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Gram-Scale Preparation of Cannflavin A from Hemp (Cannabis sativa L.) and Its Inhibitory Effect on Tryptophan Catabolism Enzyme Kynurenine-3-Monooxygenase
No full textInhibitors targeting kynurenine-3-monooxygenase (KMO), an enzyme in the neurotoxic kynurenine pathway (KP), are potential therapeutics for KP metabolites-mediated neuroinflammatory and neurodegenerative disorders. Although phytochemicals from Cannabis (C. sativa L.) have been reported to show modulating effects on enzymes involved in the KP metabolism, the inhibitory effects of C. sativa compounds, including phytocannabinoids and non-phytocannabinoids (i.e., cannflavin A; CFA), on KMO remain unknown. Herein, CFA (purified from hemp aerial material at a gram-scale) and a series of phytocannabinoids were evaluated for their anti-KMO activity. CFA showed the most active inhibitory effect on KMO, which was comparable to the positive control Ro 61-8048 (IC50 = 29.4 vs. 5.1 mu M, respectively). Furthermore, a molecular docking study depicted the molecular interactions between CFA and the KMO protein and a biophysical binding assay with surface plasmon resonance (SPR) technique revealed that CFA bound to the protein with a binding affinity of 4.1x10(-)(5) M. A competitive SPR binding analysis suggested that CFA and Ro 61-8048 bind to the KMO protein in a competitive manner. Our findings show that C. sativa derived phytochemicals, including CFA, are potential KMO inhibitors, which provides insight into the development of therapeutics targeting the KP and its related pathological conditions
Enzyme-driven oxygen-fuelled pathway selectivity of tyrosine-containing peptide oxidation evolution
No full textThe pathway selectivity of chemical evolution controlled by enzymes, with proteins and peptides as substrates, is of critical significance to determine biological processes and functions. In nature, organisms utilize tyrosinase to catalyse oxidation reactions of tyrosine to produce multifunctional compounds in different pathways. However, it remains a great challenge to manipulate the pathway selection of tyrosinase-guided chemical evolution for achieving biomaterials with on-demand functions. We herein report that controlling oxygen concentration is effective in regulating the evolution of tyrosinase-catalysed oxygenation pathways of tyrosine-containing peptides and even proteins. The melanin formation pathway predominates under oxygen-enriched conditions, while fluorescent compounds are preferentially generated under hypoxic conditions. The chemical evolution of tyrosine-containing peptides, regardless of their neighbouring amino acid types and sequences, tends to be governed by these two competitive pathways. These competitive pathways are manipulated by conformational transformation of tyrosinase active centre that is determined by oxygen concentration. Moreover, the oxygen-controlled chemical evolution of tyrosine-containing biomolecules can be broadly realized by tyrosinase to obtain melanin-based photothermal materials or multicolour fluorescent materials. This work reveals the plausible role of oxygen in the pathway selectivity of enzyme-controlled chemical evolution of tyrosine-containing peptides and verifies the possibility of fluorescent detection in living cultured melanoma cells, which provides a versatile strategy for precise design and engineering of tyrosine-involved multifunctional biomaterials
Coordinated Control of Fine-Particle and Ozone Pollution by the Substantial Reduction of Nitrogen Oxides Comment
No full textSimultaneous Extraction of Gold and Vanadium From Vanadium and Carbon-Rich Refractory Gold Minerals by Chlorination Roasting
No full textTo realize the efficient comprehensive utilization of refractory gold ore resources and environmental and economic gold extraction methods, this study investigated the optimal chlorine source for the sustained recovery of gold and vanadium from carbonaceous refractory gold ore by chlorination heat treatment. During the chlorination roasting process, the results indicated that CaCl2 has a greater chlorine supply capacity, and the reaction of refractory carbonaceous gold ore with CaCl2 was more intense than other chlorine sources. In addition, the effect of significant parameters (such as heat treatment temperature, heat treatment time, and CaCl2 additions) on gold and vanadium recovery ratios was carefully investigated. Under ideal conditions (i.e., CaCl2 concentration of 10 pct, heat treatment temperature of 1100 degrees C, heat treatment time of 4 hours, and air velocity of 1 L/min), 89.91 and 83.26 pct of gold and vanadium were recovered, respectively. In comparison, the main chemical mechanisms and phase transitions during the roasting process were studied by some analytical methods (such as scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and thermodynamic data). All alkaline chlorine sources were shown to destroy the structure of the minerals. CaCl2 was the compound with the more potent effect. Pyrite could enhance the chlorination of gold below 700 degrees C. In contrast, vanadium oxide could promote chlorination of gold above 700 degrees C. In addition, the leaching residue is primarily made of CaVO3, which can be used as a raw material for vanadium smelting. However, silicon dioxide and iron oxide will react at temperatures above 1100 degrees C, forming the "silicon oxygen" inclusion that hampered vanadium extraction
Comprehensive spectral analysis of reaction of three aldehydes with ammonium sulfate and glycine
No full textLight-absorbing brown carbon (BrC), a major contributor to global climate change, is widely studied. Compar-ative analysis showed that methylglyoxal (MG) tended to form a greater amount of aqueous BrC with AS/Gly/AS-Gly in a relatively short time, whereas 1,4-dioxane-2,5-diol (DD) tended to form darker BrC in the same reaction time. The absorption angstrom ngstro center dot m exponent (angstrom abs) over 250-400 nm and 400-480 nm in the absorption spectra combined with the index of recent autochthonous contribution (BIX), fluorescence index (FI), and humification index (HIX) in the fluorescence spectra, provided more information on the source of aqueous BrC. The absor-bance intensity order and the fluorescence intensity order were MG-AS-Gly > DD-AS-Gly > GX-AS-Gly and GX-AS-Gly > MG-AS-Gly > DD-AS-Gly, respectively. The reaction rate (K) of H2O2 oxidation and photodecompo-sition gradually increased from ultraviolet (UV) to visible (Vis) region. The short lifetime of aldehyde-amine mixtures indicates that imine BrC is photochemically unstable and easily dissolves under sunlight. The absor-bance and light decomposition rates were lowest in the GX-AS-Gly reaction system, indicating that the small amount of BrC formed by this system was more stable. The unsaturated double bonds gradually lengthened or shortened in the Maillard-type browning or aldol condensation reactions to form different numbers of product molecules. Furthermore, as these BrC reactions are strongly pH-dependent, it is necessary to measure (or control) the pH in the specific BrC system. Extensive laboratory spectroscopic comparative studies on these aqueous BrCs can be used to better understand the evolution of atmospheric BrC and its effects on climate
