Fig. 2.

Mass spectrum of the +17 charge state envelope of ^NAcαS. Following excision of the tetrameric ^NAcαS band from a BN-PAGE (4–16%) gel and diffusion of the protein into water, the exact mass for N-terminally acetylated αS was obtained (experimental monoisotopic mass, 14493.22137). The low abundance, higher molecular weight charge envelope that is also visible in this spectrum corresponds to nonspecific oxygenation of ^NAcαS. Inset: Theoretical isotope distribution and relative abundances of [M+17H]⁺¹⁷ (^NAcαS calculated monoisotopic mass, 14493.229).