Sugar-responsiveness of higher-order structures in Boronic-acid-appended amphiphiles and polypeptides

Abstract

In biological systems saccharides play important roles as signals, triggers and name tags. Saccharide structure can include a large amount of information using the specific configuration of hydroxyl groups. It has been known that phenylboronic acid can act as an artificial receptor for saccharides, because boronic acid forms complexes with saccharides rapidly and reversibly in aqueous media. When the complex is formed, the neutral sp2-hybridized boron atom changes to the anionic sp3-hybridized boron atom. We synthesized many amphiphiles and polypeptides bearing phenylboronic acids. They formed specific higher-order structures in aqueous media, which changed in response to added saccharides. For example, the phenylboronic-acid-appended-amphiphiles formed stable membranes and gels in the presence of saccharides. In addition, saccharides induced chiral orientation of the amphiphile assemblies. Although phenylboronic-acid-appended-polylysine formed a random coil structure in neutral water, added saccharides induced the coil-to-helix transition.