th  - 1987 - 51st ENC Conference

WK44
TWO-DIMENSIONAL POMMIE 13C NMR SPECTRUM EDITING.
Bruce Coxon
Center for Analytical Chemistry
National Bureau of Standards
Gaithersburg, MD 20899
The one-dimensional POMMIE (Phase Oscillations to MaxiMlze
Editing) technique has recently been dev~loped 1,2 as an
alternative to the DEPT method of spectrum editing. We have
extended the POMMIE editing method to the two-dimensional domain.
Our initial studies have focused on 2D POMMIE ~(CH)-resolved 13C
NMR spectrum editing, using the pulse sequence:-
~/2(H)-I/2~-~(H)~/2(C)-I/2~-~/2(H)~/2(H,@)z~I/2-~(H)~(C ) -
i/2~-D-~i/2-acquire 13C, decouple IH, where ~ - IJcH, D is a
delay (equal to the length of the ~(H) pulse) that was inserted
to equalize the 13C dephasing and refocusing periods, and the
pulse pair ~/2(H)~/2(H,~) consists of the multiple quantum
formation and read pulses, respectively, the latter pulse having
a variable phase shift 4.
Automated acquisitions of sets of 2D POMMIE data by three
different methods (a, b, and c) have been investigated. By use
of the phase angle set ~ - ~/2, ~/6, and 5~/6, sets of three 2D
data matrices have been acquired either (a) sequentially, or (b)
in interleaved fashion, the latter method being designed to
minimize the effects of sample or spectrometer instability.
For methods (a) and (b), the 2D POMMIE 13C subspectra were
computed from the relationships CH - data(~/2), CH 2 - data(~/6)
data(5~/6), and CH 3 - data(~/6) + data(5~/6) - data(~/2), by
using the same Pascal software that had been written earlier for
the purpose of 2D DEPT 13C NMR spectrum editing 3.
Method (c) involved the direct automated construction of
the 2D POMMIE 13C subspectra "on the fly", by means of rotating
phase shifts of the MQ read pulse and the receiver 2. This method
did not require combination of the 2D data matrices by use of
software.
2D POMMIE carbon-proton chemical shift correlated spectrum
editing has also been implemented by using the sequence:-
~/2(H)-I~2~-~(H)~/2(C)-I/2J-tl/2-~(C)-~I/2-~/2(H)~/2(H,~ ) -
i/2~-acquire 13C, decouple IH. - -
The methods have been applied experimentally to selected
peptides and carbohydrate derivatives.
[I] J. M. Bulsing, W. M. Brooks, J. Field, and D. M. Doddrell,
J. Magn. Reson. 56, 167-173 (1984).
[2] J. M. Bulsing and D. M. Doddrell, J. Magn. Reson. 61, 197-219
(1985).
[3] B. Coxon, J. Magn. Reson. 66, 230-239 (1986).