Analyzing single molecule trajectories on complex energy landscapes using replica correlation functions

Single molecule experiments bring to mind a new set of questions having to do with the statistical mechanics of uniqueness and individuality. One such question is the quantitative description of the diversity of mechanisms fo r reactions on complex landscapes. An example of this is the question of th e existence of a unique "pathway" for protein folding. These questions also arise in the theory of spin glasses. We show how single molecule experimen ts can be interpreted using replica correlation functions analogous to thos e appearing in spin glass theory. A caricature of a many conformational sta te reaction scheme appropriate for folding is analyzed in some detail. (C) 1999 Elsevier Science B.V. All rights reserved.