Fig. 3.

¹⁵N-incorporation into kinamycin D by inorganic nitrogen sources. a Scheme for feeding experiments with S. murayamaensis using ¹⁵N-labeled nitrite and nitrate. b HRMS analysis of ¹⁵N incorporation into kinamycin D when no labeled nitrogen-containing salts, 1 mM ¹⁵N-nitrite, or 1 mM ¹⁵N-nitrate, were added to the fermentation culture of S. murayamaensis. The calculated m/z ([M+H]⁺) for kinamycin D at natural abundance is 455.1091, ¹⁵N-kinamycin D is 456.1055, and ¹⁵N₂-kinamycin D is 457.1026. c ¹⁵N NMR analysis of kinamycin D isolated from fermentation cultures of S. murayamaensis revealed that ¹⁵N-nitrate and ¹⁵N-nitrite labeled the proximal nitrogen of the diazo group (highlighted in red)³⁰