title: Nanosized hybrid oligoamide foldamers: aromatic templates for the folding of multiple aliphatic units.
abstract: Oligoamide sequences comprised of both 8-amino-2-quinolinecarboxylic acid "Q" and 6-aminomethyl-2-pyridinecarboxylic acid "P" have been synthesized. It was found that the aliphatic amine of P greatly facilitates amide couplings, as opposed to the aromatic amine of Q, which enabled us to prepare sequences having up to 40 units. The conformation and conformational stability of these oligomers were characterized in the solid state using X-ray crystallography and in solution using NMR and various chromatographic techniques. Q(n) oligomers adopt very stable helically folded conformations whereas P(n) oligomers do not fold and impart conformational preferences distinct from those of Q units. When a P(n) segments is attached at the end of a Q(4) segment, a couple P units appear to follow the folding pattern imposed by the Q(n) segment, but P units remote from the Q(n) segment do not fold. When a P(n) segment is inserted between two Q(4) segments, the P(n) segment adopts the canonical helical conformation imposed by the Q units at least up to two full helical turns (n = 5). However, the overall stability of the helix tends to decrease as the number of P units increases. When noncontiguous P units separated by Q(4) segments are incorporated in a sequence, they all adopt the helical conformation imposed by Q monomers and the overall helix stability increases when helix length increases. For example, a 40mer with a sequence (PQ(4))(8) folds into a rod-like helix spanning over 16 turns with a length of 5.6 nm. This investigation thus demonstrates that remarkably long (nanometers) yet well-defined foldamers can be efficiently synthesized stepwise and that their helical stability may be continuously tuned upon controlling the ratio and sequence of P and Q monomers.
authors.affiliation: Institut Européen de Chimie et Biologie, Université de Bordeaux-CNRS UMR5248, 2 rue Robert Escarpit, 33607 Pessac, France.
authors.forename: David
authors.initials: D
authors.lastname: Sánchez-García
authors.forename: Brice
authors.initials: B
authors.lastname: Kauffmann
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kawanami
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Ihara
authors.forename: Makoto
authors.initials: M
authors.lastname: Takafuji
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Delville
authors.forename: Ivan
authors.initials: I
authors.lastname: Huc
mesh_terms: D000577:Amides / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry; D011804:Quinolines / Q000737:chemistry
chemical_list: D000577:Amides; D002264:Carboxylic Acids; D011725:Pyridines; D011804:Quinolines