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The development of new NMR methods is essential to broadening the range of NMR spectroscopy applications in the study of different systems. Recently, focus has been placed on 13C direct detection NMR spectroscopy both in solution and solid state. A suite of multidimensional NMR experiments based on 13C detection has been developed and affords an additional tool for the study of biological macromolecules that can provide more, and in some cases unique, information. The most recent development occurring during this last year has been the exploitation of 1H polarization as a starting source of exclusively heteronuclear NMR experiments geared at improving sensitivity while taking advantage of the large heteronuclear chemical shift dispersion in all dimensions of multidimensional NMR experiments. As demonstrated in several cases, these experiments are particularly well-suited to study large, intrinsically disordered proteins. The increase in instrumental and experimental sensitivity has stimulated the implementation of a variety of experimental approaches to further reduce the duration of NMR experiments (longitudinal relaxation enhancement, spectral aliasing, non-uniform sampling). These are generally referred to as the H-flip set of experiments. The suite of experiments based on 13C detection in solution shares some common and/or comple-mentary aspects to experiments in the solid state. This has sparked the development of new ex-perimental approaches in solid state and the combined use of solution and solid state NMR for the study of challenging proteins (paramagnetic, large multimeric protein assemblies).

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The H-flip experimental approach to reduce the duration of NMR experiments. The faster recovery of selected proton types in ubiquitin upon implementation of the Hflip approach is shown on the left. The (Hflip)CACO (with and without spectral folding in the indirect dimension) acquired in a few minutes on a 1 mM ubiquitin sample (right).