It was probably a typo, but just in case it wasn't - TFE stands for
trifluoroethanol (not trifluoroacetic acid). To my knowledge, negative
ellipticity at 208 and 222 nm is strictly due to the presence of an alpha
helical conformation and has nothing to do with amino acid chirality. How
much TFE are you using? You might be below a level that could have an
appreciable effect. On the other hand too much might cause other problems
(e.g. precipitation).
Hope this helps,
Russ Lehrnan
I am seeking advice from CD experts out there. I have an amphipathic
peptide with Aib (aminoisobutyric acid) in it, which is known to favour an
alpha-helical conformation. Compared to a similar peptide without Aib, it
in fact shows more structuring in acqueous solution. However, in the
presence of TFE (trifluoroacetic acid), which favours structuring of
amphipathic peptides, it shows an apparently lower helicity than the other
peptide. I was wondering if the fact that Aib is non chiral could have an
effect on the intensity of the negative band around 222 nm.
Bye and thanks, Alex Tossi
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Dr. Alessandro Tossi
Antiinfective peptides group
Dept. of Biochemistry, Biophysics and Macromolecular Chemistry
University of Trieste
Phone -- 39 40 6763673; Fax -- 39 40 6763691
email: tossi@bbcm.univ.trieste.it
http://www.bbcm.univ.trieste.it/~tossi
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