NOE difference experiment

Lexx (brownk@chem4823.usask.ca)
Wed, 22 Apr 1998 16:32:00 -0600 (CST)

I am trying to perform a standard noe difference experiment using the
technique of Kinns in which each peak in a multiplet is irradiated for a
short time using low power. I have been careful to degas the sample using
freeze-pump-thaw, measured the 90 degree pulse width using the sample in
question and cycled between three multiplets of interest and an
off-resonance point for about twelve hours on a weekend.

After the appropriate subtraction I see absolutely no noe effect
anywhere in any of the spectra taken. I know that the machine is
functioning properly and that the experiment works since I did a quick noe
difference experiment on sucrose octaacetate which worked quite well. I do
see lots of dispersive-looking peaks in the subtraction spectra which
puzzles me somewhat since the use of the 90 degree pulse is supposed to
minimize any SPT effects (Shaka et al, J. Mag. Res. 60, 479-486 (1984)).

This is a reasonably standard experiment and I am a little surprised at
the results. Anyone have any ideas/suggestions?

Keith Brown
University of Saskatchewan

-----------------------------------------------------------------------------
Conjecture: All odd numbers are prime.
Mathematician's Proof:
3 is prime. 5 is prime. 7 is prime. By induction, all
odd numbers are prime.
Physicist's Proof:
3 is prime. 5 is prime. 7 is prime. 9 is experimental
error. 11 is prime. 13 is prime ...
Engineer's Proof:
3 is prime. 5 is prime. 7 is prime. 9 is prime.
11 is prime. 13 is prime ...
Computer Scientists's Proof:
3 is prime. 3 is prime. 3 is prime. 3 is prime...