Measurements of side-chain 13C-13C residual dipolar couplings in uniformly deuterated proteins.

13C-only spectroscopy was used to measure multiple residual (13)C-(13)C dipolar couplings (RDCs) in uniformly deuterated and (13)C-labeled proteins. We demonstrate that (13)C-start and (13)C-observe spectra can be routinely used to measure an extensive set of the side-chain residual (13)C-(13)C dipolar couplings upon partial alignment of human ubiquitin in the presence of bacteriophages Pf1. We establish that, among different broadband polarization transfer schemes, the FLOPSY family can be used to exchange magnetization between a J coupled network of spins while largely decoupling dipolar interactions between these spins. An excellent correlation between measured RDCs and the 3D structure of the protein was observed, indicating a potential use of the (13)C-(13)C RDCs in the structure determination of perdeuterated proteins.