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Nucera A, Platas-Iglesias C, Carniato F, Botta M. Effect of hydration equilibria on the relaxometric properties of Gd(III) complexes: new insights into old systems. Dalton Trans 2023; 52:17229-17241. [PMID: 37955945 DOI: 10.1039/d3dt03413e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2023]
Abstract
We present a detailed relaxometric and computational investigation of three Gd(III) complexes that exist in solution as an equilibrium of two species with a different number of coordinated water molecules: [Gd(H2O)q]3+ (q = 8, 9), [Gd(EDTA)(H2O)q]- and [Gd(CDTA)(H2O)q]- (q = 2, 3). 1H nuclear magnetic relaxation dispersion (NMRD) data were recorded from aqueous solutions of these complexes using a wide Larmor frequency range (0.01-500 MHz). These data were complemented with 17O transverse relaxation rates and chemical shifts recorded at different temperatures. The simultaneous fit of the NMRD and 17O NMR data was guided by computational studies performed at the DFT and CASSCF/NEVPT2 levels, which provided information on Gd⋯H distances, 17O hyperfine coupling constants and the zero-field splitting (ZFS) energy, which affects electronic relaxation. The hydration equilibrium did not have a very important effect in the fits of the experimental data for [Gd(H2O)q]3+ and [Gd(CDTA)(H2O)q]-, as the hydration equilibrium is largely shifted to the species with the lowest hydration number (q = 8 and 2, respectively). The quality of the analysis improves however considerably for [Gd(EDTA)(H2O)q]- upon considering the effect of the hydration equilibrium. As a result, this study provides for the first time an analysis of the relaxation properties of this important model system, as well as accurate parameters for [Gd(H2O)q]3+ and [Gd(CDTA)(H2O)q]-.
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Affiliation(s)
- Alessandro Nucera
- Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale, Viale T. Michel 11, 15121 Alessandria, Italy.
| | - Carlos Platas-Iglesias
- Universidade da Coruña, Centro de Interdisciplinar de Química e Bioloxía (CICA) and Departamento de Química, Facultade de Ciencias, 15071, A Coruña, Galicia, Spain.
| | - Fabio Carniato
- Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale, Viale T. Michel 11, 15121 Alessandria, Italy.
| | - Mauro Botta
- Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale, Viale T. Michel 11, 15121 Alessandria, Italy.
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2
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Oukhatar F, Eliseeva SV, Bonnet CS, Placidi M, Logothetis NK, Petoud S, Angelovski G, Tóth É. Toward MRI and Optical Detection of Zwitterionic Neurotransmitters: Near-Infrared Luminescent and Magnetic Properties of Macrocyclic Lanthanide(III) Complexes Appended with a Crown Ether and a Benzophenone Chromophore. Inorg Chem 2019; 58:13619-13630. [DOI: 10.1021/acs.inorgchem.9b00887] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Fatima Oukhatar
- Centre de Biophysique Moléculaire, UPR 4301, CNRS, Université d’Orléans, rue Charles Sadron, 45071 Orléans, Cedex 2, France
- Department of Physiology of Cognitive Processes and MR Neuroimaging Agents, Max Planck Institute for Biological Cybernetics, Max-Planck-Ring 8, 72076 Tubingen, Germany
| | - Svetlana V. Eliseeva
- Centre de Biophysique Moléculaire, UPR 4301, CNRS, Université d’Orléans, rue Charles Sadron, 45071 Orléans, Cedex 2, France
| | - Célia S. Bonnet
- Centre de Biophysique Moléculaire, UPR 4301, CNRS, Université d’Orléans, rue Charles Sadron, 45071 Orléans, Cedex 2, France
| | - Matteo Placidi
- Department of Physiology of Cognitive Processes and MR Neuroimaging Agents, Max Planck Institute for Biological Cybernetics, Max-Planck-Ring 8, 72076 Tubingen, Germany
| | - Nikos K. Logothetis
- Department of Physiology of Cognitive Processes and MR Neuroimaging Agents, Max Planck Institute for Biological Cybernetics, Max-Planck-Ring 8, 72076 Tubingen, Germany
- Department of Imaging Science and Biomedical Engineering, University of Manchester, Manchester, M13 9PT, U.K
| | - Stéphane Petoud
- Centre de Biophysique Moléculaire, UPR 4301, CNRS, Université d’Orléans, rue Charles Sadron, 45071 Orléans, Cedex 2, France
| | - Goran Angelovski
- Department of Physiology of Cognitive Processes and MR Neuroimaging Agents, Max Planck Institute for Biological Cybernetics, Max-Planck-Ring 8, 72076 Tubingen, Germany
| | - Éva Tóth
- Centre de Biophysique Moléculaire, UPR 4301, CNRS, Université d’Orléans, rue Charles Sadron, 45071 Orléans, Cedex 2, France
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3
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Wahsner J, Gale EM, Rodríguez-Rodríguez A, Caravan P. Chemistry of MRI Contrast Agents: Current Challenges and New Frontiers. Chem Rev 2019; 119:957-1057. [PMID: 30350585 PMCID: PMC6516866 DOI: 10.1021/acs.chemrev.8b00363] [Citation(s) in RCA: 832] [Impact Index Per Article: 166.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Tens of millions of contrast-enhanced magnetic resonance imaging (MRI) exams are performed annually around the world. The contrast agents, which improve diagnostic accuracy, are almost exclusively small, hydrophilic gadolinium(III) based chelates. In recent years concerns have arisen surrounding the long-term safety of these compounds, and this has spurred research into alternatives. There has also been a push to develop new molecularly targeted contrast agents or agents that can sense pathological changes in the local environment. This comprehensive review describes the state of the art of clinically approved contrast agents, their mechanism of action, and factors influencing their safety. From there we describe different mechanisms of generating MR image contrast such as relaxation, chemical exchange saturation transfer, and direct detection and the types of molecules that are effective for these purposes. Next we describe efforts to make safer contrast agents either by increasing relaxivity, increasing resistance to metal ion release, or by moving to gadolinium(III)-free alternatives. Finally we survey approaches to make contrast agents more specific for pathology either by direct biochemical targeting or by the design of responsive or activatable contrast agents.
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Affiliation(s)
- Jessica Wahsner
- Athinoula A. Martinos Center for Biomedical Imaging and the Institute for Innovation in Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Eric M. Gale
- Athinoula A. Martinos Center for Biomedical Imaging and the Institute for Innovation in Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Aurora Rodríguez-Rodríguez
- Athinoula A. Martinos Center for Biomedical Imaging and the Institute for Innovation in Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Peter Caravan
- Athinoula A. Martinos Center for Biomedical Imaging and the Institute for Innovation in Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
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4
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Zhang B, Cheng L, Duan B, Tang W, Yuan Y, Ding Y, Hu A. Gadolinium complexes of diethylenetriamine-N-oxide pentaacetic acid-bisamide: a new class of highly stable MRI contrast agents with a hydration number of 3. Dalton Trans 2019; 48:1693-1699. [DOI: 10.1039/c8dt04478c] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Diethylenetriamine-N-oxide pentaacetic acid-bisamide-based Gd(iii) complexes with 3 coordinated water molecules have been synthesized to achieve high stability and over three times of the relaxivities of commercial MRI contrast agents.
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Affiliation(s)
- BeiBei Zhang
- Shanghai Key Laboratory of Advanced Polymeric Materials
- School of Materials Science and Engineering
- East China University of Science and Technology
- Shanghai
- China
| | - Likun Cheng
- Shanghai Key Laboratory of Advanced Polymeric Materials
- School of Materials Science and Engineering
- East China University of Science and Technology
- Shanghai
- China
| | - Bing Duan
- The State Key Laboratory of Bioreactor Engineering East China University of Science and Technology
- Shanghai
- China
| | - Weijun Tang
- Department of Radiology
- Huashan Hospital Affiliated to Fudan University
- Shanghai
- China
| | - Yuan Yuan
- The State Key Laboratory of Bioreactor Engineering East China University of Science and Technology
- Shanghai
- China
| | - Yun Ding
- Shanghai Key Laboratory of Advanced Polymeric Materials
- School of Materials Science and Engineering
- East China University of Science and Technology
- Shanghai
- China
| | - Aiguo Hu
- Shanghai Key Laboratory of Advanced Polymeric Materials
- School of Materials Science and Engineering
- East China University of Science and Technology
- Shanghai
- China
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5
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Caravan P, Esteban-Gómez D, Rodríguez-Rodríguez A, Platas-Iglesias C. Water exchange in lanthanide complexes for MRI applications. Lessons learned over the last 25 years. Dalton Trans 2019; 48:11161-11180. [DOI: 10.1039/c9dt01948k] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Coordination chemistry offers convenient strategies to modulate the exchange of coordinated water molecules in lanthanide-based contrast agents.
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Affiliation(s)
- Peter Caravan
- The Institute for Innovation in Imaging and the A. A. Martinos Center for Biomedical Imaging
- Massachusetts General Hospital
- Harvard Medical School
- Charlestown
- USA
| | - David Esteban-Gómez
- Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química
- Universidade da Coruña
- 15008 A Coruña
- Spain
| | - Aurora Rodríguez-Rodríguez
- Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química
- Universidade da Coruña
- 15008 A Coruña
- Spain
| | - Carlos Platas-Iglesias
- Centro de Investigacións Científicas Avanzadas (CICA) and Departamento de Química
- Universidade da Coruña
- 15008 A Coruña
- Spain
- The Institute for Innovation in Imaging and the A. A. Martinos Center for Biomedical Imaging
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6
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Rashid HU, Martines MAU, Jorge J, de Moraes PM, Umar MN, Khan K, Rehman HU. Cyclen-based Gd 3+ complexes as MRI contrast agents: Relaxivity enhancement and ligand design. Bioorg Med Chem 2016; 24:5663-5684. [PMID: 27729196 DOI: 10.1016/j.bmc.2016.09.069] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 09/25/2016] [Accepted: 09/28/2016] [Indexed: 12/23/2022]
Abstract
Magnetic Resonance Imaging (MRI) is a noninvasive radiology technique used to examine the internal organs of human body. It is useful for the diagnosis of structural abnormalities in the body. Contrast agents are used to increase the sensitivity of this technique. 1,4,7,10-Tetraazacyclododecane (cyclen) is a macrocyclic tetraamine. Its derivatives act as useful ligands to produce stable complexes with Gd3+ ion. Such chelates are investigated as MRI contrast agents. Free Gd3+ ion is extremely toxic for in vivo use. Upon complexation with a cyclen-based ligand, it is trapped in the preformed central cavity of the ligand resulting in the formation of a highly stable Gd3+-chelate. Better kinetic and thermodynamic stability of cyclen-based MRI contrast agents decrease their potential toxicity for in vivo use. Consequently, such agents have proved to be safest for clinical applications. Relaxivity is the most important parameter used to measure the effectiveness of a contrast agent. A number of factors influence this parameter. This article elucidates detailed strategies to increase relaxivity of cyclen-based MRI contrast agents. 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) are two key ligands derived from cyclen. They also act as building blocks for the synthesis of novel ligands. A few important methodologies for the synthesis of DOTA and DO3A derivatives are described. Moreover, the coordination geometry of chelates formed by these ligands and their derivatives is discussed as well. Novel ligands can be developed by the appropriate derivatization of DOTA and DO3A. Gd3+-chelates of such ligands prove to be useful MRI contrast agents of enhanced relaxivity, greater stability, better clearance, lesser toxicity and higher water solubility.
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Affiliation(s)
- Haroon Ur Rashid
- Department of Chemistry, Sarhad University of Science and Information Technology, Peshawar, Khyber Pakhtunkhwa, Pakistan; Institute of Chemistry, Federal University of Mato Grosso do Sul, Campo Grande, MS, Brazil.
| | | | - Juliana Jorge
- Institute of Chemistry, Federal University of Mato Grosso do Sul, Campo Grande, MS, Brazil
| | - Paula Martin de Moraes
- Institute of Chemistry, Federal University of Mato Grosso do Sul, Campo Grande, MS, Brazil
| | - Muhammad Naveed Umar
- Department of Chemistry, University of Malakand, Chakdara, Lower Dir, Khyber Pakhtunkhwa, Pakistan
| | - Kamin Khan
- Department of Chemistry, Sarhad University of Science and Information Technology, Peshawar, Khyber Pakhtunkhwa, Pakistan
| | - Hanif Ur Rehman
- Department of Chemistry, Sarhad University of Science and Information Technology, Peshawar, Khyber Pakhtunkhwa, Pakistan
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7
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Manukovsky N, Frydman V, Goldfarb D. Gd3+ Spin Labels Report the Conformation and Solvent Accessibility of Solution and Vesicle-Bound Melittin. J Phys Chem B 2015; 119:13732-41. [DOI: 10.1021/acs.jpcb.5b03523] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Nurit Manukovsky
- Departments of †Chemical Physics and ‡Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Veronica Frydman
- Departments of †Chemical Physics and ‡Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Daniella Goldfarb
- Departments of †Chemical Physics and ‡Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
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8
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Abstract
This perspective outlines strategies towards the development of MR imaging probes that our lab has explored over the last 15 years. Namely, we discuss methods to enhance the signal generating capacity of MR probes and how to achieve tissue specificity through protein targeting or probe activation within the tissue microenvironment.
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Affiliation(s)
- Eszter Boros
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Eric M Gale
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Peter Caravan
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
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9
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Lee T, Bang D, Park Y, Kim SH, Choi J, Park J, Kim D, Kim E, Suh JS, Huh YM, Haam S. Gadolinium-enriched polyaniline particles (GPAPs) for simultaneous diagnostic imaging and localized photothermal therapy of epithelial cancer. Adv Healthc Mater 2014; 3:1408-14. [PMID: 24550214 DOI: 10.1002/adhm.201300636] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 02/01/2014] [Indexed: 11/08/2022]
Abstract
By loading Gd(III) inside NIR-absorbing polyaniline nanostructures, a novel diagnostic and photothermal agent with enhanced MR sensitivity, targeting ability, and photothermal ability to treat epithelial cancer is developed.
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Affiliation(s)
- Taeksu Lee
- Department of Chemical and Biomolecular Engineering; Yonsei University; Seoul 120-749 Republic of Korea
| | - Doyeon Bang
- Department of Chemical and Biomolecular Engineering; Yonsei University; Seoul 120-749 Republic of Korea
- Active Polymer Center for Pattern Integration (APCPI), Yonsei University; Seoul 120-749 Republic of Korea
| | - Yeonji Park
- Department of Radiology; Yonsei University; Seoul 120-752 Republic of Korea
| | - Sun Hee Kim
- Korea Basic Science Institute (KBSI); Daejeon Republic of Korea
| | - Jihye Choi
- Department of Chemical and Biomolecular Engineering; Yonsei University; Seoul 120-749 Republic of Korea
| | - Joseph Park
- Department of Chemical and Biomolecular Engineering; Yonsei University; Seoul 120-749 Republic of Korea
| | - Donghun Kim
- Korea Basic Science Institute (KBSI); Daejeon Republic of Korea
| | - Eunkyoung Kim
- Department of Chemical and Biomolecular Engineering; Yonsei University; Seoul 120-749 Republic of Korea
- Active Polymer Center for Pattern Integration (APCPI), Yonsei University; Seoul 120-749 Republic of Korea
| | - Jin-Suck Suh
- Department of Radiology; Yonsei University; Seoul 120-752 Republic of Korea
| | - Yong-Min Huh
- Department of Radiology; Yonsei University; Seoul 120-752 Republic of Korea
| | - Seungjoo Haam
- Department of Chemical and Biomolecular Engineering; Yonsei University; Seoul 120-749 Republic of Korea
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10
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Preslar AT, Parigi G, McClendon MT, Sefick SS, Moyer TJ, Haney CR, Waters EA, MacRenaris KW, Luchinat C, Stupp SI, Meade TJ. Gd(III)-labeled peptide nanofibers for reporting on biomaterial localization in vivo. ACS NANO 2014; 8:7325-32. [PMID: 24937195 PMCID: PMC4216205 DOI: 10.1021/nn502393u] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 06/17/2014] [Indexed: 05/23/2023]
Abstract
Bioactive supramolecular nanostructures are of great importance in regenerative medicine and the development of novel targeted therapies. In order to use supramolecular chemistry to design such nanostructures, it is extremely important to track their fate in vivo through the use of molecular imaging strategies. Peptide amphiphiles (PAs) are known to generate a wide array of supramolecular nanostructures, and there is extensive literature on their use in areas such as tissue regeneration and therapies for disease. We report here on a series of PA molecules based on the well-established β-sheet amino acid sequence V3A3 conjugated to macrocyclic Gd(III) labels for magnetic resonance imaging (MRI). These conjugates were shown to form cylindrical supramolecular assemblies using cryogenic transmission electron microscopy and small-angle X-ray scattering. Using nuclear magnetic relaxation dispersion analysis, we observed that thermal annealing of the nanostructures led to a decrease in water exchange lifetime (τm) of hundreds of nanoseconds only for molecules that self-assemble into nanofibers of high aspect ratio. We interpret this decrease to indicate more solvent exposure to the paramagnetic moiety on annealing, resulting in faster water exchange within angstroms of the macrocycle. We hypothesize that faster water exchange in the nanofiber-forming PAs arises from the dehydration and increase in packing density on annealing. Two of the self-assembling conjugates were selected for imaging PAs after intramuscular injections of the PA C16V3A3E3-NH2 in the tibialis anterior muscle of a murine model. Needle tracts were clearly discernible with MRI at 4 days postinjection. This work establishes Gd(III) macrocycle-conjugated peptide amphiphiles as effective tracking agents for peptide amphiphile materials in vivo over the timescale of days.
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Affiliation(s)
- Adam T. Preslar
- Departments of Chemistry, Materials Science and Engineering, and Institute for BioNanotechnology in Medicine, Chemical and Biological Engineering, Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, and Center for Advanced Molecular Imaging, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Giacomo Parigi
- Magnetic Resonance Center (CERM) and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Italy
| | - Mark T. McClendon
- Departments of Chemistry, Materials Science and Engineering, and Institute for BioNanotechnology in Medicine, Chemical and Biological Engineering, Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, and Center for Advanced Molecular Imaging, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Samantha S. Sefick
- Departments of Chemistry, Materials Science and Engineering, and Institute for BioNanotechnology in Medicine, Chemical and Biological Engineering, Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, and Center for Advanced Molecular Imaging, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Tyson J. Moyer
- Departments of Chemistry, Materials Science and Engineering, and Institute for BioNanotechnology in Medicine, Chemical and Biological Engineering, Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, and Center for Advanced Molecular Imaging, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Chad R. Haney
- Departments of Chemistry, Materials Science and Engineering, and Institute for BioNanotechnology in Medicine, Chemical and Biological Engineering, Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, and Center for Advanced Molecular Imaging, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Emily A. Waters
- Departments of Chemistry, Materials Science and Engineering, and Institute for BioNanotechnology in Medicine, Chemical and Biological Engineering, Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, and Center for Advanced Molecular Imaging, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Keith W. MacRenaris
- Departments of Chemistry, Materials Science and Engineering, and Institute for BioNanotechnology in Medicine, Chemical and Biological Engineering, Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, and Center for Advanced Molecular Imaging, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Claudio Luchinat
- Magnetic Resonance Center (CERM) and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Italy
| | - Samuel I. Stupp
- Departments of Chemistry, Materials Science and Engineering, and Institute for BioNanotechnology in Medicine, Chemical and Biological Engineering, Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, and Center for Advanced Molecular Imaging, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Address correspondence to ,
| | - Thomas J. Meade
- Departments of Chemistry, Materials Science and Engineering, and Institute for BioNanotechnology in Medicine, Chemical and Biological Engineering, Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, and Center for Advanced Molecular Imaging, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Address correspondence to ,
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11
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Gale EM, Zhu J, Caravan P. Direct measurement of the Mn(II) hydration state in metal complexes and metalloproteins through 17O NMR line widths. J Am Chem Soc 2013; 135:18600-8. [PMID: 24088013 DOI: 10.1021/ja4094132] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Here we describe a simple method to estimate the inner-sphere hydration state of the Mn(II) ion in coordination complexes and metalloproteins. The line width of bulk H2(17)O is measured in the presence and absence of Mn(II) as a function of temperature, and transverse (17)O relaxivities are calculated. It is demonstrated that the maximum (17)O relaxivity is directly proportional to the number of inner-sphere water ligands (q). Using a combination of literature data and experimental data for 12 Mn(II) complexes, we show that this method provides accurate estimates of q with an uncertainty of ±0.2 water molecules. The method can be implemented on commercial NMR spectrometers working at fields of 7 T and higher. The hydration number can be obtained for micromolar Mn(II) concentrations. We show that the technique can be extended to metalloproteins or complex:protein interactions. For example, Mn(II) binds to the multimetal binding site A on human serum albumin with two inner-sphere water ligands that undergo rapid exchange (1.06 × 10(8) s(-1) at 37 °C). The possibility of extending this technique to other metal ions such as Gd(III) is discussed.
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Affiliation(s)
- Eric M Gale
- The Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital , Harvard Medical School , 149 Thirteenth Street, Suite 2301, Charlestown, Massachusetts 02129, United States
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12
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Polasek M, Caravan P. Is macrocycle a synonym for kinetic inertness in Gd(III) Complexes? Effect of coordinating and noncoordinating substituents on inertness and relaxivity of Gd(III) chelates with DO3A-like ligands. Inorg Chem 2013; 52:4084-96. [PMID: 23517079 PMCID: PMC3640422 DOI: 10.1021/ic400227k] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Gadolinium chelates with octadentate ligands are widely used as contrast agents for magnetic resonance imaging (MRI), with macrocyclic ligands based on DO3A being preferred for the high kinetic inertness of their Gd chelates. A major challenge in the design of new bifunctional MRI probes is the need to control the rotational motion of the chelate, which greatly affects its relaxivity. In this work we explored facile alkylation of a secondary amine in macrocyclic DO3A-like ligands to create a short, achiral linkage to limit the undesired internal motion of chelates within larger molecular constructs. The acetate moiety on the trans nitrogen was also replaced with either a bidentate (ethoxyacetate, L1 or methyl picolinate, L2) or bulky monodentate (methyl phosphonate, L3) donor arm to give octa- or heptadentate ligands, respectively. The resultant Gd(III) complexes were all monohydrated (q = 1) and exhibited water residency times that spanned 2 orders of magnitude (τM = 2190 ± 170, 3500 ± 90, and 12.7 ± 3.8 ns at 37 °C for GdL1, GdL2, and GdL3, respectively). Alkylation of the secondary amine with a noncoordinating biphenyl moiety resulted in coordinatively saturated q = 0 complexes of octadentate ligands L1 and L2. Relaxivities were limited by slow water exchange and/or lack of water coligand. All complexes showed decreased inertness compared to [Gd(DO3A)] despite higher ligand denticity, and inertness was further decreased upon N-alkylation. These results demonstrate that high kinetic inertness and in vivo safety of Gd chelates with macrocyclic ligands should not be generalized.
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Affiliation(s)
- Miloslav Polasek
- The Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 149 Thirteenth Street, Suite 2301, Charlestown, MA 02129
| | - Peter Caravan
- The Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 149 Thirteenth Street, Suite 2301, Charlestown, MA 02129
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13
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Astashkin AV, Nesmelov YE. Mn(2+)-nucleotide coordination at the myosin active site as detected by pulsed electron paramagnetic resonance. J Phys Chem B 2012; 116:13655-62. [PMID: 23121488 DOI: 10.1021/jp308423x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pulsed electron paramagnetic resonance at the microwave K(a) band (~30 GHz) was used to study the coordination of adenosine nucleotides to Mn(2+) at the active site of myosin ATPase and in solution. We have found that the electron spin echo (ESE) field sweep, electron-nuclear double resonance (ENDOR) and ESE envelope modulation (ESEEM) techniques are not sufficiently specific for reliable differentiation between the solvated and myosin-bound Mn·nucleotide complexes. Therefore, to directly detect binding of the Mn·nucleotide to myosin, we used nonhydrolizable nucleotide analogs, site-directed spin labeling, and pulsed electron-electron double resonance to detect spin probe-manganese dipolar interaction. We found that under substoichiometric conditions, both Mn·AMPPNP and Mn·ADP·AlF(4) form a complex with myosin, and Mn·ADP does not form such a complex. This correlates well with the biological dissociation of Mg·ADP from myosin after the hydrolysis of ATP. The analysis of (31)P ENDOR spectra reveals that in Mn·AMPPNP, Mn·ATP, and Mn·ADP at myosin or in solution, the nucleotide is coordinated to Mn(2+) by two phosphate groups, whereas in Mn·ADP·AlF(4), only one phosphate group is coordinated. The observation of two phosphates and one nitrogen in the coordination sphere of Mn·ADP in solution by ESEEM spectroscopy suggests that a significant population of Mn ions is coordinated by two ADP molecules, one of which is coordinated by phosphates, and the other one, by a nitrogen atom. The developed approach will be generally useful for monitoring the metal-protein binding when such binding does not provide reliable spectroscopic signatures.
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Affiliation(s)
- Andrei V Astashkin
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
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Moriggi L, Yaseen MA, Helm L, Caravan P. Serum albumin targeted, pH-dependent magnetic resonance relaxation agents. Chemistry 2012; 18:3675-86. [PMID: 22328098 PMCID: PMC3304010 DOI: 10.1002/chem.201103344] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Indexed: 11/11/2022]
Abstract
The objective of this work was the synthesis of serum albumin targeted, Gd(III)-based magnetic resonance imaging (MRI) contrast agents exhibiting a strong pH-dependent relaxivity. Two new complexes (Gd-glu and Gd-bbu) were synthesized based on the DO3A macrocycle modified with three carboxyalkyl substituents α to the three ring nitrogen atoms, and a biphenylsulfonamide arm. The sulfonamide nitrogen coordinates the Gd in a pH-dependent fashion, resulting in a decrease in the hydration state, q, as pH is increased and a resultant decrease in relaxivity (r(1)). In the absence of human serum albumin (HSA), r(1) increases from 2.0 to 6.0 mM(-1) s(-1) for Gd-glu and from 2.4 to 9.0 mM(-1) s(-1) for Gd-bbu from pH 5 to 8.5 at 37 °C, 0.47 T, respectively. These complexes (0.2 mM) are bound (>98.9 %) to HSA (0.69 mM) over the pH range 5-8.5. Binding to albumin increases the rotational correlation time and results in higher relaxivity. The r(1) increased 120 % (pH 5) and 550 % (pH 8.5) for Gd-glu and 42 % (pH 5) and 260 % (pH 8.5) for Gd-bbu. The increases in r(1) at pH 5 were unexpectedly low for a putative slow tumbling q=2 complex. The Gd-bbu system was investigated further. At pH 5, it binds in a stepwise fashion to HSA with dissociation constants K(d1)=0.65, K(d2)=18, K(d3)=1360 μM. The relaxivity at each binding site was constant. Luminescence lifetime titration experiments with the Eu(III) analogue revealed that the inner-sphere water ligands are displaced when the complex binds to HSA resulting in lower than expected r(1) at pH 5. Variable pH and temperature nuclear magnetic relaxation dispersion (NMRD) studies showed that the increased r(1) of the albumin-bound q=0 complexes is due to the presence of a nearby water molecule with a long residency time (1-2 ns). The distance between this water molecule and the Gd ion changes with pH resulting in albumin-bound pH-dependent relaxivity.
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Affiliation(s)
- Loïck Moriggi
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129 (USA)
| | - Mohammad A. Yaseen
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129 (USA)
| | - Lothar Helm
- Institut de Chimie Moléculaire et Biologique, Ecole Polytechnique Fédérale de Lausanne, EPFL-BCH, 1015 Lausanne (Switzerland)
| | - Peter Caravan
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129 (USA)
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15
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Bonnet CS, Tóth É. Magnetic Resonance Imaging Contrast Agents. Supramol Chem 2012. [DOI: 10.1002/9780470661345.smc104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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16
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Tircsó G, Kálmán FK, Pál R, Bányai I, Varga TR, Király R, Lázár I, Québatte L, Merbach AE, Tóth É, Brücher E. Lanthanide Complexes Formed with the Tri- and Tetraacetate Derivatives of Bis(aminomethyl)phosphinic Acid: Equilibrium, Kinetic and NMR Spectroscopic Studies. Eur J Inorg Chem 2012. [DOI: 10.1002/ejic.201101299] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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17
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Caravan P, Zhang Z. Structure-Relaxivity Relationships among Targeted MR Contrast Agents. Eur J Inorg Chem 2012; 2012:1916-1923. [DOI: 10.1002/ejic.201101364] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Strauch RC, Mastarone DJ, Sukerkar PA, Song Y, Ipsaro JJ, Meade TJ. Reporter protein-targeted probes for magnetic resonance imaging. J Am Chem Soc 2011; 133:16346-9. [PMID: 21942425 DOI: 10.1021/ja206134b] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Contrast agents for magnetic resonance imaging are frequently employed as experimental and clinical probes. Drawbacks include low signal sensitivity, fast clearance, and nonspecificity that limit efficacy in experimental imaging. In order to create a bioresponsive MR contrast agent, a series of four Gd(III) complexes targeted to the HaloTag reporter were designed and synthesized. HaloTag is unique among reporter proteins for its specificity, versatility, and the covalent interaction between substrate and protein. In similar systems, these properties produce prolonged in vivo lifetimes and extended imaging opportunities for contrast agents, longer rotational correlation times, and increases in relaxivity (r(1)) upon binding to the HaloTag protein. In this work we report a new MR contrast probe, 2CHTGd, which forms a covalent bond with its target protein and results in a dramatic increase in sensitivity. A 6-fold increase in r(1), from 3.8 to 22 mM(-1) s(-1), is observed upon 2CHTGd binding to the target protein. This probe was designed for use with the HaloTag protein system which allows for a variety of substrates (specific for MRI, florescence, or protein purification applications) to be used with the same reporter.
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Affiliation(s)
- Renee C Strauch
- Department of Molecular Biosciences, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
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Kaminker I, Sushenko A, Potapov A, Daube S, Akabayov B, Sagi I, Goldfarb D. Probing conformational variations at the ATPase site of the RNA helicase DbpA by high-field electron-nuclear double resonance spectroscopy. J Am Chem Soc 2011; 133:15514-23. [PMID: 21819147 DOI: 10.1021/ja204291d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The RNA helicase DbpA promotes RNA remodeling coupled to ATP hydrolysis. It is unique because of its specificity to hairpin 92 of 23S rRNA (HP92). Although DbpA kinetic pathways leading to ATP hydrolysis and RNA unwinding have been recently elucidated, the molecular (atomic) basis for the coupling of ATP hydrolysis to RNA remodeling remains unclear. This is, in part, due to the lack of detailed structural information on the ATPase site in the presence and absence of RNA in solution. We used high-field pulse ENDOR (electron-nuclear double resonance) spectroscopy to detect and analyze fine conformational changes in the protein's ATPase site in solution. Specifically, we substituted the essential Mg(2+) cofactor in the ATPase active site for paramagnetic Mn(2+) and determined its close environment with different nucleotides (ADP, ATP, and the ATP analogues ATPγS and AMPPnP) in complex with single- and double-stranded RNA. We monitored the Mn(2+) interactions with the nucleotide phosphates through the (31)P hyperfine couplings and the coordination by protein residues through (13)C hyperfine coupling from (13)C-enriched DbpA. We observed that the nucleotide binding site of DbpA adopts different conformational states upon binding of different nucleotides. The ENDOR spectra revealed a clear distinction between hydrolyzable and nonhydrolyzable nucleotides prior to RNA binding. Furthermore, both the (13)C and the (31)P ENDOR spectra were found to be highly sensitive to changes in the local environment of the Mn(2+) ion induced by the hydrolysis. More specifically, ATPγS was efficiently hydrolyzed upon binding of RNA, similar to ATP. Importantly, the Mn(2+) cofactor remains bound to a single protein side chain and to one or two nucleotide phosphates in all complexes, whereas the remaining metal coordination positions are occupied by water. The conformational changes in the protein's ATPase active site associated with the different DbpA states occur in remote coordination shells of the Mn(2+) ion. Finally, a competitive Mn(2+) binding site was found for single-stranded RNA construct.
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Affiliation(s)
- Ilia Kaminker
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
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Jacques V, Dumas S, Sun WC, Troughton JS, Greenfield MT, Caravan P. High-relaxivity magnetic resonance imaging contrast agents. Part 2. Optimization of inner- and second-sphere relaxivity. Invest Radiol 2011; 45:613-24. [PMID: 20808234 DOI: 10.1097/rli.0b013e3181ee6a49] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
RATIONALE AND OBJECTIVES The observed relaxivity of gadolinium-based contrast agents has contributions from the water molecule(s) that bind directly to the gadolinium ion (inner-sphere water), long-lived water molecules and exchangeable protons that make up the second-sphere of coordination, and water molecules that diffuse near the contrast agent (outer-sphere). Inner- and second-sphere relaxivity can both be increased by optimization of the lifetimes of the water molecules and protons in these coordination spheres, the rotational motion of the complex, and the electronic relaxation of the gadolinium ion. We sought to identify new high-relaxivity contrast agents by systematically varying the donor atoms that bind directly to gadolinium to increase inner-sphere relaxivity and concurrently including substituents that influence the second-sphere relaxivity. METHODS Twenty gadolinium-1,4,7,10-tetraazacyclo-dodecane-N,N',N″,N'″-tetraacetato derivatives were prepared and their relaxivity determined in presence and absence of human serum albumin as a function of temperature and magnetic field. Data was analyzed to extract the underlying molecular parameters influencing relaxivity. Each compound had a common albumin-binding group and an inner-sphere donor set comprising the 4 tertiary amine N atoms from cyclen, an α-substituted acetate oxygen atom, 2 amide oxygen atoms, an inner-sphere water oxygen atom, and a variable donor group. Each amide nitrogen was substituted with different groups to promote hydrogen bonding with second-sphere water molecules. RESULTS Relativities at 0.47 and 1.4 T, 37°C, in serum albumin ranged from 16.0 to 58.1 mM(-1)s(-1) and from 12.3 to 34.8 mM(-1)s(-1), respectively. The reduction of inner-sphere water exchange typical of amide donor groups could be offset by incorporating a phosphonate or phenolate oxygen atom donor in the first coordination sphere, resulting in higher relaxivity. Amide nitrogen substitution with pendant phosphonate or carboxylate groups increased relaxivity by as much as 88% compared with the N-methyl amide analog. Second-sphere relaxivity contributed as much as 24 and 14 mM(-1)s(-1) at 0.47 and 1.4 T, respectively. CONCLUSIONS Water/proton exchange dynamics in the inner- and second-coordination sphere can be predictably tuned by choice of donor atoms and second-sphere substituents, resulting in high-relaxivity agents.
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High relaxivity magnetic resonance imaging contrast agents. Part 1. Impact of single donor atom substitution on relaxivity of serum albumin-bound gadolinium complexes. Invest Radiol 2011; 45:600-12. [PMID: 20808235 DOI: 10.1097/rli.0b013e3181ee5a9e] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
RATIONALE AND OBJECTIVES The donor atoms that bind to gadolinium in contrast agents influence inner-sphere water exchange and electronic relaxation, both of which determine observed relaxivity. The effect of these molecular parameters on relaxivity is greatest when the contrast agent is protein bound. We sought to determine an optimal donor atom set to yield high relaxivity compounds. METHODS A total of 38 gadolinium-1,4,7,10-tetraazacyclo-dodecane-N,N',N'',N'''-tetraacetato derivatives were prepared and relaxivity was determined in the presence and absence of human serum albumin as a function of temperature and magnetic field. Each compound had a common albumin-binding group and differed only by substitution of different donor groups at one of the macrocycle nitrogens. Oxygen-17 isotope relaxometry at 7.05 T was performed to estimate water exchange rates. RESULTS Changing a single donor atom resulted in changes in water exchange rates ranging across 3 orders of magnitude. Donor groups increased water exchange rate in the order: phosphonate ∼ phenolate > α-substituted acetate > acetate > hydroxamate ∼ sulfonamide > amide ∼ pyridyl ∼ imidazole. Relaxivites at 0.47 and 1.4 T, 37°C, ranged from 12.3 to 55.6 mM(-1)s(-1) and from 8.3 to 32.6 mM(-1)s(-1) respectively. Optimal relaxivities were observed when the donor group was an α-substituted acetate. Electronic relaxation was slowest for the acetate derivatives as well. CONCLUSIONS Water exchange dynamics and relaxivity can be predictably tuned by choice of donor atoms.
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Regueiro-Figueroa M, Bensenane B, Ruscsák E, Esteban-Gómez D, Charbonnière LJ, Tircsó G, Tóth I, de Blas A, Rodríguez-Blas T, Platas-Iglesias C. Lanthanide dota-like complexes containing a picolinate pendant: structural entry for the design of Ln(III)-based luminescent probes. Inorg Chem 2011; 50:4125-41. [PMID: 21456610 DOI: 10.1021/ic2001915] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In this contribution we present two ligands based on a do3a platform containing a picolinate group attached to the fourth nitrogen atom of the cyclen unit, which are designed for stable lanthanide complexation in aqueous solutions. Potentiometric measurements reveal that the thermodynamic stability of the complexes is very high (log K = 21.2-23.5), being comparable to that of the dota analogues. Luminescence lifetime measurements performed on solutions of the Eu(III) and Tb(III) complexes indicate that the complexes are nine coordinate with no inner-sphere water molecules. A combination of density functional theory (DFT) calculations and NMR measurements shows that for the complexes of the heaviest lanthanides there is a major isomer in solution consisting of the enantiomeric pair Λ(δδδδ) and Δ(λλλλ), which provides square antiprismatic coordination (SAP) around the metal ion. Analysis of the Yb(III)-induced paramagnetic shifts unambiguously confirms that these complexes have SAP coordination in aqueous solution. For the light lanthanide ions however both the SAP and twisted-square antiprismatic (TSAP) isomers are present in solution. Inversion of the cyclen ring appears to be the rate-determining step for the Λ(δδδδ) ↔ Δ(λλλλ) enantiomerization process observed in the Lu(III) complexes. The energy barriers obtained from NMR measurements for this dynamic process are in excellent agreement with those predicted by DFT calculations. The energy barriers calculated for the arm-rotation process are considerably lower than those obtained for the ring-inversion path. Kinetic studies show that replacement of an acetate arm of dota by a picolinate pendant results in a 3-fold increase in the formation rate of the corresponding Eu(III) complexes and a significant increase of the rates of acid-catalyzed dissociation of the complexes. However, these rates are 1-2 orders of magnitude lower than those of do3a analogues, which shows that the complexes reported herein are remarkably inert with respect to metal ion dissociation.
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Affiliation(s)
- Martín Regueiro-Figueroa
- Departamento de Química Fundamental, Universidade da Coruña, Campus da Zapateira-Rúa da Fraga 10, 15008 A Coruña, Spain
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Potapov A, Song Y, Meade TJ, Goldfarb D, Astashkin A, Raitsimring A. Distance measurements in model bis-Gd(III) complexes with flexible "bridge". Emulation of biological molecules having flexible structure with Gd(III) labels attached. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 205:38-49. [PMID: 20418132 PMCID: PMC2885582 DOI: 10.1016/j.jmr.2010.03.019] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2009] [Revised: 03/30/2010] [Accepted: 03/30/2010] [Indexed: 05/18/2023]
Abstract
In this work, we continue to explore Gd(III) as a possible spin label for high-field Double Electron-Electron Resonance (DEER) based distance measurements in biological molecules with flexible geometry. For this purpose, a bis-Gd(III) complex with a flexible "bridge" was used as a model. The distances in the model were expected to be distributed in the range of 5-26 A, allowing us to probe the shortest limits of accessible distances which were found to be as small as 13 A. The upper distance limit for these labels was also evaluated and was found to be about 60 A. Various pulse duration setups can result in apparent differences in the distribution function derived from DEER kinetics due to short distance limit variations. The advantages, such as the ability to perform measurements at cryogenic temperatures and high repetition rates simultaneously, the use of very short pumping and observation pulses without mutual interference, the lack of orientational selectivity, as well as the shortcomings, such as the limited mw operational frequency range and intrinsically smaller amplitude of oscillation related to dipolar interaction as compared with nitroxide spin labels are discussed. Most probably the use of nitroxide and Gd-based labels for distance measurements will be complementary depending on the particulars of the problem and the availability of instrumentation.
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Affiliation(s)
- A. Potapov
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Y. Song
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - T. J. Meade
- Department of Chemistry; Department of Biochemistry, Cell Biology, and Molecular Biology; Neurobiology & Physiology; Department of Radiology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | - D. Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - A.V. Astashkin
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041, USA
| | - A. Raitsimring
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041, USA
- Corresponding author: Dr. A. Raitsimring, University of Arizona, Department of Chemistry, 1306 E. University Blvd, Tucson, AZ 85721. ; tel (520)621-9968; fax (520)621-8407
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Henig J, Tóth É, Engelmann J, Gottschalk S, Mayer HA. Macrocyclic Gd3+ Chelates Attached to a Silsesquioxane Core as Potential Magnetic Resonance Imaging Contrast Agents: Synthesis, Physicochemical Characterization, and Stability Studies. Inorg Chem 2010; 49:6124-38. [DOI: 10.1021/ic1007395] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jörg Henig
- Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
| | - Éva Tóth
- Le Centre de Biophysique Moléculaire, CNRS, Rue Charles Sadron, 45071 Orléans, France
| | - Jörn Engelmann
- Hochfeld-Magnetresonanz-Zentrum, Max-Planck-Institut für Biologische Kybernetik, Spemannstrasse 41, 72076 Tübingen, Germany
| | - Sven Gottschalk
- Hochfeld-Magnetresonanz-Zentrum, Max-Planck-Institut für Biologische Kybernetik, Spemannstrasse 41, 72076 Tübingen, Germany
| | - Hermann A. Mayer
- Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
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Caravan P. Protein-targeted gadolinium-based magnetic resonance imaging (MRI) contrast agents: design and mechanism of action. Acc Chem Res 2009; 42:851-62. [PMID: 19222207 DOI: 10.1021/ar800220p] [Citation(s) in RCA: 288] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Magnetic resonance imaging (MRI) is a powerful medical diagnostic technique: it can penetrate deep into tissue, provide excellent soft tissue contrast with sub-millimeter resolution, and does not employ ionizing radiation. Targeted contrast agents provide an additional layer of molecular specificity to the wealth of anatomical and functional information already attainable by MRI. However, the major challenge for molecular MR imaging is sensitivity: micromolar concentrations of Gd(III) are required to cause a detectable signal change, which makes detecting proteins by MRI a challenge. Protein-targeted MRI contrast agents are bifunctional molecules comprising a protein-targeting moiety and typically one or more gadolinium chelates for detection by MRI. The ability of the contrast agent to enhance the MR image is termed relaxivity, and it depends upon many molecular factors, including protein binding itself. As in other imaging modalities, protein binding provides the pharmacokinetic effect of concentrating the agent at the region of interest. Unique to MRI, protein binding provides the pharmacodynamic effect of increasing the relaxivity of the contrast agent, thereby increasing the MR signal. In designing new agents, optimization of both the targeting function and the relaxivity is critical. In this Account, we focus on optimization of the relaxivity of targeted agents. Relaxivity depends upon speciation, chemical structure, and dynamic processes, such as water exchange kinetics and rotational tumbling rates. We describe mechanistic studies that relate these factors to the observed relaxivities and use these findings as the basis of rational design of improved agents. In addition to traditional biochemical methods to characterize ligand-protein interactions, the presence of the metal ion enables more obscure biophysical techniques, such as relaxometry and electron nuclear double resonance, to be used to elucidate the mechanism of relaxivity differences. As a case study, we explore the mechanism of action of the serum-albumin-targeted angiography agent MS-325 and closely related compounds and show how small changes in the metal chelate can impact relaxivity. We found that, while protein binding generally improves relaxivity by slowing the tumbling rate of the complex, in some cases, the protein itself can also negatively affect hydration of the metal complex and/or inner-sphere water exchange. Drawing on these findings, we designed next-generation agents targeting albumin, fibrin, or collagen and incorporating up to four gadolinium chelates. Through judicious molecular design, we show that high-relaxivity complexes with high target affinity can be realized.
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Affiliation(s)
- Peter Caravan
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, 149 Thirteenth Street, Suite 2301, Charlestown, Massachusetts 02129
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Caravan P, Farrar CT, Frullano L, Uppal R. Influence of molecular parameters and increasing magnetic field strength on relaxivity of gadolinium- and manganese-based T1 contrast agents. CONTRAST MEDIA & MOLECULAR IMAGING 2009; 4:89-100. [PMID: 19177472 DOI: 10.1002/cmmi.267] [Citation(s) in RCA: 377] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Simulations were performed to understand the relative contributions of molecular parameters to longitudinal (r(1)) and transverse (r(2)) relaxivity as a function of applied field, and to obtain theoretical relaxivity maxima over a range of fields to appreciate what relaxivities can be achieved experimentally. The field-dependent relaxivities of a panel of gadolinium and manganese complexes with different molecular parameters, water exchange rates, rotational correlation times, hydration state, etc. were measured to confirm that measured relaxivities were consistent with theory. The design tenets previously stressed for optimizing r(1) at low fields (very slow rotational motion; chelate immobilized by protein binding; optimized water exchange rate) do not apply at higher fields. At 1.5 T and higher fields, an intermediate rotational correlation time is desired (0.5-4 ns), while water exchange rate is not as critical to achieving a high r(1). For targeted applications it is recommended to tether a multimer of metal chelates to a protein-targeting group via a long flexible linker to decouple the slow motion of the protein from the water(s) bound to the metal ions. Per ion relaxivities of 80, 45, and 18 mM(-1) s(-1) at 1.5, 3 and 9.4 T, respectively, are feasible for Gd(3+) and Mn(2+) complexes.
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Affiliation(s)
- Peter Caravan
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Department of Radiology, Harvard Medical School, 149 Thirteenth St, Charlestown, MA 02129, USA.
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Design and function of metal complexes as contrast agents in MRI. ADVANCES IN INORGANIC CHEMISTRY 2009. [DOI: 10.1016/s0898-8838(09)00202-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Kubíček V, Hamplová A, Maribé L, Mameri S, Ziessel R, Tóth É, Charbonnière L. Relaxation and luminescence studies on hydrated bipyridyl- and terpyridyl-based lanthanide complexes. Dalton Trans 2009:9466-74. [DOI: 10.1039/b913084e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Hermann P, Kotek J, Kubícek V, Lukes I. Gadolinium(III) complexes as MRI contrast agents: ligand design and properties of the complexes. Dalton Trans 2008:3027-47. [PMID: 18521444 DOI: 10.1039/b719704g] [Citation(s) in RCA: 381] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Magnetic resonance imaging is a commonly used diagnostic method in medicinal practice as well as in biological and preclinical research. Contrast agents (CAs), which are often applied are mostly based on Gd(III) complexes. In this paper, the ligand types and structures of their complexes on one side and a set of the physico-chemical parameters governing properties of the CAs on the other side are discussed. The solid-state structures of lanthanide(III) complexes of open-chain and macrocyclic ligands and their structural features are compared. Examples of tuning of ligand structures to alter the relaxometric properties of gadolinium(III) complexes as a number of coordinated water molecules, their residence time (exchange rate) or reorientation time of the complexes are given. Influence of the structural changes of the ligands on thermodynamic stability and kinetic inertness/lability of their lanthanide(III) complexes is discussed.
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Affiliation(s)
- Petr Hermann
- Department of Inorganic Chemistry, Faculty of Science, Universita Karlova (Charles University), Hlavova 2030, 128 40, Prague 2, Czech Republic
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Raitsimring AM, Astashkin AV, Baute D, Goldfarb D, Poluektov OG, Lowe MP, Zech SG, Caravan P. Determination of the hydration number of gadolinium(III) complexes by high-field pulsed 17O ENDOR spectroscopy. Chemphyschem 2007; 7:1590-7. [PMID: 16810729 DOI: 10.1002/cphc.200600138] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Pulsed 17O Mims electron-nuclear double resonance (ENDOR) spectroscopy at the W band (95 GHz) and D band (130 GHz) is used for the direct determination of the water coordination number (q) of gadolinium-based magnetic resonance imaging (MRI) contrast agents. Spectra of metal complexes in frozen aqueous solutions at approximately physiological concentrations can be obtained either in the presence or absence of protein targets. This method is an improvement over the 1H ENDOR method described previously, which involved the difference ENDOR spectrum of exchangeable protons from spectra taken in H2O and D2O. In addition to exchangeable water protons, the 1H ENDOR method is also sensitive to other exchangeable protons, and it is shown here that this method can overestimate hydration numbers for complexes with exchangeable protons at GdH distances similar to that of the coordinated water, for example, from NH groups. The 17O method does not suffer from this limitation. 17O ENDOR spectroscopy is applied to Gd(III) complexes containing zero, one, or two inner-sphere water molecules. In addition, 13C and 1H ENDOR studies were performed to assess the extent of methanol coordination, since methanol is used to produce a glass in these experiments. Under the experimental conditions used for the hydration number determination (30 mol % methanol), fewer than 15 % of the coordination sites were found to be occupied by methanol.
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Zech SG, Eldredge HB, Lowe MP, Caravan P. Protein Binding to Lanthanide(III) Complexes Can Reduce the Water Exchange Rate at the Lanthanide. Inorg Chem 2007; 46:3576-84. [PMID: 17425306 DOI: 10.1021/ic070011u] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The GdIII-based magnetic resonance imaging contrast agent MS-325 targets the blood protein serum albumin, resulting in an increased efficacy (relaxivity) as a relaxation agent. MS-325 showed different relaxivities when bound to serum albumin from different species, e.g., r1=30.5 mM-1 s-1 (rabbit) vs 46.3 mM-1 s-1 (human) at 35 degrees C and 0.47 T. To investigate the mechanism for this difference, surrogate complexes were prepared where the GdIII ion was replaced by other LnIII ions. Fluorescence lifetime measurements of the EuIII analogue indicated that the hydration number was q=1 and did not change when bound to either human, rat, rabbit, pig, or dog serum albumin. The YbIII analogue, YbL1, was prepared and characterized by 1H NMR. Line-shape analysis of the paramagnetic-shifted 1H NMR resonances in the presence of increasing amounts of human (HSA) or rabbit (RSA) serum albumin allowed estimation of the transverse relaxation rate, R2, of these resonances for the protein-bound YbL1. The rotational correlation time of YbL1 was calculated from R2, and the Yb-H distance and was tauR=8+/-1 ns when bound to HSA and 13+/-2 ns when bound to RSA. The water exchange rate at the DyIII analogue, DyL1, was determined from variable-temperature R2 measurements at 9.4 T when DyL1 was bound to either HSA or RSA. At 37 degrees C, water exchange at DyL1 was (31+/-5)x10(6) s-1 when bound to HSA but (3.8+/-0.2)x10(6) s-1 when bound to RSA. Slower water exchange upon RSA binding explains the differences in relaxivity observed. The approach of using surrogate lanthanides to identify specific molecular parameters influencing relaxivity is applicable to other protein-targeted GdIII contrast agents.
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Affiliation(s)
- Stephan G Zech
- EPIX Pharmaceuticals, 67 Rogers Street, Cambridge, Massachusetts 02142, USA
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Caravan P. Strategies for increasing the sensitivity of gadolinium based MRI contrast agents. Chem Soc Rev 2006; 35:512-23. [PMID: 16729145 DOI: 10.1039/b510982p] [Citation(s) in RCA: 1047] [Impact Index Per Article: 58.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Gadolinium(III) complexes are often used in clinical MRI to increase contrast by selectively relaxing the water molecules near the complex. There is a desire to improve the sensitivity (relaxivity) of these contrast agents in order to detect molecular targets. This tutorial review describes the molecular factors that contribute to relaxivity and illustrates with recent examples how these can be optimized. It may be of interest to senior undergraduates and more advanced researchers interested in lanthanide chemistry, biophysics, and/or molecular imaging.
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Affiliation(s)
- Peter Caravan
- EPIX Pharmaceuticals, 67 Rogers St, Cambridge, MA 02142, USA.
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