Production of 13N‐labelled molecular nitrogen for pulmonary function studies
A method for the production of 13NN either as a gas or as an injectable solution is described. The method is based on the 16O(p,α)13N reaction and water as target material. Following irradiation, the 13NO and 13NO are reduced to 13NH3, followed by NaOBr oxidation to 13NN. With a beam current of 1 μA and 20 min irradiation time the injectable solution contained 148 MBq (4 mCi) per ml.
[Show abstract] [Hide abstract] ABSTRACT: Coniferous forest nitrogen (N) budgets indicate unknown sources of N. A consistent association between limber pine (Pinus flexilis) and potential N2-fixing acetic acid bacteria (AAB) indicates that native foliar endophytes may supply subalpine forests with N. To assess whether the P. flexilis–AAB association is consistent across years, we re-sampled P. flexilis twigs at Niwot Ridge, CO and characterized needle endophyte communities via 16S rRNA Illumina sequencing. To investigate whether endophytes have access to foliar N2, we incubated twigs with 13N2-enriched air and imaged radioisotope distribution in needles, the first experiment of its kind using 13N. We used the acetylene reduction assay to test for nitrogenase activity within P. flexilis twigs four times from June to September. We found evidence for N2 fixation in P. flexilis foliage. N2 diffused readily into needles and nitrogenase activity was positive across sampling dates. We estimate that this association could provide 6.8–13.6 μg N m−2 d−1 to P. flexilis stands. AAB dominated the P. flexilis needle endophyte community. We propose that foliar endophytes represent a low-cost, evolutionarily stable N2-fixing strategy for long-lived conifers. This novel source of biological N2 fixation has fundamental implications for understanding forest N budgets.0Comments 2Citations
- "To maximize the radioactive concentration, we directed the nonlabeled prefraction to waste before the radioactive fraction was collected in a 20-ml crimp-top glass vial. To oxidize the [ ll of fresh 1.5 M NaOBr (6 N NaOH and 1.0 ml Br 2 to 7 ml H 2 O (Vaalburg et al., 1981)) to the vial. We began purging the vial with a 25 ml min À1 stream of air as soon as [ the headspace of the reaction vial to a cylindrical 2-l exposure chamber through 50 cm of 1/16-inch tubing equipped with an in-line boric acid trap (for trapping unreacted [ 13 N]NH 3 gas). "
- [Show abstract] [Hide abstract] ABSTRACT: An enzymatic synthesis of13N-glutamate from13N-labeled ammonia has been developed and optimized for routine application in myocardial imaging. A remotely controlled appratus for the synthesis is described. Results of routine production runs are briefly discussed.0Comments 3Citations
- [Show abstract] [Hide abstract] ABSTRACT: Here we explored the conditions for synthesizing [13N]N2 in a state that is suitable for the administration to plant root nodules enabling studies of nitrogen fixation. [13N]N2 was prepared batchwise, starting with [13N]NO� 3 from the 16O(p,a)13N nuclear reaction on a liquid water target. [13N]NO�3 was first reduced to [13N]NH3 using Devarda’s alloy, and then the [13N]NH3 was oxidized to [13N]N2 by hypobromite using carrier-added NH4Cl. The amounts of carrier NH4Cl and hypobromite were varied to determine the effects these parameters had on the radiochemical yield, and on the radiotracer specific activity. As expected, increasing the amount of carrier NH4Cl improved the radiochemical yield. Unexpectedly, increasing the amount of excess hypobromite from 1.6-fold to 6-fold molar equivalents (relative to NH4Cl) improved the radiochemical yield and radiotracer specific activity under all conditions of carrier NH4Cl. As a comparison, we measured [13N]N2 specific activity derived from in-target production based on a 50 lAmin irradiation driving the 14N(p,pn)13N reaction on a gaseous N2 target. The ‘wet’ radiochemistry approach afforded two advantages over the in-target approach with a �600-fold improvement in specific activity, and the ability to collect the tracer in a small volume of gas (�20mL at STP).0Comments 5Citations