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urea-bridged diferrocene: structural, electrochemical, and spectroelectrochemical studies

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Science China Chemistry 2015年第9期58卷 1444-1450页

作者： Zhong-Liang Gong Yu-Wu Zhong Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Photochemistry Institute of Chemistry Chinese Academy of Sciences

urea-bridged diferrocene derivatives N,N?-diferrocenylurea(1) and N,N?-dimethyl-N,N?-diferrocenylurea(2) were prepared and characterized. Single-crystal X-ray analysis shows that Compound 1 has a trans-trans linear conformation whereas Compound 2 has a trans-cis conformation. Both compounds display two consecutive redox couples with, respectively, E1/2 of +0.29 and +0.42 V vs. Ag/Ag Cl for 1 and +0.31 and +0.50 V for 2. Spectroelectrochemical studies show the presence of distinct intervalence charge transfer(IVCT) transitions for the one-electron-oxidized mixed-valent Compound 1+, with an estimated electronic coupling parameter of 190 cm?1. By contrast, the one-electron-oxidized Compound 2+ shows much weaker IVCT transitions.

关键词： mixed-valent compounds ferrocene electrochemistry urea spectroelectrochemistry

urea transport and hydrolysis in the rumen: A review

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Animal Nutrition 2021年第4期7卷 989-996页

作者： Samson Hailemariam Shengguo Zhao Yue He Jiaqi Wang State Key Laboratory of Animal Nutrition Institute of Animal SciencesChinese Academy of Agricultural SciencesBeijing100193China Dilla University College of Agriculture and Natural ResourceDilla P.O.Box 419Ethiopia

Inefficient dietary nitrogen(N)conversion to microbial proteins,and the subsequent use by ruminants,is a major research focus across different *** bacterial ammonia(NH3)produced due to degradation or hydrolyses of N containing compounds,such as urea,leads to an inefficiency in a host’s ability to utilize *** is a non-protein N containing compound used by ruminants as an ammonia source,obtained from feed and endogenous *** is hydrolyzed by ureases from rumen bacteria to produce NH_(3) which is used for microbial protein ***,lack of information exists regarding urea hydrolysis in ruminal bacteria,and how urea gets to hydrolysis ***,this review describes research on sites of urea hydrolysis,urea transport routes towards these sites,the role and structure of urea transporters in rumen epithelium and bacteria,the composition of ruminal ureolytic bacteria,mechanisms behind urea hydrolysis by bacterial ureases,and factors influencing urea *** review explores the current knowledge on the structure and physiological role of urea transport and ureolytic bacteria,for the regulation of urea hydrolysis and recycling in ***,underlying mechanisms of urea transportation in rumen bacteria and their physiological importance are currently unknown,and therefore future research should be directed to this subject.

关键词： urea transporter urea urea hydrolysis Ruminal bacteria

Evolution of Conformation and Dynamics of Solvents in Hydration Shell along the urea-induced Unfolding of Ubiquitin

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Chinese Journal of Polymer Science 2019年第7期37卷 708-718页

作者： Ke-Cheng Yang Feng-Chao Cui Ce Shi Wen-Duo Chen Yun-Qi Li Key Laboratory of Synthetic Rubber Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China Smart City Research Institute Zhengzhou UniversityZhengzhou 450001China

A clear diagram for the unfolding of protein induced by denaturant is a classical but still unsolved challenge. To explore the unfolded conformations of ubiquitin under different urea concentrations, we performed hybrid Monte Carlo-molecular dynamics simulations (MC-MD) guided by small angle X-ray scattering (SAXS) structural information. Conformational ensembles sampled by the hybrid MC-MD algorithm exhibited typical 3D structures at different urea concentrations. These typical structures suggested that ubiquitin was subjected to a sequential unfolding, where the native contacts between adjacent β-sheets at first were disrupted together with the exposure of hydrophobic core, followed by the conversion of remaining β-strands and helices into random coils. Ubiquitin in 8 mol·L?1 urea is almost a random coil. With the disruption of native structure, urea molecules are enriched at protein hydrated layer to stabilize newly exposed residues. Compared with water, urea molecules prefer to form hydrogen bonds with the backbone of ubiquitin, thus occupying nodes of the hydrogen bonding network that construct the secondary structure of proteins. Meanwhile, we also found that the slow dynamics of urea molecules was almost unchanged while the dynamics of water was accelerated in the hydration shell when more residues were unfolded and exposed. The former was also responsible for the stabilization of unfolded structures.

关键词： Ubiquitin Unfolding process Hydration behavior and dynamics Water and urea

Introducing urea into tirapazamine derivatives to enhance anticancer therapy

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National Science Review 2024年第4期11卷 245-253页

作者： Yajun Xu Jianlin Lv Chaoying Kong Ya Liu Kun Wang Zhaohui Tang Xuesi Chen Key Laboratory of Polymer Ecomaterials Changchun Institute of Applied ChemistryChinese Academy of Sciences School of Applied Chemistry and Engineering University of Science and Technology of China

Tirapazamine（TPZ） has been approved for multiple clinical trials relying on its excellent anticancer ***,as a typical hypoxia-activated prodrug（HAP）,TPZ did not exhibit survival advantages in Phase Ⅲ clinical trials when used in combination therapy due to the insufficient hypoxia levels in patients' *** this study,to improve the therapeutic effects of TPZ,we first introduced urea to synthesize a series of urea-containing derivatives of *** urea-containing TPZ derivatives showed increased hypoxic cytotoxicity（9.51-30.85-fold） compared with TPZ,while maintaining hypoxic ***,one of these derivatives,showed 20-fold higher cytotoxicity than TPZ while maintaining a similar hypoxic cytotoxicity *** highly efficiently deliver TPZP to the tumors and reduce its side effects on healthy tissues,we further prepared TPZP into a nanodrug with fibrin-targeting ability:***4-NPs,a vascular disrupting agent,was used to increase the fibrin level within tumors and exacerbate tumor *** being combined with CA4-NPs,FT11-TPZP-NPs can accumulate in the hypoxia-aggravated tumors and activate sufficiently to kill tumor *** a single-dose treatment,FT11-TPZP-NPs+CA4-NPs showed a high inhibition rate of 98.1% against CT26 tumor models with an initial volume of ～480 mm3and four out of six tumors were completely eliminated;it thereby exerted a significant antitumor *** study provides a new strategy for improving the therapeutic effect of TPZ and other HAPs in anticancer therapy.

关键词： tirapazamine vascular disrupting agent hypoxia-activated prodrug combretastatin A4 urea

Carbon fiber confined mixed Ni-based crystal phases with interfacial charge redistribution induced by high bond polarity for electrochemical urea-assisted hydrogen generation

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Carbon Energy 2024年第9期6卷 292-305页

作者： Chun Yin Jiaxin Li Shuli Wang Huan Wen Fulin Yang Ligang Feng School of Chemistry and Chemical Engineering Yangzhou UniversityYangzhouChina Guangxi Key Laboratory of Electrochemical Energy Materials School of Chemistry and Chemical EngineeringGuangxi UniversityNanningChina

Interfacial electronic structure modulation of nickel-based electrocata-lysts is significant in boosting energy-conversion-relevant urea oxidation reaction(UOR).Herein,porous carbon nanofibers confined mixed Ni-based crystal phases of Ni_(2)P and NiF_(2) are developed via fluorination and phosphorization of Ni coated carbon nanofiber(Ni_(2)P/NiF_(2)/PCNF),which possess sufficient mesoporous and optimized Gibbs adsorption free energy by mixed phase-induced charge *** novel system further reduces the reaction energy barrier and improves the reaction activity by addressing the challenges of low intrinsic activity,difficulty in active site formation,and insufficient synergism.A considerably high current density of 254.29 mA cm^(-2) is reached at 1.54 V versus reversible hydrogen electrode on a glass carbon electrode,and the cell voltage requires 1.39 V to get 10 mA cm^(-2) in hydrogen generation,with very good stability,about 190 mV less than that of the traditional water *** facile active phase formation and high charge transfer ability induced by asymmetric charge redistribution are found in the interface,where the urea molecules tend to bond with Ni atoms on the surface of heterojunction,and the rate-determining step is changed from CO_(2) desorption to the fourth H-atom *** work reveals a novel catalyst system by interfacial charge redistribution induced by high bond polarity for energy-relevant catalysis reactions.

关键词： carbon fiber nickel fluoride nickel phosphide urea oxidation water electrolysis

Morphology and Crystalline Structure of Inclusion Compounds Formed between Poly(ethylene glycol) and urea

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Chinese Journal of Polymer Science 2014年第9期32卷 1234-1242页

作者： Da-wei Lin Zhi Zhong Yi-ren Tang Yang Gao Ya-ning He Bao-hua Guo 徐军 Institute of Polymer Science & Engineering Department of Chemical Engineering Tsinghua University

The poly（ethylene glycol）（PEG, with Mw 2000）-urea inclusion compound （IC） crystallized at high temperature region showed two typical orientations, flat-on and edge-on crystals. 2D-XRD and polarized FTIR spectroscopy revealed that the PEG chains within urea channels were perpendicular to the substrate in fiat-on oriented crystals, while PEG chain axes were parallel to the substrate and lay along the growth direction in the edge-on crystals. FT1R absorption bands of PEG in the ICs are sensitive to orientation of the crystals. A scheme of PEG chain packing in the urea IC channel was proposed, which could explain the orientation of the crystal nucleus causing the two types of morphologies. Furthermore, functioning of PEG2000 chain end with analine had significantly influence on the morphology and orientation of the inclusion compound crystals, due to the defects caused by large terminal groups included in the urea channel.

关键词： Poly(ethylene glycol) urea Inclusion compounds Morphology Orientation.

Deactivation of Cu-SAPO-34 by urea-related deposits at low temperatures and the regeneration

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Journal of Environmental Sciences 2019年第7期31卷 43-51页

作者： Yue Ma Xiaodong Wu Junyu Zhang Rui Ran Zhichun Si Duan Weng The Key Laboratory of Advanced Materials of Ministry of Education School of Materials Science and Engineering Tsinghua University School of Environment Tsinghua University Graduate School at Shenzhen Tsinghua University

Selective catalytic reduction(SCR) with urea catalyzed by Cu-SAPO-34 is an effective method to eliminate NO_x from diesel exhaust. However, urea-related deposits may form during cold-start and urban driving due to low exhaust temperatures. The activity of CuSAPO-34 at 175°C is significantly degraded by urea exposure, and 300°C is required for regeneration. Through in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS) and temperature-programmed hydrolysis studies, the dominant stable deposit at 175°C is identified as biuret, which can be eliminated at 300°C. The urea-derived deactivation and regeneration mechanisms of Cu-SAPO-34 were compared with those of anatase-supported catalysts.

关键词： SCR urea Biuret Cu-SAPO-34 Deactivation

Modeling and simulation of urea-water-solution droplet evaporation and thermolysis processes for SCR systems

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Chinese Journal of Chemical Engineering 2016年第8期24卷 1065-1073页

作者： Xubo Gan Dongwei Yao Feng Wu Jiawei Dai Lai Wei Xingwen Li Institute of Power Machinery and Vehicular Engineering Zhejiang University

A reliable mathematical model of urea-water-solution(UWS) droplet evaporation and thermolysis is *** well known Abramzon–Sirignano evaporation model is corrected by introducing an adjustment coefficient considering the different evaporation behaviors of UWS droplet at different ambient temperatures. A semidetailed kinetic scheme of urea thermolysis is developed based on Ebrahimian's work. Sequentially, the evaporation characteristics, decomposition efficiency of a single UWS droplet and deposit formation are simulated. As a result, the relation of evaporation time, relative velocity, exhaust temperature and droplet initial diameter is presented. Synchronously, it indicates that temperature is the decisive factor for urea thermolysis. Different temperatures result in different deposit components, and deposit yield is significantly influenced by temperature and decomposition time. The current work can provide guidance for designing urea injection strategy of SCR systems.

关键词： SCR UWS evaporation urea thermolysis Semi-detailed kinetic Simulation

Plasma-enabled sensing of urea and related amides on polyaniline

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Frontiers of Chemical Science and Engineering 2016年第2期10卷 265-272页

作者： Harinarayanan Puliyalil Petr Slobodian Michal Sedlacik Ruhan Benlikaya Pavel Riha Kostya (Ken) Ostrikov Uros Cvelbar Jozef Stefan Institute (F4) Jamova cesta 39 1000 Ljubjana Slovenia Jozef Stefan International Postgraduate School Jamova cesta 39 1000 Ljubjana Slovenia Centre of Polymer Systems University Institute Tomas Bata University Trida T. Bati 5678 76001 Zlin Czech Republic Department of Secondary Science and Mathematics Education Faculty of Necatibey Education Balikesir University 10100 Balikesir Turkey Institute of Hydrodynamics Academy of Sciences Pod Patankou 5 166 12 Prague 6 Czech Republic Institute for Future Environments and Institute for Health and Biomedical Innovation School of ChemistryPhysics and Mechanical Engineering Queensland University of Technology Brisbane Queensland 4000 Australia CSIRO-QUT Joint Sustainable Materials and Devices Laboratory Commonwealth Scientific and Industrial Research Organization New South Wales 2070 Australia School of Physics The University of Sydney Sydney New South Wales 2006 Australia

The atmospheric pressure plasma jet （APPJ） was used to enhance the sensitivity of industrially important polyaniline （PANI） for detection of organic vapors from amides. The gas sensing mechanism of PANI is operating on the basis of reversible protonation or deprotonation, whereas the driving force to improve the sensitivity after plasma modifications is unknown. Herein we manage to solve this problem and investigate the sensing mechanism of atmospheric plasma treated PANI for vapor detection of amides using urea as a model. The results from various analytical techniques indicate that the plausible mechanism responsible for the improved sensi- tivity after plasma treatment is operating through a cyclic transition state formed between the functional groups introduced by plasma treatment and urea. This transition state improved the sensitivity of PANI towards 15 ppm of urea by a factor of 2.4 times PANI. This plasma treated compared to the non-treated PANI is promising for the improvement of the sensitivity and selectivity towards other toxic and carcinogenic amide analytes for gas sensing applications such as improving material proces- sing and controlling food quality.

关键词： gas sensing urea PANI amides plasma