Nat. Protoc. 8, 2449–2470 (2013); doi:10.1038/nprot.2013.145; published online 14 November 2013; corrected after print 26 February 2014

In the version of this article initially published, the amount of N-ethylmaleimide to be dissolved was incorrect; it should be 25 mg rather than 0.25 mg. It was also not specified that the N-ethylmaleimide solution should be 1 M. In addition, the catalog number from Sigma-Aldrich for sodium acetate was incorrectly given as S2889; it should be S8625. Also, it should have been stated that the sodium acetate required is · 3H2O. The errors have been corrected in the HTML and PDF versions of the article.