Nuclear Overhauser Effect

NOE Nuclear Overhauser Effect (NOE) A change in the integrated NMR absorption intensity of a nuclear spin when the NMR absorption of another spin is saturated.

Nuclear Overhauser Effect

Macromolecules or in viscous solution W 0 dominant, negative NOE at i due to s Small molecules in non-viscous solution W 2 dominant, positive NOE at i due to s

Nuclear Overhauser Effect Brownian motion and NOE

When 1/  c >>  0 (or  c 2  0 2 <<1 ) extreme narrowing limit

When 1/  c >>  0 (or  c 2  0 2 <<1 ) extreme narrowing limit For homo-nuclear  max = 0.5 For hetro-nuclear  max = 0.5  s  i )

When 1/  c ~  0 (or  c  0 ~ 1 ) M.W.~ 10 3 W 2 and W 0 effect are balanced.  max ~ 0 improvement: Change solvent ofr temperature Using rotating frame NOE

When 1/  c > 1 ) M.W. > 10 4 W 0 dominant,  max = -1 application Useful technique for assigning NMR spectra of protein

Nuclear Overhauser Effect & distance

citraconic acidmesaconic acid