Peptoids — or oligomers of N-substituted glycine — mimic biopolymers in terms of folding and some of their biological functions. These include inhibiting certain protein−protein interactions, acting as antimicrobial agents and as molecular transporters. Understanding and creating peptoids with well-defined secondary (and higher order) structures could reveal new biological applications.

Helen Blackwell and co-workers, University of Wisconsin−Madison, USA, have found that interactions of the peptoid backbone and side chains can be modeled with simple monomer-based systems. The model peptoid monomers exhibited well-defined local conformational preferences, which allowed the team to design and synthesize an acyclic peptoid trimer with a reverse-turn structure. The reverse-turn was stabilized by ortho-hydrogen bond donation from the N-aryl side chains and allowed control of the dihedral angles by forcing trans-amide geometry within the peptoid backbone.

The researchers note that peptoids with multiple N-aryl side chains could adopt highly stable, polyproline-type II peptoid helices.

• Construction of Peptoids with All Trans-Amide Backbones and Peptoid Reverse Turns via the Tactical Incorporation of N-Aryl Side Chains Capable of Hydrogen Bonding
  J. R. Stringer, J. A. Crapster, I. A. Guzei, H. E. Blackwell,
  J. Org. Chem. 2010, 75.
  DOI: 10.1021/jo101075a