NMR Spectroscopy. Alexej Jerschow, NYU Chemistry

Transcription

1 NMR Spectroscopy Alexej Jerschow, NYU Chemistry 1

2 Overview Larmor Eq Chemical Shift J-coupling 1D NMR spectra 2D NMR spectra (Imaging) Alexej Jerschow, NYU 2

3 Alexej Jerschow, NYU 3

4 For further reading: Alexej Jerschow, NYU 4

5 NMR in the sciences Proteins, DNA, drugs Glasses, semiconductors, materials Imaging Microscopy Quantum Computing Alexej Jerschow, NYU 5

6 Protein Data Bank E x p. T e c h. X-ray Diffraction and other As of 01-Apr-2003 Molecule Type Proteins, Peptdes, and Viruses Protein/ Nucleic Acid Complexes Nucleic Acids Carbohydrates total NMR Total Alexej Jerschow, NYU 6

7 Principles of NMR Spectroscopy The nucleus has a tiny magnetic moment The electron cloud determines the chemical shift Alexej Jerschow, NYU 7

8 Measurement Larmor frequency ω=γβ Alexej Jerschow, NYU 8

9 Superconducting magnet creates the large magn. field. Alexej Jerschow, NYU 9

10 10

11 Facilities Solid 400 MHz in lab. Liquid 400 and 500 MHz in department. 800eds, solid 750 and soon a 900 MHz at the New York Struct. Biol. Ctr. Alexej Jerschow, NYU 11

12 Magnetically active isotopes Alexej Jerschow, NYU 12

13 Spin Alexej Jerschow, NYU 13

14 Energy levels 2I+1 energy levels Alexej Jerschow, NYU 14

15 Alexej Jerschow, NYU 15

16 Resonance Frequencies, gyromagnetic ratios Alexej Jerschow, NYU 16

17 Magnetic Field Strengths Given in Tesla (=10 4 gauss) Given as the 1 H resonance frequency in MHz Alexej Jerschow, NYU 17

18 RF frequencies Figure 12.3: Class radiation Alexej Jerschow, NYU 18

19 Sensitivity of NMR Alexej Jerschow, NYU 19

20 Chemical shift Alexej Jerschow, NYU 20

21 Chemical shift Alexej Jerschow, NYU 21

22 Alexej Jerschow, NYU 22

23 RF frequencies Alexej Jerschow, NYU 23

24 Chemical Shift ppm scale Alexej Jerschow, NYU 24

25 Chemical shift Alexej Jerschow, NYU 25

26 Chemical Shift for certain groups Alexej Jerschow, NYU 26

27 Alexej Jerschow, NYU 27

28 J-Coupling (scalar coupling) Mainly through three bonds max. Alexej Jerschow, NYU 28

29 Heteronuclear J-coupling Alexej Jerschow, NYU 29

30 J-coupling, energy shift Alexej Jerschow, NYU 30

31 2D Correlation Spectroscopy Based on Through-bond interactions (J-couplings) COSY Through-space interactions (dipolar couplings) NOESY 1D-spectrum along the diagonal Cross-peaks indicate either spatial proximity or chemical bond Alexej Jerschow, NYU 31

32 Multidimensional NMR Alexej Jerschow, NYU 32

33 NOE struct. determ. Alexej Jerschow, NYU 33

34 COSY Alexej Jerschow, NYU 34

35 NOESY Alexej Jerschow, NYU 35

36 COSY, Lysine α HNs HN β γ δ Alexej Jerschow, NYU 36

37 NOESY, Lysine-Ala β γ β δ α α HNs HN Alexej Jerschow, NYU 37

38 COSY, Histidine HN α β γ δ ε HNs Alexej Jerschow, NYU 38

39 COSY, Alanine β α γ δ ε HNs HN Alexej Jerschow, NYU 39

40 Alexej Jerschow, NYU 40

41 The way of coupling for COSY, TOCSY and NOESY: Alexej Jerschow, NYU 41

42 NOESY, Ile-Ala Alexej Jerschow, NYU 42

43 Exercise: NOESY, Ile-His Alexej Jerschow, NYU 43

44 From: Horst Friebolin, One- and Two-Dimensional NMR Spectroscopy Alexej Jerschow, NYU 44

45 These are sagittal images of the brains of a control and Alzheimer's patient, showing the area within the parietal lobe where each spectrum was acquired. Within an Alzheimer's patient's brain the concentration of N-Acetylaspartate is found to decrease while the myo-inositol increases, when compared to normal concentrations. Rose SE, de Zubicaray GI, Wang D, Galloway GJ, Chalk JB, Eagle SC, Semple J, Doddrell DM. Magnetic Resonance Imaging 1999:17; Alexej Jerschow, NYU 45

46 Quantification of fat in the liver 1 H NMR spectrum of voxel in liver Alexej Jerschow, NYU 46

47 Chemical-Shift Imaging NMR spectra of different parts of a sample are measured (non-invasively!) Fig. 2: Chemical shift imaging on an intact juneberry fruit. Sample dimensions: 15x15 mm, thickness of selected slice: 1mm, voxel dimensions for chemical shift measurement: 234x234x1000 µ m. The right parts of the figure show the NMR spectra of the voxel selected at the positions indicated in the left parts of the figure. The spectra show the different chemical compositions of the fruit pulp ( mainly carbohydrates) and the seed ( mainly oil/fat). (D.Gross, V. Lehmann, K. Zick and T. Oerther, Bruker Report 148/2000, p. 30) Alexej Jerschow, NYU 47