Determination of 3 J ( 1 H3′ 31 P) couplings in a DNA oligomer with enhanced sensitivity employing a constant‐time TOCSY difference experiment

A constant‐time TOCSY difference experiment for the determination of 3 J ( 1 H3′ 31 P) coupling constants in non‐isotope‐labelled DNA oligonucleotides is presented. The method is tested on a DNA octamer and compared with the established constant‐time NOESY difference method. Each 3 J ( 1 H3′ 31 P) coupling constant is determined from amplitude changes caused by phosphorous decoupling, which are observable on multiple cross‐peaks, thus leading to a high accuracy of the value of the 3 J ( 1 H3′ 31 P) coupling constant. The new experiment delivers up to three times the sensitivity compared with previously reported methods. Copyright © 2011 John Wiley & Sons, Ltd.