Fig. 1.

Single-molecule FRET efficiency measurements on polyproline peptides. (A) Molecular model of a polyproline peptide used in this study. The acceptor and donor chromophore are linked to the chain by amino- and carboxyl-terminal glycine and cysteine residues, respectively. The conformation of the proline 20-mer is based on the crystal structure (28); the linkers and dyes were placed in arbitrary orientations. (B) Transfer efficiency histograms obtained from confocal single-molecule measurements on polyproline peptides of various lengths.