FIGURE 2.
Imino proton spectra of Ψ-monophosphate (ΨMP) (A), Ψcomp (B), and ΨBP (C) acquired at different temperatures between 5°C and −17.5°C. (A) ΨMP (10 mM in 10 mM Na phosphate at pH 6.4, 50 mM NaCl, 0.1 mM EDTA, in 90% H2O/10% D2O) was taken up into six capillary tubes, which were placed in a 5-mm NMR tube (fill factor of −0.25). (B) Ψcomp (2.7-mM duplex) was prepared as in A and was taken up into 10 capillary tubes, (fill factor of −0.4). (C) ΨBP (2.5 mM duplex) was prepared as in A and taken up into nine capillary tubes (fill factor of −0.3). Data were collected using a jump-return-echo pulse sequence (Sklenár and Bax 1987) on a Varian 720-MHz and 600-MHz spectrometer at the National High Magnetic Field Laboratory.