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Zhang L, Martins AF, Zhao P, Wu Y, Tircsó G, Sherry AD. Lanthanide-Based T2ex
and CEST Complexes Provide Insights into the Design of pH Sensitive MRI Agents. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201707959] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Zhang L, Evbuomwan OM, Tieu M, Zhao P, Martins AF, Sherry AD. Protonation of carboxyl groups in EuDOTA-tetraamide complexes results in catalytic prototropic exchange and quenching of the CEST signal. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2017; 375:20170113. [PMID: 29038382 PMCID: PMC5647270 DOI: 10.1098/rsta.2017.0113] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/23/2017] [Indexed: 05/29/2023]
Abstract
The CEST properties of EuDOTA-tetraamide complexes bearing pendant carboxylate and carboxyl ethyl esters were measured as a function of pH. The CEST signal from the Eu3+-bound water molecule decreased in intensity between pH 8.5 and 4.5 while the proton exchange rates (kex) increased over this same pH range. In comparison, the CEST signal in the corresponding carboxyl ester derivatives was nearly constant. Both observations are consistent with stepwise protonation of the four carboxylic acid groups over this same pH range. This indicates that negative charges on the carboxyl groups above pH 6 facilitate the formation of a strong hydrogen-bonding network in the coordination second sphere above the single Eu3+-bound water molecule, thereby decreasing prototropic exchange of protons on the bound water molecule with bulk water protons. The percentage of square antiprismatic versus twisted square antiprism coordination isomers also decreased as the appended carboxylic acid groups were positioned further away from the amide. The net effect of lowering the pH was an overall increase in kex and a quenching of the CEST signal.This article is part of the themed issue 'Challenges for chemistry in molecular imaging'.
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Burnett ME, Adebesin B, Funk AM, Kovacs Z, Sherry AD, Ekanger LA, Allen MJ, Green KN, Ratnakar SJ. Electrochemical investigation of the Eu 3+/2+ redox couple in complexes with variable numbers of glycinamide and acetate pendant arms. Eur J Inorg Chem 2017; 2017:5001-5005. [PMID: 29403330 DOI: 10.1002/ejic.201701070] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The Eu3+/2+ redox couple provides a convenient design platform for responsive pO2 sensors for magnetic resonance imaging (MRI). Specifically the Eu2+ ion provides T1w contrast enhancement under hypoxic conditions in tissues, whereas, under normoxia, the Eu3+ ion can produce contrast from chemical exchange saturation transfer in MRI. The oxidative stability of the Eu3+/2+ redox couple for a series of tetraaza macrocyclic complexes was investigated in this work using cyclic voltammetry. A series of Eu-containing cyclen-based macrocyclic complexes revealed positive shifts in the Eu3+/2+ redox potentials with each replacement of a carboxylate coordinating arm of the ligand scaffold with glycinamide pendant arms. The data obtained reveal that the complex containing four glycinamide coordinating pendant arms has the highest oxidative stability of the series investigated.
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Funk AM, Anderson BL, Wen X, Hever T, Khemtong C, Kovacs Z, Sherry AD, Malloy CR. The rate of lactate production from glucose in hearts is not altered by per-deuteration of glucose. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 284:86-93. [PMID: 28972888 PMCID: PMC5817885 DOI: 10.1016/j.jmr.2017.09.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 09/13/2017] [Accepted: 09/14/2017] [Indexed: 05/05/2023]
Abstract
This study was designed to determine whether perdeuterated glucose experiences a kinetic isotope effect (KIE) as glucose passes through glycolysis and is further oxidized in the tricarboxylic acid (TCA) cycle. Metabolism of deuterated glucose was investigated in two groups of perfused rat hearts. The control group was supplied with a 1:1 mixture of [U-13C6]glucose and [1,6-13C2]glucose, while the experimental group received [U-13C6,U-2H7]glucose and [1,6-13C2]glucose. Tissue extracts were analyzed by 1H, 2H and proton-decoupled 13C NMR spectroscopy. Extensive 2H-13C scalar coupling plus chemical shift isotope effects were observed in the proton-decoupled 13C NMR spectra of lactate, alanine and glutamate. A small but measureable (∼8%) difference in the rate of conversion of [U-13C6]glucose vs. [1,6-13C2]glucose to lactate, likely reflecting rates of CC bond breakage in the aldolase reaction, but conversion of [U-13C6]glucose versus [U-13C6,U-2H7]glucose to lactate did not differ. This shows that the presence of deuterium in glucose does not alter glycolytic flux. However, there were two distinct effects of deuteration on metabolism of glucose to alanine and oxidation of glucose in the TCA. First, alanine undergoes extensive exchange of methyl deuterons with solvent protons in the alanine amino transferase reaction. Second, there is a substantial kinetic isotope effect in metabolism of [U-13C6,U-2H7]glucose to alanine and glutamate. In the presence of [U-13C6,U-2H7]glucose, alanine and lactate are not in rapid exchange with the same pool of pyruvate. These studies indicate that the appearance of hyperpolarized 13C-lactate from hyperpolarized [U-13C6,U-2H7]glucose is not substantially influenced by a deuterium kinetic isotope effect.
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Abstract
Zinc has long been the focus of many biological investigations because of its essential role in biology including a catalytic role in many enzymes, a structural role in the many zinc finger proteins, and a physiological role in many secretory cell processes. Divalent zinc is known to be highly abundant in healthy prostate tissues and lower in prostate cancer (PCa). Given the need for newer diagnostic methods for detection of prostate cancer, zinc-responsive probes of various types have been considered as imaging tools for detecting tissue levels of zinc. Among them, recent zinc-responsive MRI probes show great promise for non-invasive detection of zinc ion secretion from the prostate and other tissues in vivo. In this review, we summarize the need for new diagnostic tools and demonstrate how responsive zinc probes and MRI could satisfy this unmet need.
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Singh J, Rustagi V, Zhang S, Sherry AD, Udugamasooriya DG. On-bead combinatorial synthesis and imaging of europium(III)-based paraCEST agents aids in identification of chemical features that enhance CEST sensitivity. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2017; 55:747-753. [PMID: 28220538 PMCID: PMC5501467 DOI: 10.1002/mrc.4588] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 02/15/2017] [Accepted: 02/16/2017] [Indexed: 05/08/2023]
Abstract
The rate of water exchange between the inner sphere of a paramagnetic ion and bulk water is an important parameter in determining the magnitude of the chemical exchange saturation transfer signal from paramagnetic CEST agents (paraCEST). This is governed by various geometric, steric and ligand field factors created by macrocyclic ligands surrounding the paramagnetic metal ion. Our previous on-bead combinatorial studies of di-peptoid-europium(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-tetraamide complexes revealed that negatively charged groups in the immediate vicinity of the metal center strongly enhances the CEST signal. Here, we report a solid phase synthesis and on-bead imaging of 76 new DOTA derivatives that are developed by coupling with a single residue onto each of the three arms of a DOTA-tetraamide scaffold attached to resin beads. This single residue predominantly carries negatively charged groups blended with various physico-chemical characteristics. We found that non-bulky negatively charged groups are best suited at the immediate vicinity of the metal ion, while positive, bulky and halogen containing moieties suppress the CEST signal. Copyright © 2017 John Wiley & Sons, Ltd.
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Farashishiko A, Plush SE, Maier KB, Dean Sherry A, Woods M. Crosslinked shells for nano-assembled capsules: a new encapsulation method for smaller Gd 3+-loaded capsules with exceedingly high relaxivities. Chem Commun (Camb) 2017; 53:6355-6358. [PMID: 28555682 PMCID: PMC5580261 DOI: 10.1039/c7cc00123a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Nano-assembled capsules can incorporate large payloads of high relaxivity Gd3+, permitting the development of highly detectable molecular imaging agents for MRI. A new encapsulating shell, based upon cross-linked peptides, is found to afford smaller capsules (127 nm average diameter) with exceptionally high per-Gd3+ relaxivities (70.7 s-1 mmolal-1).
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Moreno KX, Harrison CE, Merritt ME, Kovacs Z, Malloy CR, Sherry AD. Hyperpolarized δ-[1- 13 C]gluconolactone as a probe of the pentose phosphate pathway. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3713. [PMID: 28272754 PMCID: PMC5502806 DOI: 10.1002/nbm.3713] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 12/22/2016] [Accepted: 01/23/2017] [Indexed: 05/05/2023]
Abstract
The pentose phosphate pathway (PPP) is thought to be upregulated in trauma (to produce excess NADPH) and in cancer (to provide ribose for nucleotide biosynthesis), but simple methods for detecting changes in flux through this pathway are not available. MRI of hyperpolarized 13 C-enriched metabolites offers considerable potential as a rapid, non-invasive tool for detecting changes in metabolic fluxes. In this study, hyperpolarized δ-[1-13 C]gluconolactone was used as a probe to detect flux through the oxidative portion of the pentose phosphate pathway (PPPox ) in isolated perfused mouse livers. The appearance of hyperpolarized (HP) H13 CO3- within seconds after exposure of livers to HP-δ-[1-13 C]gluconolactone demonstrates that this probe rapidly enters hepatocytes, becomes phosphorylated, and enters the PPPox pathway to produce HP-H13 CO3- after three enzyme catalyzed steps (6P-gluconolactonase, 6-phosphogluconate dehydrogenase, and carbonic anhydrase). Livers perfused with octanoate as their sole energy source show no change in production of H13 CO3- after exposure to low levels of H2 O2 , while livers perfused with glucose and insulin showed a twofold increase in H13 CO3- after exposure to peroxide. This indicates that flux through the PPPox is stimulated by H2 O2 in glucose perfused livers but not in livers perfused with octanoate alone. Subsequent perfusion of livers with non-polarized [1,2-13 C]glucose followed by 1 H NMR analysis of lactate in the perfusate verified that flux through the PPPox is indeed low in healthy livers and modestly higher in peroxide damaged livers. We conclude that hyperpolarized δ-[1-13 C]gluconolactone has the potential to serve as a metabolic imaging probe of this important biological pathway.
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Cheshkov S, Dimitrov IE, Jakkamsetti V, Good L, Kelly D, Rajasekaran K, DeBerardinis RJ, Pascual JM, Sherry AD, Malloy CR. Oxidation of [U- 13 C]glucose in the human brain at 7T under steady state conditions. Magn Reson Med 2017; 78:2065-2071. [PMID: 28112825 DOI: 10.1002/mrm.26603] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 11/23/2016] [Accepted: 12/16/2016] [Indexed: 12/24/2022]
Abstract
PURPOSE Disorders of brain energy metabolism and neurotransmitter recycling have been implicated in multiple neurological conditions. 13 C magnetic resonance spectroscopy (13 C MRS) during intravenous administration of 13 C-labeled compounds has been used to measure turnover rates of brain metabolites. This approach, however, requires prolonged infusion inside the magnet. Proton decoupling is typically required but may be difficult to implement with standard equipment. We examined an alternative approach to monitor glucose metabolism in the human brain. METHODS 13 C-enriched glucose was infused in healthy subjects outside the magnet to a steady-state level of 13 C enrichment. Subsequently, the subjects were scanned at 7T for 60 min without 1 H decoupling. Metabolic modeling was used to calculate anaplerosis. RESULTS Biomarkers of energy metabolism and anaplerosis were detected. The glutamate C5 doublet provided information about glucose-derived acetyl-coenzyme A flux into the tricarboxylic acid (TCA) cycle via pyruvate dehydrogenase, and the bicarbonate signal reflected overall TCA cycle activity. The glutamate C1/C5 ratio is sensitive to anaplerosis. CONCLUSION Brain 13 C MRS at 7T provides information about glucose oxidation and anaplerosis without the need of prolonged 13 C infusions inside the scanner and without technical challenges of 1 H decoupling, making it a feasible approach for clinical research. Magn Reson Med 78:2065-2071, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
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Zhang L, Martins AF, Mai Y, Zhao P, Funk AM, Clavijo Jordan MV, Zhang S, Chen W, Wu Y, Sherry AD. Imaging Extracellular Lactate In Vitro and In Vivo Using CEST MRI and a Paramagnetic Shift Reagent. Chemistry 2017; 23:1752-1756. [PMID: 27987233 DOI: 10.1002/chem.201604558] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 12/07/2016] [Indexed: 12/22/2022]
Abstract
Overproduction of lactate is a hallmark of cancer, yet a method to quantitatively measure lactate production by cancer cells is not straight-forward. Chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) can potentially be used to image lactate but the small difference in chemical shift of the lactate -OH proton and water proton resonances make it challenging. Like other spectroscopic methods, CEST MRI cannot discriminate intracellular lactate from extracellular lactate. Herein, we demonstrate a relatively simple way to shift the lactate -OH proton resonance far away from water by addition of the paramagnetic shift reagent, EuDO3A, while retaining the CEST properties of lactate itself. The potential of the method was demonstrated by imaging extracellular lactate excreted from lung cancer cells in tissue culture without interference from other components in the culture media and by imaging excess lactate excreted into the bladder of a mouse.
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Niedbalski P, Parish C, Kiswandhi A, Fidelino L, Khemtong C, Hayati Z, Song L, Martins A, Sherry AD, Lumata L. Influence of Dy 3+ and Tb 3+ doping on 13C dynamic nuclear polarization. J Chem Phys 2017; 146:014303. [PMID: 28063445 PMCID: PMC5218971 DOI: 10.1063/1.4973317] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 12/14/2016] [Indexed: 12/28/2022] Open
Abstract
Dynamic nuclear polarization (DNP) is a technique that uses a microwave-driven transfer of high spin alignment from electrons to nuclear spins. This is most effective at low temperature and high magnetic field, and with the invention of the dissolution method, the amplified nuclear magnetic resonance (NMR) signals in the frozen state in DNP can be harnessed in the liquid-state at physiologically acceptable temperature for in vitro and in vivo metabolic studies. A current optimization practice in dissolution DNP is to dope the sample with trace amounts of lanthanides such as Gd3+ or Ho3+, which further improves the polarization. While Gd3+ and Ho3+ have been optimized for use in dissolution DNP, other lanthanides have not been exhaustively studied for use in C13 DNP applications. In this work, two additional lanthanides with relatively high magnetic moments, Dy3+ and Tb3+, were extensively optimized and tested as doping additives for C13 DNP at 3.35 T and 1.2 K. We have found that both of these lanthanides are also beneficial additives, to a varying degree, for C13 DNP. The optimal concentrations of Dy3+ (1.5 mM) and Tb3+ (0.25 mM) for C13 DNP were found to be less than that of Gd3+ (2 mM). W-band electron paramagnetic resonance shows that these enhancements due to Dy3+ and Tb3+ doping are accompanied by shortening of electron T1 of trityl OX063 free radical. Furthermore, when dissolution was employed, Tb3+-doped samples were found to have similar liquid-state C13 NMR signal enhancements compared to samples doped with Gd3+, and both Tb3+ and Dy3+ had a negligible liquid-state nuclear T1 shortening effect which contrasts with the significant reduction in T1 when using Gd3+. Our results show that Dy3+ doping and Tb3+ doping have a beneficial impact on C13 DNP both in the solid and liquid states, and that Tb3+ in particular could be used as a potential alternative to Gd3+ in C13 dissolution DNP experiments.
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Ren J, Sherry AD, Malloy CR. Efficient 31 P band inversion transfer approach for measuring creatine kinase activity, ATP synthesis, and molecular dynamics in the human brain at 7 T. Magn Reson Med 2016; 78:1657-1666. [PMID: 27868234 DOI: 10.1002/mrm.26560] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Revised: 10/16/2016] [Accepted: 11/03/2016] [Indexed: 01/28/2023]
Abstract
PURPOSE To develop an efficient 31 P magnetic resonance spectroscopy (MRS) method for measuring creatine kinase (CK) activity, adenosine triphosphate (ATP) synthesis, and motion dynamics in the human brain at 7 Tesla (T). METHODS Three band inversion modules differing in center frequency were used to induce magnetization transfer (MT) effect in three exchange pathways: (i) CK-mediated reaction PCr → γ-ATP; (ii) de novo ATP synthesis Pi → γ-ATP; and (iii) ATP intramolecular 31 P-31 P cross-relaxation γ-(α-) ↔ β-ATP. The resultant MT data were analyzed using a 5-pool model in the format of magnetization matrix according to Bloch-McConnell-Solomon formalism. RESULTS With a repetition time (TR) of 4 s, the scan time for each module was approximately 8 min. The rate constants were kPCr → γATP 0.38 ± 0.02 s-1 , kPi → γATP 0.19 ± 0.02 s-1 , and σγ(α) ↔ βATP 0.19 ± 0.04 s-1 , corresponding to ATP rotation correlation time τc (0.8 ± 0.2) ·10-7 s. The T1 relaxation times were Pi 7.26 ± 1.76 s, PCr 5.99 ± 0.58 s, γ-ATP 0.98 ± 0.07 s, α-ATP 0.95 ± 0.04 s, and β-ATP 0.68 ± 0.03 s. CONCLUSION Short-TR band inversion modules provide a time-efficient way of measuring brain ATP metabolism and could be useful in studying metabolic disorders in brain diseases. Magn Reson Med 78:1657-1666, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Xing Y, Jindal AK, Regueiro-Figueroa M, Le Fur M, Kervarec N, Zhao P, Kovacs Z, Valencia L, Pérez-Lourido P, Tripier R, Esteban-Gómez D, Platas-Iglesias C, Sherry AD. The Relationship between NMR Chemical Shifts of Thermally Polarized and Hyperpolarized 89 Y Complexes and Their Solution Structures. Chemistry 2016; 22:16657-16667. [PMID: 27723138 DOI: 10.1002/chem.201602901] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Indexed: 01/13/2023]
Abstract
Recently developed dynamic nuclear polarization (DNP) technology offers the potential of increasing the NMR sensitivity of even rare nuclei for biological imaging applications. Hyperpolarized 89 Y is an ideal candidate because of its narrow NMR linewidth, favorable spin quantum number (I=1/2 ), and long longitudinal relaxation times (T1 ). Strong NMR signals were detected in hyperpolarized 89 Y samples of a variety of yttrium complexes. A dataset of 89 Y NMR data composed of 23 complexes with polyaminocarboxylate ligands was obtained using hyperpolarized 89 Y measurements or 1 H,89 Y-HMQC spectroscopy. These data were used to derive an empirical equation that describes the correlation between the 89 Y chemical shift and the chemical structure of the complexes. This empirical correlation serves as a guide for the design of 89 Y sensors. Relativistic (DKH2) DFT calculations were found to predict the experimental 89 Y chemical shifts to a rather good accuracy.
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Kumas C, Fernando WS, Zhao P, Regueiro-Figueroa M, Kiefer GE, Martins AF, Platas-Iglesias C, Sherry AD. Unexpected Changes in the Population of Coordination Isomers for the Lanthanide Ion Complexes of DOTMA-Tetraglycinate. Inorg Chem 2016; 55:9297-305. [PMID: 27603690 DOI: 10.1021/acs.inorgchem.6b01390] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Lanthanide complexes with DOTA-tetraglycinate (DOTA-(gly)4) heavily favor the square antiprismatic (SAP) coordination isomer in aqueous solution, a structural feature that has made them useful as water-based paraCEST agents. In an effort to create amide-based paraCEST agents with rapid water exchange rates, we prepared the analogous tetraglycinate complexes with DOTMA, a ligand known to favor the twisted square antiprismatic (TSAP) coordination structures. Unexpectedly, NMR investigations show that the LnDOTMA-(gly)4 complexes, like the LnDOTA-(gly)4 complexes, also favor the SAP isomers in solution. This observation led to density functional theory (DFT) calculations in order to identify the energy terms that favor the SAP structures in lanthanide complexes formed with macrocyclic DOTA- and DOTMA-tetraamide ligands. The DFT calculations revealed that, regardless the nature of the ligand, the TSAP isomers present more negative hydration energies than the SAP counterparts. The extent to which the TSAP isomer is stabilized varies, however, depending on the ligand structure, resulting in different isomeric populations in solution.
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Ren J, Sherry AD, Malloy CR. A simple approach to evaluate the kinetic rate constant for ATP synthesis in resting human skeletal muscle at 7 T. NMR IN BIOMEDICINE 2016; 29:1240-8. [PMID: 25943328 PMCID: PMC4673044 DOI: 10.1002/nbm.3310] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 03/25/2015] [Accepted: 03/27/2015] [Indexed: 05/11/2023]
Abstract
Inversion transfer (IT) is a well-established technique with multiple attractive features for analysis of kinetics. However, its application in measurement of ATP synthesis rate in vivo has lagged behind the more common saturation transfer (ST) techniques. One well-recognized issue with IT is the complexity of data analysis in comparison with much simpler analysis by ST. This complexity arises, in part, because the γ-ATP spin is involved in multiple chemical reactions and magnetization exchanges, whereas Pi is involved in a single reaction, Pi → γ-ATP. By considering the reactions involving γ-ATP only as a lumped constant, the rate constant for the reaction of physiological interest, kPi→γATP , can be determined. Here, we present a new IT data analysis method to evaluate kPi→γATP using data collected from resting human skeletal muscle at 7 T. The method is based on the basic Bloch-McConnell equation, which relates kPi→γATP to m˙Pi, the rate of Pi magnetization change. The kPi→γATP value is accessed from m˙Pi data by more familiar linear correlation approaches. For a group of human subjects (n = 15), the kPi→γATP value derived for resting calf muscle was 0.066 ± 0.017 s(-1) , in agreement with literature-reported values. In this study we also explored possible time-saving strategies to speed up data acquisition for kPi→γATP evaluation using simulations. The analysis indicates that it is feasible to carry out a (31) P IT experiment in about 10 min or less at 7 T with reasonable outcome in kPi→γATP variance for measurement of ATP synthesis in resting human skeletal muscle. We believe that this new IT data analysis approach will facilitate the wide acceptance of IT to evaluate ATP synthesis rate in vivo. Copyright © 2015 John Wiley & Sons, Ltd.
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Kiswandhi A, Niedbalski P, Parish C, Kaur P, Martins A, Fidelino L, Khemtong C, Song L, Sherry AD, Lumata L. Impact of Ho(3+)-doping on (13)C dynamic nuclear polarization using trityl OX063 free radical. Phys Chem Chem Phys 2016; 18:21351-9. [PMID: 27424954 PMCID: PMC5199769 DOI: 10.1039/c6cp03954e] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We have investigated the effects of Ho-DOTA doping on the dynamic nuclear polarization (DNP) of [1-(13)C] sodium acetate using trityl OX063 free radical at 3.35 T and 1.2 K. Our results indicate that addition of 2 mM Ho-DOTA on 3 M [1-(13)C] sodium acetate sample in 1 : 1 v/v glycerol : water with 15 mM trityl OX063 improves the DNP-enhanced (13)C solid-state nuclear polarization by a factor of around 2.7-fold. Similar to the Gd(3+) doping effect on (13)C DNP, the locations of the positive and negative (13)C maximum polarization peaks in the (13)C microwave DNP sweep are shifted towards each other with the addition of Ho-DOTA on the DNP sample. W-band electron spin resonance (ESR) studies have revealed that while the shape and linewidth of the trityl OX063 ESR spectrum was not affected by Ho(3+)-doping, the electron spin-lattice relaxation time T1 of trityl OX063 was prominently reduced at cryogenic temperatures. The reduction of trityl OX063 electron T1 by Ho-doping is linked to the (13)C DNP improvement in light of the thermodynamic picture of DNP. Moreover, the presence of Ho-DOTA in the dissolution liquid at room temperature has negligible reduction effect on liquid-state (13)C T1, in contrast to Gd(3+)-doping which drastically reduces the (13)C T1. The results here suggest that Ho(3+)-doping is advantageous over Gd(3+) in terms of preservation of hyperpolarized state-an important aspect to consider for in vitro and in vivo NMR or imaging (MRI) experiments where a considerable preparation time is needed to administer the hyperpolarized (13)C liquid.
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Jin ES, Sherry AD, Malloy CR. An Oral Load of [13C3]Glycerol and Blood NMR Analysis Detect Fatty Acid Esterification, Pentose Phosphate Pathway, and Glycerol Metabolism through the Tricarboxylic Acid Cycle in Human Liver. J Biol Chem 2016; 291:19031-41. [PMID: 27432878 DOI: 10.1074/jbc.m116.742262] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Indexed: 11/06/2022] Open
Abstract
Drugs and other interventions for high impact hepatic diseases often target biochemical pathways such as gluconeogenesis, lipogenesis, or the metabolic response to oxidative stress. However, traditional liver function tests do not provide quantitative data about these pathways. In this study, we developed a simple method to evaluate these processes by NMR analysis of plasma metabolites. Healthy subjects ingested [U-(13)C3]glycerol, and blood was drawn at multiple times. Each subject completed three visits under differing nutritional states. High resolution (13)C NMR spectra of plasma triacylglycerols and glucose provided new insights into a number of hepatic processes including fatty acid esterification, the pentose phosphate pathway, and gluconeogenesis through the tricarboxylic acid cycle. Fasting stimulated pentose phosphate pathway activity and metabolism of [U-(13)C3]glycerol in the tricarboxylic acid cycle prior to gluconeogenesis or glyceroneogenesis. Fatty acid esterification was transient in the fasted state but continuous under fed conditions. We conclude that a simple NMR analysis of blood metabolites provides an important biomarker of pentose phosphate pathway activity, triacylglycerol synthesis, and flux through anaplerotic pathways in mitochondria of human liver.
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Wang JX, Merritt ME, Sherry AD, Malloy CR. Accelerated chemical shift imaging of hyperpolarized (13) C metabolites. Magn Reson Med 2016; 76:1033-8. [PMID: 27373705 DOI: 10.1002/mrm.26286] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 04/28/2016] [Accepted: 05/03/2016] [Indexed: 01/13/2023]
Abstract
PURPOSE Chemical shift imaging (CSI) has long been considered the gold standard method for in vivo hyperpolarized (13) C metabolite imaging because of its high sensitivity. However, CSI requires a large number of excitations so it is desirable to reduce the number of RF excitations and the total acquisition time. METHODS Centric phase encoding and three-dimensional compressed sensing methods were adopted into a CSI acquisition to improve efficiency and reduce the number of excitations required for imaging hyperpolarized metabolites. The new method was implemented on a GE MR750W scanner for routine real time metabolic imaging experiments. RESULTS Imaging results from phantoms and in vivo animals using hyperpolarized (13) C tracers demonstrate that when the entire CSI dataset is treated as a single object, compressed sensing can be satisfactorily applied to spectroscopic CSI. Centric k-space trajectory data collection also greatly improves the acquisition efficiency. This combination of compressed sensing CSI and acquisition time reduction was used to perform a hyperpolarized (13) C dynamic study. CONCLUSION Compressed sensing can be satisfactorily applied to conventional CSI in hyperpolarized (13) C metabolite MR imaging to reduce the number of RF excitations and accelerate the imaging speed to take advantage of conventional CSI in providing high sensitivity and a large spectral bandwidth. Magn Reson Med 76:1033-1038, 2016. © 2016 Wiley Periodicals, Inc.
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Budinger TF, Bird MD, Frydman L, Long JR, Mareci TH, Rooney WD, Rosen B, Schenck JF, Schepkin VD, Sherry AD, Sodickson DK, Springer CS, Thulborn KR, Uğurbil K, Wald LL. Toward 20 T magnetic resonance for human brain studies: opportunities for discovery and neuroscience rationale. MAGMA (NEW YORK, N.Y.) 2016; 29:617-39. [PMID: 27194154 PMCID: PMC5538368 DOI: 10.1007/s10334-016-0561-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 04/06/2016] [Accepted: 04/11/2016] [Indexed: 12/16/2022]
Abstract
An initiative to design and build magnetic resonance imaging (MRI) and spectroscopy (MRS) instruments at 14 T and beyond to 20 T has been underway since 2012. This initiative has been supported by 22 interested participants from the USA and Europe, of which 15 are authors of this review. Advances in high temperature superconductor materials, advances in cryocooling engineering, prospects for non-persistent mode stable magnets, and experiences gained from large-bore, high-field magnet engineering for the nuclear fusion endeavors support the feasibility of a human brain MRI and MRS system with 1 ppm homogeneity over at least a 16-cm diameter volume and a bore size of 68 cm. Twelve neuroscience opportunities are presented as well as an analysis of the biophysical and physiological effects to be investigated before exposing human subjects to the high fields of 14 T and beyond.
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Ren J, Sherry AD, Malloy CR. Band inversion amplifies 31 P- 31 P nuclear overhauser effects: Relaxation mechanism and dynamic behavior of ATP in the human brain by 31 P MRS at 7 T. Magn Reson Med 2016; 77:1409-1418. [PMID: 27060982 DOI: 10.1002/mrm.26236] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 02/22/2016] [Accepted: 03/14/2016] [Indexed: 01/07/2023]
Abstract
PURPOSE To develop an improved method to measure the 31 P nuclear Overhauser effect (NOE) for evaluation of adenosine triphosphate (ATP) dynamics in terms of correlation time (τc ), and contribution of dipole-dipole (DD) and chemical shift anisotropy (CSA) mechanisms to T1 relaxation of ATP in human brain. METHODS The NOE of ATP in human brain was evaluated by monitoring changes in magnetization in the β-ATP signal following a band inversion of all downfield 31 P resonances. The magnetization changes observed were analyzed using the Bloch-McConnell-Solomon formulation to evaluate the relaxation and motion dynamic parameters that describe interactions of ATP with cellular solids in human brain tissue. RESULTS The maximal transient NOE, observed as a reduction in the β-ATP signal, was 24 ± 2% upon band inversion of γ- and α-ATP, which is 2-3-fold higher than achievable by frequency-selective inversion of either γ- or α-ATP. The rate of 31 P-31 P cross relaxation (0.21 ± 0.02 s-1 ) led to a τc value of (9.1 ± 0.8) × 10-8 s for ATP in human brain. The T1 relaxation of β-ATP is dominated by CSA over the DD mechanism (60%: 40%). CONCLUSIONS The band inversion method proved effective in amplifying 31 P NOE, and thus facilitating ATP τc and relaxation measurements. This technique renders ATP a potentially useful reporter molecule for cellular environments. Magn Reson Med 77:1409-1418, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Jin ES, Moreno KX, Wang JX, Fidelino L, Merritt ME, Sherry AD, Malloy CR. Metabolism of hyperpolarized [1-(13)C]pyruvate through alternate pathways in rat liver. NMR IN BIOMEDICINE 2016; 29:466-74. [PMID: 26836042 PMCID: PMC4805436 DOI: 10.1002/nbm.3479] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 11/18/2015] [Accepted: 12/04/2015] [Indexed: 05/07/2023]
Abstract
The source of hyperpolarized (HP) [(13)C]bicarbonate in the liver during metabolism of HP [1-(13)C]pyruvate is uncertain and likely changes with physiology. Multiple processes including decarboxylation through pyruvate dehydrogenase or pyruvate carboxylase followed by subsequent decarboxylation via phosphoenolpyruvate carboxykinase (gluconeogenesis) could play a role. Here we tested which metabolic fate of pyruvate contributed to the appearance of HP [(13)C]bicarbonate during metabolism of HP [1-(13)C]pyruvate by the liver in rats after 21 h of fasting compared to rats with free access to food. The (13)C NMR of HP [(13)C]bicarbonate was observed in the liver of fed rats, but not in fasted rats where pyruvate carboxylation and gluconeogenesis was active. To further explore the relative fluxes through pyruvate carboxylase versus pyruvate dehydrogenase in the liver under typical conditions of hyperpolarization studies, separate parallel experiments were performed with rats given non-hyperpolarized [2,3-(13)C]pyruvate. (13)C NMR analysis of glutamate isolated from the liver of rats revealed that flux from injected pyruvate through pyruvate dehydrogenase was dominant under fed conditions whereas flux through pyruvate carboxylase dominated under fasted conditions. The NMR signal of HP [(13)C]bicarbonate does not parallel pyruvate carboxylase activity followed by subsequent decarboxylation reaction leading to glucose production. In the liver of healthy well-fed rats, the appearance of HP [(13)C]bicarbonate exclusively reflects decarboxylation of HP [1-(13)C]pyruvate via pyruvate dehydrogenase.
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Satapati S, Kucejova B, Duarte JAG, Fletcher JA, Reynolds L, Sunny NE, He T, Nair LA, Livingston KA, Fu X, Merritt ME, Sherry AD, Malloy CR, Shelton JM, Lambert J, Parks EJ, Corbin I, Magnuson MA, Browning JD, Burgess SC. Mitochondrial metabolism mediates oxidative stress and inflammation in fatty liver. J Clin Invest 2016; 126:1605. [PMID: 27035816 PMCID: PMC4811133 DOI: 10.1172/jci86695] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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Funk AM, Clavijo Jordan V, Sherry AD, Ratnakar SJ, Kovacs Z. Oxidative Conversion of a Europium(II)-Based T1 Agent into a Europium(III)-Based paraCEST Agent that can be Detected In Vivo by Magnetic Resonance Imaging. Angew Chem Int Ed Engl 2016; 55:5024-7. [PMID: 26954661 DOI: 10.1002/anie.201511649] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 01/22/2016] [Indexed: 11/06/2022]
Abstract
The Eu(II) complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) tetra(glycinate) has a higher reduction potential than most Eu(II) chelates reported to date. The reduced Eu(II) form acts as an efficient water proton T1 relaxation reagent, while the Eu(III) form acts as a water-based chemical exchange saturation transfer (CEST) agent. The complex has extremely fast water exchange rate. Oxidation to the corresponding Eu(III) complex yields a well-defined signal from the paraCEST agent. The time course of oxidation was studied in vitro and in vivo by T1-weighted and CEST imaging.
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Funk AM, Clavijo Jordan V, Sherry AD, Ratnakar SJ, Kovacs Z. Oxidative Conversion of a Europium(II)-BasedT1Agent into a Europium(III)-Based paraCEST Agent that can be Detected In Vivo by Magnetic Resonance Imaging. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201511649] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Fernando WS, Martins AF, Zhao P, Wu Y, Kiefer GE, Platas-Iglesias C, Sherry AD. Breaking the Barrier to Slow Water Exchange Rates for Optimal Magnetic Resonance Detection of paraCEST Agents. Inorg Chem 2016; 55:3007-14. [DOI: 10.1021/acs.inorgchem.5b02850] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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