Table 1. Mass Spectral Characterization of Protein Components Detected in Hetero-AB.

Protein	Theoretical Mass (Da)a,b	Measured Mass (Da)	Mass Error (ppm)	Deconvoluted MS Intensity	Relative Intensity
AB - 2Lys	145321	145322	7	1089472	72.5%
AB - Lys	145449	145449	0	333951	22.2%
AB	145577	145579	14	80160	5.3%

A, Theoretical mass is for fully deglycosylated protein; b, Both heavy chain A and B have glycine addition on the N-terminus.