NMR artifacts caused by decoupling of multiple-spin coherences: improved SLAP experiment

摘要

Contrary to common expectations, multiple-spin coherences containing products of proton and heteronucleus operators (e.g. HuCx, u=x, y, z) can produce not only sidebands but also noticeable centerband NMR signals of the heteronucleus during acquisition under H-1 broadband decoupling. Such centerband signals of low abundant heteronuclei can be sources of relatively strong unexpected artifacts in NMR experiments that aim to detect very weak signals from much less-abundant isotopomers, e.g. C-13-C-13 ones. These findings lead to a new design of Sign Labeled Polarization Transfer (SLAP) pulse sequence (MSS-SLAP) with improved suppression of centerband peaks that are because of singly, e.g. C-13, labeled molecules (parent peaks). The MSS-SLAP experiment and its MSS-BIRD-SLAP variant are compared with a few older SLAP versions. Copyright (c) 2015 John Wiley & Sons, Ltd.