Studies of minute quantities of natural abundance molecules using 2D heteronuclear correlation spectroscopy under 100 kHz MAS

Abstract

Two-dimensional 1H{13C} heteronuclear correlation solid-state NMR spectra of naturally abundant solid materials are presented, acquired using the 0.75-mm magic angle spinning (MAS) probe at spinning rates up to 100kHz. In spite of the miniscule sample volume (290nL), high-quality HSQC-type spectra of bulk samples as well as surface-bound molecules can be obtained within hours of experimental time. The experiments are compared with those carried out at 40kHz MAS using a 1.6-mm probe, which offered higher overall sensitivity due to a larger rotor volume. The benefits of ultrafast MAS in such experiments include superior resolution in 1H dimension without resorting to 1H–1H homonuclear RF decoupling, easy optimization, and applicability to mass-limited samples. The HMQC spectra of surface-bound species can be also acquired under 100kHz MAS, although the dephasing of transverse magnetization has significant effect on the efficiency transfer under MAS alone.