"When the use of deuterated solvents is precluded in the NMR analysis of biomolecules in their natural environment, pre-saturation solvent suppression pulse sequences are frequently employed to avoid interference from the overbearing solvent signal. However, these sequences generally require extensive re-adjustment of NMR parameters between samples. For this reason, the EXCEPT (EXponentially Converging Eradication Pulse Train) solvent suppression sequence was developed, which exhibits a tolerance of over an order of magnitude in sample T₁ variation. EXCEPT uses an innovative version of "inversion-recovery nulling" with frequency-selective, low-power adiabatic pulses and exponentially decreasing interpulse delays that effectively reduce solvent net magnetization by more than 99.9%. Low-power adiabatic pulses confer stable inversion despite B₁-inhomogeneities but are significantly longer than a standard inversion pulse. Differences between experimentally achieved suppressions and those predicted by computer simulations prompted examination of the adiabatic pulse as a source of the discrepancy. These investigations led to the development of a numerical model for predicting relaxation during frequency-selective adiabatic HS1 pulses. The utility of this model is demonstrated for a range of experimental conditions including a wide variation in sample T₁ relaxation time, RF pulse power level dampening, and most importantly, when initial net magnetization is not at thermodynamic equilibrium. Investigations of adiabatic HS1 pulses applied to non-equilibrium magnetization revealed a linear relationship between the magnitude of the magnetization before and after the HS1 pulse. The linear relationship facilitates simple and convenient implementation and optimization of NMR sequences in which adiabatic HS1 pulses are employed"--Abstract, page iv.
Winiarz, Jeffrey G.
Hogan, John Patrick
Ph. D. in Chemistry
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- EXponentially Converging Eradication Pulse Train (EXCEPT) for solvent signal suppression in investigations with variable T₁ times
- Predicting the effect of relaxation during frequency-selective adiabatic pulses
- A fast and convenient way to predict relaxation during a frequency-selective adiabatic hyperbolic secant pulse (HS1 sech pulse)
xi, 75 pages
© 2017 Annalise Rose Pfaff, All rights reserved.
Dissertation - Open Access
Electronic OCLC #
Pfaff, Annalise Rose, "Optimization of solvent suppression sequences for NMR analysis of aqueous solutions" (2017). Doctoral Dissertations. 2628.