Figure 3.

Dissection of PDX 12mers in the gas phase by surface induced dissociation (SID). (a) Representative SID spectrum for a heteromer with a single stoichiometry of 6:6 (PDX1.2/PDX1.3). Mass isolated 6:6 was collided with a surface to produce 6mers and other subcomplexes detected in the mass spectrum, which are labeled by the different symbols. The key to the symbols is on the top right. (b) Deconvoluted mass distribution of the SID spectra for 6:6 (left) and 7:5 (right). Zoom-in views of the 6mer region are shown in the insets. (c) Proposed dissociation pathways for PDX by SID. The cleavage of the 12mer in the horizontal direction is a major pathway (left). A minor pathway for cleaving in the vertical direction likely produced several other species at low abundance. (d) Heat map showing the relative abundance (normalized to max) of the released 6mer rings (vertical axis) from each stoichiometry of 12mers (horizontal axis) following the major pathway. The contribution of 6mers from minor pathways were estimated by the abundance of 4-, 5-, 7-, and 8mers and was subtracted from the raw experimental data as described in the Methods.