Hi to all,
I have to perform an experiment in order to evaluate the behaviour of a protein as the dielectric constant of the bulk varies. So I thought to study the extrinsic fluorescence of the protein with the ANS fluorescent probe in the presence of different concentrations of TFE, the fluorinated alcohol.
I was wandering if the fluorescence of ANS could be affected by ANS independently on the protein.
Thank you
Not sure about ANS but the fluorescence of other dyes such as ThT (thioflavin T) can be affected by solvent polarity so I assume that of ANS can be affected as well.
In fact here is a review article that might help, which describes changes in fluorescence for a number of dyes (including ANS) with solvent
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440933/
One thing I remember about ANS from the good old days of "molten globulology" (where the science seemed as solid as the current "oligomer hypothesis" for amyloids) is that ANS is a charged dye (negatively charged sulfate). So ANS does not only bind to exposed hydrophobic patches but to positively charged groups. I think it's good to exercise particular care with any acid-induced "molten globules". There are also some weird kinetic effects with ANS binding.
Yes, ANS is a known environment-sensitive probe that will display higher emission in hydrophobic environments. It will surely change its emission in response to changes in the solvent, independently of the possible changes in protein conformation.
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