Sequence-dependence of secondary structure formation. II. Effect of nearest neighbour interactions on the β-structure formation of host-guest peptides

The conformational influence of the insertion of two guest amino acids into a homooligopeptide consisting of L-Val residues was investigated by circular dichroism and infrared spectroscopy. L-Ala, L-Ile and L-Leu were chosen as guest amino acids and their β-structure disrupting properties studied with respect to size and symmetry of their side-chains. These studies were complemented by investigations concerning the aggregation behaviour of the various peptides by means of gel permeation chromatography. It is shown that the tendency of the various peptides to form β-structures and to aggregate increases with increasing similarity in the spatial size of the side-chains between guest and host amino acids. The impact of those results on the prediction of peptide secondary structure as well as their importance for peptide synthesis is briefly discussed.