OFF-RESONANCE NMR ON NITROGEN-15 IN GUANOSINE and PHASE CYCLING OF QUADRUPOLAR NMR ON OXYGEN-17 IN SILICA.
Malave, Peter.
2011
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Abstract: Nuclear magnetic resonance in the solid state provides a wealth of
inter- and intramolecular interactions that can be utilized to provide useful physical
information. Chemical shift, dipolar, J-coupling, and quadrupolar interactions are all
present in the solid state and provide complementary information on molecular structure and
dynamics. In this work, dipolar, J-coupling, and ... read morequadrupolar interactions are studied.
Lee-Goldburg off-resonance excitation is employed on a sample of
15N enriched guanosine to determine inter and intramolecular
nitrogen-hydrogen distances and the scalar J-coupling constant. Satellite transition magic
angle spinning is employed on an 17O enriched sample in silica
to experimentally study phase cycling effects. Lee-Goldburg decoupling on guanosine is
employed to determine scalar coupling in 15N bonded to
1H in guanosine. Experimental results are compared to
theoretically predicted results. Results show scaling factors of 0.47 ± 0.03 and
0.39 ± 0.13 compared to theoretical values of 0.58. Also, a hydrogen bond shift
in the resonance frequencies is postulated. Lee-Goldburg cross polarization on guanosine is
used to probe inter-nuclear distances of 15N bonded to
1H in guanosine. Results are compared to x-ray crystal
structures where positions of protons are energetically optimized. Simulation of
experimental results is also used to compare x-ray bond lengths to Lee-Goldburg cross
polarization results. The Lee-Goldburg results for N-H and N-H2
bonds show stronger agreement with simulation than x-ray results. Differences in distances
range from 0.01 to 0.05 Å. N-H hydrogen bond distances are also compared. Finally,
phase cycling effects are studied in satellite transition magic angle spinning experiments
on 17O in silica. Results show that a variety of phase cycles
for the final pulse in the pulse sequence can be employed to give quantitatively the same
result. On the other hand, phase cycles for the first and second pulses may significantly
alter the spectrum, showing more coherences for smaller numbers of phase
cycles.
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Physics.
Advisor: William Oliver.
Committee: Leon Gunther, Larry Ford, Roger Tobin, and Bernie Gerstein.
Keyword: Physics.read less - ID:
- nk322s03b
- Component ID:
- tufts:20915
- To Cite:
- TARC Citation Guide EndNote
