INEPT-Insensitive Nuclei Enhanced Polarization Transfer

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INEPT-Insensitive Nuclei Enhanced Polarization Transfer

  1. 1. INEPT ( Insensitive Nuclei Enhanced Polarization Transfer )«Enhancement of Nuclear Magnetic Resonance Signals by Polarization Transfer» Gareth A. Morris, Ray Freeman, JACS 101:3, 1979 Emine Can Biomolecular structure and dynamics in solution, 2012
  2. 2. The sensitivity of NMR Signal • Nuclear Magnetic Moment ∝ ɣ SNR ∝ • Nuclear Larmour Frequency ∝ ω ɣ ω2 ω1/2= |ɣ|5/2 B03/2 • Boltzman Polarization ∝ ω • Noise in the coil ∝
  3. 3. Sensitivity Enhancement INEPT: Transfer of the polarization from strongly magnetic proton spins to weakly magnetic nuclei (15N, 29Si...) by using J-couplings between the spins.
  4. 4. Pulse sequence for INEPT τ=1/4JIz+Sz
  5. 5. Pulse sequence for INEPT τ=1/4JIz+Sz Iy+Sz
  6. 6. Pulse sequence for INEPT τ=1/4JIz+Sz Iy+Sz
  7. 7. Pulse sequence for INEPT τ=1/4JIz+Sz Iy+Sz
  8. 8. Pulse sequence for INEPT τ=1/4JIz+Sz Iy+Sz
  9. 9. Pulse sequence for INEPT τ=1/4JIz+Sz Iy+Sz [Iycos(πJ2τ)+2IxSzsin(πJ2τ)]-Sz = [Iycos(Πj2(1/4J))+2IxSzsin(Πj2(1/4J))]-Sz = [Iycos(Π/2)+2IxSzsin(Π/2)]-Sz = 2IxSz-Sz
  10. 10. Pulse sequence for INEPT τ=1/4JIz+Sz Iy+Sz [Iycos(πJ2τ)+2IxSzsin(πJ2τ)]-Sz 2IzSy+Sy = [Iycos(Πj2(1/4J))+2IxSzsin(Πj2(1/4J))]-Sz = [Iycos(Π/2)+2IxSzsin(Π/2)]-Sz = 2IxSz-Sz
  11. 11. Results BI2IzSy + BSSy transferred non-transferred BI =10|BS| Components of the INEPT Spectrum for the case of 1H-15N system * Spin Dynamics M.Levitt, p421
  12. 12. Results INEPT• Enhancement factor• Repetition time NOE• Nuclei with negative ɣ UnenhancedEnhancement factor:X 11B 13C 15N 29Si 57Fe 103Rh 109Ag 119Sn 183WNOE 2.56 2.99 -3.94 -1.52 16.48 -16.89 -9.75 -0.41 13.02INEPT 3.12 3.98 9.87 5.03 30.95 31.77 21.50 2.81 24.04
  13. 13. Refocussed INEPT Precess the anti-phase components into phase before aquisition. Decoupled spectrum+ Increased intensity with polarization transfer 2IxSz-Sz -2IzSx-Sx -Sy-2IzSx transferred non-transferred BI =10|BS|
  14. 14. Results Single 90 degree pulse Proton decoupled INEPT Refocussed INEPT * Spin Dynamics M.Levitt, p422
  15. 15. Thanks!emine.can[at]epfl.chReferences:1) G.A.Morris, R.Freeman, JACS, 101:3 19792) M. Levitt , ‘Spin Dynamics’ 20053) J.K.M.Sanders, B. Hunter ‘Modern NMR Spectroscopy’ 2nd Edition

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