Controlled Stability of the Triple-Stranded Helical Structure of a β-1,3-Glucan with a Chromophoric Aromatic Moiety at a Peripheral Position

We synthesized a semiartificial β‐1,3‐glucan, curdlan with dialkylaniline groups (CUR‐DA), that bears chromophoric aromatic groups at its peripheral positions. Spectroscopic studies as well as microscopic observations indicate that CUR‐DA adopts a triple‐stranded helical structure in water‐ or methanol‐rich solutions of dimethyl sulfoxide (DMSO). This triple‐stranded helical structure exhibits high thermal stability and resistance to base, attributes that are similar to those of the triple‐stranded helical structure of native β‐1,3‐glucans such as schizophyllan. Moreover, we found that the stability of the triple‐stranded helical structure can be easily modulated by solvent composition and metal‐ion (Zn2+) binding. As β‐1,3‐glucan polysaccharides are known to serve as “polymeric” hosts, including certain DNA molecules, carbon nanotubes, and conjugated polymers, and complexation occurs only with the single‐stranded structure, this information is very useful for the creation of these attractive polymeric composites, the controlled release of DNA, and so on. Twisted nature: A semiartificial β‐1,3‐glucan that bears chromophoric aromatic groups at its peripheral positions adopts a triple‐stranded helical configuration in water‐ and methanol‐rich dimethyl sulfoxide. The stability of this structure can be controlled by solvent composition and metal‐ion binding.