In the main part of the talk two homonuclear decoupling schemes for 13C- and 13C,15N-labeled molecules are introduced and their effect studied on example molecules. The first decoupling scheme uses bandselective refocusing on the X-nucleus (BASEREX) [1], which for example allows real-time homodecoupling of a selected carbon region and is of particular interest for intrinsically disordered proteins. As a result, selective Ha,Ca (SHACA-)HSQC experiments at physiological pH and temperature with slightly improved resolution compared to conventional 1H,15N-HSQCs can be obtained [2].
The second scheme is designed for effective real-time decoupling of amino or imino protons in 15N,13C-labed molecules. Previously published amide decoupling schemes involve HOBS/BASHD or 1H,15N-BIRD elements, which lead to unfavorable water suppression and residual linebroadening due to longrange 1H,13C-couplings [3,4]. The proposed scheme instead relies on 1H,13C-BIRD elements, which allows a dramatically improved water treatment and full removal of coupling-based linebroadening. Up to a factor three in signal intensity and signalwidths could be obtained for small folded and intrinsically disordered proteins [5].
BASEREX demonstrates the need of a reliable treatment of coupling evolution during shaped pulses [1], which is used for optimal control based optimization of pulse sandwiches that either suppress [6] or maximize coupling evolution during pulse applications [7]. If time allows, other new developments like Caliphatic-selective pulse shapes at 1.2 GHz spectrometers [8] are presented.