Hydrophobic Aib/Ala peptides solubilize in water through formation of supramolecular assemblies

Abstract

The synthesis of the N-protected (blocked) homo-peptide esters from the chiral C-alpha-ethyl, C-alpha-n-pentylglycine was performed in solution to the hexapeptide level. The conformational propensity exhibited by these oligomers in chloroform solution and in the crystal state was assessed by use of FTIR absorption, NMR, and X-ray diffraction. The results indicated that fully extended helical structures (2.0(5)-helices) are overwhelmingly adopted irrespective of the peptide main-chain length. This oligomeric series is of great interest as it is characterized by the longest C (i) (alpha) ,aEuro broken vertical bar, C (i+1) (alpha) (per residue) separation achievable in the class of chiral, rigid, helical peptide spacers based on alpha-amino acids

Biomimetic Nanoarchitectures for Light Harvesting: Self-Assembly of Pyropheophorbide-Peptide Conjugates

“…Meaningful differences appear already at the level of a monomer. The peptide chain in both solvents takes an α-helical conformation, in agreement with the experimental findings (see Figure S2a and refs and ). Methanol appears to be a good solvent, where the chain moves freely and explores several relative orientations with respect to PPh.…”

“…In the studied conjugate, the PPh moiety is covalently linked to an artificial peptide H-Ala-(Aib-Ala) 7 -OH ( ap ) (Scheme and the Supporting Information). In water, this sequence shows a strong propensity to maintain the same helical conformation as in organic solvents and to form supramolecular self-assembled structures . Here the self-assembly properties of the peptide in water are exploited to promote the controlled aggregation of the conjugate by solvent tuning. , …”

“…In water, this sequence shows a strong propensity to maintain the same helical conformation as in organic solvents 23 and to form supramolecular self-assembled structures. 24 Here the self-assembly properties of the peptide in water are exploited to promote the controlled aggregation of the conjugate by solvent tuning. 25,26 The self-assembly of the peptide moieties also constrains the organization of the hydrophobic PPh pigments attached as side chains, 14,16 promoting, in this case, the formation of strongly coupled aggregates, as verified in the absorption and circular dichroism (CD) spectra (Figure 1).…”

From Folding to Assembly: Functional Supramolecular Architectures of Peptides Comprised of Non‐Canonical Amino Acids

“…The observed phenomena were thought to be due to dimerization of the single helix through π – π stacking of aromatic moieties, which further extended to create a network and ultimately arranged into a spherical assembly. [ 76 ]…”

Removing the C-terminal protecting group enlarges the crystal size: Z–(Gly–Aib)2–OH·H2O

“…Deprotection of the N-or C-terminal of these peptides is expected to alter the hydrogen-bonding scheme from intramolecular to intermolecular hydrogen bonds, to modify the structure and to facilitate crystallization. C-Terminal deprotection enables the formation of crystals also in the case of chiral Z-Ala 3 -(Aib-Ala) 4 -OMe (Longo et al, 2013). We present here the structure of the achiral tetrapeptide Z-Gly-Aib-Gly-Aib-OHÁH 2 O (Z is benzyloxycarbonyl, Aib is -aminoisobutyric acid and Gly is glycine).…”