Application of dipolar coupling data to the refinement of the solution structure of the Sarcin-Ricin loop RNA

Residual dipolar couplings can provide the long-range information that most NMR solution structures lack. The use of such data in protein structure de terminations is now fairly routine, but even though these data should be mu ch more useful for nucleic acids, their application to nucleic acid structu re determination is still in its infancy. Here we present a method for prod ucing accurate, dipolar-refined structures of nucleic acids that is more ef ficient than those used previously, and apply it to E73, a 29 nucleotide RN A that includes the sarcin-ricin loop from rat 28S rRNA. The results enable us to address the differences between the crystal structure of E73 and the solution structure proposed for it previously.