SCIENCE OF THE TOTAL ENVIRONMENT
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2019
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IF 5.589
Jing Wei,Chen Tu,Guodong Yuan,Yongqiang Zhou,Hailong Wang,Jian Lu
Multiple spectroscopic technologies and chemometric analyses were combined to explore the compositional characteristics and Cu binding performance of biochar-derived dissolved organic matter (DOM). The DOM samples were extracted from biochars produced from lignocellulose-rich rapeseed cake (RSC) by pyrolysis at 300, 500, and 700 °C (i.e., RSC300, RSC500, RSC700). Fourier transform infrared spectroscopy (FTIR) and carbon K-edge near-edge X-ray absorption fine structure spectroscopy (NEXAFS) analyses were combined to elucidate the molecular-level C species in the DOM. With the increasing pyrolysis temperature, DOM aromaticity increased, whereas the proportion of metal complexing sites (e.g., carboxyl and phenolic groups) decreased. Fluorescence excitation-emission matrix (EEM) spectroscopy with parallel factor analysis (PARAFAC) indicated that biochar DOM, irrespective of pyrolysis temperature, was mostly composed of three types of humic-like components (C1–C3), and a small amount of a protein-like component (C4). As charring temperature increased, DOM concentrations decreased substantially, but the humic-like C3 with abundant aromatic structures became predominant. Fluorescence quenching experiment and two-dimensional correlation spectroscopy (2D-COS) analysis suggested that the preferential Cu(II) binding fractions of the DOM were the humic-like substances. Moreover, the quenching curve fitting results for individual components indicated that despite the Cu(II) binding affinity was slightly enhanced as the pyrolysis temperature increased, the binding capacities of the four components decreased. In general, the DOM components from RSC biochar exhibited limited Cu(II) binding capacities (2.18–17.7 μmol L −1 ). Results from this study improved understanding of the mechanisms by which biochar DOM interacts with Cu, and provided tools for fast screening of biochars to reduce their environmental risks.
研究领域:
环境科学
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土壤化学
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DOI
PubMed
高影响因子
FOOD CHEMISTRY
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2022
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IF 9.231
Yu-Zhu Zhu,Kai Chen,Yu-Lin Chen,Changjun Zhang,Yuan-Yuan Xie,Robert C. Hider,Tao Zhou
In order to develop the tyrosinase inhibitors with potential application in food industry, a series of stilbene-hydroxypyridinone hybrids were prepared. Among these compounds, 1h was found to possess the most potent tyrosinase inhibitory effect on both monophenolase and diphenolase activities, with IC 50 values of 2.72 μM and 15.86 μM, respectively. The inhibitory effect of 1h on monophenolase activity was 4.6 times that of kojic acid . An inhibition kinetic assay indicated that 1h was a mixed-type and reversible inhibitor. The copper-binding and reducing ability assays, molecular docking study, intrinsic and ANS–binding fluorescence assays indicated that copper coordination and reduction is likely to be the causative mechanism for 1h -induced inhibition on tyrosinase. The results of color measurement and browning index determination indicated that treatment with 1h retarded effectively the browning of freshly-cut apples during their storage. Meanwhile, PPO and POD activities in apple slices were found to be effectively inhibited.
研究领域:
食品科学
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生物化学
✓ 已验证
DOI
高影响因子
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
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2017
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IF 3.807
Wenjun Yu,Rongshui Wang,Haiyan Huang,Huijun Xie,Shuning Wang
Agrobacterium tumefaciens S33 can grow with nicotine as the sole source of carbon, nitrogen, and energy via a novel hybrid of the pyridine pathway and the pyrrolidine pathway. Characterization of the enzymes involved in the hybrid pathway is important for understanding its biochemical mechanism. Here, we report that the molybdenum-containing nicotine dehydrogenase (NdhAB), which catalyzes the initial step of nicotine degradation, is located in the periplasm of strain S33, while the 6-hydroxynicotine oxidase and 6-hydroxypseudooxynicoine oxidase are in the cytoplasm. This is consistent with the fact that NdhA has a Tat signal peptide. Interestingly, an open reading frame (ORF) adjacent to the ndhAB gene was verified to encode a copper-containing electron carrier, pseudoazurin (Paz), which has a signal peptide typical of bacterial Paz proteins. Both were transported into the periplasm after being produced in the cytoplasm. We purified NdhAB from the periplasmic fraction of strain S33 and found that with Paz as the physiological electron acceptor, NdhAB catalyzed the hydroxylation of nicotine at a specific rate of 110.52 ± 8.09 μmol · min−1 · mg of protein−1, where the oxygen atom in the hydroxyl group of the product 6-hydroxynicotine was derived from H2O. The apparent Km values for nicotine and Paz were 1.64 ± 0.07 μM and 3.61 ± 0.23 μM, respectively. NAD(P)+, O2, and ferredoxin could not serve as electron acceptors. Disruption of the paz gene disabled the strain for nicotine degradation, indicating that Paz is required for nicotine catabolism in the strain. These findings help our understanding of electron transfer during nicotine degradation in bacteria.IMPORTANCE Nicotine is a toxic and addictive N-heterocyclic aromatic alkaloid produced in tobacco. Its catabolism in organisms and degradation in tobacco wastes have become major concerns for human health and the environment. Bacteria usually decompose nicotine using the classical strategy of hydroxylating the pyridine ring with the help of activated oxygen by nicotine dehydrogenase, which binds one molybdopterin, two [2Fe2S] clusters, and usually one flavin adenine dinucleotide (FAD) as well. However, the physiological electron acceptor for the reaction is still unknown. In this study, we found that the two-component nicotine dehydrogenase from Agrobacterium tumefaciens S33, naturally lacking an FAD-binding domain, is located in the periplasmic space and uses a copper-containing electron carrier, pseudoazurin, as its physiological electron acceptor. We report here the role of pseudoazurin in a reaction catalyzed by a molybdopterin-containing hydroxylase occurring in the periplasmic space. These results provide new biochemical knowledge on microbial degradation of N-heterocyclic aromatic compounds.
研究领域:
微生物学
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生物化学
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环境科学
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分子生物学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
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