نتایج جستجو برای: pyrazines
تعداد نتایج: 236 فیلتر نتایج به سال:
BACKGROUND Interannual variability in precipitation, particularly drought, can affect lignocellulosic crop biomass yields and composition, and is expected to increase biofuel yield variability. However, the effect of precipitation on downstream fermentation processes has never been directly characterized. In order to investigate the impact of interannual climate variability on biofuel productio...
The pyrazine ring is a part of many polycyclic compounds of biological and/or industrial significance; examples are quinoxalines, phenazines, and bio-luminescent natural products pteridines, flavins and their derivatives. All these compounds are characterized by a low lying unoccupied π-molecular orbital and by the ability to act as bridging ligand. Due to these two properties 1,4-diazines, and...
The unique flavor of peanuts that develops during roasting is the primary driving force for consumption peanut products. Although rarely consumed raw, raw state contains precursors involved in transformations lead to distinct development roasted peanuts. Volatile compounds extracted from headspace above and samples runner virginia market types by solid phase microextraction were characterized u...
We report herein the microwave assisted synthesis, without solvents and catalysts, of 6-substituted quinoxalines and 7-substituted pyrido[2,3b]pyrazines. The compounds were obtained in good yields and short reaction times using the mentioned procedure and two new structures are reported. A complete ¹H- and ¹³C-NMR assignment was performed using 1D and 2D-NMR. Additionally, an in vitro screening...
Monomers with large surface area and high quantum yield, that is fluorescent flippers, have been engineered into twisted push-pull oligomers to create membrane probes with high mechanosensitivity and long fluorescence lifetime. Here, the synthesis and characterization of thieno[3,4]pyrazines and 2,1,3-benzothiadiazoles are described in comparison with the original dithienothiophene S,S-dioxides...
Profiles of volatile metabolites of 150 urine samples from normal individuals and 40 samples from subjects with diabetes mellitus have been studied by gas chromatography and mass spectrometry. The technique involves adsorption of the urinary headspace volatiles on Tenax GC, heat desorption with helium, trapping on a cooled precolumn, and chromatography on 100-m X 0.50-mm i.d. nickel columns. In...
"Padrón-type" peppers are a small variety of Capsicum annuum cultivated mainly in Galicia, Spain. To compare the effects of freezing and freeze-drying on the volatile components of Padrón-type peppers, preserved samples are analyzed by means of dynamic headspace sampling on an adsorbent followed by microwave desorption into a gas chromatograph equipped with a mass spectrometric detector. Sixty-...
Copper-catalyzed aerobic oxidative C-H/N-H coupling between simple ketones and diamines was developed toward the synthesis of a variety of pyrazines. Various substituted ketones were compatible for this transformation. Preliminary mechanistic investigations indicated that radical species were involved. X-ray absorption fine structure experiments elucidated that the Cu(II) species 5 coordinated ...
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