| RESEARCH |
Foldable polymer can take the heat A "thermophilic" polymer with a folded structure that is stable at high temperatures has been synthesized by chemistry professor Alexander D. Q. Li, postdoc Wei Wang, and their colleagues at Washington State University [J. Am. Chem. Soc., 125, 5248 (2003)]. The polymer consists of perylene tetracarboxylic diimide chromophores alternated with single-stranded DNA. The polymer folds so that the perylenes line up in the center and the DNA forms hairpin structures (shown). The order in the structure is monitored by optical absorption of the perylene chromophores, which changes as the polymer folds and unfolds. The folded structure is stabilized by hydrophobic interactions between the perylene units at high temperatures and by hydrogen bonding between complementary DNA sequences at low temperatures. Unlike most weak interactions, hydrophobic forces appear to strengthen as the temperature increases. The structure can be unfolded by introducing DNA complementary to that in the thermophilic polymer. Such polymers could be used as DNA biosensors or molecular actuators. |
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