Helicates, Peptide-Helicates and Metal-Assisted Stabilization of Peptide Microstructures - Metallofoldamers: Supramolecular Architectures from Helicates to Biomimetics - page 273

8
Helicates, Peptide-Helicates and
Metal-Assisted Stabilization of Peptide
Microstructures
Markus Albrecht
Institut f¨r Organische Chemie, RWTH Aachen University, Germany
8.1 Introduction
Amino acids and their oligomers, peptides and proteins are of essential biological impor-
tance. In proteins, structure and function is combined in an exceptionally elegant way.
The specific features of the single amino acid components, which depend on the nature of
the side chain functionalities (polarity, etc.), are crucial for the structural arrangement -
the folding. Specific properties are introduced by the action and interaction of those sim-
ple groups on the periphery of the peptide [1].
Due to the high number of donor atoms hidden in peptides, they are excellent chelating
ligands for metal ions [2,3]. Coordinated metals are often involved in reaction centers or
might just act as connecting units to stabilize specific structures. In nature, examples are
found for both of those situations:
1. A representative example for proteins in which the metal is the reactive moiety, which
promotes chemical reactivity, is the class of carboxypeptidases. In this group of
enzymes zinc(II) is the active metal center which facilitates the cleavage of peptidic
bonds [4].
2. The same metal, zinc(II), is present in the zinc finger proteins. Here the metal coordi-
nates to histidine and cysteine residues and acts as a connecting unit that arranges the