th  - 1988 - 51st ENC Conference

-- VOLUME LOCALIZED SPECTRAL EDITING USING ZERO
QUANTUM COHERENCE CREATED IN A STIMULATED ECHO
1 1 4 [ PUI~E SEQUENCE: Christopher H. Sotak and Dominique M. Free-
man, General Electric NMR Instruments, Fremont, CA, 94539.
With the advent of myriad pulsed field gradient methods for volume localization, it is now
possible to obtain reasonable in vivo specua from a region of interest based upon an image. For
protons, we have found the STimulated Echo (STE) technique (1-4) to give good results. Unfor-
tunately, the direct observation protonated metabolites /n vivo is frequendy precluded by the pres-
ence of interfering resonances. Consequently, some method of spectral editing is usually required,
in conjunction with the localization technique, to extract the metabolite information.
We have developed a volume localized spectral editing technique using zero quantum
coherences (ZQC's) created in a STE pulse sequence (5). In addition to localization, the STE
sequence (Figu£roe 1) generates ZQ (and higher order) coherences in coupled spin systems following
the first two 90 pulses. The ZQC's evolve during the interval t 1 and manifest themselves as an
amplitude modulation of the corresponding single quantum sign~tl generated following the third
90 pulse. The ZQ modulation frequency equals the chemical shift difference (in Hz) between the
coupled spins. Noncoupled spins, on the other hand, experience no modulation during the t 1
period since isolated spin-lf2 nuclei only undergo single quantum transitions. Subtracting two
volume localized spectra with the appropriate ZQ evolution periods constructively adds signal
from metabolites with coupled spins and cancels signal from interfering noncoupled resonances.
In addition to discriminating against noncoupled spins, it is also possible to distinguish
among various types of coupled spin systems based upon differences in their ZQ frequencies.
These frequencies are elucidated in a two-dimensional experiment where the ZQ evolution period
is incremented. Subsequent two-dimensional Fourier transformation yields a plot of chemical shift
vs. ZQ modulation frequency. Peaks due to coupled metabolites are separated in the ZQ fre-
quency domain based upon chemical shift differences between the respective coupled spins. Peaks
due to noncoupled spins appear at zero frequency.
We have applied these techniques /n vivo to measure 5 to 10 mM lactate concentrations in
implanted mouse tumors in the presence of interfering lipid resonances.
1. J. Frahm, K. D. Merboldt, and W. Hanicke, J. Magn. Reson. 72, 502 (1987).
2. G. McKinnon, Works in Progress, 5th Annual Meeting of the Society of Magnetic Resonance
in Medicine, Montreal, August 19-22, 1986, 168.
3. J. Granot, J. Magn. Reson. 70, 488 (1986).
4. R. Kimmieh and D. Hoepfel, J. Magn. Reson. 72, 379 (1987).
5. C.H. Sotak and D. M. Freeman, J. Magn. Reson., in press, (1988).
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I [ USE OF PURE ABSORPTION PHASE 31p/IH 2D COLOC
NMR SPECTRA FOR ASSIGNMENT OF zip SIGNALS OF OLIGONUCLEOTIDES:
Josepha M. Fu, Stephen A. Schroeder, Claude R. Jones*, Robert Santini* and David G. Goren-
stein*, Department of Chemistry, Purdue University, W. Lafayette, IN 47907
Chemical shift data in 31p NMR spectroscopy serves as an important probe of the conformation
and dynamics of nucleic acids. A major limitation in the use of zip NMR has been the difficuly
in assigning the signals. An 1tO labeling methodology has previously been used for assigning
the zip signals, however, this methodology is rather costly and time consuming. A 2D 31p _
1H COLOC NMR approach is shown to provide a staightforward, convenient alternative for
assigning the zip of even moderately sized oligonucleotide duplexes. The COLOC pulse sequence
was modified to emphasize 31p _ 1H scalar couplings and to produce pure absorption ph~qe
spectra. The 31p _ l H COLOC spectra showed enhanced sensitivity and resolution relative to 31p
- 1H heteronuclear correlation spectra. The 31p chemical shifts of the self-complementary 14 base
pair oligonucleotide, d(TGTGAGCGCTCACA)2, were determined from the COLOC spectrum,
based upon IH assignments determined by 2D 1H - tH COSY and NOESY spectra. The zip
assignments were verified by 1~O labeling. The zip chemical shifts of another oligonucleotide,
d(TATGAGCGCTCATA)2, were also determined by 31p _ l H COLOC and 1H - IH COSY and
NOESY.
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