. Author manuscript; available in PMC: 2016 Aug 16.

Published in final edited form as: Biochemistry. 2016 Aug 1;55(32):4519–4532. doi: 10.1021/acs.biochem.5b01132

Table 1.

Site	Peptide	Native (Area)	N15-labeled(Area)	Modified (%)
C46	DPVQCSR	14,214,288	15,332,719	7.3
C53	DVVICPDASLEDAK	69,277,937	229,809,312	70.0
C106	GLIAAICAGPTALLAHEIGFGSK	268,610,760	1,179,067,215	77.2^A

Quantitation of estimated glutathionylation of cysteines of DJ-1. Glutathionylation of cysteine residues 46, 53, and 106 were estimated using unmodified ¹⁵N DJ-1 as an internal standard. Quantification of modified tryptic peptides were estimated by subtraction of the peak areas of the non-modified peptides in the treated ¹⁴N-samples from those in the untreated ¹⁵N-samples (Supplemental Figure 3).

Example of calculation of extent of glutathionylation of Cys106: 1,179,067,215 (¹⁵N non-modified area) - 268,610,760 (¹⁴N non-modified area) = 910,456,455 (estimated area of the glutathionylated peptide). 910,456,455 (estimated are of the glutathionylated peptide) / 1,179,067,215 (¹⁵N non-modified area) × 100 = 77.2% (Estimated percentage of glutathionylated peptide as compared to total internal standard).