Electron-Nuclear Interactions

13C Direct‐detection biomolecular NMR

“…The first question that arises on 13 C direct-detection biomolecular NMR is why one should switch from 1 H to 13 C direct-detection as heteronuclei ( 13 C, 15 N) can be observed with much higher sensitivity through so called inverse detection methods (1,2). Indeed the majority of NMR experiments routinely applied to study biological macromolecules rely on these methods (3)(4)(5)).…”

“…Indeed the majority of NMR experiments routinely applied to study biological macromolecules rely on these methods (3)(4)(5)). The answer resides in the intrinsic properties of 13 C compared with 1 H nuclei that provide information in those cases where proton NMR is bound to fail. The large gyromagnetic ratio of 1 H, responsible for the high 1 H sensitivity, is the well-known source of the large proton dipolar interactions which may broaden the NMR lines in large or paramagnetic molecules.…”

“…Furthermore, chemical shifts, J couplings and residual dipolar couplings, as well as relaxation rates provide a wealth of data useful in the study of a protein and its interactions. Thus, thanks to the tremendous improvement in instrumental sensitivity experienced lately (9, 10) a number of exclusively heteronuclear NMR experiments based on 13 C direct-detection protonless NMR have been developed that constitute a complete set to study proteins (9,(11)(12)(13)(14)(15)(16). Novel experiments are also being developed for the study of DNA and RNA (17,18).…”

“…The two approaches have many aspects in common, starting from the basic experimental building blocks (3,(19)(20)(21). The novel aspects that need to be addressed to convert 13 C direct detection into a useful routinely applicable tool, mainly related to the problem of homonuclear decoupling in the direct acquisition dimension, are presented here along with a selection of the most useful 13 C direct-detection protonless NMR experiments demonstrated on a cyclic octapeptide, hymenistatin. Advantages and limitations of reintroducing proton magnetization as the starting point of 13 C direct-detection NMR experiments are discussed.…”

“…The novel aspects that need to be addressed to convert 13 C direct detection into a useful routinely applicable tool, mainly related to the problem of homonuclear decoupling in the direct acquisition dimension, are presented here along with a selection of the most useful 13 C direct-detection protonless NMR experiments demonstrated on a cyclic octapeptide, hymenistatin. Advantages and limitations of reintroducing proton magnetization as the starting point of 13 C direct-detection NMR experiments are discussed. Tips and tricks for the experimental set-up, including reference to the hardware, are finally presented using as an example a widely used protein, ubiquitin.…”