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Harrabi R, Halbritter T, Alarab S, Chatterjee S, Wolska-Pietkiewicz M, Damodaran KK, van Tol J, Lee D, Paul S, Hediger S, Sigurdsson ST, Mentink-Vigier F, De Paëpe G. AsymPol-TEKs as efficient polarizing agents for MAS-DNP in glass matrices of non-aqueous solvents. Phys Chem Chem Phys 2024; 26:5669-5682. [PMID: 38288878 PMCID: PMC10849081 DOI: 10.1039/d3cp04271e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 01/22/2024] [Indexed: 02/03/2024]
Abstract
Two polarizing agents from the AsymPol family, AsymPol-TEK and cAsymPol-TEK (methyl-free version) are introduced for MAS-DNP applications in non-aqueous solvents. The performance of these new biradicals is rationalized in detail using a combination of electron paramagnetic resonance spectroscopy, density functional theory, molecular dynamics and quantitative MAS-DNP spin dynamics simulations. By slightly modifying the experimental protocol to keep the sample temperature low at insertion, we are able to obtain reproducable DNP-NMR data with 1,1,2,2-tetrachloroethane (TCE) at 100 K, which facilitates optimization and comparison of different polarizing agents. At intermediate magnetic fields, AsymPol-TEK and cAsymPol-TEK provide 1.5 to 3-fold improvement in sensitivity compared to TEKPol, one of the most widely used polarizing agents for organic solvents, with significantly shorter DNP build-up times of ∼1 s and ∼2 s at 9.4 and 14.1 T respectively. In the course of the work, we also isolated and characterized two diastereoisomers that can form during the synthesis of AsymPol-TEK; their difference in performance is described and discussed. Finally, the advantages of the AsymPol-TEKs are demonstrated by recording 2D 13C-13C correlation experiments at natural 13C-abundance of proton-dense microcrystals and by polarizing the surface of ZnO nanocrystals (NCs) coated with diphenyl phosphate ligands. For those experiments, cAsymPol-TEK yielded a three-fold increase in sensitivity compared to TEKPol, corresponding to a nine-fold time saving.
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Affiliation(s)
- Rania Harrabi
- Univ. Grenoble Alpes, CEA, CNRS, IRIG, MEM, 38000 Grenoble, France.
| | - Thomas Halbritter
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland.
| | - Shadi Alarab
- Univ. Grenoble Alpes, CEA, CNRS, IRIG, MEM, 38000 Grenoble, France.
| | - Satyaki Chatterjee
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland.
| | | | - Krishna K Damodaran
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland.
| | - Johan van Tol
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32301, USA.
| | - Daniel Lee
- Univ. Grenoble Alpes, CEA, CNRS, IRIG, MEM, 38000 Grenoble, France.
| | - Subhradip Paul
- Univ. Grenoble Alpes, CEA, CNRS, IRIG, MEM, 38000 Grenoble, France.
| | - Sabine Hediger
- Univ. Grenoble Alpes, CEA, CNRS, IRIG, MEM, 38000 Grenoble, France.
| | - Snorri Th Sigurdsson
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland.
| | - Frederic Mentink-Vigier
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32301, USA.
| | - Gaël De Paëpe
- Univ. Grenoble Alpes, CEA, CNRS, IRIG, MEM, 38000 Grenoble, France.
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Georges T, Chèvre R, Cousin SF, Gervais C, Thureau P, Mollica G, Azaïs T. 43Ca MAS-DNP NMR of Frozen Solutions for the Investigation of Calcium Ion Complexation. ACS OMEGA 2024; 9:4881-4891. [PMID: 38313477 PMCID: PMC10831850 DOI: 10.1021/acsomega.3c08292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 12/11/2023] [Accepted: 12/26/2023] [Indexed: 02/06/2024]
Abstract
Calcium ion complexation in aqueous solutions is of paramount importance in biology as it is related to cell signaling, muscle contraction, or biomineralization. However, Ca2+-complexes are dynamic soluble entities challenging to describe at the molecular level. Nuclear magnetic resonance appears as a method of choice to probe Ca2+-complexes. However, 43Ca NMR exhibits severe limitations arising from the low natural abundance coupled to the low gyromagnetic ratio and the quadrupolar nature of 43Ca, which overall make it a very unreceptive nucleus. Here, we show that 43Ca dynamic nuclear polarization (DNP) NMR of 43Ca-labeled frozen solutions is an efficient approach to enhance the NMR receptivity of 43Ca and to obtain structural insights about calcium ions complexed with representative ligands including water molecules, ethylenediaminetetraacetic acid (EDTA), and l-aspartic acid (l-Asp). In these conditions and in combination with numerical simulations and calculations, we show that 43Ca nuclei belonging to Ca2+ complexed to the investigated ligands exhibit rather low quadrupolar couplings (with CQ typically ranging from 0.6 to 1 MHz) due to high symmetrical environments and potential residual dynamics in vitrified solutions at a temperature of 100 K. As a consequence, when 1H→43Ca cross-polarization (CP) is used to observe 43Ca central transition, "high-power" νRF(43Ca) conditions, typically used to detect spin 1/2 nuclei, provide ∼120 times larger sensitivity than "low-power" conditions usually employed for detection of quadrupolar nuclei. These "high-power" CPMAS conditions allow two-dimensional (2D) 1H-43Ca HetCor spectra to be readily recorded, highlighting various Ca2+-ligand interactions in solution. This significant increase in 43Ca NMR sensitivity results from the combination of distinct advantages: (i) an efficient 1H-mediated polarization transfer from DNP, resembling the case of low-natural-abundance spin 1/2 nuclei, (ii) a reduced dynamics, allowing the use of CP as a sensitivity enhancement technique, and (iii) the presence of a relatively highly symmetrical Ca environment, which, combined to residual dynamics, leads to the averaging of the quadrupolar interaction and hence to efficient high-power CP conditions. Interestingly, these results indicate that the use of high-power CP conditions is an effective way of selecting symmetrical and/or dynamic 43Ca environments of calcium-containing frozen solution, capable of filtering out more rigid and/or anisotropic 43Ca sites characterized by larger quadrupolar constants. This approach could open the way to the atomic-level investigation of calcium environments in more complex, heterogeneous frozen solutions, such as those encountered at the early stages of calcium phosphate or calcium carbonate biomineralization events.
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Affiliation(s)
- Tristan Georges
- Sorbonne
Université, CNRS, Laboratoire de Chimie de la Matière
Condensée de Paris (LCMCP), 4 Place Jussieu, 75005 Paris, France
| | - Romain Chèvre
- Aix
Marseille Univ, CNRS, ICR, 13397 Marseille, France
| | | | - Christel Gervais
- Sorbonne
Université, CNRS, Laboratoire de Chimie de la Matière
Condensée de Paris (LCMCP), 4 Place Jussieu, 75005 Paris, France
| | | | | | - Thierry Azaïs
- Sorbonne
Université, CNRS, Laboratoire de Chimie de la Matière
Condensée de Paris (LCMCP), 4 Place Jussieu, 75005 Paris, France
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Liang L, Shang C, Chen K, Hou G. Supercycled R-symmetry sequences for robust heteronuclear polarization transfer in solid-state NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 344:107310. [PMID: 36334491 DOI: 10.1016/j.jmr.2022.107310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 10/09/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
Herein, we introduce supercycle of R-symmetry sequences (SR-sequences) and incomplete supercycle schemes of R-symmetry sequences (iSR-I- and iSR-II-sequences) to improve the robustness of PRESTO for heteronuclear polarization transfer in MAS NMR. The constructions of SR- and iSR-I/II- sequences are based on the different phase-inverted supercycles of R-symmetry sequences, and such supercycles can suppress the influence of CSA, resonance offset and RF mismatch when incorporated into the PRESTO method. Moreover, the SR- and iSR-II-sequences are more efficient in suppressing the interference of homonuclear dipolar coupling. The improved robustness of SR-, iSR-I- and iSR-II-PRESTO over the original R-PRESTO has been verified by numerical simulations and NMR experiments on NH4H2PO4 and gamma-alumina at fast MAS conditions. It is also important to note that the SR- and iSR-II-PRESTO can greatly lengthen the transverse relaxation times and lead to much higher polarization transfer efficiency compared to R-PRESTO, thanks to their superior tolerance to RF inhomogeneity and homonuclear dipolar coupling.
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Affiliation(s)
- Lixin Liang
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chao Shang
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kuizhi Chen
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
| | - Guangjin Hou
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China.
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Gómez J, Rankin A, Trébosc J, Pourpoint F, Tsutsumi Y, Nagashima H, Lafon O, Amoureux JP. Improved NMR transfer of magnetization from protons to half-integer spin quadrupolar nuclei at moderate and high magic-angle spinning frequencies. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2021; 2:447-464. [PMID: 37904781 PMCID: PMC10539806 DOI: 10.5194/mr-2-447-2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 06/01/2021] [Indexed: 11/01/2023]
Abstract
Half-integer spin quadrupolar nuclei are the only magnetic isotopes for the majority of the chemical elements. Therefore, the transfer of polarization from protons to these isotopes under magic-angle spinning (MAS) can provide precious insights into the interatomic proximities in hydrogen-containing solids, including organic, hybrid, nanostructured and biological solids. This transfer has recently been combined with dynamic nuclear polarization (DNP) in order to enhance the NMR signal of half-integer quadrupolar isotopes. However, the cross-polarization transfer lacks robustness in the case of quadrupolar nuclei, and we have recently introduced as an alternative technique a D -RINEPT (through-space refocused insensitive nuclei enhancement by polarization transfer) scheme combining a heteronuclear dipolar recoupling built from adiabatic pulses and a continuous-wave decoupling. This technique has been demonstrated at 9.4 T with moderate MAS frequencies, ν R ≈ 10 -15 kHz, in order to transfer the DNP-enhanced 1 H polarization to quadrupolar nuclei. Nevertheless, polarization transfers from protons to quadrupolar nuclei are also required at higher MAS frequencies in order to improve the 1 H resolution. We investigate here how this transfer can be achieved at ν R ≈ 20 and 60 kHz. We demonstrate that the D -RINEPT sequence using adiabatic pulses still produces efficient and robust transfers but requires large radio-frequency (rf) fields, which may not be compatible with the specifications of most MAS probes. As an alternative, we introduce robust and efficient variants of the D -RINEPT and PRESTO (phase-shifted recoupling effects a smooth transfer of order) sequences using symmetry-based recoupling schemes built from single and composite π pulses. Their performances are compared using the average Hamiltonian theory and experiments at B 0 = 18.8 T on γ -alumina and isopropylamine-templated microporous aluminophosphate (AlPO4 -14), featuring low and significant 1 H-1 H dipolar interactions, respectively. These experiments demonstrate that the 1 H magnetization can be efficiently transferred to 27 Al nuclei using D -RINEPT with SR 4 1 2 (2700 90180 ) recoupling and using PRESTO with R 22 2 7 (1800 ) or R 16 7 6 (2700 90180 ) schemes at ν R = 20 or 62.5 kHz, respectively. The D -RINEPT and PRESTO recoupling schemes complement each other since the latter is affected by dipolar truncation, whereas the former is not. We also analyze the losses during these recoupling schemes, and we show how these magnetization transfers can be used at ν R = 62.5 kHz to acquire in 72 min 2D HETCOR (heteronuclear correlation) spectra between 1 H and quadrupolar nuclei, with a non-uniform sampling (NUS).
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Affiliation(s)
- Jennifer S. Gómez
- Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, Lille, 59000, France
| | - Andrew G. M. Rankin
- Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, Lille, 59000, France
- present address: Sorbonne Université, CNRS, Collège de
France, Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), 4 place Jussieu, Paris, 75005, France
| | - Julien Trébosc
- Univ. Lille, CNRS, INRAE, Centrale Lille, Univ. Artois, FR 2638 –
IMEC – Fédération Chevreul, Lille, 59000, France
| | - Frédérique Pourpoint
- Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, Lille, 59000, France
| | - Yu Tsutsumi
- Bruker Japan, 3-9 Moriya, Kanagawa, Yokohama, Kanagawa,
221-0022, Japan
| | - Hiroki Nagashima
- Interdisciplinary Research Center for Catalytic Chemistry, National
Institute of Advanced Industrial Science and Technology (AIST), 1-1-1
Higashi, Tsukuba, Ibaraki, 305-8565, Japan
| | - Olivier Lafon
- Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, Lille, 59000, France
- Institut Universitaire de France, 1 rue Descartes, Paris, 75231,
France
| | - Jean-Paul Amoureux
- Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, Lille, 59000, France
- Riken NMR Science and Development Division, Yokohama, Kanagawa, 230-0045, Japan
- Bruker Biospin, 34 rue de l'industrie, Wissembourg, 67166, France
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