Table 4. Sequences for the IA-modified peptide fragments of Cys32 and Cys250 after hAS3MT-catalyzed the iAs³⁺ methylation.

Sequence site	Mr (calc)	GSH system		Cys system		DTT system		TCEP system
		Mr (expt)	ppm	Mr (expt)	ppm	Mr (expt)	ppm	Mr (expt)	ppm
24–44	2320.21	2320.15	−25.86	2319.71	−215.54	2320.08	−56.03	2319.96	−107.76
24–41	1913.96	1914.18	114.93	1914.23	141.05	1914.13	88.81	1913.87	−47.03
242–258	2054.04	2054.35	150.90	2054.34	146.03	2054.31	131.43	2053.81	−111.99
242–251	1245.61	1245.78	136.46	1245.52	−72.26	1245.72	88.30	1245.39	−176.65
246–261	1915.01	1914.89	−62.67	1915.12	57.44	1915.99	−15.67	1915.04	15.67
246–258	1526.77	1526.69	−52.40	1526.65	−78.60	1526.71	−39.3	1526.58	−124.46

Values of Mr (expt) are calculated from the results of MALDI-TOF-MS in Figure 3. ND represents the peptide fragment is not detected.