Fig. 4. Diverse peptide shapes realized by the oligo-l/d-NMAs. (a) A list of peptide shapes realized by hexameric l/d-NMA oligomers. The stable conformations of l-NMA and d-NMA residues were connected with trans amides, and the resulting structures were optimized by DFT calculations to generate the model structures. Among the possible 64 diastereomers, six stereoisomers that have intramolecular steric crashes are omitted (their possible conformations are shown in Fig. S13†). Considering that the remained 58 stereoisomers are 29 enantiomer pairs, only 29 diastereomers that are not enantiomers with each other are shown. The hexamers that were experimentally examined are highlighted by black squares. (b) Solution structure of a hexameric oligomer llddll. A representative conformation in the highest population cluster from the McMD simulations is shown. (c) A crystal structure of llddll obtained by XFEL crystallography. (d) Solution structure of lllldl. A representative conformation in the highest population cluster from the McMD simulations is shown. For (b and d), the non-neighboring hydrogen pairs with significant NOE signals are indicated by red arrows. For (b–d), hydrogens are omitted for clarity, and the dihedral angle (φ, ψ) pair of each NMA residue is plotted on the Ramachandran-type plot of l-NMA residue on the right using a magenta circle. To discuss l- and d-NMA residues on the same plot, the sign of each dihedral angle value of the d-NMA residues was reserved, and then the values were plotted. (e) The PMI plot of the predicted shape of llddllddll (red circle) and llllllllll (green circle). (f–g) A SMART-EM analysis taken at 50 fps and an electron dose rate of 3.8–4.9 × 10⁶ e⁻ nm⁻² s⁻¹ of the llddllddll decamer (f) and the llllllllll decamer (g). A stable conformation predicted from the shapes of the l/d-NMA residue is shown (left). A simulated TEM image (second from left). The TEM image of the oligomer on an amino-CNT (second from right). A molecular model (right). (h–i) The conformations of llddllddll (h) and llllllllll (i) from MD simulations that match the observed TEM images. The time from the beginning of the observation is shown below the conformation. Dihedral angles (φ, ψ) of each l/d-NMA residue of the observed conformers are plotted on the Ramachandran-type plot of l-NMA as magenta circles. To discuss l- and d-NMA residues on the same plot, the sign of each dihedral angle value of the d-NMA residues was reserved, and then the values were plotted.