Low power supercycled TPPM decoupling

Abstract

Improving the spectral sensitivity and resolution of biological solids is one of the long-standing problems in nuclear magnetic resonance (NMR) spectroscopy. In this report, we introduce low-power supercycled variants of two-pulse phase-modulated (TPPM) sequence for heteronuclear decoupling. The utility of the sequence is shown by improvements in the transverse relaxation time of observed nuclei (with ¹H decoupling) with its application to different samples (uniformly ¹³C, ¹⁵N, ²H-labeled GB1 back-exchanged with 25% H${}_2$O and 75% D${}_2$O, uniformly ¹³C, ¹⁵N, ²H-labeled human derived Asyn fibril back-exchanged with 100% H${}_2$O and uniformly ¹³C, ¹⁵N -labeled human derived Asyn fibril) at fast MAS using low radiofrequency (RF) fields. To understand the effect of spinning speed, the transverse relaxation time is monitored under different spinning frequencies. In comparison to existing heteronuclear decoupling sequences, the supercycled TPPM (sTPPM) sequence significantly improves the spectral sensitivity and resolution and is robust towards $B_1$ inhomogeneity and decoupler offset.