Nat. Chem. Biol. 7, 401–404 (2011); published online 17 June 2011; corrected after print 14 July 2011
In the version of this article initially published, there was an error in the abstract that stated an increase in the configurational entropy hinders folding, but it should read that there is a decrease in the configurational entropy that hinders folding. The error has been corrected in the HTML and PDF versions of the article.