Supramolecular Chirality: Vesicle-to-Chiral Helix Transition of the Micelles Consisting of a Sugar-Bearing Calix[4]arene Surfactant

Supramolecular self-assembly and the resulting chiral transfer from the molecular level to the nanoscale is a major topic in modern supramolecular chemistry. We synthesized a galactose-bearing calix[4]­arene surfactant (chiral) and mixed it with a primary amine-bearing analogue (achiral). The mixture showed strong induced circular dichroism (ICD) at an almost 3:2 molar ratio of the two surfactants, and exothermic heat was observed upon mixing. The magnitude of Δ<i>H</i> was comparable to that of van der Waals interactions. This phenomenon indicated that the ICD can be ascribed to the formation of a new supramolecular assembly in which the stoichiometric interaction between the two molecules leads to complexation and the resultant complex has chiral morphology. Transmission electron microscopy and small-angle X-ray scattering showed that the galactose-bearing surfactant forms vesicles, and the mixing induces a transition from the vesicles to threadlike cylinders with a diameter of ∼3.0 nm. We presume that these cylinder are twisted because of chiral transfer from the chiral galactose moiety and show ICD

X‑ray Scattering from Immunostimulatory Tetrapod-Shaped DNA in Aqueous Solution To Explore Its Biological Activity–Conformation Relationship

We carried out synchrotron X-ray scattering experiments from four DNA supermolecules designed to form tetrapod shapes; these supermolecules had different sequences but identical numbers of total base pairs, and each contained an immunostimulatory CpG motif. We confirmed that the supermolecules did indeed form the expected tetrapod shape. The sample that had the largest radius of gyration (<i>R</i>_g) induced the most cytokine secretion from cultured immune cells. Structural analysis in combination with a rigid tetrapod model and an atomic scale DNA model revealed that the larger <i>R</i>_g can be ascribed to dissociation of the DNA double strands in the central connecting portion of the DNA tetrapod. This finding suggests that the biological activity is related to the ease with which single DNA strands can be formed