Abstract:
1
H double quantum (DQ)/1
H single quantum
(SQ) correlation solid-state NMR spectroscopy is widely used to
obtain internuclear 1
H−1
H proximities, especially at fast magicangle spinning (MAS) rate (>60 kHz). However, to date, 1
H
signals are not well-resolved because of intense 1
H−1
H
homonuclear dipolar interactions even at the attainable maximum
MAS frequencies of ∼100 kHz and/or under 1
H−1
H
homonuclear dipolar decoupling irradiations. Here we introduce
novel three-dimensional (3D) experiments to resolve the 1
H
DQ/1
H SQ correlation peaks using the additional 13C dimension.
Although the low natural abundance of 13C (1.1%) significantly
reduces the sensitivities, the 1
H indirect measurements alleviate
this issue and make this experiment possible even in naturally
abundant samples. The two different implementations of 13C/1
H DQ/1
H SQ correlations and 1
H DQ/13C/1
H SQ correlations
are discussed and demonstrated using L-histidine·HCl·H2O at natural abundance to reveal the local 1
H−1
H networks near each 13C. In addition, the complete 1
H resonance assignments are achieved from a single 3D 13C/1
H DQ/1
H SQ experiment. We have
also demonstrated the applicability of our proposed method on a biologically relevant molecule, capsaicin.
