A Helical, Aromatic, Peptide Nanotube

Abstract

[Structure: see text] The self-assembly in the crystal state of the terminally protected, linear dipeptide Boc-(S,S)c3diPhe-(R,R)c3diPhe-NHiPr (1) through intermolecular hydrogen bonds leads to the formation of a supramolecular helix of large diameter (18 A), internally decorated with phenyl rings. As a result, a hollow helical channel large enough to accommodate guest molecules is observed. This supramolecular structure differs from previous examples of peptide nanotubes. Compound 1 incorporates a highly restricted cyclopropane phenylalanine analogue (c3diPhe) with remarkable conformational properties.

Protein Segments with Conformationally Restricted Amino Acids Can Control Supramolecular Organization at the Nanoscale

“…For example, we have carried out a structural study [22][23][24][25][26][27][28][29][30][31][32] stheoretical and experimentalsof Ac n c residues (n ) 3-6) incorporating one or more phenyl substituents at the position. Steric and electronic interactions between the peptide backbone and the rigidly held aromatic substituent have proved useful in stabilizing different types of -turns or in inducing novel turn types never observed before.…”

A terminally protected dipeptide: from crystal structure and self-assembly, through co-assembly with carbon-based materials, to a ternary catalyst for reduction chemistry in water

“…[18,19,[23][24][25][26] This property is also shared by our terminally protected dipeptide Boc-L-Cys(Me)-L-Leu-OMe (1) that crystallizes in the hexagonal space group P6 5 . [18,19,[23][24][25][26] This property is also shared by our terminally protected dipeptide Boc-L-Cys(Me)-L-Leu-OMe (1) that crystallizes in the hexagonal space group P6 5 .…”

“…[7][8][9][10][11][12][13][14][15][16][17] More specifically, nanotubes and nanofibers predominate as molecular architectures among the self-assemblies formed by short, unprotected peptides [18][19][20][21] of which the phenylalanine homo-dipeptide H-Phe-Phe-OH is the most extensively investigated example (for review, see ref. [23][24][25][26] Here, we present our data on the hydrophobic, terminally protected dipeptide Boc-L-Cys(Me)-L-Leu-OMe (1) [where Boc is tert-butoxycarbonyl, Cys(Me) is S-methyl cysteine, and OMe is methoxy] ( Figure 1A) that was crystallographically characterized and subsequently was found to be able to hierarchically self-assemble producing nano-, microand macroscale tubes and organogels that we eventually exploited to incorporate guest molecules such as gold nanoparticles, C 60 fullerene and multiwall carbon nanotubes (MWCNTs). Notably, such architectures may adsorb or entrap other molecules, thus generating ordered hybrid materials.…”

Helical screw‐sense preferences of peptides based on chiral, Cα‐tetrasubstituted α‐amino acids

“…The results of an NMR investigation on the homo‐tetrapeptide alkylamide Boc‐[( R,R )‐c 3 diPhe] 4 ‐NH i Pr in CDCl 3 solution are fully consistent with a right‐handed 3 10 ‐helical conformation. Conversely, in the X‐ray diffraction structure of Boc‐( S,S )‐c 3 diPhe‐( R,R )‐c 3 diPhe‐NH i Pr, the heterochiral sequence folds in a type‐I′ β‐turn conformation, in which the ( S,S ) residue is left‐handed helical ( ϕ 1 , ψ 1 = +65°,+35°), whereas the ( R,R ) residue adopts a conformation falling in the bridge region of the conformational map with ϕ positive and ψ negative ( ϕ 2 , ψ 2 = +89°, −16°).…”