Capturing exchange using periodic radiofrequency irradiation

J Magn Reson. 2018 Nov;296:79-84. doi: 10.1016/j.jmr.2018.09.001. Epub 2018 Sep 5.

Abstract

The dynamics of spin system coupled by chemical exchange between two sites with different chemical shifts during periodic radiofrequency (RF) irradiation was here investigated. When the instantaneous π-flip of effective frequency during the course of frequency sweep was applied, a significant increase of exchange-induced relaxation rate constants was observed for small tip angle of magnetization in the laboratory frame of reference. This increase of the rate constants corresponds to the side bands generated by the periodic irradiation during the RF pulses. The exchange - induced relaxation rate constants depend on the exchange conditions, the RF power and the irradiation period. The described phenomenon promises applications for studying protein dynamics and for generating exchange specific relaxation contrasts in MRI.

Keywords: Bloch - McConnell equations; Chemical exchange; Periodic RF irradiation; RAFFn.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Computer Simulation
  • Image Interpretation, Computer-Assisted
  • Magnetic Resonance Imaging / methods
  • Magnetic Resonance Spectroscopy / methods*
  • Magnets
  • Radio Waves*