Molecular packing structure analysis of foldecture via powder x-ray diffraction

Abstract

Peptide foldamers, which are known for having rigid secondary structure, create self-assembled structures with unique three-dimensional morphologies in aqueous surfactant solution. These structures are named foldecture, im-plying that the molecular architecture consists of foldamer. Unlike the common peptide self-assembled structures, foldecture has a high crystallinity, and thus the identifying molecular packing structure is essential to comprehend and analyze the distinctive properties such as shape evolution, anisotropic surface characteristics and magnetic field susceptibility. In this vein, it is indispensable to study the establishment of structural analysis methodology which is applicable to various types of foldectures. In this dissertation, the structure determination methodology of molecular packing structure and various appli-cation results for foldectures via powder X-ray diffraction experiment are discussed. It is possible to solve the structure solely from one-dimensional diffraction data, as restraints including intramolecular hydrogen bond were set up for mimicking rigid secondary structure of the foldamers constituting the foldecture. On the other hand, the crystallographic preferred orientation prediction based on the morphology of the foldecture could reveal the rela-tionship between the symmetry of foldecture appearance and the symmetry operations in the unit lattice. In addition, this information allows the designation of the crystallographic plane exposed on the foldecture surface and deter-mination of the type and direction of intermolecular interactions between peptide foldamers through anisotropic microstrain analysis. It is expected that these results can be the preliminary research for understanding self-assem-bly mechanism and establishing new foldecture design principle.