Jan Blahut , Matthias J. Brandl , Riddhiman Sarkar , Bernd Reif , Zdeněk Tošner
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引用次数: 1
Abstract
We have recently introduced optimal-control derived pulse sequences for sensitivity-enhanced heteronuclear correlation NMR experiments of solid proteins. Preservation of equivalent coherence transfer pathways using transverse-mixing pulses (TROP) in multidimensional pulse schemes allows to increase the sensitivity of the experiments by more than a factor of per each indirect dimension. In this article, we present homonuclear CA-CO transverse-mixing elements (homoTROP) that are based on dipolar interactions and achieve similar gains as the heteronuclear TROP pulses described previously. Both transfer elements were subsequently implemented in 3D se-hCAcoNH and se-hCOcaNH, that together with the previously introduced 3D se-hCANH and se-hCONH experiments yield a complete set of sensitivity-enhanced protein backbone assignment experiments. In contrast to the J-coupling based methods that are used at fast (60 kHz) and ultrafast MAS (>100 kHz), the homoTROP experiments employ about 10-times shorter mixing times making use of the larger magnitude of the dipolar coupling in comparison to the J couplings. The experiments are demonstrated using a microcrystalline, perdeuterated sample of the chicken alpha-spectrin SH3 domain in which all exchangeable sites are fully back-substituted with protons. We evaluated the gains in efficiency in all experiments site-specifically observing that the se-hCAcoNH and se-hCOcaNH experiments yield an increase in sensitivity by a factor of 1.36±0.09 and at least a factor of 1.8 with respect to the conventional hcoCAcoNH and hCOcaNH J-based experiments.