A 13C-detection NMR approach for large glycoproteins

NMR spectroscopy has great potential to provide us with information on structure and dynamics at atomic resolution of glycoproteins in solution. In larger glycoproteins, however, the detrimental fast 1H transverse relaxation renders the conventional 1H-detected NMR experiments difficult. 13C direct detection potentially offers a valuable alternative to 1H detection to overcome the fast T2 relaxation. Here, we applied 13C-detected NMR methods to observe the NMR signals of 13C-labeled glycans attached to the Fc fragment of immunoglobulin G with a molecular mass of 56 kDa. Spectral analysis revealed that a 13C-detected 13C–13C NOESY experiment is highly useful for spectral assignments of the glycans of large glycoproteins. This approach would be, in part, complementary to 13C–13C TOCSY and 1H-detection experiments.