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Updated: Jun 21, 2025

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
Cross polarization stability in multidimensional NMR spectroscopy of biological solids
Benjamin D Harding1, Alexander M Barclay2, Dennis W Piehl3
1Biophysics Graduate Program, University of Wisconsin-Madison, Madison, WI 53706 USA; Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706 USA.
None:
Magic-angle spinning (MAS) solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a powerful and versatile technique for probing structure and dynamics in large, insoluble biological systems at atomic resolution. With many recent advances in instrumentation and polarization methods, technology development in SSNMR remains an active area of research and presents opportunities to further improve data collection, processing, and analysis of samples with low sensitivity and complex tertiary and quaternary structures. SSNMR spectra are often collected as multidimensional data, requiring stable experimental conditions to minimize signal fluctuations (t1 noise). In this work, we examine the factors adversely affecting signal stability as well as strategies used to mitigate them, considering laboratory environmental requirements, configuration of amplifiers, and pulse sequence parameter selection. We show that Thermopad® temperature variable attenuators (TVAs) can partially compensate for the changes in amplifier output power as a function of temperature and thereby ameliorate one significant source of instability for some spectrometers and pulse sequences. We also consider the selection of tangent ramped cross polarization (CP) waveform shapes, to balance the requirements of sensitivity and instrumental stability. These findings collectively enable improved stability and overall performance for CP-based multidimensional spectra of microcrystalline, membrane, and fibrous proteins performed at multiple magnetic field strengths.
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