Guanidinium chloride-induced spectral perturbations of 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid confound interpretation of data on molten globule states

Anal Biochem. 2011 Sep 1;416(1):126-8. doi: 10.1016/j.ab.2011.04.022. Epub 2011 Apr 20.


We describe limitations in the use of 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (bis-ANS) to examine unfolding intermediates associated with guanidinium chloride (GuHCl)-induced protein denaturation. Several studies have used alterations in fluorescence emission of bis-ANS to quantify the population of "molten globule" states. Our findings indicate that the observed changes in bis-ANS spectroscopic properties could originate from the interactions of bis-ANS and GuHCl and the aggregation of the dye at higher GuHCl concentrations. We posit that in the absence of additional complementary structural or spectroscopic measurements, the use of bis-ANS emission alone to monitor protein conformations can be misleading.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anilino Naphthalenesulfonates / chemistry*
  • Dose-Response Relationship, Drug
  • Guanidine / analysis
  • Guanidine / pharmacology*
  • Protein Conformation / drug effects
  • Protein Denaturation / drug effects
  • Protein Unfolding / drug effects
  • Proteins / chemistry*
  • Spectrometry, Fluorescence
  • Structure-Activity Relationship


  • Anilino Naphthalenesulfonates
  • Proteins
  • 5,5'-bis(8-(phenylamino)-1-naphthalenesulfonate)
  • Guanidine