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Journal of Colloid and Interface Science Jun 2024Electrochemical nitrate reduction reaction (NORR) offers a cost-effective and environmentally friendly method to simultaneously yield valuable NHand alleviate...
Electrochemical nitrate reduction reaction (NORR) offers a cost-effective and environmentally friendly method to simultaneously yield valuable NHand alleviate NOpollution under mild operating conditions.However, this complicated eight-electron reaction suffers from low selectivity and Faradaic efficiency, which highlight the importance of developing efficient catalysts, but still a critical challenge. Here, a theoretical screening is performed on transition metal-tetragonal carbon nitride (TM@T-CN) as active and selective electrocatalysts for NORR, where detailed reaction mechanisms and activity origins are explored. In addition, five-step screening criteria and volcano plots enable fast prescreening among numerous candidates.We identify that V@T-CN and Cr@T-CN are promising candidates with low overpotentials and high selectivity and stability. In particular, a significant negative correlation between the adsorption strength ofnitrate and the Gibbs free energy for the last proton-electron coupling step (*NH→*NH) was existed, which is considerably advantaged to track the activity trend and reveal the origin of activity. This work provides theoretical insights into the rational design of TM-N/C catalysts for NORR andpaves a valuable electrochemical screening framework for other multi-step reactions.
PubMed: 38941929
DOI: 10.1016/j.jcis.2024.06.178 -
Bioorganic & Medicinal Chemistry Jun 2024This study explored the potential of perfumery compounds as sources of transient receptor potential ankyrin 1 (TRPA1) inhibitors that could be formulated for effective...
This study explored the potential of perfumery compounds as sources of transient receptor potential ankyrin 1 (TRPA1) inhibitors that could be formulated for effective delivery to the skin and airways. A highly potent, small, and selective TRPA1 inhibitor, 2-methyl-4-phenyl-1-pentanol (1), was discovered in perfumery compounds. Compound 1 demonstrated promising inhibitory activity against a broad range of TRPA1 agonists. A single stereoisomer of 1 was identified as the most effective TRPA1 inhibitor, indicating the potential for stereoselective synthesis to enhance its potency. Additionally, the structure-activity relationship of 1 was evaluated to elucidate the structural features of TRPA1 inhibitors within the fragrance-like compounds. Notably, the topical application of 1 alleviated sensory irritation in individuals with sensitive skin, while the inhalation of 1 resulted in a significant reduction in ammonia irritation, underscoring its efficacy in both skin and airway applications.
PubMed: 38941887
DOI: 10.1016/j.bmc.2024.117812 -
Ecotoxicology and Environmental Safety Jun 2024Following ion-adsorption rare earth mining, the residual tailings experience considerable heavy metal contamination and gradually evolve into a pollution source....
Following ion-adsorption rare earth mining, the residual tailings experience considerable heavy metal contamination and gradually evolve into a pollution source. Therefore, the leaching characteristics and environmental impact of heavy metals in ion-adsorption rare earth tailings require immediate and thorough investigation. This study adopted batch and column experiments to investigate the leaching behaviour of heavy metals in tailings and assess the impact of tailings on paddy soil, thereby providing a scientific basis for environmental protection in mining areas. The results showed that Mn, Zn, and Pb contents were 431.67, 155.05, and 264.33 mg·kg, respectively, which were several times higher than their respective background values, thereby indicating significant heavy metal contamination in the tailings. The batch leaching experiment indicated that Mn and Pb were priority control heavy metals. Heavy metals were divided into fast and slow leaching stages. The Mn and Pb leaching concentrations far exceeded environmental limits. The DoseResp model perfectly fitted the leaching of all heavy metals from the tailings (R > 0.99). In conjunction with the findings of the column experiment and correlation analysis, the chemical form, rainfall pH, ammonia nitrogen, and mineral properties were identified as the primary factors controlling heavy metal release from tailings. Rainfall primarily caused heavy metal migration in the acid-extraction form from the tailings. The tailing leachate not only introduced heavy metals into the paddy soil but also caused the transformation of the chemical form of heavy metals in the paddy soil, further exacerbating the environmental risk posed by heavy metals. The study findings are significant for environmental conservation in mining areas and implementing environmentally friendly practices in rare earth mining.
PubMed: 38941660
DOI: 10.1016/j.ecoenv.2024.116642 -
Chemphyschem : a European Journal of... Jun 2024Cu-exchanged chabazite (Cu-CHA) is widely applied for ammonia assisted selective catalytic reduction of nitrogen oxides (NH3-SCR). The Cu+ ions are at low temperatures...
Cu-exchanged chabazite (Cu-CHA) is widely applied for ammonia assisted selective catalytic reduction of nitrogen oxides (NH3-SCR). The Cu+ ions are at low temperatures solvated by NH3 forming mobile [Cu(NH3)2]+ complexes. The dynamic behaviour of the complexes is critical as O2 adsorption requires a pair of complexes to form a [Cu2(NH3)4O2]2+ peroxo-species over which NO couples with NH3. Here we introduce a first principles-based kinetic Monte Carlo approach to explore the effect of the Al-distribution on the reaction kinetics of NH3-SCR over Cu-CHA. The method allows us to scrutinize the interplay between the pairing of [Cu(NH3)2]+ complexes and the reaction landscape for the NH3-SCR reaction over the peroxo-complex. The Al-distribution affects the stability of the [Cu(NH3)2]+ pairs as well as the kinetic parameters of the SCR-reaction. The turn-over frequency is determined by the stability of the [Cu(NH3)2]+ pairs and the relative strength of NO and NH3 adsorption once a pair is present. The results establish the hierarchy of effects that influences the performance of Cu-CHA over NH3-SCR and provide a computational basis for further development of the Cu-CHA material.
PubMed: 38941111
DOI: 10.1002/cphc.202400558 -
Inorganic Chemistry Jun 2024Silica nanotubes have significant applications in various fields, including thermal insulation, self-cleaning, and catalysis. Currently, the synthesis methods of silica...
Silica nanotubes have significant applications in various fields, including thermal insulation, self-cleaning, and catalysis. Currently, the synthesis methods of silica nanotubes are mostly limited to the template method. In this work, a template-free strategy and vapor-phase approach were used to prepare silica nanotubes. Poly(methylhydrosiloxane) (PMHS) was hydrolyzed and condensed in a high-temperature closed reactor by using ammonia as a catalyst. The resulting product was then subjected to template-free self-assembly to synthesize silica nanotubes incorporating methyl groups. The silica nanotubes were synthesized under varying conditions, resulting in lengths ranging from 50 nm to several micrometers, exterior diameters between 40 and 120 nm, and wall thicknesses varying from 7 to 30 nm. The synthesized products underwent morphology analysis using TEM and FESEM for morphology analysis, elemental composition analysis using XPS, and chemical structure identification using FTIR, and the possible formation mechanism of silica nanotubes formation was also speculated. Furthermore, the coatings formed by silica nanotubes exhibited remarkable superhydrophobic self-cleaning properties with a water contact angle of 162° and a rolling angle of less than 1°.
PubMed: 38941071
DOI: 10.1021/acs.inorgchem.4c01856 -
Biochemistry Jun 2024Human ornithine transcarbamylase (hOTC) is a mitochondrial transferase protein involved in the urea cycle and is crucial for the conversion of toxic ammonia to urea....
Human ornithine transcarbamylase (hOTC) is a mitochondrial transferase protein involved in the urea cycle and is crucial for the conversion of toxic ammonia to urea. Structural analysis coupled with kinetic studies of rat, bovine, and other transferase proteins has identified residues that play key roles in substrate recognition and conformational changes but has not provided direct evidence for all of the active residues involved in OTC function. Here, computational methods were used to predict the likely active residues of hOTC; the function of these residues was then probed with site-directed mutagenesis and biochemical characterization. This process identified previously reported active residues, as well as distal residues that contribute to activity. Mutation of active site residue D263 resulted in a substantial loss of activity without a decrease in protein stability, suggesting a key catalytic role for this residue. Mutation of predicted second-layer residues H302, K307, and E310 resulted in significant decreases in enzymatic activity relative to that of wild-type (WT) hOTC with respect to l-ornithine. The mutation of fourth-layer residue H107 to produce the hOTC H107N variant resulted in a 66-fold decrease in catalytic efficiency relative to that of WT hOTC with respect to carbamoyl phosphate and a substantial loss of thermal stability. Further investigation identified H107 and to a lesser extent E98Q as key residues involved in maintaining the hOTC quaternary structure. This work biochemically demonstrates the importance of D263 in hOTC catalytic activity and shows that residues remote from the active site also play key roles in activity.
PubMed: 38940639
DOI: 10.1021/acs.biochem.4c00206 -
Journal of Integrative Plant Biology Jun 2024
PubMed: 38940574
DOI: 10.1111/jipb.13734 -
Veterinary Radiology & Ultrasound : the... Jun 2024A 1-year-old Miniature Horse filly was presented for chronic lethargy and hyporexia. Elevated liver enzymes, bile acids, and ammonia were noted on bloodwork. The primary...
A 1-year-old Miniature Horse filly was presented for chronic lethargy and hyporexia. Elevated liver enzymes, bile acids, and ammonia were noted on bloodwork. The primary differential diagnosis was a portosystemic shunt (PSS). Three-phase computed tomographic angiography findings were consistent with a transhepatic portosystemic shunt. Percutaneous liver biopsy confirmed severe diffuse hepatic changes, most likely due to chronic pyrrolizidine alkaloid toxicosis, and medical management was elected. Based on an extensive literature review, this is the first report of a transhepatic portosystemic collateral vessel in a horse. Computed tomographic angiography is feasible and useful for the diagnosis of PSS in miniature horses.
PubMed: 38940068
DOI: 10.1111/vru.13401 -
Chemical Communications (Cambridge,... Jun 2024Here we present a hybrid catalytic pathway for efficient synthesis of 5-aminomethyl-2-furancarboxylic acid (AMFC), a bio-based nylon-6 analogue monomer, from...
Here we present a hybrid catalytic pathway for efficient synthesis of 5-aminomethyl-2-furancarboxylic acid (AMFC), a bio-based nylon-6 analogue monomer, from 5-hydroxymethylfurfural (HMF). This method combines homogeneous-catalyzed selective oxidation of HMF to 5-formyl-2-furancarboxylic acid (FFCA) with heterogeneous-catalyzed reductive amination using ammonia as the nitrogen source. Through this relay strategy, we achieve significant enhancements in overall efficiency, resulting in isolation yields of up to 92% for highly selective and scalable AMFC production from HMF.
PubMed: 38939946
DOI: 10.1039/d4cc02474e -
JACC. Advances May 2024It is not known whether the transition from obesity and severe obesity, as 2 different metabolic disease entities, affect flow-mediated and, thus, endothelium-dependent...
BACKGROUND
It is not known whether the transition from obesity and severe obesity, as 2 different metabolic disease entities, affect flow-mediated and, thus, endothelium-dependent epicardial vasodilation.
OBJECTIVES
The purpose of this study was to investigate the effect of obesity and severe obesity on flow-mediated epicardial vasomotion with positron emission tomography/computed tomography-determined longitudinal decrease in myocardial blood flow (MBF) from the base-to-apex direction of the left ventricle or gradient.
METHODS
N-ammonia positron emission tomography/computed tomography evaluated global MBF during pharmacologically induced hyperemia and at rest for assessment of coronary microvascular function. In addition, the Δ longitudinal MBF gradient (hyperemia minus rest) was determined. Patients were then grouped according to the body mass index (BMI) into normal weight (NW) (BMI 20.0-24.9 kg/m, n = 27), overweight (OW) (BMI 25.0-29.9 kg/m, n = 29), obesity (OB) (BMI 30.0-39.9 kg/m, n = 53), and severe obesity (morbid obesity: BMI ≥40 kg/m, n = 43).
RESULTS
Compared to NW, left ventricular Δ longitudinal MBF gradient progressively declined in OW and OB (0.04 ± 0.09 mL/g/min vs -0.11 ± 0.14 mL/g/min and -0.15 ± 0.11 mL/g/min; ≤ 0.001, respectively) but not significantly in SOB (-0.01 ± 0.11 mL/g/min, = 0.066). Regadenoson-induced global hyperemic MBF was lower in OB than in NW (1.88 ± 0.40 mL/g/min vs 2.35 ± 0.32 mL/g/min; ≤ 0.001), while comparable between NW and SOB (2.35 ± 0.32 mL/g/min vs 2.26 ± 0.40 mL/g/min; = 0.302). The BMI of the study population was associated with the Δ longitudinal MBF gradient in a U-turn fashion (r = 0.362, standard error of the estimate = 0.124; < 0.001).
CONCLUSIONS
Increased body weight associates with abnormalities in coronary circulatory function that advances from an impairment flow-mediated, epicardial vasodilation in overweight and obesity to coronary microvascular dysfunction in obesity, not observed in severe obesity. The U-turn of flow-mediated epicardial vasomotion outlines obesity and severe obesity to affect epicardial endothelial function differently.
PubMed: 38939628
DOI: 10.1016/j.jacadv.2024.100936