The Energy Landscape

If proteins existed in unique structures, with each atom always in the same place, there would be no need to introduce the concepts of an energy landscape and of conformational substates. Single protein experiments would give the same results as experiments on ensembles and would therefore be unnecessary; this Nobel conference would not have taken place. Proteins would be rigid and could not function. In reality, proteins can assume a very large number of somewhat different conformations [1, 2]. In some cases, such as prions and ameloid fibers, the protein conformation may change completely. In other cases, conformational motions activate enzymes, permit access to active sites, or cleave chemical bonds. The energy landscape is the conceptual framework in which these motions and reactions can be described. Here we sketch the experiments that led us to the concepts of substates and landscapes and describe their importance for the interpretation of single-molecule experiments. For surveys, see for instance the papers presented at a conference on landscapes [3]. Some of the data and concepts treated here were discussed from a different point of view [4] at an earlier Nobel Symposium on Structure and Dynamics of Biological Systems.

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