Nuclear spin hyperpolarization enhances NMR sensitivity but typically requires complex infrastructure. Signal Amplification by Reversible Exchange (SABRE)—a parahydrogen-based hyperpolarization method—can be performed using a remarkably low-cost polarizer (< $100) consisting only of magnetic coils and a standard PC sound card, with no need for magnetic shielding. However, under these conditions, SABRE requires direct spin-spin coupling between parahydrogen and the target nucleus, which limits its application for remote heteronuclear spins, such as 77Se in biologically significant selenium-nitrogen heterocycles (e.g., antioxidants, antiviral, and antitumor agents).
This work demonstrates a way to overcome the distance limitation between nuclei. A method for 15N-mediated polarization transfer using oscillating magnetic fields in the audio frequency range has been developed. As a proof of concept, an 11,600-fold enhancement of the 77Se NMR signal (>6% polarization) was achieved in a setup based on a 9.4 T NMR spectrometer without shielding the external magnetic field, using a selenadiazole derivative. These results suggest that selenadiazole-based compounds are particularly well-suited for this strategy and lay the groundwork for its extension to other selenium-containing molecules. The developed approach opens up new opportunities for the application of affordable hyperpolarization in biomedical research, particularly for studying the structure and functions of biologically active selenium-containing compounds using NMR methods.
Markelov, D. A., Kiryutin, A. S., Borisov, A. V., Kosenko, I. D., Godovikov, I. A., & Yurkovskaya, A. V. (2025). 77Se Hyperpolarization Enabled by Reversible Parahydrogen Exchange and Audio-Frequency Magnetic Fields at 0.1 mT. The Journal of Physical Chemistry Letters, 16, 10621-10626.https://doi.org/10.1021/acs.jpclett.5c02693
Relaxation times of nuclear spins often serve as a valuable source of information on the dynamics of various biochemical processes. Measuring relaxation as a function of the external magnetic field strength has proven extremely useful for studying weak ligand-protein interactions. This work demonstrates that monitoring the relaxation of long-lived singlet order, rather than longitudinal magnetization, extends the capabilities of this approach.
The magnetic field dependence of the relaxation rates for both longitudinal magnetization and singlet order was studied for the methylene protons of alanyl-glycine dipeptide and citrate in the presence of human serum albumin (HSA). As a result, the singlet-order relaxation rate proved to be more sensitive to ligand-protein interaction, providing a higher contrast for different HSA concentrations.
To assess the binding process parameters in more detail, a simple analytical relaxation model was used to fit the experimental field dependencies for both the singlet-order relaxation rate and the spin-lattice relaxation time T₁. The applicability of this approach was also tested in experiments with trimethylsilylpropanoic acid (TSP), used as a competitor for ligand binding to HSA.
The obtained results demonstrate a significant increase in the sensitivity of the NMR method to weak intermolecular interactions, opening new avenues for studying biochemical processes and for drug screening.
Two-dimensional NMR spectroscopy, first proposed by Jean Jeener and implemented by Aue, Bartholdi, and Ernst, transformed NMR into a powerful tool for chemistry, materials science, structural biology, and medicine. The application of two-dimensional NMR (2D-NMR) methods enhanced both the spectral resolution and the information content of NMR spectra by revealing correlations between nuclei through chemical bonds or through space. The foundation of 2D-NMR lies in the ability to control which interactions govern the evolution of the spin system, or to choose which information is displayed in each spectral dimension. In modern NMR spectrometers, control over nuclear spin systems is typically achieved by applying precisely defined sequences of radiofrequency pulses and delays.
A fundamentally different method for selecting how a spin system evolves was proposed by Pines and coworkers for solids and later extended to liquids. It involves reducing the magnetic field to values so small that its interaction with spins becomes negligible compared to internal interactions, such as dipole-dipole and scalar couplings. It is now possible to generate magnetic fields in the range of a few nanotesla (or less), so that scalar couplings between like protons can become larger than the Zeeman interaction in the zero- to ultralow-field (ZULF) regime. In this chapter, we summarize the experience and results of recent studies that utilize evolution under ZULF conditions to control the evolution of spin systems in 2D-NMR.
The article investigates the interaction of nickel(II) diazadiphosphacyclooctane complexes with molecular hydrogen (H₂), focusing on the intermediates formed during the heterolytic splitting of H₂. Using multinuclear NMR spectroscopy and parahydrogen-induced polarization, the researchers were able to detect and characterize nickel(II) dihydrogen and hydride complexes, which are key intermediates in the process. The study demonstrates that the addition of H₂ to these nickel complexes leads to the formation of products where H₂ is split heterolytically, with one hydrogen atom bound to the nickel center and the other to a nitrogen atom in the ligand. The use of parahydrogen allowed for the observation of the short-lived nickel(II) dihydrogen complex, which had previously only been predicted computationally. The experiments also revealed that the reaction is reversible and that the stability and exchange properties of the complexes can be probed using chemical exchange saturation transfer (CEST) and partially negative line (PANEL) experiments. The findings provide new insights into the mechanism of H₂ activation by nickel-based catalysts and highlight the utility of advanced NMR techniques for studying such processes. The findings advance our understanding of how hydrogen can be split and activated in nickel-based catalytic systems by directly observing reactive intermediates that were previously inaccessible. These insights are important for developing more efficient catalysts for hydrogen production, storage, and utilization—processes that underpin sustainable and clean energy technologies.
Tenoxicam (TXM) is a non-steroidal anti-inflammatory drug with promising potential in cancer therapy. Unlike other members of the oxicam family, TXM displays an unusual behavior: in both its pure crystalline form and in its solvates, it appears mainly as a zwitterion (ZWC), even though it can theoretically exist in two other tautomeric forms—the β-keto-enolic (BKE) and β-diketone (BDK) structures.
To understand why TXM prefers the zwitterionic state, we combined experimental techniques with computational modeling to study how the solvent environment and internal non-covalent interactions influence its tautomerization. Our results show that solvent polarity has only a minor effect on TXM crystallization. This finding enabled us to synthesize and characterize, for the first time, five new solvates that all contain TXM in the zwitterionic form.
Using quantum-chemical analysis based on Natural Bond Orbital (NBO) theory, we identified a key non-covalent interaction—an S-bond between the sulfur atom of the thiophenyl group and the carbonyl oxygen—that stabilizes the zwitterionic structure and directs the crystallization pathway. These results highlight the broader importance of S-bonding in drug design, a factor that remains underappreciated in current medicinal chemistry.
The discovery that S-bonding stabilizes the zwitterionic form of tenoxicam provides a new perspective for designing pharmaceuticals with enhanced stability and efficacy. Recognizing the contribution of such subtle intramolecular interactions could help medicinal chemists develop better anti-inflammatory and anticancer drugs by fine-tuning molecular properties at the atomic level.
Two-dimensional NMR spectroscopy is a key method for studying the structure and dynamics of biological macromolecules, but its major limitation is low sensitivity: acquiring high-quality spectra often requires minutes to hours. In this work, we demonstrate that a bioactive derivative of the sunflower trypsin inhibitor-1 (SFTI-1), a 14-amino-acid peptide, can be detected much faster by combining parahydrogen-induced polarization (PHIP) with ultrafast 2D NMR spectroscopy.
PHIP activity was introduced into the peptide by incorporating O-propargyl-L-tyrosine. In one-dimensional PHIP experiments, we observed a signal enhancement of roughly 1200-fold compared to conventional NMR. This dramatic gain in sensitivity enables the acquisition of 2D correlation spectra of low-concentration SFTI-1 samples in less than 10 seconds using ultrafast single-scan techniques. As a demonstration, PHIP-enhanced ultrafast single-scan TOCSY spectra of SFTI-1 are presented.
These results illustrate how hyperpolarization can overcome fundamental sensitivity limits in biomolecular NMR.
Combining parahydrogen-induced polarization with ultrafast 2D NMR offers a powerful solution to one of the principal challenges in biomolecular research—detecting and analyzing molecules at very low concentrations or with limited sample stability. This technological advance has potential to speed up structural biology studies and facilitate new applications in biomedical analysis and drug discovery.
2018
This work presents an experimental method that enables fast field-cycling Nuclear Magnetic Resonance (NMR) measurements across an exceptionally broad magnetic-field range, from 5 nanotesla up to 10 tesla. The technique uses a hybrid approach: high magnetic fields are achieved by placing the sample in the inhomogeneous stray field of an NMR spectrometer, while fields below 2 millitesla are generated inside a magnetic shield mounted on the spectrometer and controlled by a custom coil system.
This setup allows routine measurements of T₁ relaxation times and nuclear Overhauser effect (NOE) parameters over the entire field range. For coupled proton–carbon spin systems, a single common T₁ is observed at low fields, where the spins become strongly coupled. In some cases, ultralow-field conditions also provide access to heteronuclear long-lived spin states. Furthermore, efficient coherent polarization transfer in proton–carbon systems is detected at ultralow fields, manifested as quantum oscillations in the polarization dynamics. These capabilities open new possibilities for the analysis and controlled manipulation of heteronuclear spin systems.
By providing access to a wide range of magnetic-field environments, this method empowers researchers to dissect molecular relaxation phenomena and spin dynamics in much greater detail than previously possible. Its flexibility paves the way for novel advances in hyperpolarization science, imaging, and molecular diagnostics, with far-reaching impacts for medicine, chemistry, and materials science.
Zhukov, I. V., Kiryutin, A. S., Yurkovskaya, A. V., Grishin, Y. A., Vieth, H.-M., Ivanov, K. L., Field-cycling NMR experiments in ultra-wide magnetic field range: relaxation and coherent polarization transfer. Phys. Chem. Chem. Phys. 2018, 20, 12396-12405. http://doi.org/10.1039/C7CP08529J PCCP inside cover
This article provides an overview of chemically induced dynamic nuclear polarization (CIDNP), with special emphasis on its time-resolved implementation and its applications in biological research. We outline the key principles of how nuclear polarization is generated in liquids at high magnetic fields through the spin-sorting mechanism. The method’s ability to enhance NMR signals is described alongside its unique capability to probe ultrafast reactions of short-lived free radicals formed in biologically important molecules.
We also discuss how CIDNP can be used to extract structural and magnetic properties of these transient radical species. Furthermore, the fundamentals of protein CIDNP are introduced, followed by examples illustrating how time-resolved CIDNP provides insight into protein structure, folding, and dynamic behavior.
The review highlights significant scientific progress in using time-resolved CIDNP to observe and characterize fleeting radical intermediates and molecular dynamics at room temperature. These advances are transforming bio-NMR by addressing challenges in detecting transient species, which are crucial in understanding processes like electron transfer, protein folding, and DNA repair, and open avenues for the development of new diagnostic and therapeutic tools in medicine and biotechnology.
This work presents a universal and efficient NMR method for generating long-lived singlet spin states from ordinary longitudinal magnetization in pairs of coupled spin-½ nuclei. The technique is based on adiabatically ramping the radiofrequency (RF) field, which induces controlled transitions between the singlet and triplet states of the spin pair.
We show that this approach performs equally well for both strongly and weakly coupled spin systems and achieves a conversion efficiency that reaches the theoretical limit. The method enables reliable creation and readout of long-lived singlet order, supports the preservation of hyperpolarization, and is applicable to nearly equivalent spins in specially designed molecules as well as to low-field NMR experiments. As an example, singlet states of methylene protons in peptides are analyzed.
Enabling efficient generation and preservation of singlet spin order substantially increases the lifetime of nuclear polarization, providing a practical route for probing slow biomolecular processes, conducting sensitive hyperpolarized NMR experiments, and even contributing to the implementation of quantum information storage using molecular systems.
Pravdivtsev, A. N., Kiryutin, A. S., Yurkovskaya, A. V., Vieth, H.-M., Ivanov, K. L., Robust conversion of singlet spin order in coupled spin-1/2 pairs by adiabatically ramped RF-fields. J. Magn. Reson. 2016, 273, 56-64. http://doi.org/10.1016/j.jmr.2016.10.003 Cover
In this work, we present a new way to transfer hyperpolarization between nuclear spins that interact through scalar coupling. The method uses special points called level anti-crossings (LACs), where the energy levels of the spin system come very close to each other and allow efficient mixing of spin states. To create these LAC conditions, a radiofrequency (RF) field with carefully chosen frequency and strength is applied.
We demonstrate the approach using a symmetric four-spin system that models molecules often used in para-hydrogen–based hyperpolarization experiments. We identify where the LACs occur, determine how the sign of the resulting polarization changes, and study how the efficiency of polarization transfer depends on the RF-field settings. The experimental results match the theoretical predictions very well. Overall, this LAC-based strategy provides a powerful and general tool for controlling and directing hyperpolarization in molecules with many coupled spins.
This study presents a new method for transferring nuclear spin hyperpolarization by exploiting level anti-crossings (LACs) created in the rotating frame of an NMR experiment through a precisely tuned radiofrequency (RF) field. By adjusting the RF amplitude and frequency, the authors demonstrate that it is possible to induce strong, controllable mixing of nuclear spin states, enabling efficient transfer of polarization between scalar-coupled spins in multispin systems. The method is demonstrated using para-hydrogen–induced polarization (PHIP) in a symmetric AA′MM′ four-spin system, where predicted LAC positions, polarization signs, and transfer efficiencies match experimental observations with high accuracy. The study further shows that both sudden and adiabatic switching of the RF field influence the resulting polarization pattern, offering additional control over polarization pathways .
By enabling direct and efficient polarization transfer at high magnetic fields on standard NMR hardware, this approach removes key obstacles to hyperpolarization in complex spin systems. It can help expand advanced NMR and MRI research into new areas, supporting improved sensitivity in structural, catalytic, and biomedical applications.
Pravdivtsev, A. N.; Yurkovskaya, A. V.; Lukzen, N. N.; Vieth, H. M.; Ivanov, K. L., Exploiting level anti-crossings (LACs) in the rotating frame for transferring spin hyperpolarization. Phys. Chem. Chem. Phys. 2014, 16 (35), 18707-18719. https://doi.org/10.1039/C4cp01445f
In this study, we present a theoretical framework that explains how para-hydrogen–induced polarization (PHIP) is created and transferred in molecules containing several interacting nuclear spins. The model applies to any magnetic field strength. It relies on the fact that scalar spin–spin coupling is the main factor responsible for forming PHIP and redistributing it within a molecule. At low magnetic fields, these interactions make the spins strongly coupled, allowing the polarization to be efficiently and coherently shared among them.
We illustrate these effects using a three-spin system and compare the predicted spectra with available experimental data. Using a fast field-cycling setup that rapidly moves the entire NMR probe, we measured PHIP spectra over a wide range of fields—from 0.1 mT to 7 T. The experiments were performed on ethylbenzene formed from the reaction of para-hydrogen with styrene. We also analyzed the polarization of catalyst-bound ethylbenzene and the initial styrene molecules.
This work provides the first experimental determination of the full magnetic-field dependence of PHIP. The measured spectra match the simulations extremely well, not only for the strongly polarized CH₂ and CH₃ groups of ethylbenzene but also for its weakly polarized aromatic protons. Additionally, the results show that the exact way the magnetic field is varied over time has a strong influence on the observed PHIP patterns. Overall, our findings confirm that scalar spin–spin couplings are the key factor controlling PHIP behavior and demonstrate how this theory can guide future applications of hyperpolarization.
The article presents a comprehensive theoretical and experimental study of para-hydrogen-induced polarization (PHIP) in multi-spin systems, focusing on how scalar spin–spin interactions govern the formation and transfer of hyperpolarization at variable magnetic fields. The research develops a theoretical framework for describing PHIP in systems with an arbitrary number of coupled spins, and demonstrates its application through experiments on ethylbenzene and styrene, where PHIP spectra were measured across a wide range of magnetic fields. The study shows that the field dependence and time profile of field variation significantly affect the PHIP patterns, and that scalar spin–spin coupling is the main factor responsible for polarization transfer. The results are in excellent agreement with simulations, confirming the accuracy of the theoretical approach and providing new tools for optimizing PHIP experiments.
The work provides a unified theory and experimental validation for the mechanisms that make PHIP a powerful tool for hyperpolarization, paving the way for developing more precise NMR and MRI methods. Its insights into coupling mechanisms and field cycling empower the rational design of hyperpolarized probes for analytical, medical, and biochemical research.
Korchak, S. E., Ivanov, K. L., Yurkovskaya, A. V., Vieth, H.-M., Para-hydrogen induced polarization in multi-spin systems studied at variable magnetic field. Phys. Chem. Chem. Phys. 2009, 11, 11146-11156. http://doi.org/10.1039/B914188j Cover
Research and development | Move up
Recent inventions from the laboratory include a method for acquiring high-resolution two-dimensional correlation spectra for diamagnetic substances using spontaneous spin mixing in ultraweak magnetic fields, and a universal thermostat design that delivers uniform temperature for NMR samples and works across a wide range of commercial NMR magnets.
Patent No. 2746064 C1 Russian Federation, IPC G01R 33/46. Method for complete correlation NMR spectroscopy with nuclear spin mixing in ultralow magnetic field : No. 2020126154 : filed 03.08.2020 : published 06.04.2021 / A. S. Kiryutin, Yu. A. Grishin, I. V. Zhukov [et al.] ; applicant Federal State Budgetary Institution of Science Institute "International Tomography Center" of the Siberian Branch of the Russian Academy of Sciences. – EDN VOLMLQ.
Patent No. 2818882 C1 Russian Federation, IPC G01N 24/08, G01R 33/31. Large-volume internal thermostat for NMR spectrometer magnet : No. 2023134319 : filed 21.12.2023 : published 06.05.2024 / A. A. Samsonenko, N. A. Artyukhova, A. S. Kiryutin, S. L. Weber ; applicant Federal State Budgetary Institution of Science Institute "International Tomography Center" of the Siberian Branch of the Russian Academy of Sciences. – EDN LICFWZ.
NMR analysis Software Development | Move up
In collaboration with the Laboratory of Theoretical Spin Chemistry (LTSС), software was developed for parameter optimization in experiments creating long-lived singlet states via adiabatic radiofrequency pulse methods.
