Artículos de revistas: "Nitroaromatic molecules"

1

Su, Xin Fang. "Density Functional Studies on the Standard Heats of Formation for Nitroaromatic Molecules". Advanced Materials Research 1095 (marzo de 2015): 415–18. http://dx.doi.org/10.4028/www.scientific.net/amr.1095.415.

Texto completo

Resumen

The standard heats of formation for 12 nitroaromatic molecules in gas at 298 K were calculated at B3P86/6-311G** levels using different isodesmic reactions. Comparison between the computational results and the experimental values reveals that using methane as reference compound to design isodesmic reaction is able to predict satisfactory results of heats of formation for ortho-substituted nitroaromatic molecules; however, using benzene as reference compound is able to give agreement with experimental data for meta-substituted and para-substituted nitroaromatic molecules.

Los estilos APA, Harvard, Vancouver, ISO, etc.

2

Su, Xin Fang, Wei Huang y Hai Ying Wu. "Assessment of PBE0 Calculation of C-NO₂ Bond Dissociation Energies for Nitroaromatic System". Advanced Materials Research 915-916 (abril de 2014): 675–78. http://dx.doi.org/10.4028/www.scientific.net/amr.915-916.675.

Texto completo

Resumen

Density functional theory (DFT) is used to calculate the C-NO2bond dissociation energies (BDEs) in nitrobenzene; 3-amino-nitrobenze; 4-amino-nitrobenze; 1,3-dinitrobenzene; 1,4-dinitrobenzene; 2-methyl-nitrobenzene; 4-methyl-nitrobenzene and 1,3,5-trinitrobenzene nitroaromatic molecular system. B3P86 and PBE0 methods in combination with 6-31G** and 6-311G** basis sets are employed. Comparison between the computational results and the experimental values reveals that the calculated C-NO2bond BDEs can be improved from B3P86 to PBE0 functional. Level of theory employing PBE0/6-311G** is found to be sufficiently reliable to compute BDEs of C-NO2bond for nitroaromatic molecules with an average absolute error of 0.98 kcal mol-1.

Los estilos APA, Harvard, Vancouver, ISO, etc.

3

Cha, Inhwan, Seohyun Baek, Sun Gu Song, Junggong Kim, Ho Keun Lee, Jongman Lee, Kyung-su Kim y Changsik Song. "Inter- and Intra-Hydrogen Bonding Strategy to Control the Fluorescence of Acylhydrazone-Based Conjugated Microporous Polymers and Their Application to Nitroaromatics Detection". Macromol 1, n.º 3 (15 de septiembre de 2021): 234–42. http://dx.doi.org/10.3390/macromol1030016.

Texto completo

Resumen

Acylhydrazone-based fluorescent conjugated microporous polymers (CMPs) with inter-and intra-hydrogen bonding-controlled emissive properties were prepared. The synthesized CMPs (BH-CMP and ABH-CMP) were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, solid-state 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy, and photoluminescence spectroscopy. Interestingly, BH-CMP exhibited emission enhancement via adsorption of water molecules, whereas the emission of ABH-CMP, which possesses free amine groups, decreased upon the addition of water molecules. The differences in the emission trends of BH-CMP and ABH-CMP in the presence of water molecules originate from the formation of different hydrogen-bonding networks in each CMP. The acylhydrazone-based CMPs were applied to the detection of nitroaromatic compounds. As a result, ABH-CMP in DMF exhibited high selectivity for 1,3,5-trinitrotoluene (TNT) over other nitroaromatic compounds nitrobenzene, 1-chloro-4-nitrobenzene, 2,3-dichloronitrobenzene, and 2,4-dinitrotoluene.

Los estilos APA, Harvard, Vancouver, ISO, etc.

4

Zhao, Shu-Man, Zhao-Feng Qiu, Zou-Hong Xu, Zi-Qing Huang, Yue Zhao y Wei-Yin Sun. "Fluorescent Zn(ii) frameworks with multicarboxylate and pyridyl N-donor ligands for sensing specific anions and organic molecules". Dalton Transactions 51, n.º 9 (2022): 3572–80. http://dx.doi.org/10.1039/d1dt04052a.

Texto completo

Resumen

Three new Zn(ii)-based frameworks were fabricated and their fluorescence and sensing properties for specific anions and organic molecules such as benzaldehyde (BZH) and nitroaromatic compounds (NACs) were examined.

Los estilos APA, Harvard, Vancouver, ISO, etc.

5

Nakagaki, Ryoichi, Kiyoshi Mutai, Mitsuo Hiramatsu, Hideyuki Tukada y Saburo Nakakura. "Magnetic field effects upon photochemistry of bichromophoric chain molecules containing nitroaromatic and arylamino moieties: Elucidation of reaction mechanism and control of reaction yields". Canadian Journal of Chemistry 66, n.º 8 (1 de agosto de 1988): 1989–96. http://dx.doi.org/10.1139/v88-321.

Texto completo

Resumen

The photochemistry of bichromophoric species containing nitroaromatic and arylamino moieties has been studied in the presence and absence of an external magnetic field. Photolysis products are an unsubstituted arylamine, a nitrosoaromatic species (Product 1), and a nitroaromatic compound (Product 2). On application of the magnetic field, the formation yield for Product 1 decreases and that for Product 2 correspondingly increases, whereas the consumption of the starting material and the release of the unsubstituted arylamine are independent of the magnetic field. Analysis of the magnetic field effects shows that the hyperfine coupling mechanism predominates and that the photoreaction takes place in the triplet manifold of the nitroaromatic moiety. Application of the magnetic field may cause an appreciable change in the relative yield of cage and escape products, i.e., the branching ratio of competitive processes.

Los estilos APA, Harvard, Vancouver, ISO, etc.

6

Ju, Kou-San y Rebecca E. Parales. "Nitroaromatic Compounds, from Synthesis to Biodegradation". Microbiology and Molecular Biology Reviews 74, n.º 2 (junio de 2010): 250–72. http://dx.doi.org/10.1128/mmbr.00006-10.

Texto completo

Resumen

SUMMARY Nitroaromatic compounds are relatively rare in nature and have been introduced into the environment mainly by human activities. This important class of industrial chemicals is widely used in the synthesis of many diverse products, including dyes, polymers, pesticides, and explosives. Unfortunately, their extensive use has led to environmental contamination of soil and groundwater. The nitro group, which provides chemical and functional diversity in these molecules, also contributes to the recalcitrance of these compounds to biodegradation. The electron-withdrawing nature of the nitro group, in concert with the stability of the benzene ring, makes nitroaromatic compounds resistant to oxidative degradation. Recalcitrance is further compounded by their acute toxicity, mutagenicity, and easy reduction into carcinogenic aromatic amines. Nitroaromatic compounds are hazardous to human health and are registered on the U.S. Environmental Protection Agency's list of priority pollutants for environmental remediation. Although the majority of these compounds are synthetic in nature, microorganisms in contaminated environments have rapidly adapted to their presence by evolving new biodegradation pathways that take advantage of them as sources of carbon, nitrogen, and energy. This review provides an overview of the synthesis of both man-made and biogenic nitroaromatic compounds, the bacteria that have been identified to grow on and completely mineralize nitroaromatic compounds, and the pathways that are present in these strains. The possible evolutionary origins of the newly evolved pathways are also discussed.

Los estilos APA, Harvard, Vancouver, ISO, etc.

7

Yan, Jingjing, Alexander D. Carl, Alex R. Maag, John C. MacDonald, Peter Müller, Ronald L. Grimm y Shawn C. Burdette. "Detection of adsorbates on emissive MOF surfaces with X-ray photoelectron spectroscopy". Dalton Transactions 48, n.º 14 (2019): 4520–29. http://dx.doi.org/10.1039/c8dt04404j.

Texto completo

Resumen

The luminescence of azobenzene chromophore struts in a metal organic framework is quenched by nitroaromatic guests. X-ray photoelectron spectroscopic methods verify the emission changes are due to the surface adsorption of the guest molecules rather than encapsulation.

Los estilos APA, Harvard, Vancouver, ISO, etc.

8

Francisco da Silva, Amauri, Antonio João da Silva Filho, Mário Vasconcellos y Otávio Luís de Santana. "One-Electron Reduction Potentials: Calibration of Theoretical Protocols for Morita–Baylis–Hillman Nitroaromatic Compounds in Aprotic Media". Molecules 23, n.º 9 (24 de agosto de 2018): 2129. http://dx.doi.org/10.3390/molecules23092129.

Texto completo

Resumen

Nitroaromatic compounds—adducts of Morita–Baylis–Hillman (MBHA) reaction—have been applied in the treatment of malaria, leishmaniasis, and Chagas disease. The biological activity of these compounds is directly related to chemical reactivity in the environment, chemical structure of the compound, and reduction of the nitro group. Because of the last aspect, electrochemical methods are used to simulate the pharmacological activity of nitroaromatic compounds. In particular, previous studies have shown a correlation between the one-electron reduction potentials in aprotic medium (estimated by cyclic voltammetry) and antileishmanial activities (measured by the IC50) for a series of twelve MBHA. In the present work, two different computational protocols were calibrated to simulate the reduction potentials for this series of molecules with the aim of supporting the molecular modeling of new pharmacological compounds from the prediction of their reduction potentials. The results showed that it was possible to predict the experimental reduction potential for the calibration set with mean absolute errors of less than 25 mV (about 0.6 kcal·mol−1).

Los estilos APA, Harvard, Vancouver, ISO, etc.

9

Malval, Jean-Pierre, Marion Cranney, Sylvain Achelle, Huriye Akdas-Kiliç, Jean-Luc Fillaut, Nolwenn Cabon, Françoise Robin-le Guen, Olivier Soppera y Yann Molard. "Porosity-driven large amplitude dynamics for nitroaromatic sensing with fluorescent films of alternating D–π–A molecules". Chemical Communications 55, n.º 95 (2019): 14331–34. http://dx.doi.org/10.1039/c9cc07227f.

Texto completo

Resumen

Very large amplitude nitroaromatic sensing dynamics are observed upon a structural change within an alternating D–π–A chromophore initially configured to promote densely cofacial self-packing at a macromolecular scale.

Los estilos APA, Harvard, Vancouver, ISO, etc.

10

Marshall, A., A. Clark, R. Jennings, K. W. D. Ledingham, J. Sander y R. P. Singhal. "Laser-induced dissociation, ionization and fragmentation processes in nitroaromatic molecules". International Journal of Mass Spectrometry and Ion Processes 116, n.º 2 (julio de 1992): 143–56. http://dx.doi.org/10.1016/0168-1176(92)80124-j.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

11

Ture, Satish Ashok, Shruthy D. Pattathil, Bertrand Zing Zing y Venkataraman Abbaraju. "Fluorescence Sensing of Some Important Nitroaromatic Compounds by Using Polyaniline Ag Composite". Micro 3, n.º 1 (9 de febrero de 2023): 224–38. http://dx.doi.org/10.3390/micro3010016.

Texto completo

Resumen

Conducting polymers (CPs) have contributed significantly to the field of sensing. The sensing of nitroaromatic compounds by fluorescence has recently gained more attention due to its sensitivity and selectivity. In this study, polyaniline (PANI) was functionalized by forming a polyaniline-Ag (PANI-Ag) composite and used as a fluorophore for sensing. The nitro groups present in nitroaromatic compounds (NACs) such as 2,4,6-trinitrophenol (picric acid-TNP) and Dinitrobenzene (DNB) act as electron-accepting molecules and quench the fluorescence of polymer chains by showing an amplified quenching effect in which trace amounts of electron-accepting NACs quench emissions of several fluorophore units. The PANI-Ag composite synthesized by interfacial polymerization was analyzed using UV-vis spectroscopy and Fourier-transform infrared (FTIR) spectroscopy for determination of molecular structure; X-ray powder diffraction (XRD) and scanning electron microscopy (SEM/EDAX) for its morphology, which is cubic crystalline silver; and thermogravimetric analysis (TGA) for the thermal stability. The fluorescence quenching mechanism was deduced from the Stern–Volmer plot. The quenching constant value (Ksv) obtained from the Stern–Volmer (S–V) plot was found to be Ksv = 0.1037 × 106 M−1 (TNP) and Ksv = 0.161 × 104 M−1 (DNB). The plot shows a single mechanism with formation of an exciplex complex for TNP with a photoinduced electron transfer (PET) mechanism. The limit of detection (LOD) is found to be TNP = 5.58 × 10−7 M, whereas DNB = 23.30 × 10−6 M shows that the PANI-Ag composite is a potential fluorophore for sensing of nitroaromatic compounds in trace levels.

Los estilos APA, Harvard, Vancouver, ISO, etc.

12

Murray, Jane S., Pat Lane y Peter Politzer. "Relationships between impact sensitivities and molecular surface electrostatic potentials of nitroaromatic and nitroheterocyclic molecules". Molecular Physics 85, n.º 1 (mayo de 1995): 1–8. http://dx.doi.org/10.1080/00268979500100891.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

13

Jensen, S., K. Tan, W. Lustig, D. Kilin, J. Li, Y. J. Chabal y T. Thonhauser. "Quenching of photoluminescence in a Zn-MOF sensor by nitroaromatic molecules". Journal of Materials Chemistry C 7, n.º 9 (2019): 2625–32. http://dx.doi.org/10.1039/c8tc06281a.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

14

Park, Miso, Lakshmi N. Cella, Wilfred Chen, Nosang V. Myung y Ashok Mulchandani. "Carbon nanotubes-based chemiresistive immunosensor for small molecules: Detection of nitroaromatic explosives". Biosensors and Bioelectronics 26, n.º 4 (diciembre de 2010): 1297–301. http://dx.doi.org/10.1016/j.bios.2010.07.017.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

15

Kose, Muhammet Erkan, Barbara A. Harruff, Yi Lin, L. Monica Veca, Fushen Lu y Ya-Ping Sun. "Efficient Quenching of Photoluminescence from Functionalized Single-Walled Carbon Nanotubes by Nitroaromatic Molecules". Journal of Physical Chemistry B 110, n.º 29 (julio de 2006): 14032–34. http://dx.doi.org/10.1021/jp063251o.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

16

Lu, Wei, Xiao Dong, Lili Qiu, Zequn Yan, Zihui Meng, Min Xue, Xuan He y Xueyong Liu. "Colorimetric sensor arrays based on pattern recognition for the detection of nitroaromatic molecules". Journal of Hazardous Materials 326 (marzo de 2017): 130–37. http://dx.doi.org/10.1016/j.jhazmat.2016.12.024.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

17

Politzer, Peter, Jorge M. Seminario y Paul R. Bolduc. "A proposed interpretation of the destabilizing effect of hydroxyl groups on nitroaromatic molecules". Chemical Physics Letters 158, n.º 5 (junio de 1989): 463–69. http://dx.doi.org/10.1016/0009-2614(89)87371-3.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

18

FANG, Ming, Ming, Zhe LI y Yao FU. "Substituent Effect on the C-NO2and N-NO2Bond Dissociation Energies of Nitroaromatic Molecules". Chinese Journal of Chemistry 26, n.º 6 (junio de 2008): 1122–28. http://dx.doi.org/10.1002/cjoc.200890200.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

19

Nguyen, Thao Phuong Le, Thao Thanh Bui, Bao Kim Doan, Linh Phuong Bui, Tam Hoang Luu, Chau Duc Tran, Tung Viet Tuan Tran, Tsutomu Yokozawa y Ha Tran Nguyen. "Synthesis of a conjugated molecular triad based on 9,9-dioctyl-9H-fluorene for fluorescence sensing to determine mesotrione". Ministry of Science and Technology, Vietnam 65, n.º 1 (15 de marzo de 2023): 14–18. http://dx.doi.org/10.31276/vjste.65(1).14-18.

Texto completo

Resumen

A conjugated molecular triad based on pyrene and 9,9-dioctyl-9H-fluorene has been successfully synthesised via the Suzuki cross-coupling reaction with yield of 48%. In this polymerization, the Pd(PPh3)4 has been used as the catalytic in the presence of K2CO3 as base in a mixture of toluene/ethanol/H2O at 80oC under N2. The chemical structures of the conjugated molecules were determined via Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR) that proved the chemical structure of 1,1’-(9,9-dioctyl-9H-fluorene-2,7-diyl)dipyrene. The optical properties of the molecules were investigated via UV-Vis in different concentration that exhibited the maximum absorption of 340 nm. The conjugated molecular triad also have been investigated by fluorescence spectroscopy that showed a mission peak at 475 nm under the excitation of 350 nm of wavelength. In addition, the 1,1’-(9,9-dioctyl-9H-fluorene-2,7-diyl)dipyrene exhibited a fluorescence quenching as a chemosensor in the presence of mesotrione, a nitroaromatic herbicide. This phenomenon proved the efficient energy and electron transfer from a photo-excited pyrene moiety to the ground state electron-deficient mesotrione as a result of Forster resonance energy transfer (FRET) mechanism.

Los estilos APA, Harvard, Vancouver, ISO, etc.

20

Lessner, Daniel J., Rebecca E. Parales, Shakti Narayan y David T. Gibson. "Expression of the Nitroarene Dioxygenase Genes in Comamonas sp. Strain JS765 and Acidovorax sp. Strain JS42 Is Induced by Multiple Aromatic Compounds". Journal of Bacteriology 185, n.º 13 (1 de julio de 2003): 3895–904. http://dx.doi.org/10.1128/jb.185.13.3895-3904.2003.

Texto completo

Resumen

ABSTRACT This work reports a genetic analysis of the expression of nitrobenzene dioxygenase (NBDO) in Comamonas sp. strain JS765 and 2-nitrotoluene dioxygenase (2NTDO) in Acidovorax sp. strain JS42. Strains JS765 and JS42 possess identical LysR-type regulatory proteins, NbzR and NtdR, respectively. NbzR/NtdR is homologous to NahR, the positive salicylate-responsive transcriptional activator of the naphthalene degradation genes in Pseudomonas putida G7. The genes encoding NBDO and 2NTDO in each strain are cotranscribed, and transcription starts at the same site within identical promoter regions for each operon. Results from a lacZ reporter gene fusion demonstrated that expression of NBDO and 2NTDO is induced by multiple aromatic compounds, including an array of nitroaromatic compounds (nitrobenzene, 2-, 3-, and 4-nitrotoluene, 2,4- and 2,6-dinitrotoluene, and aminodinitrotoluenes), as well as salicylate and anthranilate. The nitroaromatic compounds appear to be the actual effector molecules. Analysis of β-galactosidase and 2NTDO activities with strain JS42 demonstrated that NtdR was required for induction by all of the inducing compounds, high basal-level expression of 2NTDO, and complementation of a JS42 ntdR null mutant. Complementation with the closely related regulators NagR (from Ralstonia sp. strain U2) and NahR restored only induction by the archetype inducers, salicylate or salicylate and anthranilate, respectively, and did not restore the high basal level of expression of 2NTDO. The mechanism of 2NTDO gene regulation in JS42, and presumably that of NBDO gene regulation in JS765, appear similar to that of NahR-regulated genes in Pseudomonas putida G7. However, NbzR and NtdR appear to have evolved a broader specificity in JS42 and JS765, allowing for recognition of nitroaromatic compounds while retaining the ability to respond to salicylate and anthranilate. NtdR is also the first example of a nitroarene-responsive LysR-type transcriptional activator.

Los estilos APA, Harvard, Vancouver, ISO, etc.

21

Dai, Jingjing, Michael Zambrana y Maria Fidalgo. "Amino-functionalized Fluorescent Carbon Dots for Chemical Sensing". MRS Advances 1, n.º 19 (2016): 1365–70. http://dx.doi.org/10.1557/adv.2016.169.

Texto completo

Resumen

ABSTRACTQuantum dots have been applied in sensing with success, but their use in environmental applications has been questioned due to their heavy metal content. Carbon dots are fluorescent nanoparticles that offer a promising alternative to quantum dots for sensing, due to their low cost, benign fabrication process and negligible environmental impact. Fluorescence sensors are specially suited for detection of nitroaromatic compounds such as 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT), since they can quench the emission of excited species. When combined to Molecularly Imprinted Polymers (MIPs), the sensors become specific to the imprinted target molecules. Amino-functionalized carbon dots (CDs) with high photoluminescence were fabricated. The CDs were characterized with respect to their surface charge, surface chemistry, particle size distribution, and photoluminescence properties (PL). A molecularly imprinted polymer with template of DNT was combined with fluorescent carbon dots via a simple covalent reaction. The ability of aqueous DNT to quench amino CDs fluorescence was tested for concentrations in the range of 1mM to 50 mM. It can be concluded that the amino carbon dots can be used in fluorescent-labeled MIP systems and that they provide a feasible method for the detection of DNT, and potentially other nitroaromatic compounds, in environmental water samples.

Los estilos APA, Harvard, Vancouver, ISO, etc.

22

Rice, Betsy M., Samir Sahu y Frank J. Owens. "Density functional calculations of bond dissociation energies for NO2 scission in some nitroaromatic molecules". Journal of Molecular Structure: THEOCHEM 583, n.º 1-3 (abril de 2002): 69–72. http://dx.doi.org/10.1016/s0166-1280(01)00782-5.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

23

Lopatin, B. V. "Interaction of vibrations of atomic groups for the example of molecules of nitroaromatic compounds". Journal of Applied Spectroscopy 43, n.º 4 (octubre de 1985): 1137–39. http://dx.doi.org/10.1007/bf00662331.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

24

Zobel, J. Patrick y Leticia González. "Nonadiabatic Dynamics Simulation Predict Intersystem Crossing in Nitroaromatic Molecules on a Picosecond Time Scale". ChemPhotoChem 3, n.º 9 (13 de junio de 2019): 833–45. http://dx.doi.org/10.1002/cptc.201900108.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

25

Xiang, Zhonghua y Dapeng Cao. "Synthesis of Luminescent Covalent-Organic Polymers for Detecting Nitroaromatic Explosives and Small Organic Molecules". Macromolecular Rapid Communications 33, n.º 14 (17 de abril de 2012): 1184–90. http://dx.doi.org/10.1002/marc.201100865.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

26

Nainsi, Nainsi y Nibedita Banik. "Detection of Picric Acid: By Fluorescent Chemosensor (Nitro-Aromatic Compound): A Short Review". Material Science Research India 20, SpecialIssue1 (31 de diciembre de 2023): 40–47. http://dx.doi.org/10.13005/msri.20.special-issue1.05.

Texto completo

Resumen

ABSTRACT: The most abundant and valuable class of chemicals currently used in industries are referred to as nitroaromatic compounds. These are compounds that include organic molecules and, more importantly, at least one nitro- group in the ring. As we already know, chemistry is currently known for using a variety of fluorescent techniques. Picric acid (O2N)3C6H2OH) is an organic compound also known as 2, 4, 6-trinitrophenol (TNP), according to the IUPAC. It is extensively used in the industries of dyes, leather, fireworks, and matches. In this review, author tried to explain how to detect picric acid through fluorescent Chemosensor. It helps in the synthesis of fluorescent Nanoscopic objects or compounds.

Los estilos APA, Harvard, Vancouver, ISO, etc.

27

Miseviciene, Lina, Zilvinas Anusevicius, Jonas Sarlauskas y Narimantas Cenas. "Reduction of nitroaromatic compounds by NAD(P)H:quinone oxidoreductase (NQO1): the role of electron-accepting potency and structural parameters in the substrate specificity." Acta Biochimica Polonica 53, n.º 3 (21 de agosto de 2006): 569–76. http://dx.doi.org/10.18388/abp.2006_3329.

Texto completo

Resumen

We aimed to elucidate the role of electronic and structural parameters of nitroaromatic compounds in their two-electron reduction by NAD(P)H:quinone oxidoreductase (NQO1, DT-diaphorase, EC 1.6.99.2). The multiparameter regression analysis shows that the reactivity of nitroaromatic compounds (n=38) increases with an increase in their single-electron reduction potential and the torsion angle between nitrogroup(s) and the aromatic ring. The binding efficiency of nitroaromatics in the active center of NQO1 exerted a less evident role in their reactivity. The reduction of nitroaromatics is characterized by more positive entropies of activation than the reduction of quinones. This points to a less efficient electronic coupling of nitroaromatics with the reduced isoalloxazine ring of FAD, and may explain their lower reactivity as compared to quinones. Another important but poorly understood factor enhancing the reactivity of nitroaromatics is their ability to bind at the dicumarol/quinone binding site in the active center of NQO1.

Los estilos APA, Harvard, Vancouver, ISO, etc.

28

Miliukiene, Valė y Narimantas Čėnas. "Cytotoxicity of Nitroaromatic Explosives and their Biodegradation Products in Mice Splenocytes: Implications for their Immunotoxicity". Zeitschrift für Naturforschung C 63, n.º 7-8 (1 de agosto de 2008): 519–25. http://dx.doi.org/10.1515/znc-2008-7-809.

Texto completo

Resumen

Nitroaromatic explosives like 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenyl-Nmethyl- nitramine (tetryl) comprise an important group of toxic environmental pollutants, whose toxicity is mainly attributed to the flavoenzyme electrontransferase-catalyzed redox cycling of their free radicals (oxidative stress) and DT-diaphorase [NAD(P)H:quinone oxidoreductase, NQO1, EC 1. 6.99.2]-catalyzed formation of alkylating nitroso and/or hydroxylamine metabolites. Because of the incomprehensive data on the immunotoxic effects of nitroaromatic explosives, we have studied the structure-cytotoxicity relationships in the action of tetryl, TNT as well as its amino and hydroxylamino metabolites, and related nitroaromatic compounds towards mouse splenocyte cells. The protective effects of desferrioxamine and the antioxidant N,N′-diphenyl-p-phenylene diamine against the cytotoxicity of TNT and other nitroaromatics showed that the oxidative stress-type cytotoxicity mechanism takes place. In addition, the cytotoxicity of nitroaromatics is also partly prevented by an inhibitor of NQO1, dicumarol. The cytotoxicity of the amino metabolites of TNT is also partly prevented by α- naphthoflavone and isoniazide, which points to the involvement of cytochromes P-450 in their activation. In general the cytotoxicity of nitroaromatics in splenocytes increases with an increase in their single-electron reduction potential, Eζ . This points to the prevailing mechanism of the oxidative stress-type cytotoxicity. The obtained structure-activity relationship and the studies of other mammalian cell lines showed that the immunotoxic potential of nitroaromatic explosives may decrease in the order tetryl ≥TNT ≥ hydroxylamino metabolites of TNT > amino and diamino metabolites of TNT.

Los estilos APA, Harvard, Vancouver, ISO, etc.

29

Hromadová, Magdaléna, Romana Sokolová, Lubomír Pospíšil, Štěpánka Lachmanová, Nicolangelo Fanelli y Stefania Giannarelli. "Host–Guest interaction of pesticide bifenox with cyclodextrin molecules. An electrochemical study". Collection of Czechoslovak Chemical Communications 74, n.º 11-12 (2009): 1647–64. http://dx.doi.org/10.1135/cccc2009509.

Texto completo

Resumen

The reduction of nitroaromatic compound bifenox (methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate) was studied in aprotic solvents in the absence or presence of cyclodextrin (CD) molecules of different cavity sizes. βCD and γCD form complexes with bifenox in DMSO with the complex formation constants (5 ± 2) × 102 M–1 [βCD–bifenox] and (3 ± 1) × 102 M–1 [γCD–bifenox], respectively. Bifenox yields a relatively stable anion radical in dimethyl sulfoxide, which is further reduced at more negative potentials by an overall addition of three electrons and four protons to the corresponding phenylhydroxylamine. In the presence of βCD the first reduction wave of bifenox becomes irreversible, it is shifted towards more positive potentials and the uptake of more than one electron is observed (up to four electrons during the exhaustive electrolysis). The first reduction wave of bifenox is not affected by the addition of glucose confirming that a simple availability of protons from the OH groups is not the main factor in further transformation of anion radical in the presence of βCD. The complex formation with βCD facilitates the protonation and additionally protects the molecule from disintegration into 2,4-dichlorophenol. A yield of 2,4-dichlorophenol decreases in the order βCD, γCD and αCD, respectively.

Los estilos APA, Harvard, Vancouver, ISO, etc.

30

Lauzier, Annie, Claudia Goyer, Luc Ruest, Ryszard Brzezinski, Don L. Crawford y Carole Beaulieu. "Effect of amino acids on thaxtomin A biosynthesis by Streptomyces scabies". Canadian Journal of Microbiology 48, n.º 4 (1 de abril de 2002): 359–64. http://dx.doi.org/10.1139/w02-031.

Texto completo

Resumen

The regulatory effect of amino acids on the production of thaxtomin A, a phytotoxin produced by Streptomyces scabies, was investigated. Tryptophan had an important inhibitory effect on the toxin biosynthesis in all five strains of S. scabies tested. Two other aromatic amino acids (tyrosine and phenylalanine) also inhibited thaxtomin A biosynthesis, while aliphatic amino acids did not cause an important decline in thaxtomin A production. Methylation of tryptophan prevented or reduced the inhibitory effect on thaxtomin A biosynthesis. In spite of the inhibitory action of tryptophan and phenylalanine on thaxtomin A production, incorporation of these radiolabeled molecules into thaxtomin A confirmed that they are metabolic precursors for the biosynthesis of the phytotoxin.Key words: thaxtomin A, phytotoxin, Streptomyces scabies, common scab, nitroaromatic compounds, amino acids.

Los estilos APA, Harvard, Vancouver, ISO, etc.

31

Liu, Weitao, Wajid Ali, Ye Liu, Mingliang Li y Ziwei Li. "Sensitive Detection of Trace Explosives by a Self-Assembled Monolayer Sensor". Micromachines 14, n.º 12 (29 de noviembre de 2023): 2179. http://dx.doi.org/10.3390/mi14122179.

Texto completo

Resumen

Fluorescence probe technology holds great promise in the application of trace explosive detection due to its high sensitivity, fast response speed, good selectivity, and low cost. In this work, a designed approach has been employed to prepare the TPE-PA-8 molecule, utilizing the classic aggregation-induced emission (AIE) property of 1,1,2,2-tetraphenylethene (TPE), for the development of self-assembled monolayers (SAMs) targeting the detection of trace nitroaromatic compound (NAC) explosives. The phosphoric acid acts as an anchoring unit, connecting to TPE through an alkyl chain of eight molecules, which has been found to play a crucial role in promoting the aggregation of TPE luminogens, leading to the enhanced light-emission property and sensing performance of SAMs. The SAMs assembled on Al2O3-deposited fiber film exhibit remarkable detection performances, with detection limits of 0.68 ppm, 1.68 ppm, and 2.5 ppm for trinitrotoluene, dinitrotoluene, and nitrobenzene, respectively. This work provides a candidate for the design and fabrication of flexible sensors possessing the high-performance and user-friendly detection of trace NACs.

Los estilos APA, Harvard, Vancouver, ISO, etc.

32

Xu, Liming, Jing Wu, Weiqiang Zhou, Fengxing Jiang, Hui Zhang, Rui Wang, Aiqin Liang, Jingkun Xu y Xuemin Duan. "Using nitroaromatic fused-heterocycle molecules as nitrogen source to hugely boost the capacitance performance of graphene". Electrochimica Acta 354 (septiembre de 2020): 136703. http://dx.doi.org/10.1016/j.electacta.2020.136703.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

33

Karikalan, Natarajan, Subbiramaniyan Kubendhiran, Shen-Ming Chen, Periyasamy Sundaresan y Raj Karthik. "Electrocatalytic reduction of nitroaromatic compounds by activated graphite sheets in the presence of atmospheric oxygen molecules". Journal of Catalysis 356 (diciembre de 2017): 43–52. http://dx.doi.org/10.1016/j.jcat.2017.09.012.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

34

Osorio, Manuel I., Nicolás Bruna, Víctor García, Lisdelys González-Rodríguez, Matías S. Leal, Francisco Salgado, Matías Vargas-Reyes, Fernando González-Nilo, José M. Pérez-Donoso y Osvaldo Yáñez. "Structural Factors That Determine the Activity of the Xenobiotic Reductase B Enzyme from Pseudomonas putida on Nitroaromatic Compounds". International Journal of Molecular Sciences 24, n.º 1 (26 de diciembre de 2022): 400. http://dx.doi.org/10.3390/ijms24010400.

Texto completo

Resumen

Xenobiotic reductase B (XenB) catalyzes the reduction of the aromatic ring or nitro groups of nitroaromatic compounds with methyl, amino or hydroxyl radicals. This reaction is of biotechnological interest for bioremediation, the reuse of industrial waste or the activation of prodrugs. However, the structural factors that explain the binding of XenB to different substrates are unknown. Molecular dynamics simulations and quantum mechanical calculations were performed to identify the residues involved in the formation and stabilization of the enzyme/substrate complex and to explain the use of different substrates by this enzyme. Our results show that Tyr65 and Tyr335 residues stabilize the ligands through hydrophobic interactions mediated by the aromatic rings of these aminoacids. The higher XenB activity determined with the substrates 1,3,5-trinitrobenzene and 2,4,6-trinitrotoluene is consistent with the lower energy of the highest occupied molecular orbital (LUMO) orbitals and a lower energy of the homo orbital (LUMO), which favors electrophile and nucleophilic activity, respectively. The electrostatic potential maps of these compounds suggest that the bonding requires a large hydrophobic region in the aromatic ring, which is promoted by substituents in ortho and para positions. These results are consistent with experimental data and could be used to propose point mutations that allow this enzyme to process new molecules of biotechnological interest.

Los estilos APA, Harvard, Vancouver, ISO, etc.

35

Bailey-Darland, Sullivan, Taylor D. Krueger y Chong Fang. "Ultrafast Spectroscopies of Nitrophenols and Nitrophenolates in Solution: From Electronic Dynamics and Vibrational Structures to Photochemical and Environmental Implications". Molecules 28, n.º 2 (6 de enero de 2023): 601. http://dx.doi.org/10.3390/molecules28020601.

Texto completo

Resumen

Nitrophenols are a group of small organic molecules with significant environmental implications from the atmosphere to waterways. In this work, we investigate a series of nitrophenols and nitrophenolates, with the contrasting ortho-, meta-, and para-substituted nitro group to the phenolic hydroxy or phenolate oxygen site (2/3/4NP or NP−), implementing a suite of steady-state and time-resolved spectroscopic techniques that include UV/Visible spectroscopy, femtosecond transient absorption (fs-TA) spectroscopy with probe-dependent and global analysis, and femtosecond stimulated Raman spectroscopy (FSRS), aided by quantum calculations. The excitation-dependent (400 and 267 nm) electronic dynamics in water and methanol, for six protonated or deprotonated nitrophenol molecules (three regioisomers in each set), enable a systematic investigation of the excited-state dynamics of these functional “nanomachines” that can undergo nitro-group twisting (as a rotor), excited-state intramolecular or intermolecular proton transfer (donor–acceptor, ESIPT, or ESPT), solvation, and cooling (chromophore) events on molecular timescales. In particular, the meta-substituted compound 3NP or 3NP− exhibits the strongest charge-transfer character with FSRS signatures (e.g., C–N peak frequency), and thus, does not favor nitroaromatic twist in the excited state, while the ortho-substituted compound 2NP can undergo ESIPT in water and likely generate nitrous acid (HONO) after 267 nm excitation. The delineated mechanistic insights into the nitro-substituent-location-, protonation-, solvent-, and excitation-wavelength-dependent effects on nitrophenols, in conjunction with the ultraviolet-light-induced degradation of 2NP in water, substantiates an appealing discovery loop to characterize and engineer functional molecules for environmental applications.

Los estilos APA, Harvard, Vancouver, ISO, etc.

36

Dong, Bao-Xia, Yong-Mei Pan, Wen-Long Liu y Yun-Lei Teng. "An Ultrastable Luminescent Metal–Organic Framework for Selective Sensing of Nitroaromatic Compounds and Nitroimidazole-Based Drug Molecules". Crystal Growth & Design 18, n.º 1 (4 de diciembre de 2017): 431–40. http://dx.doi.org/10.1021/acs.cgd.7b01430.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

37

Boopathy, R. y C. F. Kulpa. "Nitroaromatic compounds serve as nitrogen source for Desulfovibrio sp. (B strain)". Canadian Journal of Microbiology 39, n.º 4 (1 de abril de 1993): 430–33. http://dx.doi.org/10.1139/m93-062.

Texto completo

Resumen

A sulfate-reducing bacterium, Desulfovibrio sp. (B strain), isolated from a continuous anaerobic digester, used various nitroaromatic compounds such as 2,4-dinitrophenol, 2,4-dinitrotoluene, and 2,6-dinitrotoluene as sole nitrogen sources for growth and also used these compounds as electron acceptors in the absence of sulfate in the culture medium. More than 60% of the nitroaromatics were transformed within 6 days of incubation. The organism also used aniline as sole nitrogen source, but not as an electron acceptor. Desulfovibrio sp. (B strain) did not use nitroaromatics as sole source of carbon and energy. The nitro groups in the aromatic ring were reduced and reductively deaminated to ammonia, which was used as nitrogen source, leaving the aromatic ring intact. Even though this organism did not degrade the nitroaromatics completely, it may be useful in degrading nitroaromatics in contaminated soil and water containing other aromatic degraders in a syntrophic culture system under anaerobic conditions.Key words: anaerobic process, biotransformation, nitroaromatics, aniline, Desulfovibrio sp.

Los estilos APA, Harvard, Vancouver, ISO, etc.

38

Shao, Juxiang, Xinlu Cheng y Xiangdong Yang. "Density functional calculations of bond dissociation energies for removal of the nitrogen dioxide moiety in some nitroaromatic molecules". Journal of Molecular Structure: THEOCHEM 755, n.º 1-3 (noviembre de 2005): 127–30. http://dx.doi.org/10.1016/j.theochem.2005.08.008.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

39

Yang, Hong, Mi Zhou, Huarong Li, Tong Wei, Can Tang, Yang Zhou y Xinping Long. "Effects of Low-level Lipid Peroxidation on the Permeability of Nitroaromatic Molecules across a Membrane: A Computational Study". ACS Omega 5, n.º 10 (6 de marzo de 2020): 4798–806. http://dx.doi.org/10.1021/acsomega.9b03462.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

40

Marshall, A., A. Clark, K. W. D. Ledingham, J. Sander y R. P. Singhal. "Laser ionisation studies of nitroaromatic and NOx(x = 1 or 2) molecules in the region 224–238 nm". International Journal of Mass Spectrometry and Ion Processes 125, n.º 2-3 (junio de 1993): R21—R26. http://dx.doi.org/10.1016/0168-1176(93)80052-g.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

41

Marchisio, Andrea y Jean-Marc Tulliani. "Semiconducting Metal Oxides Nanocomposites for Enhanced Detection of Explosive Vapors". Ceramics 1, n.º 1 (25 de junio de 2018): 98–119. http://dx.doi.org/10.3390/ceramics1010009.

Texto completo

Resumen

In recent years, the detection of ultratraces of nitroaromatic compounds (NACs), such as 2,4,6-trinitrotoluene (TNT), has gained considerable attention due to associated problems related to environment, security against terrorists and health. The principle of NACs detection is simple since any explosive emits a rather small, but detectable number of molecules. Thus, numerous detection techniques have been developed throughout the years, but their common limitations are rather large sizes and weights, high power consumption, unreliable detection with false alarms, insufficient sensitivity and/or chemical selectivity, and hyper-sensitivity to mechanical influences associated with very high price. Thus, there is a strong need of cheap, rapid, sensitive, and simple analytical methods for the detection and monitoring of these explosives in air. Semiconducting metal oxides (SMOs) allow the preparation of gas sensors able to partially or totally overcome these drawbacks, and this paper aims to shortly review the most recent SMOs nanocomposites able to sense explosives.

Los estilos APA, Harvard, Vancouver, ISO, etc.

42

Zhang, Linyuan, Jung Hyun Son, Zhe Bai, Wei Zhang, Ling Li, Lina Wang y Jianmin Chen. "Characterizing Atmospheric Brown Carbon and Its Emission Sources during Wintertime in Shanghai, China". Atmosphere 13, n.º 6 (20 de junio de 2022): 991. http://dx.doi.org/10.3390/atmos13060991.

Texto completo

Resumen

Atmospheric brown carbon (BrC) is a kind of organic aerosol that efficiently absorbs ultraviolet-visible light and has an impact on climate forcing. We conducted an in-depth field study on ambient aerosols at a monitoring point in Shanghai, China, aiming to investigate the potential emission sources, molecular structures, and the contributions to light absorptions of ambient BrC chromophores. The results indicated that nine molecules were identified as nitroaromatic compounds, five of which (4-nitrophenol, 4-nitrocatechol, 2-nitro-1-naphthol, 3-methyl-4-nitrocatechol, and 2-methyl-4-nitrophenol) usually came from biomass burning or were produced from the photo-oxidation of anthropogenic volatile organic compounds (e.g., toluene, benzene) under high-NOx conditions. 4-nitrophenol was the strongest BrC chromophore and accounted for 13% of the total aerosol light absorption at λ = 365 nm. The estimated light absorption of black carbon was approximately three times the value of methanol-soluble BrC at λ = 365 nm. The ratios of K+/OC and K+/EC, and the correlations with WSOC, OC, HULIS-C and K+, and MAE values of methanol extracts also indicated that the primary emissions from biomass burning contributed more aerosol light absorption compared to the secondary formation during the wintertime in Shanghai. Therefore, biomass burning control is still the most urgent strategy for reducing BrC in Shanghai.

Los estilos APA, Harvard, Vancouver, ISO, etc.

43

Pajuelo-Corral, Oier, Laura Razquin-Bobillo, Sara Rojas, Jose Angel García, Duane Choquesillo-Lazarte, Alfonso Salinas-Castillo, Ricardo Hernández, Antonio Rodríguez-Diéguez y Javier Cepeda. "Lanthanide(III) Ions and 5-Methylisophthalate Ligand Based Coordination Polymers: An Insight into Their Photoluminescence Emission and Chemosensing for Nitroaromatic Molecules". Nanomaterials 12, n.º 22 (11 de noviembre de 2022): 3977. http://dx.doi.org/10.3390/nano12223977.

Texto completo

Resumen

The work presented herein reports on the synthesis, structural and physico-chemical characterization, luminescence properties and luminescent sensing activity of a family of isostructural coordination polymers (CPs) with the general formula [Ln2(μ4-5Meip)3(DMF)]n (where Ln(III) = Sm (1Sm), Eu (2Eu), Gd (3Gd), Tb (4Tb) and Yb (5Yb) and 5Meip = 5-methylisophthalate, DMF = N,N-dimethylmethanamide). Crystal structures consist of 3D frameworks tailored by the linkage between infinite lanthanide(III)-carboxylate rods by means of the tetradentate 5Meip ligands. Photoluminescence measurements in solid state at variable temperatures reveal the best-in-class properties based on the capacity of the 5Meip ligand to provide efficient energy transfers to the lanthanide(III) ions, which brings intense emissions in both the visible and near-infrared (NIR) regions. On the one hand, compound 5Yb displays characteristic lanthanide-centered bands in the NIR with sizeable intensity even at room temperature. Among the compounds emitting in the visible region, 4Tb presents a high QY of 63%, which may be explained according to computational calculations. At last, taking advantage of the good performance as well as high chemical and optical stability of 4Tb in water and methanol, its sensing capacity to detect 2,4,6-trinitrophenol (TNP) among other nitroaromatic-like explosives has been explored, obtaining high detection capacity (with Ksv around 105 M−1), low limit of detection (in the 10−6–10−7 M) and selectivity among other molecules (especially in methanol).

Los estilos APA, Harvard, Vancouver, ISO, etc.

44

Ahn, Hyun y Suhyuk Choi. "Membraneless Ionic Liquid Droplet Nanoprobe for Vapor Sensing and Gas Phase Scanning Electrochemical Microscopy". ECS Meeting Abstracts MA2023-02, n.º 62 (22 de diciembre de 2023): 2945. http://dx.doi.org/10.1149/ma2023-02622945mtgabs.

Texto completo

Resumen

Gas phase sensing of volatile chemicals is a critical area of research relevant to biomedical diagnosis and environmental hazard assessment. Among various types of sensors, electrochemical sensors garnered attention as cost-effective and portable methods. Most electrochemical sensors needed the membrane to prevent solvent evaporation for detecting the gaseous species. However, the presence of the membrane induced slow response time due to the penetration of gas molecules through the membrane. To improve the systems, a membraneless ionic liquid droplet nanoprobe was developed. Gaseous species can permeate the thin ionic liquid layer, which was also used as the electrolytes, and react on the electrode in extremely fast response. Furthermore, nano-sized electrode makes available to detect sensitively with low charging capacitance. Using the probe type form factor, application to gas phase scanning electrochemical microscopy (SECM) was attempted with high spatial resolution. Oxygen detection, the most commonly studied, was implemented for the first application of the ionic liquid nanoprobe. The limit of detection of this probe was 13 ppm, which is extremely good for electrochemical oxygen sensors. Also, the fast response (< 0.1 s) made the mapping of oxygen concentration using SECM. The nanoprobe showed more than a hundred times better spatial resolution (several micrometer scale) than the previous gas phase SECM study mapping the oxygen. As the application of this oxygen probe, Li-air battery analysis can be conducted. Oxygen was used in the reaction at the cathode of the Li-air battery. As mapping the oxygen concentration above the cathode, It is expected that structural causes for the irreversibility at the cathode can also be found. As oxygen sensing, other electrochemical active gaseous species can be detected with the electrochemical sensor. Trinitrotoluene is a well-known explosive compound, and it can be detected in electrochemistry. Due to its low vapor pressure, di-nitroaromatic compounds, like dinitrotoluene (DNT), dinitrobenzene (DNB), and dinitrophenol (DNP), were used as explosive footprints, which have higher vapor pressure and have often been identified as marker molecules. Using our ionic liquid nanoprobe, we developed the nitroaromatic compounds (NACs) sensor for real-time detection of trace vapors, without any sample pre-treatment and at room temperature. Furthermore, in a simulated airport carousel, real-time and preemptive NACs detection was demonstrated with fast response time. As oxygen detection, gas phase SECM was conducted and 3D mapping capability of the differential vapor pressure was demonstrated, exercising the potential of the NACs nanoprobe in locating the source of an explosive risk. With the sensitive sensing performance of nanoprobe, it can be used as breath analysis. There are several biomarkers to indicate certain diseases. For example, acetone is a representative biomarker of diabetes. Using this sensing platform, acetone sensing was implemented, and it may be used for the initial detection of diabetes.

Los estilos APA, Harvard, Vancouver, ISO, etc.

45

Nivinskas, H., R. L. Koder, Z. Anusevicius, J. Sarlauskas, A. F. Miller y N. Cenas. "Two-electron reduction of nitroaromatic compounds by Enterobacter cloacae NAD(P)H nitroreductase: description of quantitative structure-activity relationships." Acta Biochimica Polonica 47, n.º 4 (31 de diciembre de 2000): 941–49. http://dx.doi.org/10.18388/abp.2000_3949.

Texto completo

Resumen

Enterobacter cloacae NAD(P)H:nitroreductase catalyzes the reduction of a series of nitroaromatic compounds with steady-state bimolecular rate constants (kcat/Km) ranging from 10(4) M(-1) s(-1) to 10(7) M(-1) s(-1), and oxidizing 2 moles NADH per mole mononitrocompound. Oxidation of excess NADH by polynitrobenzenes including explosives 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenyl-N-methylnitramine (tetryl), has been observed as a slower secondary process, accompanied by O2 consumption. This type of 'redox cycling' was not related to reactions of nitroaromatic anion-radicals, but was caused by the autoxidation of relatively stable reaction products. The logs kcat/Km of all the compounds examined exhibited parabolic dependence on their enthalpies of single-electron- or two-electron (hydride) reduction, obtained by quantum mechanical calculations. This type of quantitative structure-activity relationships shows that the reactivity of nitroaromatics towards E. cloacae nitroreductase depends mainly on their hydride accepting properties, but not on their particular structure, and does not exclude the possibility of multistep hydride transfer.

Los estilos APA, Harvard, Vancouver, ISO, etc.

46

Marshall, A., A. Clark, R. M. Deas, C. Kosmidis, K. W. D. Ledingham, W. Peng y R. P. Singhal. "Sensitive atmospheric pressure detection of nitroaromatic compounds and NO x (x= 1,2) molecules in an ionization chamber using resonance-enhanced multi-photon ionization". Analyst 119, n.º 8 (1994): 1719. http://dx.doi.org/10.1039/an9941901719.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

47

Čėnas, Narimantas, Aušra Nemeikaitė-Čėnienė y Lidija Kosychova. "Single- and Two-Electron Reduction of Nitroaromatic Compounds by Flavoenzymes: Mechanisms and Implications for Cytotoxicity". International Journal of Molecular Sciences 22, n.º 16 (8 de agosto de 2021): 8534. http://dx.doi.org/10.3390/ijms22168534.

Texto completo

Resumen

Nitroaromatic compounds (ArNO2) maintain their importance in relation to industrial processes, environmental pollution, and pharmaceutical application. The manifestation of toxicity/therapeutic action of nitroaromatics may involve their single- or two-electron reduction performed by various flavoenzymes and/or their physiological redox partners, metalloproteins. The pivotal and still incompletely resolved questions in this area are the identification and characterization of the specific enzymes that are involved in the bioreduction of ArNO2 and the establishment of their contribution to cytotoxic/therapeutic action of nitroaromatics. This review addresses the following topics: (i) the intrinsic redox properties of ArNO2, in particular, the energetics of their single- and two-electron reduction in aqueous medium; (ii) the mechanisms and structure-activity relationships of reduction in ArNO2 by flavoenzymes of different groups, dehydrogenases-electrontransferases (NADPH:cytochrome P-450 reductase, ferredoxin:NADP(H) oxidoreductase and their analogs), mammalian NAD(P)H:quinone oxidoreductase, bacterial nitroreductases, and disulfide reductases of different origin (glutathione, trypanothione, and thioredoxin reductases, lipoamide dehydrogenase), and (iii) the relationships between the enzymatic reactivity of compounds and their activity in mammalian cells, bacteria, and parasites.

Los estilos APA, Harvard, Vancouver, ISO, etc.

48

Wen, Hai-Ying, Li-Bin Pan, Shu-Rong Ma, Xin-Yu Yang, Jia-Chun Hu, Hai-Fan Zhao, Zeng-Qiang Gao, Yu-Hui Dong, Yan Wang y Heng Zhang. "Structural basis for the transformation of the traditional medicine berberine by bacterial nitroreductase". Acta Crystallographica Section D Structural Biology 78, n.º 10 (27 de septiembre de 2022): 1273–82. http://dx.doi.org/10.1107/s2059798322008373.

Texto completo

Resumen

The bacterial nitroreductases (NRs) NfsB and NfsA are conserved homodimeric FMN-dependent flavoproteins that are responsible for the reduction of nitroaromatic substrates. Berberine (BBR) is a plant-derived isoquinoline alkaloid with a large conjugated ring system that is widely used in the treatment of various diseases. It was recently found that the gut microbiota convert BBR into dihydroberberine (dhBBR, the absorbable form) mediated by bacterial NRs. The molecular basis for the transformation of BBR by the gut microbiota remains unclear. Here, kinetic studies showed that NfsB from Escherichia coli (EcNfsB), rather than EcNfsA, is responsible for the conversion of BBR to dhBBR in spite of a low reaction rate. The crystal structure of the EcNfsB–BBR complex showed that BBR binds into the active pocket at the dimer interface, and its large conjugated plane stacks above the plane of the FMN cofactor in a nearly parallel orientation. BBR is mainly stabilized by π-stacking interactions with both neighboring aromatic residues and FMN. Structure-based mutagenesis studies further revealed that the highly conserved Phe70 and Phe199 are important residues for the conversion of BBR. The structure revealed that the C6 atom of BBR (which receives the hydride) is ∼7.5 Å from the N5 atom of FMN (which donates the hydride), which is too distant for hydride transfer. Notably, several well ordered water molecules make hydrogen-bond/van der Waals contacts with the N1 atom of BBR in the active site, which probably donate protons in conjunction with electron transfer from FMN. The structure–function studies revealed the mechanism for the recognition and binding of BBR by bacterial NRs and may help to understand the conversion of BBR by the gut microbiota.

Los estilos APA, Harvard, Vancouver, ISO, etc.

49

Lesanavičius, Mindaugas, Daisuke Seo, Gintarė Maurutytė y Narimantas Čėnas. "Redox Properties of Bacillus subtilis Ferredoxin:NADP+ Oxidoreductase: Potentiometric Characteristics and Reactions with Pro-Oxidant Xenobiotics". International Journal of Molecular Sciences 25, n.º 10 (14 de mayo de 2024): 5373. http://dx.doi.org/10.3390/ijms25105373.

Texto completo

Resumen

Bacillus subtilis ferredoxin:NADP+ oxidoreductase (BsFNR) is a thioredoxin reductase-type FNR whose redox properties and reactivity with nonphysiological electron acceptors have been scarcely characterized. On the basis of redox reactions with 3-acetylpyridine adenine dinucleotide phosphate, the two-electron reduction midpoint potential of the flavin adenine dinucleotide (FAD) cofactor was estimated to be −0.240 V. Photoreduction using 5-deazaflavin mononucleotide (5-deazaFMN) as a photosensitizer revealed that the difference in the redox potentials between the first and second single-electron transfer steps was 0.024 V. We examined the mechanisms of the reduction of several different groups of non-physiological electron acceptors catalyzed by BsFNR. The reactivity of quinones and aromatic N-oxides toward BsFNR increased when increasing their single-electron reduction midpoint redox potentials. The reactivity of nitroaromatic compounds was lower due to their lower electron self-exchange rate, but it exhibited the same trend. A mixed single- and two-electron reduction reaction was characteristic of quinones, whereas reactions involving nitroaromatics proceeded exclusively via the one-electron reduction reaction. The oxidation of FADH• to FAD is the rate-limiting step during the oxidation of fully reduced FAD. The calculated electron transfer distances in the reaction with nitroaromatics were close to those of other FNRs including the plant-type enzymes, thus demonstrating their similar active site accessibility to low-molecular-weight oxidants despite the fundamental differences in their structures.

Los estilos APA, Harvard, Vancouver, ISO, etc.

50

Lesanavičius, Mindaugas, Daisuke Seo y Narimantas Čėnas. "Thioredoxin Reductase-Type Ferredoxin: NADP+ Oxidoreductase of Rhodopseudomonas palustris: Potentiometric Characteristics and Reactions with Nonphysiological Oxidants". Antioxidants 11, n.º 5 (19 de mayo de 2022): 1000. http://dx.doi.org/10.3390/antiox11051000.

Texto completo

Resumen

Rhodopseudomonas palustris ferredoxin:NADP+ oxidoreductase (RpFNR) belongs to a novel group of thioredoxin reductase-type FNRs with partly characterized redox properties. Based on the reactions of RpFNR with the 3-acetylpyridine adenine dinucleotide phosphate redox couple, we estimated the two-electron reduction midpoint potential of the FAD cofactor to be −0.285 V. 5-Deaza-FMN-sensitized photoreduction revealed −0.017 V separation of the redox potentials between the first and second electron transfer events. We examined the mechanism of oxidation of RpFNR by several different groups of nonphysiological electron acceptors. The kcat/Km values of quinones and aromatic N-oxides toward RpFNR increase with their single-electron reduction midpoint potential. The lower reactivity, mirroring their lower electron self-exchange rate, is also seen to have a similar trend for nitroaromatic compounds. A mixed single- and two-electron reduction was characteristic of quinones, with single-electron reduction accounting for 54% of the electron flux, whereas nitroaromatics were reduced exclusively via single-electron reduction. It is highly possible that the FADH· to FAD oxidation reaction is the rate-limiting step during the reoxidation of reduced FAD. The calculated electron transfer distances in the reaction with quinones and nitroaromatics were close to those of Anabaena and Plasmodium falciparum FNRs, thus demonstrating their similar “intrinsic” reactivity.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Artículos de revistas sobre el tema "Nitroaromatic molecules"

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros