Construction of alpha-helix peptides with beta-cyclodextrin and dansyl units and their conformational and molecular sensing properties

In order to apply de novo peptide design to molecular sensing, we designed and synthesized alpha-helical peptides with P-cyclodextrin (beta-CDx) as a binding site and a dansyl unit (Dns) as a fluorescence sensing site. The co nformational and molecular sensing properties of the peptides with beta-CDx and Dns in various positions were investigated. Circular dichroism and flu orescence measurements revealed that beta-CDx and Dns form intramolecular c omplexes which depend on their positions in the peptides. In the 17 residua l peptides named EK3 and EK3R, in which beta-CDx and Dns were introduced at the fourth and the eighth positions (EK3) or at the eighth and the fourth positions (EK3R), Dns was deeply included in the CDx cavity and formed a mo re stable self-inclusion complex with CDx than in the peptides EK6 and EK6R , in which these moieties were at the eighth and the fifteenth positions or at the fifteenth and the eighth positions, respectively. The stability of the self-inclusion complex between beta-CDx and Dns controlled the alpha-he lix structure as well as the binding and sensing abilities for the exogenou s guests. These results demonstrate the usefulness of peptide tertiary stru cture for arranging CDx and other functional units, and suggest that this a pproach is important in the development of a new type of CDx-based sensory system.