What techniques are used in the modern pulse sequences to reduce radiation damping issues?
Could you give some examples?
asked Jan 28 '10 at 08:15
Radiation damping artifacts in aqueous solutions of biomolecules are primarily due to the large water magnetization. These artifacts are minimized by 1) ensuring that water magnetization vector remains in the +z direction during the entire pulse sequence. This can be achieved by using shape selective proton RF pulses that excite the signals of the sample but do not affect the water frequencies. OR 2) The water magnetization is selectively rotated into the transverse plane and a pulsed field gradient is applied and this results in loss of coherence, so that the net magnetization due to the water signal is nearly zero. 3) For high Q-probes/spectrometers: use a delay that allows the water magnetization vector (initially in the transverse plane along with other desired magnetization vectors) to return to the z-axis due to radiation damping, thereby eliminating the need for a selective pulse and subsequently record the signals due to the remaining (solute) transverse magnetization vectors. (See Journal of Magnetic Resonance, B 112:200 (1996); J. Chem. Phys. 91:5895(1989 ; J Magn. Reson. B. 106:86 (1995); J. Biomol. NMR 4:735 (1994).
answered Feb 11 '10 at 10:00