Enhancing NMR Sensitivity of Natural-Abundance Low-γ Nuclei by Ultrafast Magic-Angle-Spinning Solid-State NMR Spectroscopy.
Although magic-angle-spinning (MAS) solid-state NMR spectroscopy has been able to provide piercing atomic-level insights into the structure and dynamics of various solids, the poor sensitivity has limited its widespread application, especially when the sample amount is limited. Herein, we demonstrate the feasibility of acquiring high S/N ratio natural-abundance13C NMR spectrum of a small amount of sample (≈2.0 mg) by using multiple-contact cross polarization (MCP) under ultrafast MAS. As shown by our data from pharmaceutical compounds, the signal enhancement achieved depends on the number of CP contacts employed within a single scan, which depends on the T1ρof protons. The use of MCP for fast 2D1H/13C heteronuclear correlation experiments is also demonstrated. The significant signal enhancement can be greatly beneficial for the atomic-resolution characterization of many types of crystalline solids including polymorphic drugs and nanomaterials.
Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan, 48109-1055, USA.
Rongchun
R
Zhang
Department of Pharmaceutical Science, The University of Michigan, Ann Arbor, Michigan, 48109-1055, USA.
Yitian
Y
Chen
Department of Pharmaceutical Science, The University of Michigan, Ann Arbor, Michigan, 48109-1055, USA.
Nair
N
Rodriguez-Hornedo
Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan, 48109-1055, USA. ramamoor@umich.edu.
Ayyalusamy
A
Ramamoorthy
D066241:Carbon-13 Magnetic Resonance Spectroscopy; D007052:Ibuprofen / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*
D007052:Ibuprofen
NMR spectroscopy; cross-polarization; signal enhancement; structure elucidation; ultrafast MAS