Residual chemical shift anisotropy

Residual chemical shift anisotropy (RCSA) is another parameter that is being incorporated into the structure elucidation toolbox. As its name suggests, RCSA is similar to residual dipolar coupling (RDC) in that it requires partial alignment of the sample so that differences between the aligned and unaligned states can be measured.

Residual dipolar coupling

Traditionally, NMR structure elucidation has relied upon analysis of chemical shifts, coupling constants, and NOEs. In most cases this is sufficient but occasionally mistakes have been made. Recently, additional NMR observables have been introduced to the structure elucidation toolkit that reduce the chances of getting things wrong. One of these observables is residual dipolar coupling or RDC.