Total Correlation Spectroscopy across All NMR-Active Nuclei by Mixing at Zero Field
Ivan V. Zhukov, Alexey S. Kiryutin, Fabien Ferrage, Gerd Buntkowsky, Alexandra V. Yurkovskaya, Konstantin L. Ivanov
Abstract
Multidimensional nuclear magnetic resonance (NMR) is based on a combination of well-established building blocks for polarization transfer. These blocks are used to design correlation experiments through one or a few chemical bonds or through space. Here, we introduce a building block that enables polarization transfer across all NMR-active nuclei in a coupled network of spins: isotropic mixing at zero and ultralow field (ZULF). Exploiting mixing under ZULF-NMR conditions, heteronuclear TOtal Correlation SpectroscopY (TOCSY) experiments were developed to highlight coupled spin networks. We demonstrate 1H–13C and 1H–15N correlations in ZULF–TOCSY spectra of labeled amino acids, which allow one to obtain cross-peaks among all heteronuclei belonging to the same coupled network, even when the direct interaction between them is negligible. We also demonstrate the potential of ZULF–TOCSY to analyze complex mixtures on a growth medium of isotope-labeled biomolecules. ZULF–TOCSY enables the quick identification of individual compounds in the mixture by their coupled spin networks. The ZULF–TOCSY method will lead to the development of a new toolbox of experiments to analyze complex mixtures by NMR.