1H-NMR analysis was performed on a Varian Inova 600-MHz spectrometer. The sample was deuterium-exchanged by lyophilization from D2O (2 X by sonication for a half hour, and lyophilization), and then dissolved in 0.7 mL D2O for NMR analysis (sonication for a half hour, followed by centrifugation at 3500 rpm for a half hour and transfer of the supernatant to the NMR tube). Since this procedure left considerable insoluble material, the process of sonication in D2O, centrifugation, and transfer was repeated to produce a second sample for comparison with the first. 1H-NMR 1-D and 2-D TOCSY (total correlation spectroscopy), and NOESY (nuclear Overhauser effect spectroscopy) experiments, as well as 1H-detected 1H-13C-gHSQC (gradient heteronuclear single quantum correlation) and -gHMBC (gradient heteronuclear multiple-bond correlation) experiments were performed at 25(C on the first sample. Proton and carbon chemical shifts were measured relative to internal acetone standard s ((=2.225 ppm and 29.9 ppm, respectively). A 1H-NMR 1-D spectrum of the second sample was obtained purely for comparison of spectral features and peak integration. Complete 1H- and 13C-resonance assignments were obtained by TOCSY and HSQC experiments, and the average repeating structure elucidated from interpretation of the HMBC and NOESY experiments.
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