We study the photodissociation dynamics of nitrous oxide using the time-sliced ion veloc- ity imaging technique at three photolysis wavelengths of 134.20, 135.30, and 136.43 nm. The O（^1Sj=0）＋N2（XI∑g＋） product ...We study the photodissociation dynamics of nitrous oxide using the time-sliced ion veloc- ity imaging technique at three photolysis wavelengths of 134.20, 135.30, and 136.43 nm. The O（^1Sj=0）＋N2（XI∑g＋） product channels were investigated by measuring images of the O（iSj=0） products. Vibrational states of N2（XI∑g＋） products were fully resolved in the images. Product total kinetic energy releases （TKER） and the branching ratios of vibrational states of N2 products were determined. It is found that the most populated vibrational states of N2 products are v--2 and v--3. The angular anisotropy parameters （8 values） were also derived. The β values are very close to 2 at low vibrational states of the correlated N2 （X1 ∑g＋） products at all three photolysis wavelengths, and gradually decrease to about 1.4 at v--7. This indicates the dissociation is mainly through a parallel transition state to form products at lower vibrational states, and the highly vibrational exited products are from a more bent configuration. This is consistent with the observed shift of the most intense rotational structure in the TKER as the vibrational quantum number increases.展开更多
The effects of carbon （C） and nitrogen （N） sources on N utilization and biosynthesis of amino acids were examined in the germinating spores of the arbuscular mycorrhizal （AM） fungus Glomus intraradices Schenck ...The effects of carbon （C） and nitrogen （N） sources on N utilization and biosynthesis of amino acids were examined in the germinating spores of the arbuscular mycorrhizal （AM） fungus Glomus intraradices Schenck ＆ Smith after exposure to various N substrates, CO2, glucose, and/or root exudates. The N uptake and de novo biosynthesis of amino acids were analyzed using stable isotopic labeling with mass spectrometric detection. High-performance liquid chromatography-based analysis was used to measure amino acid levels. In the absence of exogenous N sources and in the presence of 25 mL L^-1 CO2, the germinating AM fungal spores utilized internal N storage as well as C skeletons derived from the degradation of storage lipids to biosynthesize the free amino acids, in which serine and glycine were produced predominantly. The concentrations of internal amino acids increased gradually as the germination time increased from 0 to 1 or 2 weeks. However, asparagine and glutamine declined to the low levels; both degraded to provide the biosynthesis of other amino acids with C and N donors. The availability of exogenous inorganic N （ammonium and nitrate） and organic N （urea, arginine, and glutamine） to the AM fungal spores using only CO2 for germination generated more than 5 times more internal free amino acids than those in the absence of exogenous N. A supply of exogenous nitrate to the AM fungal spores with only CO2 gave rise to more than 10 times more asparagine than that without exogenous N. In contrast, the extra supply of exogenous glucose to the AM fungal spores generated a significant enhancement in the uptake of exogenous N sources, with more than 3 times more free amino acids being produced than those supplied with only exogenous CO2. Meanwhile, arginine was the most abundant free amino acid produced and it was incorporated into the proteins of AM funsal spores to serve as an N storage compound.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.21403207 and No.21473173）, the China Postdoctoral Science Foundation （No.2014M551810 and No.2015TS0659）, and the University of Science and Technology of China. We thank Jia-yue Yang, Tian-gang Yang and Wei-qing Zhang for stimulated discussions.
文摘We study the photodissociation dynamics of nitrous oxide using the time-sliced ion veloc- ity imaging technique at three photolysis wavelengths of 134.20, 135.30, and 136.43 nm. The O（^1Sj=0）＋N2（XI∑g＋） product channels were investigated by measuring images of the O（iSj=0） products. Vibrational states of N2（XI∑g＋） products were fully resolved in the images. Product total kinetic energy releases （TKER） and the branching ratios of vibrational states of N2 products were determined. It is found that the most populated vibrational states of N2 products are v--2 and v--3. The angular anisotropy parameters （8 values） were also derived. The β values are very close to 2 at low vibrational states of the correlated N2 （X1 ∑g＋） products at all three photolysis wavelengths, and gradually decrease to about 1.4 at v--7. This indicates the dissociation is mainly through a parallel transition state to form products at lower vibrational states, and the highly vibrational exited products are from a more bent configuration. This is consistent with the observed shift of the most intense rotational structure in the TKER as the vibrational quantum number increases.
基金Supported by the National Natural Science Foundation of China (No. 30970101)
文摘The effects of carbon （C） and nitrogen （N） sources on N utilization and biosynthesis of amino acids were examined in the germinating spores of the arbuscular mycorrhizal （AM） fungus Glomus intraradices Schenck ＆ Smith after exposure to various N substrates, CO2, glucose, and/or root exudates. The N uptake and de novo biosynthesis of amino acids were analyzed using stable isotopic labeling with mass spectrometric detection. High-performance liquid chromatography-based analysis was used to measure amino acid levels. In the absence of exogenous N sources and in the presence of 25 mL L^-1 CO2, the germinating AM fungal spores utilized internal N storage as well as C skeletons derived from the degradation of storage lipids to biosynthesize the free amino acids, in which serine and glycine were produced predominantly. The concentrations of internal amino acids increased gradually as the germination time increased from 0 to 1 or 2 weeks. However, asparagine and glutamine declined to the low levels; both degraded to provide the biosynthesis of other amino acids with C and N donors. The availability of exogenous inorganic N （ammonium and nitrate） and organic N （urea, arginine, and glutamine） to the AM fungal spores using only CO2 for germination generated more than 5 times more internal free amino acids than those in the absence of exogenous N. A supply of exogenous nitrate to the AM fungal spores with only CO2 gave rise to more than 10 times more asparagine than that without exogenous N. In contrast, the extra supply of exogenous glucose to the AM fungal spores generated a significant enhancement in the uptake of exogenous N sources, with more than 3 times more free amino acids being produced than those supplied with only exogenous CO2. Meanwhile, arginine was the most abundant free amino acid produced and it was incorporated into the proteins of AM funsal spores to serve as an N storage compound.
