Symmetry Principles in the Nuclear Magnetic Resonance

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Chemistry: Symmetry/Asymmetry".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 7079

Special Issue Editor

Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
Interests: NMR; dDNP; MAS-DNP; PHIP

Special Issue Information

Dear Colleagues,

Symmetry is a theoretical concept with applications in all major scientific domains. The notion lies at the heart of fundamental laws of nature and serves as an important tool for understanding the properties of complex systems, both classical and quantum. In nuclear magnetic resonance, symmetry has been applied to both liquid and solid-state investigations. As an example, it has been used to classify NMR spectra in complex spin systems, the nature of long-lived nuclear spin probes, and it is at the very core of a number of relevant and cutting-edge techniques, such as PHIP (ParaHydrogen Induced Polarisation), SABRE (Signal Amplification ByReversible Exchange) and DNP (Dynamic Nuclear Polarisation), currently used to elucidate a number of important problems.

The aim of the present Special Issue is to emphasize the role of symmetry in modern NMR investigations. Specifically, it will consider how the manifestation of symmetry and symmetry-breaking laws can help in conceiving, designing and interpreting many important chemical and physical problems.

We are soliciting contributions (research and review articles) covering a broad range of topics on symmetry and hyperpolarised NMR, including (though not limited to) the following:

- Permutation versus point group and molecular symmetries. What should be used in NMR?;

- Symmetry and symmetry-breaking in nuclear long-lived states;

- Symmetry in ParaHydrogen-Induced Polarisation (PHIP) and Signal Amplification by Reversible Exchange;

- Symmetry in solid-state NMR;

- Symmetry in the context of Dynamic Nuclear Polarisation.

Dr. Gabriele Stevanato
Guest Editor

Manuscript Submission Information

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Published Papers (3 papers)

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Research

27 pages, 17811 KiB  
Article
Symmetry Constraints on Spin Order Transfer in Parahydrogen-Induced Polarization (PHIP)
by Andrey N. Pravdivtsev, Danila A. Barskiy, Jan-Bernd Hövener and Igor V. Koptyug
Symmetry 2022, 14(3), 530; https://doi.org/10.3390/sym14030530 - 04 Mar 2022
Cited by 5 | Viewed by 3055
Abstract
It is well known that the association of parahydrogen (pH2) with an unsaturated molecule or a transient metalorganic complex can enhance the intensity of NMR signals; the effect is known as parahydrogen-induced polarization (PHIP). During recent decades, numerous methods were proposed [...] Read more.
It is well known that the association of parahydrogen (pH2) with an unsaturated molecule or a transient metalorganic complex can enhance the intensity of NMR signals; the effect is known as parahydrogen-induced polarization (PHIP). During recent decades, numerous methods were proposed for converting pH2-derived nuclear spin order to the observable magnetization of protons or other nuclei of interest, usually 13C or 15N. Here, we analyze the constraints imposed by the topological symmetry of the spin systems on the amplitude of transferred polarization. We find that in asymmetric systems, heteronuclei can be polarized to 100%. However, the amplitude drops to 75% in A2BX systems and further to 50% in A3B2X systems. The latter case is of primary importance for biological applications of PHIP using sidearm hydrogenation (PHIP-SAH). If the polarization is transferred to the same type of nuclei, i.e., 1H, symmetry constraints impose significant boundaries on the spin-order distribution. For AB, A2B, A3B, A2B2, AA’(AA’) systems, the maximum average polarization for each spin is 100%, 50%, 33.3%, 25%, and 0, respectively, (where A and B (or A’) came from pH2). Remarkably, if the polarization of all spins in a molecule is summed up, the total polarization grows asymptotically with ~1.27N and can exceed 2 in the absence of symmetry constraints (where N is the number of spins). We also discuss the effect of dipole–dipole-induced pH2 spin-order distribution in heterogeneous catalysis or nematic liquid crystals. Practical examples from the literature illustrate our theoretical analysis. Full article
(This article belongs to the Special Issue Symmetry Principles in the Nuclear Magnetic Resonance)
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10 pages, 2261 KiB  
Article
Rotating-Frame Overhauser Transfer via Long-Lived Coherences
by Florin Teleanu, Alexandru Topor, Diana Serafin, Aude Sadet and Paul R. Vasos
Symmetry 2021, 13(9), 1685; https://doi.org/10.3390/sym13091685 - 13 Sep 2021
Viewed by 1653
Abstract
Solution-state distance restraints for protein structure determination with Ångström-level resolution rely on through-space transfer of magnetization between nuclear spins. Such magnetization transfers, named Overhauser effects, occur via dipolar magnetic couplings. We demonstrate improvements in magnetization transfer using long-lived coherences (LLCs)—singlet-triplet superpositions that are [...] Read more.
Solution-state distance restraints for protein structure determination with Ångström-level resolution rely on through-space transfer of magnetization between nuclear spins. Such magnetization transfers, named Overhauser effects, occur via dipolar magnetic couplings. We demonstrate improvements in magnetization transfer using long-lived coherences (LLCs)—singlet-triplet superpositions that are antisymmetric with respect to spin-permutation within pairs of coupled magnetic nuclei—as the magnetization source. Magnetization transfers in the presence of radio-frequency irradiation, known as ‘rotating-frame’ Overhauser effects (ROEs), are predicted by theory to improve by the use of LLCs; calculations are matched by preliminary experiments herein. The LLC-ROE transfers were compared to the transmission of magnetization via classical transverse routes. Long-lived coherences accumulate magnetization on an external third proton, K, with transfer rates that depended on the tumbling regime. I,S K transfers in the LLC configuration for (I,S) are anticipated to match, and then overcome, the same transfer rates in the classical configuration as the molecular rotational correlation times increase. Experimentally, we measured the LLC-ROE transfer in dipeptide AlaGly between aliphatic protons in different residues K = AlaHα and (I,S) = GlyHα1,2 over a distance dK,I,S = 2.3 Å. Based on spin dynamics calculations, we anticipate that, for such distances, a superior transfer of magnetization occurs using LLC-ROE compared to classical ROE at correlation times above τC=10 ns. The LLC-ROE effect shows potential for improving structural studies of large proteins and offering constraints of increased precision for high-affinity protein-ligand complexes in slow tumbling in the liquid state. Full article
(This article belongs to the Special Issue Symmetry Principles in the Nuclear Magnetic Resonance)
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15 pages, 7563 KiB  
Article
An Examination of Factors Influencing Small Proton Chemical Shift Differences in Nitrogen-Substituted Monodeuterated Methyl Groups
by Stuart J. Elliott, O. Maduka Ogba, Lynda J. Brown and Daniel J. O’Leary
Symmetry 2021, 13(9), 1610; https://doi.org/10.3390/sym13091610 - 02 Sep 2021
Cited by 1 | Viewed by 2335
Abstract
Monodeuterated methyl groups have previously been demonstrated to provide access to long-lived nuclear spin states. This is possible when the CH2D rotamers have sufficiently different populations and the local environment is chiral, which foments a non-negligible isotropic chemical shift difference between [...] Read more.
Monodeuterated methyl groups have previously been demonstrated to provide access to long-lived nuclear spin states. This is possible when the CH2D rotamers have sufficiently different populations and the local environment is chiral, which foments a non-negligible isotropic chemical shift difference between the two CH2D protons. In this article, the focus is on the N-CH2D group of N-CH2D-2-methylpiperidine and other suitable CH2D-piperidine derivatives. We used a combined experimental and computational approach to investigate how rotameric symmetry breaking leads to a 1H CH2D chemical shift difference that can subsequently be tuned by a variety of factors such as temperature, acidity and 2-substituted molecular groups. Full article
(This article belongs to the Special Issue Symmetry Principles in the Nuclear Magnetic Resonance)
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