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The Bloch-Siegert shift is a phenomenon in NMR spectroscopy and atomic physics in which the observed resonance frequency is changed by the presence of an off-resonance applied field. In NMR, it occurs especially in the context of homonuclear decoupling. Here we develop a practical method for homonuclear decoupling that avoids inducing Bloch-Siegert shifts. This approach enables accurate observation of the resonance frequencies of decoupled nuclear spins. We apply this method to increase the resolution of the HNCA experiment. We also observe a doubling in sensitivity for a 30 kDa protein. We demonstrate the use of band-selective C decoupling to produce amino acid-specific line shapes, which are valuable for assigning resonances to the protein sequence. Finally, we assign the backbone of a 30 kDa protein, Human Carbonic Anhydrase II, using only HNCA experiments acquired with band-selective decoupling schemes, and instrument time of one week.
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http://dx.doi.org/10.1038/s41467-018-05400-4 | DOI Listing |
Sci Adv
August 2025
Department of Chemistry, Tokyo Metropolitan University, Hachioji, 192-0397 Tokyo, Japan.
To study the structure and dynamics of proteins by nuclear magnetic resonance (NMR), sequence-specific assignment is needed, which can be obtained by acquiring and analyzing multiple triple-resonance experiments with the three-dimensional TROSY-HNCA, the most sensitive stand-alone experiment with which sequential assignment is, in principle, possible. However, gaining an unambiguous assignment solely from this spectrum is generally not possible because amino acid-type information cannot be gleaned only from the C shifts and the low resolution in the C dimension, which is limited by the homonuclear coupling of the C and C nuclei. Here, super-resolution NMR is applied to the TROSY-HNCA and HNcoCA experiments, yielding pseudo-decoupling, which results in a four- to fivefold resolution enhancement in the C dimension, essential for the assignment, which allows for straightforward assignment of proteins as large as 500 residues based on simulations.
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July 2025
National Magnetic Resonance Facility at Madison (NMRFAM), University of Wisconsin-Madison, Madison, WI, USA.
Nuclear magnetic resonance (NMR) spectroscopy is a powerful technique with broad impact across the physical and life sciences, and ultrahigh field (UHF), gigahertz-class NMR spectrometers offer exceptional performance, including superior resolution and sensitivity. In solid-state NMR (SSNMR), resolution is primarily constrained by instrumentation rather than molecular tumbling, making it well suited for studying large and complex systems. To fully leverage UHF magnets for SSNMR, it is essential to eliminate line broadening arising from magnetic field drift and couplings among the nuclear spins.
View Article and Find Full Text PDFUnlabelled: NMR spectroscopy is a powerful technique with broad impact across the physical and life sciences, and ultra-high field, GHz-class NMR spectrometers offer exceptional overall performance including superior resolution and sensitivity. While the resolution is fundamentally limited by molecular tumbling for solution NMR, solid-state NMR (SSNMR) is constrained only by instrumentation, making it well-suited for studying large and complex systems. To fully leverage UHF magnets for magic-angle-spinning SSNMR, it is essential to eliminate linebroadening arising from magnetic field drift and couplings among the nuclear spins.
View Article and Find Full Text PDFMagn Reson Chem
July 2025
Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India.
The selective refocusing (SERF) and its modified experiments have permitted the unambiguous assignment of peaks and the straightforward determination of J. However, they suffer from the presence of intense axial peaks and the evolution of undesirable couplings in the spectra. In partially addressing these challenges, the Clean-G-SERF sequence, a modified version of the gradient-enhanced SERF-based experiment (G-SERF), has been designed to suppress all the axial peaks and eradicate the unwanted evolution, while retaining only the couplings pertaining to the selectively excited proton.
View Article and Find Full Text PDFChembiochem
June 2025
Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Department of Electronic Science, The MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, Xiamen University, Xiamen, 361005, China.
H nuclear magnetic resonance (NMR) spectroscopy plays an important role in the pharmaceutical industry, but for complex substances, spectral analysis is challenging due to the narrow chemical shift range and signal splitting caused by scalar coupling. Pure shift techniques can suppress scalar coupling, improving spectral resolution. This article provides a review of pure shift techniques, including the main homonuclear broadband decoupling experiments and the methods for obtaining optimal pure shift spectra with the assistance of deep learning.
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