Resonance assignments very large proteins

The interpretation of one- and two-dimensional spectra of large biomolecules such as proteins and nucleic acids is usually impossible due to the large number of highly degenerated peaks. Hence, even for the medium-sized molecules, it is necessary to use isotopic enrichment with and nuclei, and to perform triple-resonance 3D NMR experiments for resonance assignment and extraction of structural constraints. However, as we pointed out above, the resolution of conventionally acquired 3D spectra, is limited by sampling requirements. Therefore, it is rarely possible to obtain line widths close to the natural ones in a reasonable time, even for very fast-relaxing molecules. The conventional 4D spectra, such as or... 

In 2001, the stmcture of the transmembrane domain of OmpA (Fig. 2a) was solved in DPC micelles, and it represented the largest membrane protein stmcture (19 kDa) to have been solved by NMR at that time (25). TROSY triple-resonance experiments enabled a large number of the residues to be assigned for the deuterated protein. Relatively limited stmcture restraints (NOEs, dihedral angles, interstrand hydrogen bonds) revealed an eight-stranded 3 barrel stmcture for the transmembrane domain of this ion chaimel that was very similar to the existing X-ray stmcture. 

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