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Upstream product

• 488-17-5 3-methylbenzene-1,2-diol 
• 534-52-1 6-methyl-2,4-dinitrophenol 
• 78312-28-4 5-nitro-2,3-dimethoxytoluene 

Relevant academic research and scientific papers

Development of a liquid chromatographic method based on ultraviolet-visible and electrospray ionization mass spectrometric detection for the identification of nitrocatechols and related tracers in biomass burning atmospheric organic aerosol

Rationale: Studying the chemical composition of biomass burning aerosol (BBA) is very important in order to assess their impact on the climate and the biosphere. In the present study, we focus on the characterization of some newly recognized biomass burning aerosol tracers including methyl nitrocatechols, nitroguaiacols and 4-nitrocatechol, but also on nitrophenols, methyl nitrophenols and nitrosalicylic acids, using liquid chromatography tandem mass spectrometry. Methods: For the purpose of their separation and detection in atmospheric aerosol, a new chromatographic method was initially developed based on reversed-phase chromatography coupled with ultraviolet/visible (UV/Vis) detection. The method was afterwards transferred to a liquid chromatography/electrospray ionization linear ion trap mass spectrometry (LC/ESI-LITMS) system in order to identify the targeted analytes in winter aerosol from the city of Maribor, Slovenia, using their chromatographic retention times and characteristic (-)ESI product ion (MS2) spectra. Results: The fragmentation patterns of analytes obtained with LITMS are presented. Additional nitro-aromatic compounds (m/z 168 and 182) closely related to the targeted nitrocatechols and nitroguaiacols were detected in the aerosol. According to their MS2 spectra these compounds could be attributed to methyl homologues of methyl nitrocatechols and nitroguaiacols. Conclusions: The proposed LC/MS method results in a better separation and specificity for the targeted analytes. Several nitro-aromatic compounds were detected in urban BBA. The LC/MS peak intensity of the newly detected methyl nitrocatechols and nitroguaiacols is comparable to that of the methyl nitrocatechols, which also qualifies them as suitable molecular tracers for secondary biomass burning aerosol.

IMIDAXOPYROLONE COMPOUND AND APPLICATION THEREOF

Disclosed is a novel class of MDM2-p53 inhibitor compounds having an imidaxopyrolone structure, and specifically disclosed are compounds represented by formulas (I-1) and (I-2) and pharmaceutically acceptable salts thereof. (I-1), (I-2)

Nitrocatechols versus nitrocatecholamines as novel competitive inhibitors of neuronal nitric oxide synthase: Lack of the aminoethyl side chain determines loss of tetrahydrobiopterin-antagonizing properties

6-Nitrocatecholamines were recently described as novel neuronal nitric oxide synthase inhibitors competing with both L-arginine and tetrahydrobiopterin (BH4). We report now that simple nitrocatechols are also competitive inhibitors, lacking however BH4-antagonizing properties. It is argued that 6-nitrocatecholamines interact with the L-arginine- and BH4-binding sites through the nitrocatechol and aminoethyl moieties, respectively.

Comparison of Substituted 2-Nitrophenol Degradation by Enzyme Extracts and Intact Cells

The first catabolic pathway enzyme, nitrophenol oxygenase, transforms o-nitrophenol (ONP) to catechol. Thirteen of 16 substituted nitrophenols tested were actively transformed by both enzyme preparations and intact cells yielding a wide range of Km (Ks) and Vmax. Individual chemicals in binary mixtures demonstrated competitive inhibition. Chemical and physical characteristics (electron withdrawal, size, and position of substitution on the 2-nitrophenol ring) affected degradation kinetics. The strongest correlation were between Km or Vmax values and electron withdrawal, though there was also evidence for effects relating to position and size of substitution on the aromatic ring. Kinetic parameters determined for enzyme preparations did not correlate to those determined for intact cells. Though enzyme reactivity ultimately determined whether a given chemical would be transformed, the transformation by intact cells was apparently affected by factors other than those directly impacting the initial catabolic enzyme.