Skip to main content
. Author manuscript; available in PMC: 2015 Oct 24.
Published in final edited form as: Anal Chem. 2015 Oct 6;87(19):9829–9837. doi: 10.1021/acs.analchem.5b02217

Figure 4.

Figure 4

Drift time (DT) distribution of hIAPP and hIAPP–Cu(II) ions reveal the differentiated conformers for the triply charged and the quadruply charged states. (a) The spectrum of [hIAPP + 3H]3+ was deconvoluted using two Gaussian functions. The smaller shoulder peak corresponds to a conformation with CCS of 611 Å2, whereas the larger peak matches a structure with CCS of 647 Å2. Likewise, the spectrum of [hIAPP + Cu(II) + H]3+ has two peaks with nearly identical CCS values as those of [hIAPP + 3H]3+. (b–d) The quadruply charged hIAPP is present as (b) protonated, (c) potassiated, and (d) sodiated ions. The DT distribution for [hIAPP + 4H]4+ and [hIAPP + Cu(II) + 2H]4+ reveal two distinct conformations with CCSs of 594 and 748 Å2. The spectrum of [hIAPP + 3H + K]4+ displays a major peak with CCS of 748 Å2 and a minor peak with CCS of ~684 Å2. The spectrum of [hIAPP + Cu(II) + H + K]4+ reveals three peaks, with a dominant one at CCS of 748 Å2, a small one at CCS of 684 Å2, and an almost negligible peak at CCS of 594 Å2. hIAPP was detected with the sodiated ions in the form of [hIAPP + 3H + Na]4+. Using Gaussian functions, the DT distribution spectrum was deconvoluted into two peaks with CCSs of 594 and 748 Å2.