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. Author manuscript; available in PMC: 2015 Sep 4.
Published in final edited form as: Nat Commun. 2014 Sep 4;5:4786. doi: 10.1038/ncomms5786

Figure 1. Widespread occurrence of transient A•T and G•C+ Hoogsteen base-pairs in canonical duplex DNA.

Figure 1

(a) The equilibrium between Watson-Crick and Hoogsteen base-pairs. Shown are the average forward (kA) and reverse (kB) rate constants and populations of Watson-Crick (pA) and Hoogsteen (pB) base-pairs obtained in this study. (b) DNA duplexes used in this study. Base-pairs targeted for relaxation dispersion measurements are highlighted with a star. (c) Representative off-resonance 13C and 15N R1ρ relaxation dispersion profiles showing chemical exchange outside TA and CA steps of canonical duplex DNA. Spin lock powers (Hz) are shown in the inset. Data are fit to Equation 2. Error bars represent experimental uncertainty (one standard deviation) estimated from monoexponential fitting of duplicate R1ρ data and analysis of signal-to-noise. See Methods for buffer conditions.