Levinthal's Question Revisited, and Answered

Attempts to answer the Levinthal question "How proteins fold to give such a unique structure" are discussed. In the first part of this article, we focus on a few reasons as to why the solution to the protein-folding problem (PFP) has been elusive for a very long time. One is a result of the misinterpretation of Anfinsen's Thermodynamic hypothesis which led to the conclusion that the native structure of a protein must be at a global minimum of the Gibbs energy. The second is the result of the adherence to the hydrophobic paradigm, and at the same time ignoring a whole repertoire of hydrophilic effects. It is argued that switching from a target-based to a caused-based approach, and adopting the hydrophilic paradigm leads straightforwardly to a simple answer to Levinthal's question, as well as to a solution of the PFP.