Fig. 3.
Nearest-neighbor sequence context alters the NMR of a G/A mismatch. Model 2 × 3′-purine (CxA) and 2 × 3′-pyrimidine (AxC) sequence contexts extremes were examined (shown in middle). (A) 1H NMR spectra of the aromatic region; CxA (Upper) and AxC (Lower) sequence context recorded at 298 K in D2O solutions. Resonances at the mismatch (G5; A16, maroon), flanking sequence (red), and additional residues (gray) are labeled. (B) 31P spectra (proton decoupled) of CxA (Upper) and AxC (Lower) duplexes recorded at 298 K in D2O solutions. Phosphodiester resonances were assigned by using 2D 31P-1H correlation spectra. (C) Imino proton spectra of CxA (Upper) and AxC (Lower) duplexes recorded at 288 K in H2O solutions. Imino protons at the mismatch (G5, maroon), flanking sequences (red), and additional residues (black) are labeled. (D) Individual base pair lifetime τop of AxC and CxA duplexes at 276 K and 288 K. Note that G7 of AxC is nearly insensitive to the catalyst at this temperature.