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the zinc ions from the polymer, the characteristic absorption and CD signals for the
triple helix resumed.
12.5 Conclusions and Outlook
Much progress has been made in synthetic foldamers in the last two decades [1-7]. The
incorporation of metal-binding sites on a foldamer backbone or at the side chains allows
one to tune the conformation of a foldamer by potentially strong metal-ligand complex-
ation. In the meantime, the conformational properties of a foldamer can greatly influence
its coordination to the metal [115]. Such interplay opens up exciting opportunities for
both the metal and the foldamer, enabling new applications in many areas, including
molecular recognition, sensing, and material synthesis.
The examples described in this chapter point to a need to deepen our understanding of
the interactions between metal ions and conformationally mobile foldamer chains.
Depending on the exact role of the metal - as a connector of two foldamer fragments [27]
or as a guest to bind with a multidentate foldamer host - the conformation of the foldamer
may have very different effects on the metal-binding. The positive cooperativity found in
oligocholates [69] represents the tip of the iceberg for the potential of foldamers as bio-
mimetic supramolecular hosts. Chemists have always wanted to duplicate nature's exqui-
site ability to control structure, function, reactivity, and energy transfer with
biofoldamers. Too many times have chemists failed to recreate the functions of proteins
when they cut out “irrelevant” peptides and attempted to mimic enzyme active sites by
rigid small-molecule constructs. It is becoming clear in many cases that a wide variety of
“conformational communication” exists between the active site and remote peptide chains
and is essential to the function of the protein. A deeper understanding of cooperative con-
formational change is a fundamental challenge but is also the key to unlock nature's
secrets in using weak noncovalent interactions to construct receptors with high affinity
and specificity.
In comparison to the dynamic materials found in the biological world, what chemists
have created so far is primitive. Nonetheless, as a Chinese proverb puts it, a journey of a
thousand miles begins with a single step. Molecular recognition is at the heart of biology.
Supramolecular interactions are critical to the performance of materials. Controlled
mechanical movements formerly considered only possible with biofoldamers have
already been realized by Lehn and coworkers in abiotic oligoheterocycles [78,83,85,86].
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