S(3)E-E.COSY methods for the measurement of (19)F associated scalar and dipolar coupling constants.
A (1)H-(19)F spin state selective excitation (S(3)E) pulse sequence element has been applied in combination with (1)H homonuclear mixing to create E.COSY-type experiments designed to measure scalar J(HF2') and J(HH2') and residual dipolar D(HF2') and D(HH2') couplings in 2'-deoxy-2'-fluoro-sugars. The (1)H-(19)F S(3)E pulse sequence element, which resembles a simple INEPT sequence, achieves spin-state-selective correlation between geminal (1)H-(19)F spin pairs by linear combination of in-phase (19)F magnetization and anti-phase magnetization evolved from (1)H. Since the S(3)E sequence converts both (19)F and (1)H steady-state polarization into observable coherences, an approximately twofold signal increase is observed for fully relaxed (1)H-(19)F spin pairs with respect to a standard (1)H coupled (19)F 1D experiment. The improved sensitivity and resolution afforded by the use of (1)H-(19)F S(3)E E.COSY-type experiments for measuring couplings is demonstrated on the nucleoside 9-(2',3'-dideoxy-2'-fluoro-beta-D-threo-pentofuranosyl)adenine (beta-FddA) and on a selectively 2'-fluorine labeled 21mer RNA oligonucleotide.
Luy
B
B
Center for Advanced Research in Biotechnology, University of Maryland and the National Institute for Standards and Technology, 9600 Gudelsky Drive, Rockville, Maryland 20850, USA.
Barchi
J J
JJ
Marino
J P
JP
D003903:Deuterium; D005461:Fluorine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*
D005461:Fluorine; D003903:Deuterium