Dynamic 19F NMR spectra of G3-FAF-modified (a) NarI-dC/-2 and (b) NarI-dT/-2 deletion duplexes. Spectra were obtained at seven standard temperatures (5, 10, 20, 30, 40, 50, and 60 °C. Additional temperatures (15, 22, 25, 35 °C) were used for NarI-dT/-2 to clarify coalescent exchange process (see text). (c) 19F NMR NOESY/exchange spectra of NarI-dT/-2 recorded at 5 and 15 °C.