Artifact-free ultralow-temperature DNP-enhanced NMR of molecular assemblies at natural isotopic abundance.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41417898.
- Also identified by DOI 10.1126/sciadv.aeb0337 and PMC identifier 12716396.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Magic-angle spinning dynamic nuclear polarization (MAS-DNP) has greatly increased solid-state NMR sensitivity, enabling multidimensional correlation experiments (e.g., <sup>13</sup>C-<sup>13</sup>C and <sup>13</sup>C-<sup>15</sup>N) at natural isotopic abundance. Yet, these experiments often suffer from <i>t</i><sub>1</sub>-noise, an artifact that obscures weak cross-peaks, especially in natural abundance samples. Here, we present a method to suppress <i>t</i><sub>1</sub>-noise in <sup>13</sup>C-<sup>13</sup>C double-quantum-single-quantum (DQ-SQ) spectra by converting DQ coherences into longitudinal two-spin order (<i>zz</i>-terms), enabling selective removal of uncoupled <sup>13</sup>C magnetization. This <i>zz</i>-filter, compatible with both <i>J</i>- and dipolar-based sequences, markedly improves the spectral quality on both commercial (100 K) and custom-built helium-spinning (30 K) MAS-DNP setups. Up to a fivefold increase in signal-to-noise ratio in the indirect dimension allows detection of previously hidden long-range correlations, including intermolecular contacts. This method yields the first artifact-free <sup>13</sup>C-<sup>13</sup>C DQ-SQ spectrum at 30 K, expanding the analytical reach of MAS-DNP NMR for characterizing molecular assemblies at natural abundance.