期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：20
页码：11333-11338
DOI：10.1073/pnas.1534664100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Under conditions where macromolecules are aligned very weakly with respect to an external magnetic field, Brownian diffusion no longer averages internuclear dipole-dipole interactions to zero. The resulting residual dipolar coupling, although typically 3 orders of magnitude weaker than in a fully aligned sample, can readily be measured by solution NMR methods. To date, application of this idea has focused primarily on pairs of nuclei separated by one or two covalent bonds, where the internuclear separation is known and the measured dipolar coupling provides direct information on the orientation of the internuclear vector. A method is described that allows observation of dipolar interactions over much larger distances. By decoupling nearest-neighbor interactions, it is readily possible to observe direct dipolar interactions between protons separated by up to 12 A. The approach is demonstrated for the DNA dodecamer d(CGCGAATTCGCG)2, where direct interactions are observed between protons up to three base pairs apart.
