Abstract
We describe the solution assembly of polymer–cyclic peptide conjugates into nanotubes, by direct in situ measurements. The conjugates were assembled by exploiting the β-sheet assembly of the alt(D,L) cyclic octapeptide core. The conjugated polymer permits solubilization of the peptide and the resulting nanotubes, thus allowing for the first time the direct study of the assembly mechanism of this system. The resulting materials present unique properties for a wide range of applications. We find that the polymer can act to both shield the peptide core from the solvent and to put strain on the peptide core through steric repulsions. By controlling both the solvent mixture and the length of the polymer, control over the length of the resulting nanotubes can be obtained. In addition, monitoring the assembly with temperature allows the strength of the assembly to be probed, adding evidence for a co-operative mechanism of assembly. Finally, selective deuteration of the polymer component in SANS analyses leads to the precise measurement of the nanotubes core dimensions, and by cross-linking the polymeric shell, the structure of the nanotubes in solution are confirmed by transmission electron microscopy (TEM). This study establishes the fundamentals needed for the design and control of these new materials.
Highlights
The supramolecular stacking of cyclic peptides (CPs) has emerged in recent years as a remarkably versatile approach to the formation of organic nanotubes
Selective deuteration of the polymer component in small angle neutron scattering (SANS) analyses leads to the precise measurement of the nanotubes core dimensions, and by cross-linking the polymeric shell, the structure of the nanotubes in solution are confirmed by transmission electron microscopy (TEM)
We investigate the effect of polymer DP, solvent conditions, and temperature on the assembly, and for the rst time extrapolate an enthalpy of association for the nonalkylated CPs
Summary
The supramolecular stacking of cyclic peptides (CPs) has emerged in recent years as a remarkably versatile approach to the formation of organic nanotubes. The choice of amino acid residues can be used to control the pore chemistry to a certain extent, as well as the external functionality of the nanotube through the side chains, which project equatorially from the core.[7,8,9]. The versatility of this approach to nanotube formation has opened up much promise for applications as diverse as transmembrane ion channels and antibacterial agents, biosensors, In this work, we study in situ the assembly of CPs modi ed with polymeric chains and investigate the factors that control
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