2. Structure determination by NMR
NMR principles
Data acquisition
Spectra process
xwinnmr、nmrpipe、nmrview
Assignment
Data Analysis
Structure determination
InsightII、Xplor
Structural analysis
Procheck、Molmol

3. NMR principles Energy Levels Transitions low energy state
high energy state
Transitions
Proton
radiation
emission

4. NMR principles Energy Level Diagrams E = g h B
When placed in a magnetic field of strength B
u = g B gH=42.58 MHz / T
The energy, E, of a photon is related to its frequency,
E = hu h = 6.626x10-34 J s
E = g h B
References: Introduction To Magnetic Resonance Chapman and Hall, London 1967

5. NMR principles
CW NMR Experiment

6. NMR principles
Boltzmann Statistics

7. NMR principles Relaxation T1 Processes At equilibrium Mo = Mz
spin-lattice relaxation time (T1)
longitudinal relaxation time (T1)
At equilibrium
Mo = Mz
Mx 、 My = 0

8. NMR principles
Relaxation
T1 Processes
Mz = Mo ( 1 - e-t/T1 )

9. NMR principles
Relaxation
T2 Processes –Precession (Larmor frequency)

10. NMR principles Relaxation T2 Processes spin-spin relaxation time (T2)
transverse relaxation time (T2)

11. NMR principles Relaxation T2 Processes
Two factors contribute to T2 1) molecular interactions (said to lead to a pure pure T2 molecular effect) 2) variations in B0 (said to lead to an inhomogeneous T2 effect
1/T2* = 1/T2 + 1/T2inhomo.
MXY =MXYoe-t/T2

12. NMR principles
Relaxation

13. NMR principles Excitation by radio frequency pulses q = 2pgtB1
  q is the rotation angle about
q = 2pgtB1
 t is the length of time for the field
B1 is the applied field

14. NMR principles Excitation by radio frequency pulses q = 2pgt B1
Short intense pulses (so called hard pulses) are unselective and excite a broad region of the spectrum.
Long weak pulses (so called soft pulses) are selective and excite only a narrow region around the transmitter frequency.

15. NMR principles
Evolution of magnetization in the xy plane after excitation by an RF pulse
In the coil of the probe head, the precession of magnetization in the xy plane induces a very weak RF signal (μV), the so called free induction decay (FID), which is amplified and recorded during the acquisition time t2 (typically 0.1s to 5 s).

16. NMR principles Chemical Shift - chemical environment B = Bo (1-s)
deshielding
d : ppm
d = (n - nREF) x106/nREF
n : Hz

17. NMR principles
Spin-Spin Coupling-Nuclei which are close to one another exert an influence on each other's effective magnetic field.

18. NMR principles
Spin-Spin

19. NMR principles
Spin-Spin Coupling -example

20. NMR principles
The Time Domain NMR Signal and Fourier transform FT

21. NMR principles
2D NMR spectroscopy

22. NMR principles
2D NMR spectroscopy

23. NMR principles
2D NMR spectroscopy

24. NMR principles
Example – COSY

25. NMR principles
Example – COSY

26. NMR principles
COSY-CH3CH2OH OH
CH2
CH3

27. NMR principles
Example – COSY, CH3CH2OH OH
CH2
CH3

28. NMR principles
Example – COSY, CH3CH2OH OH
CH2
CH3

29. NMR principles
TOCSY-Relayed H-H correlation

30. NMR principles
DQF-COSY and COSY

31. NMR principles
DQF-COSY

32. NMR principles
DQF-COSY

33. NMR principles
DQF-COSY and COSY

34. NMR principles
NOESY- Through space interaction

35. NMR principles
NOESY- Through space interaction

36. NMR principles
NOESY- Through space interaction