Figure 2.

(a) The influence of selected crowder peptides (denoted above the spectra), which mimic membrane proteins with different structures and locations, on the orientation of the antimicrobial peptide PGLa, labeled with CF₃-Phg in position 13, was examined on the basis of solid-state ¹⁹F-NMR spectra. The spectra are indicative of the insertion of PGLa into the membrane in the presence of the crowder. Spectra fingerprints of S-, T-, and I-state are colored in red, blue, and green, respectively. In case of the coexistence of several spectral fingerprints, the pattern is highlighted that caused the highest level of agreement with the respective pattern of the pure PGLa sample in the data analysis. Spectra were acquired of samples at a PGLa:lipid molar ratio of 0.5:100 (left column within each set) and 2.5:100 (right column in each set), and at temperatures from 15 °C (lowest spectrum) to 55 °C, varied in steps of 5 °C. The gel-to-fluid phase transition temperature of DMPC is indicated by “Tm”. A second peptide was added, to result in a total peptide:lipid molar ratio of 5:100. Several crowders were tested: (a) reference spectra without crowder, (b) with gramicidin S (GS), (c) with gramicidin A (GA), (d) with MSI-103, (e) with MAP, (f) with magainin 2 (MAG2).