Fig. 6.

Secondary structures and molecular packing modes. a, b CD and FTIR spectra of the designed peptides at 8 mM except for Ac-I₃GGK-NH₂ at 16 mM. For clarity, the CD spectra of Ac-I₃NGK-NH₂ and Ac-I₃LGK-NH₂ are given in Supplementary Figures 3b and 6b, respectively, but also indicating the formation of β-sheet conformations. c ¹H-¹³C CP spectrum of [¹⁵N]Ile1[1-¹³C]Ile3-Ac-I₃QGK-NH₂ nanoribbons. Rotational sidebands are denoted by asterisks and the down arrow denotes natural abundance ¹³C signals. d Experimental ¹³C{¹⁵N} REDOR data (black dots) of [¹⁵N]Ile1[1-¹³C]Ile3-Ac-I₃QGK-NH₂ nanoribbons. The REDOR curve (black solid line) was fitted by SIMPSON using one intra-strand and two inter-strand ¹³C-¹⁵N spin pairs with corresponding ¹³C-¹⁵N distances of 8.8, 7.4, and 8.1 Å, respectively, which were extracted from the one-residue shift packing mode (inset). The anti-parallel trimer with one-residue shift shown in the inset (¹³C: pink or green sphere and ¹⁵N: blue sphere) was the central core of an Ac-I₃QGK-NH₂ oligomer of 6 strands × 4 sheets during MD simulations. To demonstrate fitting uncertainty, the dashed lines were calculated using the indicated inter-strand ¹³C-¹⁵N distances