Fig. 1.

The folding-unfolding exchange of the TmCsp protein. a The chemical structure of 5-fluoro tryptophan (5FW; left) and a schematic presentation of the (un-) folding of TmCsp, which contains 5FW residues at positions 7 and 29 (Protein Data Bank, PDB ID 1G6P Kremer et al. 2001). b ¹⁹F spectra of TmCsp at 333 K, 343 K and 373 K with assignments for Trp7 and Trp29. The peak labeled with an asterisk results from a small impurity in the sample. This impurity resonates outside the displayed spectral window at the two lower temperatures