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. 2016 Nov 16;1(3):1–21. doi: 10.1159/000451076

Fig. 2.

Fig. 2

FTIR spectra of MB and S-MB in the structure-promoting solvents hexafluoroisopropanol (HFIP), methanol (MeOH) and ethanol (EtOH), the detergent SDS (sodium dodecyl sulfate), and the phospholipids POPG and DPPC. Methanol and ethanol are solvents of intermediate polarity that mimic the polar head group domain of phospholipid bilayers, while HFIP represents the more hydrophobic interior of the lipid bilayer. a Stacked FTIR spectra of MB in 40% HFIP (i.e., 40% HFIP/60% deuterated-sodium phosphate buffer, pH 7.4), 100% MeOH (i.e., 100% methanol), 100% EtOH (i.e., 100% ethanol), SDS, POPG, and DPPC. b Stacked FTIR spectra of S-MB in 40% HFIP, 100% MeOH, 100% EtOH, SDS, POPG, and DPPC. a, b The IR spectra for MB and S-MB each show dominant α-helical components centered at 1,657-1,651 cm-1 (arrows), with minor bands at ∼1,637-1,613 cm-1 (arrow at 1,620 cm-1) denoting β-sheet. Peptide concentrations were 470 μM for solvent spectra and 10:1 lipid:peptide (mole:mole) for lipid spectra. The abscissa (left to right) is 1,740-1,560 cm-1, while the ordinate represents absorption (in arbitrary units).