Nuclear Overhauser Effect (NOENOE)
• A change in the integrated NMR absorption intensity of a nuclear spin when the NMR absorption of another spin is saturated.
Macromolecules or in viscous solution
W0 dominant, negative NOE at i due to s
Small molecules in non-viscous solution
W2 dominant, positive NOE at i due to s
2262
2260
2261
1
121
21
3
csi
c
csi
c
ci
ci
rW
rW
rW
When 1/c >>0 (or c2
02 <<1 ) extreme narrowing limit
6260611223
rW
rW
rW ccc
When 1/c >> 0 (or c2 0
2 <<1 )
extreme narrowing limit
6260611223
rW
rW
rW ccc
2/1/2126
/212
2 6
6
021
02
0
0
r
r
WWW
WW
I
IIs
c
cii
For homo-nuclear max = 0.5
For hetro-nuclear max = 0.5 si)
When 1/c ~ 0 (or c 0 ~ 1 ) M.W.~ 103
W2 and W0 effect are balanced. max ~ 0
improvement:
• Change solvent ofr temperature
• Using rotating frame NOE
When 1/c < 0 (or c 0 >> 1 ) M.W. > 104
W0 dominant , max = -1
application
Useful technique for assigning NMR spectra of protein