Structural distributions from single-molecule measurements as a tool for molecular mechanics

► A mechanical view is an attractive alternative for predicting the behavior of complex molecules. ► We propose using structural distribution from smFRET to extract molecular mechanical properties. ► Short poly-l-proline peptides were used to experimentally illustrate this new approach. ► The effective persistence lengths were found to be size-dependent. ► This is the first experimental evidence of such behavior on the molecular level.