(SE)-E-3-E.COSY methods for the measurement of F-19 associated scalar and dipolar coupling constants

A H-1-F-19 spin state selective excitation ((SE)-E-3) pulse sequence elemen t has been applied in combination with IH homonuclear mixing to create E.CO SY-type experiments designed to measure scalar J(HF2') and J(HH2') and resi dual dipolar D-HF2' and D-HH2' couplings in 2'-deoxy-2'-fluoro-sugars. The H-1-F-19 (SE)-E-3 pulse sequence element, which resembles a simple INEPT se quence, achieves spin-state-selective correlation between geminal H-1-F-19 spin pairs by linear combination of in-phase F-19 magnetization and anti-ph ase magnetization evolved from H-1. Since the (SE)-E-3 sequence converts bo th F-19 and H-1 steady-state polarization into observable coherences, an ap proximately twofold signal increase is observed for fully relaxed H-1-F-19 spin pairs with respect to a standard H-1 coupled F-19 1D experiment. The i mproved sensitivity and resolution afforded by the use of H-1-F-19 (SE)-E-3 E.COSY-type experiments for measuring couplings is demonstrated on the nuc leoside 9-(2',3'-dideoxy-2'-fluoro-beta -D-threo-pentofuranosyl)adenine (be ta -FddA) and on a selectively 2'-fluorine labeled 21mer RNA oligonucleotid e.