Abstract
Three tripeptides Boc-Phe-Aib-Val-OMe (1), Boc-Leu-Aib-p-NA-NO2 (2) and Boc-Pro-Aib-m-NA-NO2 (3) (Aib: alpha-aminoisobutyric acid; p- and m-NA: para- and meta-nitroaniline) have been designed by incorporating aromatic rings to study the self-assembly and fibril formation. Single crystal X-ray diffraction studies show that all the peptides adopt turn-like structures that are self-assembled through intermolecular hydrogen bonds and van der Waals interactions to create layers of beta-sheets. Solvent dependent NMR titration and CD studies show that the turn structures of the peptides also exist in the solution phase. The field emission scanning electron microscopic (FE-SEM) images of the peptides in the solid state reveal fibrillar structures of flat morphology that are formed through beta-sheet mediated self-assembly of the preorganized turn building blocks.
Highlights
The design and synthesis of appropriate peptide subunits for desired supramolecular architecture is an important area of current research
In this paper we are interested in designing small synthetic peptides that exhibit turn structures, and have the potential to form supramolecular β-sheets through molecular self-assembly
The solvent dependence of the NH chemical shifts, that is demonstrated in this CDCl3-(CD3)2SO titration experiment, indicates that Aib(2)-NH is free and m-NA(3)-NH is hydrogen bonded in peptide 3 with ∆δ values as 0.97 and -0.06 ppm respectively, indicating a β-turn structure
Summary
The design and synthesis of appropriate peptide subunits for desired supramolecular architecture is an important area of current research. 1A reveals a type II' β-turn-like structure with Phe(1) and Aib(2) occupying the i + 1 and i + 2 positions respectively (Fig. 2).
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