1. Magnetic Resonance MSN 506 Notes

2. Overview Essential magnetic resonance Measurement of magnetic resonance Spectroscopic information obtained by magnetic resonance –1D –2D Correlation and spin transfer related MR

3. Magnetic Resonance Nuclei and electrons carry spin (magnetic dipole moment) g is called the gyromagnetic ratio or g-factorgyromagnetic ratio Nuclear magneton (unit for nuclear magnetic spins) Bohr magneton (unit for electron magnetic spins) μ B = 9.274 009 × 10 -24 J·T-1JT μ N = 5.050 783 × 10 -27 J·T-1JT

4. Energy of dipole in an external magnetic field

5. NMR spectrometer

6. Free Induction Decay The spins that are in a non-equilibrium initial position lose energy by radiating and return to equilibrium state The released electromagnetic energy is picked up by coils

7. Free Induction Decay Field generated per spin is very small Large number of atoms/molecules (10 23 ) can produce measurable signal if they add up coherently Bolztmann Factor Field Uniformity If B field is not uniform, spins at different locations oscillate at different frequencies Small portion of spins have net effect at room temperature Solvents should be chosen so as not to confuse the experiment

8. Couplings Local magnetic field of a nuclei is affected by its surroundings Atom 1 Atom 2 Nuclei produce fields at each others location Electrons in bonds produce fields at nuclei locations

9. Couplings are used to identify bond structure of molecules

10. Dephasing There are characteristic times for energy loss and phase loss, which can also be measured by MR

11. 2D NMR Measures correlations between NMR lines by pulsed excitation Correlations indicate closely placed nuclei The complicated 1D NMR spectrum of a protein molecule does not say much about the molecular structure

12. Correlation measurement

13. 2D correlations help you estimate structure