Siberian Branch of Russian Academy of Sciences

Recent Highlights

5 May 2020

In a recent work, for the first time NMR spectroscopy of hyperpolarized xenone and proton MRI were simultaneously applied for visualization of heterogeneous catalytic reaction with measurement of reagents-to-products conversion degree and temperature control.

The ability to use molecular hydrogen, H2, as a buffer gas in spin exchange optical pumping of noble gases enables the production of hydrogen gas containing a low percentile (5%) of hyperpolarized (HP) 129Xe as a tracer for in situ NMR spectroscopy of hydrogenation reactions. It is demonstrated that the xenon chemical shift, observed in the porous space of Pt-containing alumina pellets, can be used to monitor the temperature changes under rapidly progressing, nonsteady-state conditions during start-up of the catalytic reaction. Standard proton MR imaging was successfully applied to provide in situ evaluation of conversion for the catalyst used in this work.



The results are published in:
D.B. Burueva, E.V. Pokochueva, X. Wang, M. Filkins, A. Svyatova, S.P. Rigby, C. Wang, G.E. Pavlovskaya, K.V. Kovtunov, T. Meersmann, I.V. Koptyug.  In situ monitoring of heterogeneous catalytic hydrogenation via 129Xe NMR spectroscopy and proton MRI, ACS Catal., 10, 1417-1422 (2020). 
DOI: 10.1021/acscatal.9b05000

16 March 2020

Tissue protection from oxidative stress by antioxidants is of vital importance for cellular metabolism. The lens mostly consists of fiber cells lacking nuclei and organelles, having minimal metabolic activity; therefore, the defense of the lens tissue from the oxidative stress strongly relies on metabolites. Protein-free extracts from lenses and gills of freshwater fish, Sander lucioperca and Rutilus rutilus lacustris, were subjected to analysis using high-field 1H NMR spectroscopy and HPLC with optical and high-resolution mass spectrometric detection. It was found that the eye lenses of freshwater fish contain high concentrations of ovothiol A (OSH), i.e., one of the most powerful antioxidants exciting in nature. OSH was identified and quantified in millimolar concentrations. The concentration of OSH in the lens and gills depends on the fish genus and on the season. A possible mechanism of the reactive oxygen species deactivation in fish lenses is discussed. This work is the first to report on the presence of OSH in vertebrates. The presence of ovothiol in the fish tissue implies that it may be a significantly more common antioxidant in freshwater and marine animals than was previously thought.


The results are published in:

Yanshole, V.V.; Yanshole, L.V.; Zelentsova, E.A.; Tsentalovich, Yu. P.

Ovothiol A is the Main Antioxidant in Fish Lens. Metabolites, 9(5), 95. 2019

(DOI: 10.3390/metabo9050095)

5 February 2020

In their recent work, scientists of ITC for the first time proposed the original and efficient method for studying the permeability of metal-organic frameworks (MOFs) using Electron Paramagnetic Resonance (EPR) spectroscopy.

Metal-organic frameworks (MOFs) are the promising nanomaterials for separation of molecules with close dimensions and structures, such as various types of isomers. The efficiency of separation can be greatly enhanced if the apertures of the nanosized windows, controlling the diffusion of a particular molecule inside the cavities, are fine-tuned by external stimuli. We report the new approach for precise measurement of window sizes in ZIF-8 MOF and employ it in efficient separation of xylenes, which is of high practical importance. For this sake, we synthesized ZIF-8 with embedded stable nitroxides in the pores and applied electron paramagnetic resonance spectroscopy for in situ kinetic measurement of the diffusion of various guest molecules through the material. Slight variation of temperature within 298-333 K allowed tuning of the windows and reaching optimum conditions for separation of p-, m-, and o-xylenes with the efficiency up to 92−95%. The developed methodology provides deeper understanding of steric and kinetic aspects of molecular diffusion in ZIF-8 and paves the way to rational optimization of other MOF-based separation applications.

The results are published in:

D. M. Polyukhov, A. S. Poryvaev, S. A. Gromilov, M. V. Fedin // Precise Measurement and Controlled Tuning of Effective Window Sizes in ZIF-8 Framework for Efficient Separation of Xylenes // Nano Letters 19 (2019) 6506-6510.  10.1021/acs.nanolett.9b02730

5 December 2019

Signal Amplification by Reversible Exchange (SABRE) is a promising method for NMR signal enhancement and production of hyperpolarized molecules. As nuclear spin relaxation times of heteronuclei are usually much longer than those of protons, SABRE‐based hyperpolarization of heteronuclei in molecules is highly important in the context of biomedical applications. In this work, we demonstrate that the SLIC‐SABRE technique can be successfully used to hyperpolarize 15N nuclei in dalfampridine. The high polarization level of ca. 8 % achieved in this work made it possible to acquire 15N MR images at natural abundance of the 15N nuclei for the first time.

The results are published in Chemistry - A European Journal.

15N Hyperpolarization of Dalfampridine at Natural Abundance for Magnetic Resonance Imaging.

I. V. Skovpin, A. Svyatova, N. Chukanov, E. Y. Chekmenev, K. V. Kovtunov, I. V. Koptyug. Chemistry - A European Journal. 25 (55), 12694-12697. (DOI: 10.1002/chem.201902724)

7 November 2019

In their recent paper, scientists of ITC, together with colleagues from NIOCH SB RAS, for the first time demonstrated that the photoexcited triplet fullerenes can be successfully employed as spin labels for nanometer scale distance measurements in biomolecules by means of Electron Paramagnetic Resonance (EPR).

Precise nanoscale distance measurements by pulsed EPR spectroscopy play a crucial role in structural studies of biomolecules. The properties of the spin labels used in this approach determine the sensitivity limits, attainable distances, and proximity to biological conditions. Herein, we propose and validate the use of photoexcited fullerenes as spin labels for pulsed dipolar (PD) EPR distance measurements. Hyperpolarization and the narrower spectrum of fullerenes compared to other triplets (e.g., porphyrins) boost the sensitivity, and superior relaxation properties allow PD EPR measurements up to a near-room temperature. This approach is demonstrated using fullerene-nitroxide and fullerene-triarylmethyl pairs, as well as a supramolecular complex of fullerene with nitroxide-labeled protein. Photoexcited triplet fullerenes can be considered as new spin labels with outstanding spectroscopic properties for future structural studies of biomolecules.

The results are published in:

O. A. Krumkacheva, I. O. Timofeev, L. V. Politanskaya, Y. F. Polienko, E. V. Tretyakov, O. Yu. Rogozhnikova, D. V. Trukhin, V. M. Tormyshev, A. S. Chubarov, E. G. Bagryanskaya, M. V. Fedin // Triplet Fullerenes as Prospective Spin Labels for Nanoscale Distance Measurements by Pulsed Dipolar EPR // Angew. Chem. Int. Ed. 58 (2019) 13271–13275.  10.1002/anie.201904152

16 October 2019

Two‐dimensional NMR spectroscopy is one of the most important spectroscopic tools for the investigation of biological macromolecules. However, due to the low sensitivity of NMR spectroscopy, it takes usually from several minutes to many hours to record such spectra. Here, the possibility of detecting a bioactive derivative of the sunflower trypsin inhibitor‐1 (SFTI‐1), a tetradecapeptide, by combining parahydrogen‐induced polarization (PHIP) and ultrafast 2D NMR spectroscopy is shown. The PHIP activity of the inhibitor was achieved by labeling with O ‐propargyl‐l ‐tyrosine. In 1D PHIP experiments a signal enhancement of a factor of approximately 1200 compared to standard NMR was found. This enhancement permits measurement of 2D NMR correlation spectra of low‐concentrated SFTI‐1 in less than 10 seconds, employing ultrafast single‐scan 2D NMR detection. As experimental examples PHIP‐assisted ultrafast single‐scan TOCSY spectra of SFTI‐1 are shown. 

The work was done in cooperation with Technical University of Darmstadt (Germany).

 The results are published in Chemistry - a European Journal (hot paper + cover), DOI: 10.1002/chem.201900079