Binary Exo-Chiralities in the Peptide α-Helix Studied by Circular Dichroism

Abstract

Chirality is a property present across all scales, from the atomic to the macroscopic world, that mediates crucial processes such as drug recognition, plant growth or transcription of genetic information. Living beings are homochiral, since nature has evolved into a single handedness that can be transmitted from the monomers to macromolecules such as alpha helical peptides, mostly present in nature folded into right handed helices. These supramolecular chiral structures expose functional groups from the monomer sidechains towards the exterior of the helix, creating another layer of information on its surface. Such information can be topologically distributed and is crucial for peptide functionality and assembly into higher order structures. Chiral complex topologies, like binary exohelical ones, represent a superior level of biomacromolecular chirality and constitute the main focus of this thesis. Small alpha helical peptides emerge as the perfect templates for studying these exochiralities and their combination. Solid phase peptide synthesis inherent sequence control allows the creation of tailored unique exohelices based on different repetition patterns. Side chain functionalization of amino acids in these repeated positions with chromophores allows structural elucidation of such exohelices by circular dichroism.