Comment on "Monte Carlo Simulation of a First-Order Transition for Protein Folding"

The article by Hao and Scheraga 1 states that it is the first application of the so-called “entropic sampling Monte Carlo (ESMC) ” method 2 to the protein folding problem: “It should be noted that the earlier procedures are all aimed at simple systems such as spin lattices and fluids”. However, there already exists an earlier work that introduced the same method to the protein folding problem 3. In the latter article the method was referred to as “multicanonical Monte Carlo (MMC) ” 4-7. Although MMC was quoted in Ref. 1, Hao and Scheraga failed in recognizing the identity of ESMC to the earlier MMC method. The reason is possibly that the authors of Refs. 1,2 seem not to have been aware of Refs. 6,7, where the idea and numerical methodology had been more explicitly stated than in Refs. 4,5. These latter works (Refs. 6,7) had already appeared in print before Ref. 2 was submitted for publication. The erratum of Ref.2 corrects for this neglect, but Hao and Scheraga 1 do not refer to this erratum. It is the purpose of this comment to give a simple proof that the two superficially differently looking approaches are identical. Essentially, we follow some earlier private correspondence of one of the authors with Lee 8.