Peptides as bioorganic models

Abstract

This article develops the possibility of using conformationally rigid peptides as bioorganic model systems. Stereochemical constraints on peptide backbone folding may be introduced by the judicious use of sequences containing α-aminoisobutyric acid and proline. The design of synthetic peptide models of 3₁₀-helical and β-turn conformations is reviewed. Attempts at generating model antiparallel β-sheet peptides are discussed. The use of disulphide crosslinks is illustrated in the application of cystine peptides to generate models for β-turn and antiparallel β-sheet conformations. Using a conformationally well-defined backbone as a skeleton attempts to generate models for protein binding sites are examined. Helical retinylidene-lysine peptides are introduced as models for the bacteriorhodopsin chromophore. Lysine containing peptides and chiral diamines are explored as model-binding sites for bilirubin and gossypol. An attempt to model the active site disulphide loop of the redox protein, thioredoxin, is described.