Alternating DNA and π-conjugated sequences. Thermophilic foldable polymers

Abstract

Foldable polymers with alternating single-strand deoxyribonucleic acid and planar conjugated organic perylene tetracarboxylic diimide units were found to self-organize into loosely folded nanostructures. Upon heating, the loosely folded structures become more ordered as evidenced by π-stacking in the perylene segments. The folding and unfolding processes driven by the molecular interactions of adjacent perylenes were monitored in both aqueous and organic solutions. Heat-promoted folding, or inverse temperature behavior, which originates from positive enthalpy changes, was only observed in water. Therefore, we attributed this inverse temperature dependence to hydrophobic effects rather than π-π molecular orbital overlap between the perylene planes. These findings shed light on the design of new thermophiles in protein engineering as well as the construction of macromolecular-based nanodevices with actuator and sensory properties. Copyright © 2003 American Chemical Society.