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New methods for measuring 1H–31P coupling constants in nucleic acids

New pulse sequences for the measurement of 1H–31P coupling constants in the backbone of DNA duplexes are presented. They have a resemblance to HMBC but the constant J dephasing delay is exploited for heteronuclear J modulation so that the peaks in the two‐dimensional spectrum appear as doublets with splittings scaled relative to the 31P chemical shifts. The new pulse sequences have been applied to a self‐complementary octamer DNA duplex 5′‐CGCTAGCG‐3′ (CTAG). Copyright © 2000 John Wiley & Sons, Ltd.