1
|
Wenckebach WT, Capozzi A, Patel S, Ardenkjær-Larsen JH. Direct measurement of the triple spin flip rate in dynamic nuclear polarization. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 327:106982. [PMID: 33932911 DOI: 10.1016/j.jmr.2021.106982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 03/08/2021] [Accepted: 04/11/2021] [Indexed: 06/12/2023]
Abstract
A previous study of the effect of Gadolinium doping on the dynamic polarization (DNP) of 13C using trityls showed that the rate at which the polarization builds up is almost independent of the Gadolinium concentration, while the electron spin-lattice relaxation rate varies over an order of magnitude. In this paper we analyze the polarization build-up in detail and show that in this case DNP is due to the cross-effect (CE) and that the build-up rate can be quantitatively interpreted as the rate of the triple spin flips responsible for the CE. Thus this build-up rate presents a direct measurement of this triple spin flip rate.
Collapse
Affiliation(s)
- W Th Wenckebach
- National High Magnetic Field Laboratory, University of Florida, Gainesville, FL, USA; Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
| | - A Capozzi
- Center for Hyperpolarization in Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Building 349, 2800 Kgs Lyngby, Denmark
| | - S Patel
- Center for Hyperpolarization in Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Building 349, 2800 Kgs Lyngby, Denmark
| | - J H Ardenkjær-Larsen
- Center for Hyperpolarization in Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Building 349, 2800 Kgs Lyngby, Denmark
| |
Collapse
|
2
|
Di Mauro GM, Hardin NZ, Ramamoorthy A. Lipid-nanodiscs formed by paramagnetic metal chelated polymer for fast NMR data acquisition. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2020; 1862:183332. [PMID: 32360741 PMCID: PMC7340147 DOI: 10.1016/j.bbamem.2020.183332] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/21/2020] [Accepted: 04/27/2020] [Indexed: 02/07/2023]
Abstract
Lipid-nanodiscs have been shown to be an exciting innovation as a membrane-mimicking system for studies on membrane proteins by a variety of biophysical techniques, including NMR spectroscopy. Although NMR spectroscopy is unique in enabling the atomic-resolution investigation of dynamic structures of membrane-associated molecules, it, unfortunately, suffers from intrinsically low sensitivity. The long data acquisition often used to enhance the sensitivity is not desirable for sensitive membrane proteins. Instead, paramagnetic relaxation enhancement (PRE) has been used to reduce NMR data acquisition time or to reduce the amount of sample required to acquire an NMR spectra. However, the PRE approach involves the introduction of external paramagnetic probes in the system, which can induce undesired changes in the sample and on the observed NMR spectra. For example, the addition of paramagnetic ions, as frequently used, can denature the protein via direct interaction and also through sample heating. In this study, we show how the introduction of paramagnetic tags on the outer belt of polymer-nanodiscs can be used to speed-up data acquisition by significantly reducing the spin-lattice relaxation (T1) times with minimum-to-no alteration of the spectral quality. Our results also demonstrate the feasibility of using different types of paramagnetic ions (Eu3+, Gd3+, Dy3+, Er3+, Yb3+) for NMR studies on lipid-nanodiscs. Experimental results characterizing the formation of lipid-nanodiscs by the metal-chelated polymer, and their increased tolerance toward metal ions are also reported.
Collapse
Affiliation(s)
- Giacomo M Di Mauro
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Nathaniel Z Hardin
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA; Biophysics and Chemistry Department, The University of Michigan, Ann Arbor, MI 48109-1055, USA; Macromolecular Science and Engineering, The University of Michigan, Ann Arbor, MI 48109-1055, USA; Biomedical Engineering, The University of Michigan, Ann Arbor, MI 48109-1055, USA.
| |
Collapse
|
3
|
Hardin NZ, Kocman V, Di Mauro GM, Ravula T, Ramamoorthy A. Metal‐Chelated Polymer Nanodiscs for NMR Studies. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201910118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Nathaniel Z. Hardin
- Biophysics Program and Department of ChemistryUniversity of Michigan Ann Arbor MI 48109-1055 USA
| | - Vojč Kocman
- Biophysics Program and Department of ChemistryUniversity of Michigan Ann Arbor MI 48109-1055 USA
| | - Giacomo M. Di Mauro
- Biophysics Program and Department of ChemistryUniversity of Michigan Ann Arbor MI 48109-1055 USA
| | - Thirupathi Ravula
- Biophysics Program and Department of ChemistryUniversity of Michigan Ann Arbor MI 48109-1055 USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program and Department of ChemistryUniversity of Michigan Ann Arbor MI 48109-1055 USA
| |
Collapse
|
4
|
Hardin NZ, Kocman V, Di Mauro GM, Ravula T, Ramamoorthy A. Metal-Chelated Polymer Nanodiscs for NMR Studies. Angew Chem Int Ed Engl 2019; 58:17246-17250. [PMID: 31529579 PMCID: PMC6861636 DOI: 10.1002/anie.201910118] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 09/11/2019] [Indexed: 01/20/2023]
Abstract
Paramagnetic relaxation enhancement (PRE) is commonly used to speed up spin lattice relaxation time (T1 ) for rapid data acquisition in NMR structural studies. Consequently, there is significant interest in novel paramagnetic labels for enhanced NMR studies on biomolecules. Herein, we report the synthesis and characterization of a modified poly(styrene-co-maleic acid) polymer which forms nanodiscs while showing the ability to chelate metal ions. Cu2+ -chelated nanodiscs are demonstrated to reduce the T1 of protons for both polymer and lipid-nanodisc components. The chelated nanodiscs also decrease the proton T1 values for a water-soluble DNA G-quadruplex. These results suggest that polymer nanodiscs functionalized with paramagnetic tags can be used to speed-up data acquisition from lipid bilayer samples and also to provide structural information from water-soluble biomolecules.
Collapse
Affiliation(s)
- Nathaniel Z Hardin
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Vojč Kocman
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Giacomo M Di Mauro
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Thirupathi Ravula
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program and Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| |
Collapse
|
5
|
Kocman V, Di Mauro GM, Veglia G, Ramamoorthy A. Use of paramagnetic systems to speed-up NMR data acquisition and for structural and dynamic studies. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019; 102:36-46. [PMID: 31325686 PMCID: PMC6698407 DOI: 10.1016/j.ssnmr.2019.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 07/10/2019] [Accepted: 07/11/2019] [Indexed: 05/05/2023]
Abstract
NMR spectroscopy is a powerful experimental technique to study biological systems at the atomic resolution. However, its intrinsic low sensitivity results in long acquisition times that in extreme cases lasts for days (or even weeks) often exceeding the lifetime of the sample under investigation. Different paramagnetic agents have been used in an effort to decrease the spin-lattice (T1) relaxation times of the studied nuclei, which are the main cause for long acquisition times necessary for signal averaging to enhance the signal-to-noise ratio of NMR spectra. Consequently, most of the experimental time is "wasted" in waiting for the magnetization to recover between successive scans. In this review, we discuss how to set up an optimal paramagnetic relaxation enhancement (PRE) system to effectively reduce the T1 relaxation times avoiding significant broadening of NMR signals. Additionally, we describe how PRE-agents can be used to provide structural and dynamic information and can even be used to follow the intermediates of chemical reactions and to speed-up data acquisition. We also describe the unique challenges and benefits associated with the application of PRE to solid-state NMR spectroscopy, explaining how the use of PREs is more complex for membrane mimetic systems as PREs can also be exploited to change the alignment of oriented membrane systems. Functionalization of membrane mimetics, such as bicelles, can provide a controlled region of paramagnetic effect that has the potential, together with the desired alignment, to provide crucial biologically relevant structural information. And finally, we discuss how paramagnetic metals can be utilized to further increase the dynamic nuclear polarization (DNP) effects and how to preserve the enhancements when dissolution DNP is implemented.
Collapse
Affiliation(s)
- Vojč Kocman
- Department of Chemistry, University of Michigan, Ann Arbor, MI, USA; Biophysics, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA
| | | | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, University of Michigan, Ann Arbor, MI, USA; Biophysics, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA.
| |
Collapse
|
6
|
Parish C, Niedbalski P, Wang Q, Khashami F, Hayati Z, Liu M, Song L, Lumata L. Effects of glassing matrix deuteration on the relaxation properties of hyperpolarized 13C spins and free radical electrons at cryogenic temperatures. J Chem Phys 2019; 150:234307. [PMID: 31228902 PMCID: PMC6588520 DOI: 10.1063/1.5096036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 05/20/2019] [Accepted: 06/03/2019] [Indexed: 11/14/2022] Open
Abstract
Glassing matrix deuteration could be a beneficial sample preparation method for 13C dynamic nuclear polarization (DNP) when large electron paramagnetic resonance (EPR) width free radicals are used. However, it could yield the opposite DNP effect when samples are doped with small EPR width free radicals. Herein, we have investigated the influence of solvent deuteration on the 13C nuclear and electron relaxation that go along with the effects on 13C DNP intensities at 3.35 T and 1.2 K. For 13C DNP samples doped with trityl OX063, the 13C DNP signals decreased significantly when the protons are replaced by deuterons in glycerol:water or DMSO:water solvents. Meanwhile, the corresponding solid-state 13C T1 relaxation times of trityl OX063-doped samples generally increased upon solvent deuteration. On the other hand, 13C DNP signals improved by a factor of ∼1.5 to 2 upon solvent deuteration of samples doped with 4-oxo-TEMPO. Despite this 13C DNP increase, there were no significant differences recorded in 13C T1 values of TEMPO-doped samples with nondeuterated or fully deuterated glassing matrices. While solvent deuteration appears to have a negligible effect on the electron T1 relaxation of both free radicals, the electron T2 relaxation times of these two free radicals generally increased upon solvent deuteration. These overall results suggest that while the solid-phase 13C DNP signals are dependent upon the changes in total nuclear Zeeman heat capacity, the 13C relaxation effects are related to 2H/1H nuclear spin diffusion-assisted 13C polarization leakage in addition to the dominant paramagnetic relaxation contribution of free radical centers.
Collapse
Affiliation(s)
- Christopher Parish
- Department of Physics, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
| | | | - Qing Wang
- Department of Physics, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
| | - Fatemeh Khashami
- Department of Physics, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
| | | | | | - Likai Song
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
| | - Lloyd Lumata
- Department of Physics, University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
| |
Collapse
|
7
|
Capozzi A, Patel S, Wenckebach WT, Karlsson M, Lerche MH, Ardenkjær-Larsen JH. Gadolinium Effect at High-Magnetic-Field DNP: 70% 13C Polarization of [U- 13C] Glucose Using Trityl. J Phys Chem Lett 2019; 10:3420-3425. [PMID: 31181932 DOI: 10.1021/acs.jpclett.9b01306] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We show that the trityl electron spin resonance (ESR) features, crucial for an efficient dynamic nuclear polarization (DNP) process, are sample-composition-dependent. Working at 6.7 T and 1.1 K with a generally applicable DNP sample solvent mixture such as water/glycerol plus trityl, the addition of Gd3+ leads to a dramatic increase in [U-13C] glucose polarization from 37 ± 4% to 69 ± 3%. This is the highest value reported to date and is comparable to what can be achieved on pyruvic acid. Moreover, performing ESR measurements under actual DNP conditions, we provide experimental evidence that gadolinium doping not only shortens the trityl electron spin-lattice relaxation time but also modifies the radical g-tensor. The latter yielded a considerable narrowing of the ESR spectrum line width. Finally, in the frame of the spin temperature theory, we discuss how these two phenomena affect the DNP performance.
Collapse
Affiliation(s)
- Andrea Capozzi
- Center for Hyperpolarization in Magnetic Resonance, Department of Health Technology , Technical University of Denmark , Building 349 , 2800 Kongens Lyngby , Denmark
| | - Saket Patel
- Center for Hyperpolarization in Magnetic Resonance, Department of Health Technology , Technical University of Denmark , Building 349 , 2800 Kongens Lyngby , Denmark
| | - W Thomas Wenckebach
- Paul Scherrer Institute , CH-5232 Villigen , Switzerland
- National High Magnetic Field Laboratory, UF, AMRIS , Gainesville , Florida 32611 , United States
| | - Magnus Karlsson
- Center for Hyperpolarization in Magnetic Resonance, Department of Health Technology , Technical University of Denmark , Building 349 , 2800 Kongens Lyngby , Denmark
| | - Mathilde H Lerche
- Center for Hyperpolarization in Magnetic Resonance, Department of Health Technology , Technical University of Denmark , Building 349 , 2800 Kongens Lyngby , Denmark
| | - Jan Henrik Ardenkjær-Larsen
- Center for Hyperpolarization in Magnetic Resonance, Department of Health Technology , Technical University of Denmark , Building 349 , 2800 Kongens Lyngby , Denmark
- GE Healthcare , Park Alle 295 , 2605 Brøndby , Denmark
| |
Collapse
|
8
|
Jähnig F, Himmler A, Kwiatkowski G, Däpp A, Hunkeler A, Kozerke S, Ernst M. A spin-thermodynamic approach to characterize spin dynamics in TEMPO-based samples for dissolution DNP at 7 T field. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 303:91-104. [PMID: 31030064 DOI: 10.1016/j.jmr.2019.04.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 04/12/2019] [Accepted: 04/19/2019] [Indexed: 06/09/2023]
Abstract
The spin dynamics of dissolution DNP samples consisting of 4.5 M [13C]urea in a mixture of (1/1)Vol glycerol/water using 4-Oxo-TEMPO as a radical was investigated. We analyzed the DNP dynamics as function of radical concentration at 7 T and 3.4 T static magnetic field as well as function of deuteration of the solvent matrix at the high field. The spin dynamics could be reproduced in all cases, at least qualitatively, by a thermodynamic model based on spin temperatures of the nuclear Zeeman baths and an electron non-Zeeman (dipolar) bath. We find, however, that at high field (7 T) and low radical concentrations (25 mM) the nuclear spins do not reach the same spin temperature indicating a weak coupling of the two baths. At higher radical concentrations, as well as for all radical concentrations at low field (3.4 T), the two nuclear Zeeman baths reach the same spin temperature within experimental errors. Additionally, the spin system was prepared with different initial conditions. For these cases, the thermodynamic model was able to predict the time evolution of the system well. While the DNP profiles do not give clear indications to a specific polarization transfer mechanism, at high field (7 T) increased coupling is seen. The EPR line shapes cannot clarify this in absence of ELDOR type experiments, nevertheless DNP profiles and dynamics under frequency-modulated microwave irradiation illustrate the expected increase in coupling between electrons with increasing radical concentration.
Collapse
Affiliation(s)
- Fabian Jähnig
- Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Aaron Himmler
- Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Grzegorz Kwiatkowski
- Institute for Biomedical Engineering, University and ETH Zürich, Gloriastrasse 35, 8092 Zürich, Switzerland
| | - Alexander Däpp
- Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Andreas Hunkeler
- Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH Zürich, Gloriastrasse 35, 8092 Zürich, Switzerland
| | - Matthias Ernst
- Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland.
| |
Collapse
|
9
|
Ravera E, Takis PG, Fragai M, Parigi G, Luchinat C. NMR Spectroscopy and Metal Ions in Life Sciences. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201800875] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Enrico Ravera
- Magnetic Resonance Center (CERM) and Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP); Via L. Sacconi 6 50019 Sesto Fiorentino Italy
- Department of Chemistry “Ugo Schiff”; University of Florence; Via della Lastruccia 3 50019 Sesto Fiorentino Italy
| | - Panteleimon G. Takis
- Giotto Biotech S.R.L.; Via Madonna del Piano 6 50019 Sesto Fiorentino (FI) Italy
| | - Marco Fragai
- Magnetic Resonance Center (CERM) and Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP); Via L. Sacconi 6 50019 Sesto Fiorentino Italy
- Department of Chemistry “Ugo Schiff”; University of Florence; Via della Lastruccia 3 50019 Sesto Fiorentino Italy
| | - Giacomo Parigi
- Magnetic Resonance Center (CERM) and Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP); Via L. Sacconi 6 50019 Sesto Fiorentino Italy
- Department of Chemistry “Ugo Schiff”; University of Florence; Via della Lastruccia 3 50019 Sesto Fiorentino Italy
| | - Claudio Luchinat
- Magnetic Resonance Center (CERM) and Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP); Via L. Sacconi 6 50019 Sesto Fiorentino Italy
- Department of Chemistry “Ugo Schiff”; University of Florence; Via della Lastruccia 3 50019 Sesto Fiorentino Italy
| |
Collapse
|
10
|
Niedbalski P, Kiswandhi A, Parish C, Wang Q, Khashami F, Lumata L. NMR Spectroscopy Unchained: Attaining the Highest Signal Enhancements in Dissolution Dynamic Nuclear Polarization. J Phys Chem Lett 2018; 9:5481-5489. [PMID: 30179503 DOI: 10.1021/acs.jpclett.8b01687] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Dynamic nuclear polarization (DNP) via the dissolution method is one of the most successful methods for alleviating the inherently low Boltzmann-dictated sensitivity in nuclear magnetic resonance (NMR) spectroscopy. This emerging technology has already begun to positively impact chemical and metabolic research by providing the much-needed enhancement of the liquid-state NMR signals of insensitive nuclei such as 13C by several thousand-fold. In this Perspective, we present our viewpoints regarding the key elements needed to maximize the NMR signal enhancements in dissolution DNP, from the very core of the DNP process at cryogenic temperatures, DNP instrumental conditions, and chemical tuning in sample preparation to current developments in minimizing hyperpolarization losses during the dissolution transfer process. The optimization steps discussed herein could potentially provide important experimental and theoretical considerations in harnessing the best possible sensitivity gains in NMR spectroscopy as afforded by optimized dissolution DNP technology.
Collapse
Affiliation(s)
- Peter Niedbalski
- Department of Physics , The University of Texas at Dallas , 800 West Campbell Road , Richardson , Texas 75080 , United States
| | - Andhika Kiswandhi
- Department of Physics , The University of Texas at Dallas , 800 West Campbell Road , Richardson , Texas 75080 , United States
| | - Christopher Parish
- Department of Physics , The University of Texas at Dallas , 800 West Campbell Road , Richardson , Texas 75080 , United States
| | - Qing Wang
- Department of Physics , The University of Texas at Dallas , 800 West Campbell Road , Richardson , Texas 75080 , United States
| | - Fatemeh Khashami
- Department of Physics , The University of Texas at Dallas , 800 West Campbell Road , Richardson , Texas 75080 , United States
| | - Lloyd Lumata
- Department of Physics , The University of Texas at Dallas , 800 West Campbell Road , Richardson , Texas 75080 , United States
| |
Collapse
|
11
|
Parish C, Niedbalski P, Kiswandhi A, Lumata L. Dynamic nuclear polarization of carbonyl and methyl 13C spins of acetate using 4-oxo-TEMPO free radical. J Chem Phys 2018; 149:054302. [PMID: 30089385 DOI: 10.1063/1.5043378] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Hyperpolarization of 13C-enriched biomolecules via dissolution dynamic nuclear polarization (DNP) has enabled real-time metabolic imaging of a variety of diseases with superb specificity and sensitivity. The source of the unprecedented liquid-state nuclear magnetic resonance spectroscopic or imaging signal enhancements of >10 000-fold is the microwave-driven DNP process that occurs at a relatively high magnetic field and cryogenic temperature. Herein, we have methodically investigated the relative efficiencies of 13C DNP of single or double 13C-labeled sodium acetate with or without 2H-enrichment of the methyl group and using a 4-oxo-TEMPO free radical as the polarizing agent at 3.35 T and 1.4 K. The main finding of this work is that not all 13C spins in acetate are polarized with equal DNP efficiency using this relatively wide electron spin resonance linewidth free radical. In fact, the carbonyl 13C spins have about twice the solid-state 13C polarization level of methyl 13C spins. Deuteration of the methyl group provides a DNP signal improvement of methyl 13C spins on a par with that of carbonyl 13C spins. On the other hand, both the double 13C-labeled [1,2-13C2] acetate and [1,2-13C2, 2H3] acetate have a relative solid-state 13C polarization at the level of [2-13C] acetate. Meanwhile, the solid-state 13C T1 relaxation times at 3.35 T and 1.4 K were essentially the same for all six isotopomers of 13C acetate. These results suggest that the intramolecular environment of 13C spins plays a prominent role in determining the 13C DNP efficiency, while the solid phase 13C T1 relaxation of these samples is dominated by the paramagnetic effect due to the relatively high concentration of free radicals.
Collapse
Affiliation(s)
- Christopher Parish
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
| | - Peter Niedbalski
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
| | - Andhika Kiswandhi
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
| | - Lloyd Lumata
- Department of Physics, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, USA
| |
Collapse
|
12
|
Sirusi AA, Suh EH, Kovacs Z, Merritt ME. The effect of Ho 3+ doping on 13C dynamic nuclear polarization at 5 T. Phys Chem Chem Phys 2018; 20:728-731. [PMID: 29242884 PMCID: PMC5761062 DOI: 10.1039/c7cp07198a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Dissolution dynamic nuclear polarization was introduced in 2003 as a method for producing hyperpolarized 13C solutions suitable for metabolic imaging. The signal to noise ratio for the imaging experiment depends on the maximum polarization achieved in the solid state. Hence, optimization of the DNP conditions is essential. To acquire maximum polarization many parameters related to sample preparation can be modulated. Recently, it was demonstrated that Ho3+, Dy3+, Tb3+, and Gd3+ complexes enhance the polarization at 1.2 K and 3.35 T when using the trityl radical as the primary paramagnetic center. Here, we have investigated the influence of Ho-DOTA on 13C solid state DNP at 1.2 K and 5 T. We have performed 13C DNP on [1-13C] sodium acetate in 1 : 1 (v/v) water/glycerol with 15 mM trityl OX063 radicals in the presence of a series of Ho-DOTA concentrations (0, 0.5, 1, 2, 3, 5 mM). We have found that adding a small amount of Ho-DOTA in the sample preparation not only enhances the 13C polarization but also decreases the buildup time. The optimum Ho-DOTA concentration was 2 mM. In addition, the microwave sweep spectrum changes character in a manner that suggests both the cross effect and thermal mixing are active mechanisms for trityl radical at 5 T and 1.2 K.
Collapse
Affiliation(s)
- Ali A. Sirusi
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, USA
| | - Eul Hyun Suh
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA
| | - Zoltan Kovacs
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA
| | - Matthew E. Merritt
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, USA
| |
Collapse
|