For the sample solely composed of DLPC and cholesterol (sample 1) the acyl chain distance is a = 4.94 ± 0.01 Å . The shortening of the acyl chain distance a appears more pronounced for the homodimeric species 4 (sample 2) at a helix-to-lipid ratio of 1/20 (P/L = 1/10) but is even stronger for the hairpin species 5 at the same helix-to-lipid ratio (P/L = 1/20). Considering the recognition system 3/6 (equimolar) at RH = 94% (sample 5), the shortening of a is less distinct but can also be assigned to a lower helix-to-lipid ratio of 1/40 (P/L = 1/20). The concentration effect can be factored out by comparing different samples (3 and 4) of the hairpin species at P/L = 1/20 and P/L = 1/40, respectively, showing that higher peptide concentration yields shorter lipid chain distances. It can further be concluded that the recognition system 3/6 (equimolar ratio) at RH = 94% (sample 5) has less impact on a than the respective hairpin peptide 5 (sample 4) at identical P/L = 1/40. The values for the lipid chain correlation length n follow an almost opposing trend as that observed for a. Peptide incorporation generally leads to an increase in n. In principle, the homodimer (4), hairpin (5), and recognition system (3/6) structures are designed to adopt an identical secondary structure with respect to their TMDs. In the case of the hairpin structure 2, due to a decline in helix propensity compared to the homodimeric species 1 as revealed by CD spectroscopy , it was assumed that the hairpin structure exhibits steric clashes in the reverse-turn region leading to a less perfect alignment of the double strands and a broadening of the helix diameter. Therefore, the self-associated homodimer 4 should provide a closer alignment enabled by hydrogen bonding of the two antiparallel-oriented strands. The PNA recognition system 3/6 leading to an aggregation of two of the double helices in a close contact state would yield more than a doubled lateral occupied area within the lipid bilayer (Fig. 2c) . Under these circumstances, the lateral dimensions of the peptide species are supposed to increase in the order: homodimer (4) ? hairpin (5) ? recognition system (3/6).