Table 2. Residues photolabeled in a tryptic fragment of Japanese Firefly Luciferase (340-QGYGLTETTSAIIITPEGDDKPGASGK-366)^{a n} identified by LTQ–FT mass spectrometry and MSMS.

Agent	Alcohol µM	ATP	Time ms	Residue Photolabeled	Charge	R t, min	Xcorr	bMH+	Accuracycppm
Parent peptided					+3	25.8	5.5	2707.93	0.58
7-azioctanol	100	+	200		Photolabeled peptide not detected
	100	−	∞	D358	+3	21.8	6.0	2836.05	0.70
	100	+	∞		Photolabeled peptide rarely detected
3-azioctanol	100	+	200		Photolabeled peptide not detected
	100	−	∞	D358	+3	22.7	5.5	2836.05	0.70
	100	+	∞		Photolabeled peptide not detected
3-azibutanol	1000	+	200	D358	+3	20.3	5.8	2779.93	0.58
	1000	−	∞	D358	+3	17.3	6.2	2779.93	0.58
	1000	+	∞		Photolabeled peptide not detected
TFD-benzyl alcohol	100	+	200	S349e	+3	24.8	5.0	2894.39	0.96

^a–dSame as Table 1.

^ePhotoincorporation was either in Ser-249 or Ala-250. The latter residue is rarely labeled by aromatic diazirines.