首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >18O isotope shift in 15N NMR analysis of biological N-oxidations: H2O-NO2- exchange in the ammonia-oxidizing bacterium Nitrosomonas
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18O isotope shift in 15N NMR analysis of biological N-oxidations: H2O-NO2- exchange in the ammonia-oxidizing bacterium Nitrosomonas

机译:生物N-氧化的15N NMR分析中的18O同位素位移:氨氧化细菌亚硝化单胞菌中的H2O-NO2-交换

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摘要

The 18O/16O shifts in 15N NMR were determined for nitrite (0.13 ppm or 4.2 Hz at 7.05 T) and nitrate (0.056 ppm or 1.7 Hz at 7.05 T) at neutral pH. The technique, which allows clear differentiation between 16O and 18O derivatives of 15N, was used to assess the source of oxygens in nitrite produced by oxidation of ammonia in Nitrosomonas. The two oxygens of nitrite produced by cell-catalyzed oxidation of ammonia or hydroxylamine had the 16O/18O isotope composition of water. Nitrosomonas is shown to catalyze the rapid exchange of oxygen between nitrite and water. The exchange reaction required the concomitant oxidation of ammonia. The amount of nitrite exchanged could exceed the amount of ammonia oxidized by a factor of 3. This exchange explains previous difficulties in the determination of the source of nitrite oxygen in ammonia oxidation. When cells oxidized [15N]ammonia in the presence of a great excess of exogenous [14N]nitrite, 20% of one oxygen in the resulting [15N]nitrite was derived from dioxygen. Dioxygen is apparently the source of at least one oxygen in nitrite produced by Nitrosomonas.
机译:测定亚硝酸盐(0.13 ppm或4.2 Hz在7.05 T时)和硝酸盐(0.056)在 15 N NMR中的 18 O / 16 O位移在中性pH值下在7.05 T时为ppm或1.7 Hz)该技术可以清楚地区分 15 N的 16 O和 18 O衍生物,用于评估产生的亚硝酸盐中的氧气来源在亚硝化单胞菌中被氨氧化。细胞氨催化氨或羟胺氧化生成的亚硝酸盐中的两个氧具有水的 16 O / 18 O同位素组成。亚硝化单胞菌可催化亚硝酸盐与水之间的氧气快速交换。交换反应需要同时氧化氨。交换的亚硝酸盐的量可能比被氧化的氨水的量大3倍。这种交换解释了以前在确定氨氧化中亚硝酸盐氧源方面的困难。当细胞在大量过量的外源性[ 14 N]亚硝酸盐存在下氧化[ 15 N]氨时,生成的[ 15]中一种氧的20% N]亚硝酸盐衍生自双氧。显然,亚硝化单孢菌产生的亚硝酸盐中至少有一种氧气的来源是双氧。

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