Parallelogram plate shaped foldecture from the controlled self-assembly of α/β-peptide foldamer

The Diverse World of Foldamers: Endless Possibilities of Self-Assembly

“…Beyond the foldectures based on 12-helices of β-foldamers already reported in Section 2.3 , Lee’s group also extensively studied the aqueous self-assembly in solid shapes of surfactant-containing solutions of 1:1 alternating α–β foldamers showing the repetition of the Aib- trans -ACPC sequence, as shown in Figure 24 a [ 261 , 262 , 263 , 264 , 265 ]. In all of these studies, the exact packing mode could be ascertained by an intelligent use of high-resolution powder X-ray diffraction (PXRD), whereas the morphologies of self-assembled nanostructures were observed by SEM and additional information could be obtained by applying various physico-chemical analyses, such as differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and FT-IR.…”

“…The addition of a concentrated THF stock solution of 11-helix hexamer Boc-(Aib-ACPC) 3 -OBn, depicted by R 2 = OBn in Figure 24 a, to excess aqueous solutions of nonionic surfactant Pluronic 123 (P123) at different concentrations (0, 0.015 and 8 g L −1 ) led to foldectures varying from long rods with a parallelogram section (in distilled water) to parallelogram plate shapes (in the most concentrated P123 solution) [ 261 ]. As in the other cases previously reported for β-peptides, starting from the common prismatic nucleation network characterized by the maximization of hydrophobic packing, in pure water the growth occurred much faster on the two most apolar faces, thus obtaining the rod-shaped morphology.…”

“… ( a ) General structure of alternating Aib-ACPC hexamers and heptamers (Refs. [ 261 , 262 , 263 , 264 , 265 ]); ( b ) SEM images of foldectures created from Boc-(Aib-ACPC) 3 -OBn added to P123 aqueous solutions at (top) 0.0 g L −1 , (middle) 0.015 g L −1 , and (bottom) 8 g L −1 , and plausible mechanism for the formation of parallelogram plate-shaped foldectures. The common prismatic nucleation network is composed of alternating antiparallel layers (in blue and red) that have the highly hydrophobic faces lying in the b-c plane, whereas the hydrophilic faces lie in the two other planes.…”

“…In pure water, the growth occurs much faster along the a direction, in order to avoid the increase in exposed hydrophobic surface (rod-shaped morphology) while in the presence of P123 the growth along axis a is suppressed and the elongation occurs in the other two directions (parallelogram plate-shaped foldectures) (adapted with permission from Ref. [ 261 ]); ( c ) SEM images of foldectures self-assembled from Boc-(Aib-ACPC) 3 -Aib-OBn in distilled water (F 0 , also with representations) and in 8 g L −1 (F 1 ), 24 g L −1 (F 2 ), 40 g L −1 (F 3 ), and 48 g L −1 (F 4 ) aqueous solutions of P123 (insets: TEM images with scale bars = 1 µm) (adapted with permission from Ref. [ 262 ]); ( d ) General structure of alternating Aib-ACPC pentamers with different caps (Ref.…”

“…The common prismatic nucleation network is composed of alternating antiparallel layers (in blue and red) that have the highly hydrophobic faces lying in the b-c plane, whereas the hydrophilic faces lie in the two other planes. In pure water, the growth occurs much faster along the a direction, in order to avoid the increase in exposed hydrophobic surface (rod-shaped morphology) while in the presence of P123 the growth along axis a is suppressed and the elongation occurs in the other two directions (parallelogram plate-shaped foldectures) (adapted with permission from Ref [261][262]…”