Nuclear Overhauser Effect

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.

Nuclear Overhauser Effect

021

02

0

0

2 WWW

WW

I

IIs

ii

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

Nuclear Overhauser EffectBrownian motion and NOE

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

Nuclear Overhauser Effect & distance

cfr

6

1NOE

citraconic acid mesaconic acid