High-power H-1 composite pulse decoupling provides artifact free exchange-mediated saturation transfer (EST) experiments

Abstract

Exchange-mediated saturation transfer (EST) provides critical information regarding dynamics of molecules. In typical applications EST is studied by either scanning a wide range of N-15 chemical shift offsets where the applied N-15 irradiation field strength is on the order of hundreds of Hertz or, scanning a narrow range of N-15 chemical shift offsets where the applied N-15 irradiation field-strength is on the order of tens of Hertz during the EST period. The H-1 decoupling during the EST delay is critical as incomplete decoupling causes broadening of the EST profile, which could possibly result in inaccuracies of the extracted kinetic parameters and transverse relaxation rates. Currently two different H-1 decoupling schemes have been employed, intermittently applied 180 pulses and composite-pulse-decoupling (CPD), for situations where a wide range, or narrow range of N-15 chemical shift offsets are scanned, respectively. We show that high-power CPD provides artifact free EST experiments, which can be universally implemented regardless of the offset range or irradiation field-strengths. (C) 2016 Elsevier Inc. All rights reserved.