Fig. 3: DNP-enhanced 13C-13C-NMR correlation experiment.
From: Overhauser enhanced liquid state nuclear magnetic resonance spectroscopy in one and two dimensions
a 13C NMR spectrum of ethyl acetoacetate-1,2,3,4-13C4 18 (carbon numbering in blue) and its tautomer 19 (carbon numbering in red), 500 mM in CCl4 with 25 mM TEMPONE-15N-d16 under DNP (red, 32 scans) and Boltzmann (blue, 32 scans) conditions. Errors of enhancements ε are estimated between 10–20%. b Pulse sequence for 2D 13C TOCSY with 90° and 180° pulses (green narrow and wide rectangles, respectively), heteronuclear decoupling (WALTZ16), MW irradiation, and isotropic mixing pulse train (FLOPSY-16) (“Methods”). Time delays δ1 and δ2 were set to 2 ms and 3 ms, respectively (Methods), t1 was incremented. 13C-TOCSY spectra of the same sample DNP (c, 8 scans) and Boltzmann (d, 16 scans), both with an optimized τmix ≈ 9.4 ms. Dashed green lines represent correlations within EAA and red lines within its tautomer. Sample temperature was ~300 K, MW irradiation \({P}_{{MW}} \, \approx \, 40\) W. Experimental time is given in the inset. Source data are provided as a Source Data file60.
