Multifarious Polymorphism of a Multiblock Amphiphilic Macrocycle Bearing Thermally Responsive Polyether Segment

Formation of multiple crystalline phases of a multiblock amphiphilic macrocycle <b>AT2B</b> is demonstrated. <b>AT2B</b> forms a single crystal (Cr-α) by vapor diffusion and shows reversible single-crystal-to-single-crystal transition between two crystalline phases (Cr-α and Cr-β) by a temperature change, and crystalline <b>AT2B</b> (Cr-β) melts at 422 K, and the cooling rate from the melt influences the phase of the solid formed. By cooling at 1.0 K min^–1, <b>AT2B</b> forms crystalline phases (Cr-γ and Cr-δ), which are different from both Cr-α and Cr-β. On the other hand, cooling at 2.0 K min^–1 results in the formation of an amorphous phase, and a mechanical stress also triggers a crystal-to-amorphous solid transition. Interestingly, the amorphous solid crystallizes to give the fifth crystalline phase (Cr-γ) upon heating before melting. It is suggested that these multiple phase transitions are driven by thermal conformational changes at the tetraethylene glycol chains of <b>AT2B</b>

Ion Permeation by a Folded Multiblock Amphiphilic Oligomer Achieved by Hierarchical Construction of Self-Assembled Nanopores

A multiblock amphiphilic molecule <b>1</b>, with a tetrameric alternating sequence of hydrophilic and hydrophobic units, adopts a folded structure in a liposomal membrane like a multipass transmembrane protein, and is able to transport alkali metal cations through the membrane. Hill’s analysis and conductance measurements, analyzed by the Hille equation, revealed that the tetrameric assembly of <b>1</b> forms a 0.53 nm channel allowing for permeation of cations. Since neither <b>3</b>, bearing flexible hydrophobic units and forming no stacked structures in the membrane, nor <b>2</b>, a monomeric version of <b>1</b>, is able to transport cations, the folded conformation of <b>1</b> in the membrane is likely essential for realizing its function. Thus, function and hierarchically formed higher-order structures of <b>1</b>, is strongly correlated with each other like proteins and other biological macromolecules

Micrometer-Size Vesicle Formation Triggered by UV Light

Vesicle formation is a fundamental kinetic process related to the vesicle budding and endocytosis in a cell. In the vesicle formation by artificial means, transformation of lamellar lipid aggregates into spherical architectures is a key process and known to be prompted by e.g. heat, infrared irradiation, and alternating electric field induction. Here we report UV-light-driven formation of vesicles from particles consisting of crumpled phospholipid multilayer membranes involving a photoactive amphiphilic compound composed of 1,4-bis­(4-phenylethynyl)­benzene (BPEB) units. The particles can readily be prepared from a mixture of these components, which is casted on the glass surface followed by addition of water under ultrasonic radiation. Interestingly, upon irradiation with UV light, micrometer-size vesicles were generated from the particles. Neither infrared light irradiation nor heating prompted the vesicle formation. Taking advantage of the benefits of light, we successfully demonstrated micrometer-scale spatiotemporal control of single vesicle formation. It is also revealed that the BPEB units in the amphiphile are essential for this phenomenon