Positive-mode single-ion LC-MS chromatograms showing that NapI can hydroxylate
but not desaturate the 6-deaza analogue of L-Arg, L-indospicine. The front three
traces are from a control lacking the co-substrate, 2OG. The middle traces are
from analysis of a reaction carried out under atmospheric O2. The
rear traces are from a reaction under 18O2. Coloring
coding of the traces is: black,
m/z = 174 (indospicine);
green, m/z = 190
(H16O-indospicine); gray,
m/z = 192 (H18O-indospicine);
blue, m/z = 172
(dehydroindospicine; not observed).