Fig. 4. The loop of SPM-1 adopts distinct conformations in solution. (A) ¹⁹F-NMR spectra of folded di-Zn(ii)-SPM-1* (top) and denatured SPM-1* (bottom) revealed distinct signals (The peak labeled * may correspond to an intermediate state between non-denatured and denatured states); (B) views of the SPM-1 α3 region in ‘closed’ and ‘open’ conformations, showing the different position of Tyr-152 (the residue which was substituted for Cys, derivatized with CF₃COCH₂Br, to give a Enz–SCH₂COCF₃ species).