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 containingα-aminoisobutyric acid and proline. The design of synthetic peptide models of 3₁₀-helical and β-turn conformations is reviewed. Attempts at generating model antiparallelβ-sheet peptides are discussed. The use of disulphide crosslinks is illustrated in the application of cystine peptides to generate models forβ-turn and antiparallelβ-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.

This article reviews recent¹HNMR studies on peptides carried out in the author’s laboratory. Methods for the delineation of hydrogen bonded NH groups are discussed and exemplified by studies of conformationally constrained peptides. The application of concentration dependences ofNMR parameters for NH groups in peptides to the study of peptide aggregation in apolar solvents is considered. Investigations on chemotactic peptide analogs and suzukacillin fragments are briefly summarized. Nuclear-Overhauser effect studies on β-sheet and β-turn conformational models are described.NMR studies on conformational transitions accompanying dissolution of single crystals are illustrated by a study of a peptide containing a -Pro-Pro- segment.