Introduction to Unnatural Foldamers - Metallofoldamers: Supramolecular Architectures from Helicates to Biomimetics - page 80

Figure 2.42 A well folded and stable construct that encapsulates the heavy metals Hg II ,
Cd II and Pb II with high affinity and predefined coordination geometry. Reprinted with permis-
sion from Ref. [113]. Copyright 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

a-peptides with helix bundle tertiary structure [112]. They recently reported, in collabora-
tion with the Pecoraro group, the preparation of a single polypeptide chain capable of
binding metal ions with a high affinity and predefined coordination geometry (Figure
2.42) [113]. An understanding of the biochemistry of the binding of heavy metals to a
single polypeptide chain is potentially useful for the development of peptide-based water
purification systems or sensors for specific heavy metal ions.
Several groups have reported homogeneous b-peptides that accomplish the first step of
the hierarchical approach, self-assembly to discrete helix bundles in aqueous solution
[114]. Schepartz and coworkers recently reported that certain b

3 -peptides self-assemble
in aqueous solution into discrete bundles of unique structure and defined stoichiometry
[115]. The thermodynamic stability of a b-peptide bundle can be enhanced by optimizing
the length of these four interhelical salt bridges (Figure 2.43). These results provide
another critical step in the “bottom-up” formation of b-peptide assemblies with defined
sizes, reproducible structures and sophisticated function.

Figure 2.43 Ribbon diagram of the Zwit-EYYK octamer as determined by X-ray crystallogra-
phy. Reprinted with permission from Ref. 115a]. Copyright 2011 WILEY-VCH Verlag GmbH &
Co. KGaA, Weinheim.