Table I. Mean intensity of the monoisotopic (M+H⁺) ion peaks of inhibitor-sensitive and resistant peptides. This analysis was performed for the peptides in Figure 4.

	MG-132			Epoxomicin
	14N	15N	15N+Inh.	14N	15N	15N+Inh.
Sensitive (n = 31)	13461	11092	7026 (63%)c	3001	2489	1644 (66%)c
Resistant (n = 5)	2818	2364a	1657 (70%)c	551	356b	176 (49%)c
Ratio	4.8	4.7	4.2	5.4	7.0	9.3

^a Range: 537 to 5030. As many as 20 inhibitor-sensitive peptides (64.5%) had higher intensity.

^b Range: 56 to 602. As many as 17 inhibitor-sensitive peptides (54.8%) had higher intensity.

^c Percent values are relative to peptides labeled in the absence of inhibitor (¹⁵N).