Analysis of ternary mixtures of dinucleoside and complementary
mononucleosides. Top: AU + A + U. The c(AU)4 macrocycle
having a low chelate cooperativity is expected to self-sort the mixture,
to a small extent, leading to different associated species. Bottom: GC + G + C. On the contrary, the
high cooperativity of the c(GC)4 macrocycle leads mainly to a narcissistically self-sorted
mixture of c(GC)4 and the G:C complex. (a, a′) Titration experiments
of a 1:1 mixture of mononucleosides onto a dinucleoside solution monitored
in the 8–15 ppm region of the 1H NMR spectra, where
the most relevant H-bonded proton signals are found: (a) AU + 1:1 A + U in CDCl3:CCl4 (2:3) and (a′) GC + 1:1 G + C in THF-D8. (b, b′) Evolution
of the 8–15 ppm region of the 1H NMR spectra as
a function of temperature for (b) a 1:1:1 mixture of AU + A + U and (b′) a 1:2:2 mixture
of GC + G + C. (c, c′) NOESY spectra at τm = 500 ms and (d, d′) DOSY spectra for (c, d)
a 1:1:1 mixture of AU + A + U in CDCl3:CCl4 (2:3) and (c′, d′)
a 1:2:2 mixture of GC + G + C in THF-D8 (see Figure S5A–D for more details). For proton NMR codes, see Figure 1.