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

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

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

NMR principles CW NMR Experiment

NMR principles Boltzmann Statistics

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

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

NMR principles Relaxation T2 Processes –Precession (Larmor frequency)

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

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

NMR principles Relaxation

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

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.

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).

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

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

NMR principles Spin-Spin

NMR principles Spin-Spin Coupling -example

NMR principles The Time Domain NMR Signal and Fourier transform FT

NMR principles 2D NMR spectroscopy

NMR principles 2D NMR spectroscopy

NMR principles 2D NMR spectroscopy

NMR principles Example – COSY

NMR principles Example – COSY

NMR principles COSY-CH3CH2OH OH CH2 CH3

NMR principles Example – COSY, CH3CH2OH OH CH2 CH3

NMR principles Example – COSY, CH3CH2OH OH CH2 CH3

NMR principles TOCSY-Relayed H-H correlation

NMR principles DQF-COSY and COSY

NMR principles DQF-COSY

NMR principles DQF-COSY

NMR principles DQF-COSY and COSY

NMR principles NOESY- Through space interaction

NMR principles NOESY- Through space interaction

NMR principles NOESY- Through space interaction