA). After stepwise regression, the optimal model included radiotherapy, primary site surgery, Ann Arbor Stage, chemotherapy, histological subtype, and age at diagnosis. The C-index, area under the receiver operating characteristic curve, and DCA suggested that the nomogram had improved discriminatory ability and clinical benefit compared with the Ann Arbor staging system. In summary, this study established an effective nomogram to predict CSS in patients with BC-PTML and assist clinicians in developing effective individualized treatment strategies.

Identification and Structure Analysis of an Unusual Halohydrin Dehalogenase for Highly Chemo-, Regio- and Enantioselective Bio-Nitration of Epoxides.

We report the discovery of an unusual halohydrin dehalogenase, HHDHamb, that can work under relatively low acidic conditions and extremely low temperatures for the bio-nitration of epoxides using nitrite as a nitrating agent. The bio-nitration strategy exhibits high chemo-, regio-, and enantioselectivity, catalyzing the kinetic resolution of various epoxides to enantiopure ß-nitroalcohols with nitro-bearing stereocenters in up to 41 % isolated yield and >99 % enantiomeric excess (ee). Additionally, the bio-nitration method displays a high reaction efficiency and can be performed on a gram scale. We also solved the crystal structure of HHDHamb to understand the possible structural determinants of chemoselectivity control in the bio-nitration reaction.

The antioxidant activities of flavonoids in Jerusalem artichoke (Helianthus tuberosus L.) leaves and their quantitative analysis.

The main targets of this work were to evaluate the antioxidative properties of flavonoids in Jerusalem artichoke (Helianthus tuberosus L.) leaves and quantitatively determine their contents. 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis (3-ethylbenzothiazoline)-6-sulphonic acid (ABTS) and hydroxyl free radicals scavenging assays were performed to determine their antioxidative capacities. The validated ultra high-performance liquid chromatography-quadrupole-time-of-flight/mass spectrometry (UHPLC-Q-TOF/MS) method was subsequently applied to the quality evaluation of eleven batches of Jerusalem artichoke leaves grown in different habitats at different harvesting time. Results indicated that two flavonoids isolated from Jerusalem artichoke leaves showed stronger antioxidant effects than the positive control, butylated hydroxytoluene (BHT). And the total contents of the two flavonoids in the Jerusalem artichoke leaves of flowering stage from Dalian, Liaoning Province, China, were the highest, their contents varied significantly depending on region and harvesting time. This study indicated that the leaves of Jerusalem artichoke possessed excellent antioxidant properties, highlighting their candidacy as natural antioxidants, which could be utilized therapeutically to protect the body from diseases caused by oxidative stress.

Assembling γ-graphyne surrounding TiO2 nanotube arrays: an efficient p-n heterojunction for boosting photoelectrochemical water splitting.

Photoelectrochemical water splitting is an excellent strategy for hydrogen generation and it is pivotal to the development of photoanodes with sufficient sunlight harvesting, rapid charge separation, and enhanced electron injection efficiency. In this work, we rationally constructed a γ-graphyne/TiO2 (GY/TiO2) p-n heterojunction in which p-type γ-graphyne nanosheets were distributed in the three-dimensional space surrounding TiO2 nanotube arrays. The GY/TiO2 photoanode achieves a photocurrent density of 0.75 mA cm-2 at 1.23 V (vs. RHE), 1.7 times that of bare TiO2, and extends the electron lifetime of TiO2 from 0.51 to 1.16 ms. The improvement arises from moderate γ-graphyne modification, contributing to broadened light absorption, the suppressed recombination of electron-hole pairs, an increase in charge transfer, and a higher injection efficiency of surface electrons. This work provides a reliable approach for the utilization and conversion of sustainable solar energy.