Introduction to the Special Feature on Single-Molecule Chemistry and Biology

Abstract

The advent of experiments in single-molecule chemistry ≈20 years ago (1, 2) generated a new type of molecular spectroscopy and provided new ways of looking at the dynamics and reactions of biomolecules. In ordinary ensemble experiments, one measures the average over a large number of molecules, so that individual differences between molecules are unobservable. Early spectroscopic studies of single molecules in low-temperature solids showed that each molecule in the ensemble had a distinct spectrum, that the individual spectrum was time-dependent, and that the distribution of molecular properties was often counterintuitive.