1
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Houszka N, Mikula H, Svatunek D. Substituent Effects in Bioorthogonal Diels-Alder Reactions of 1,2,4,5-Tetrazines. Chemistry 2023; 29:e202300345. [PMID: 36853623 PMCID: PMC10946812 DOI: 10.1002/chem.202300345] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 02/27/2023] [Accepted: 02/28/2023] [Indexed: 03/01/2023]
Abstract
1,2,4,5-Tetrazines are increasingly used as reactants in bioorthogonal chemistry due to their high reactivity in Diels-Alder reactions with various dienophiles. Substituents in the 3- and 6-positions of the tetrazine scaffold are known to have a significant impact on the rate of cycloadditions; this is commonly explained on the basis of frontier molecular orbital theory. In contrast, we show that reactivity differences between commonly used classes of tetrazines are not controlled by frontier molecular orbital interactions. In particular, we demonstrate that mono-substituted tetrazines show high reactivity due to decreased Pauli repulsion, which leads to a more asynchronous approach associated with reduced distortion energy. This follows the recent Vermeeren-Hamlin-Bickelhaupt model of reactivity increase in asymmetric Diels-Alder reactions. In addition, we reveal that ethylene is not a good model compound for other alkenes in Diels-Alder reactions.
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Affiliation(s)
- Nicole Houszka
- Institute of Applied Synthetic ChemistryTU WienGetreidemarkt 91060ViennaAustria
| | - Hannes Mikula
- Institute of Applied Synthetic ChemistryTU WienGetreidemarkt 91060ViennaAustria
| | - Dennis Svatunek
- Institute of Applied Synthetic ChemistryTU WienGetreidemarkt 91060ViennaAustria
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2
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Poulie CBM, Sporer E, Hvass L, Jørgensen JT, Kempen PJ, Lopes van den Broek SI, Shalgunov V, Kjaer A, Jensen AI, Herth MM. Bioorthogonal Click of Colloidal Gold Nanoparticles to Antibodies In vivo. Chemistry 2022; 28:e202201847. [PMID: 35851967 DOI: 10.1002/chem.202201847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Indexed: 01/07/2023]
Abstract
Combining nanotechnology and bioorthogonal chemistry for theranostic strategies offers the possibility to develop next generation nanomedicines. These materials are thought to increase therapeutic outcome and improve current cancer management. Due to their size, nanomedicines target tumors passively. Thus, they can be used for drug delivery purposes. Bioorthogonal chemistry allows for a pretargeting approach. Higher target-to-background drug accumulation ratios can be achieved. Pretargeting can also be used to induce internalization processes or trigger controlled drug release. Colloidal gold nanoparticles (AuNPs) have attracted widespread interest as drug delivery vectors within the last decades. Here, we demonstrate for the first time the possibility to successfully ligate AuNPs in vivo to pretargeted monoclonal antibodies. We believe that this possibility will facilitate the development of AuNPs for clinical use and ultimately, improve state-of-the-art patient care.
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Affiliation(s)
- Christian B M Poulie
- Department of Drug Design and Pharmacology Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark
| | - Emanuel Sporer
- Center for Nanomedicine and Theranostics, DTU Health Technology, Technical University of Denmark (DTU), Ørsteds Plads 345C, 2800, Lyngby, Denmark
| | - Lars Hvass
- Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark.,Cluster for Molecular Imaging Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Jesper T Jørgensen
- Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark.,Cluster for Molecular Imaging Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Paul J Kempen
- National Centre for Nano Fabrication and Characterization, Technical University of Denmark (DTU), Ørsteds Plads 347, 2800, Lyngby, Denmark
| | - Sara I Lopes van den Broek
- Department of Drug Design and Pharmacology Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark
| | - Vladimir Shalgunov
- Department of Drug Design and Pharmacology Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark
| | - Andreas Kjaer
- Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark.,Cluster for Molecular Imaging Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Andreas I Jensen
- Center for Nanomedicine and Theranostics, DTU Health Technology, Technical University of Denmark (DTU), Ørsteds Plads 345C, 2800, Lyngby, Denmark
| | - Matthias M Herth
- Department of Drug Design and Pharmacology Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark.,Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark
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3
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Torres-García D, van de Plassche MAT, van Boven E, van Leeuwen T, Groenewold MGJ, Sarris AJC, Klein L, Overkleeft HS, van Kasteren SI. Methyltetrazine as a small live-cell compatible bioorthogonal handle for imaging enzyme activities in situ. RSC Chem Biol 2022; 3:1325-1330. [DOI: 10.1039/d2cb00120a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 09/07/2022] [Indexed: 11/21/2022] Open
Abstract
Bioorthogonal chemistry combines well with activity-based protein profiling, as it allows for the introduction of detection tags without significantly influencing the physiochemical and biological functions of the probe.
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Affiliation(s)
- Diana Torres-García
- Leiden Institute of Chemistry and The Institute for Chemical Immunology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Merel A. T. van de Plassche
- Leiden Institute of Chemistry and The Institute for Chemical Immunology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Emma van Boven
- Leiden Institute of Chemistry and The Institute for Chemical Immunology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Tyrza van Leeuwen
- Leiden Institute of Chemistry and The Institute for Chemical Immunology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Mirjam G. J. Groenewold
- Leiden Institute of Chemistry and The Institute for Chemical Immunology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Alexi J. C. Sarris
- Leiden Institute of Chemistry and The Institute for Chemical Immunology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Luuk Klein
- Leiden Institute of Chemistry and The Institute for Chemical Immunology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Herman S. Overkleeft
- Leiden Institute of Chemistry and The Institute for Chemical Immunology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Sander I. van Kasteren
- Leiden Institute of Chemistry and The Institute for Chemical Immunology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
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4
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La-Venia A, Dzijak R, Rampmaier R, Vrabel M. An Optimized Protocol for the Synthesis of Peptides Containing trans-Cyclooctene and Bicyclononyne Dienophiles as Useful Multifunctional Bioorthogonal Probes. Chemistry 2021; 27:13632-13641. [PMID: 34241924 DOI: 10.1002/chem.202102042] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Indexed: 11/06/2022]
Abstract
Despite the great advances in solid-phase peptide synthesis (SPPS), the incorporation of certain functional groups into peptide sequences is restricted by the compatibility of the building blocks with conditions used during SPPS. In particular, the introduction of highly reactive groups used in modern bioorthogonal reactions into peptides remains elusive. Here, we present an optimized synthetic protocol enabling installation of two strained dienophiles, trans-cyclooctene (TCO) and bicyclononyne (BCN), into different peptide sequences. The two groups enable fast and modular post-synthetic functionalization of peptides, as we demonstrate in preparation of peptide-peptide and peptide-drug conjugates. Due to the excellent biocompatibility, the click-functionalization of the peptides can be performed directly in live cells. We further show that the introduction of both clickable groups into peptides enables construction of smart, multifunctional probes that can streamline complex chemical biology experiments such as visualization and pull-down of metabolically labeled glycoconjugates. The presented strategy will find utility in construction of peptides for diverse applications, where high reactivity, efficiency and biocompatibility of the modification step is critical.
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Affiliation(s)
- Agustina La-Venia
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16000, Prague, Czech Republic.,Current address: Instituto de Química Rosario, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario-CONICET, Suipacha 531, S2002LRK, Rosario, Argentina
| | - Rastislav Dzijak
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16000, Prague, Czech Republic
| | - Robert Rampmaier
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16000, Prague, Czech Republic
| | - Milan Vrabel
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16000, Prague, Czech Republic
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5
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Pandya DN, Henry KE, Day CS, Graves SA, Nagle VL, Dilling TR, Sinha A, Ehrmann BM, Bhatt NB, Menda Y, Lewis JS, Wadas TJ. Polyazamacrocycle Ligands Facilitate 89Zr Radiochemistry and Yield 89Zr Complexes with Remarkable Stability. Inorg Chem 2020; 59:17473-17487. [PMID: 33169605 DOI: 10.1021/acs.inorgchem.0c02722] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Over the last three decades, the chemistry of zirconium has facilitated antibody development and the clinical management of disease in the precision medicine era. Scientists have harnessed its reactivity, coordination chemistry, and nuclear chemistry to develop antibody-based radiopharmaceuticals incorporating zirconium-89 (89Zr: t1/2 = 78.4 h, β+: 22.8%, Eβ+max = 901 keV; EC: 77%, Eγ = 909 keV) to improve disease detection, identify patients for individualized therapeutic interventions. and monitor their response to those interventions. However, release of the 89Zr4+ ion from the radiopharmaceutical remains a concern, since it may confound the interpretation of clinical imaging data, negatively affect dosimetric calculations, and hinder treatment planning. In this report, we relate our novel observations involving the use of polyazamacrocycles as zirconium-89 chelators. We describe the synthesis and complete characterization of zirconium 2,2',2″,2‴-(1,4,7,10-tetraazacyclotridecane-1,4,7,10-tetrayl)tetraacetic acid (Zr-TRITA), zirconium 3,6,9,15-Tetraazabicyclo[9.3.1] pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (Zr-PCTA), and zirconium 2,2',2″-(1,4,7-triazacyclononane-1,4,7-triyl)triacetic acid (Zr-NOTA). In addition, we elucidate the solid-state structure of each complex using single-crystal X-ray diffraction analysis. Finally, we found that [89Zr]Zr-PCTA and [89Zr]Zr-NOTA demonstrate excellent stability in vitro and in vivo and provide a rationale for these observations. These innovative findings have the potential to guide the development of safer and more robust immuno-PET agents to improve precision medicine applications.
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Affiliation(s)
- Darpan N Pandya
- Department of Radiology, University of Iowa, Iowa City, Iowa 52242, United States
| | - Kelly E Henry
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Cynthia S Day
- Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109, United States
| | - Stephen A Graves
- Department of Radiology, University of Iowa, Iowa City, Iowa 52242, United States
| | - Veronica L Nagle
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Thomas R Dilling
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Akesh Sinha
- Department of Radiology, University of Iowa, Iowa City, Iowa 52242, United States
| | - Brandie M Ehrmann
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Nikunj B Bhatt
- Department of Radiology, Columbia University, New York, New York 10032, United States
| | - Yusuf Menda
- Department of Radiology, University of Iowa, Iowa City, Iowa 52242, United States
| | - Jason S Lewis
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Thaddeus J Wadas
- Department of Radiology, University of Iowa, Iowa City, Iowa 52242, United States
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6
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Pretargeted Nuclear Imaging and Radioimmunotherapy Based on the Inverse Electron-Demand Diels-Alder Reaction and Key Factors in the Pretargeted Synthetic Design. CONTRAST MEDIA & MOLECULAR IMAGING 2019; 2019:9182476. [PMID: 31531006 PMCID: PMC6732628 DOI: 10.1155/2019/9182476] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 06/20/2019] [Accepted: 08/01/2019] [Indexed: 11/18/2022]
Abstract
The exceptional speed and biorthogonality of the inverse electron-demand Diels-Alder (IEDDA) click chemistry between 1,2,4,5-tetrazines and strained alkene dienophiles have made it promising in the realm of pretargeted imaging and therapy. During the past 10 years, the IEDDA-pretargeted strategies have been tested and have already proven capable of producing images with high tumor-to-background ratios and improving therapeutic effect. This review will focus on recent applications of click chemistry ligations in the pretargeted imaging studies of single photon emission computed tomography (SPECT), positron emission tomography (PET), and pretargeted radioimmunotherapy investigations. Additionally, the influence factors of stability, reactivity, and pharmacokinetic properties of TCO tag modified immunoconjugates and radiolabeled Tz derivatives were also summarized in this article, which should be carefully considered in the system design in order to develop a successful pretargeted methodology. We hope that this review will not only equip readers with a knowledge of pretargeted methodology based on IEDDA click chemistry but also inspire synthetic chemists and radiochemists to develop pretargeted radiopharmaceutical components in a more innovative way with various influence factors considered.
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7
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Dong P, Wang X, Zheng J, Zhang X, Li Y, Wu H, Li L. Recent Advances in Targeting Nuclear Molecular Imaging Driven by Tetrazine Bioorthogonal Chemistry. Curr Med Chem 2019; 27:3924-3943. [PMID: 31267851 DOI: 10.2174/1386207322666190702105829] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 04/18/2019] [Accepted: 05/03/2019] [Indexed: 02/05/2023]
Abstract
Molecular imaging techniques apply sophisticated technologies to monitor, directly or indirectly, the spatiotemporal distribution of molecular or cellular processes for biomedical, diagnostic, or therapeutic purposes. For example, Single-Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) imaging, the most representative modalities of molecular imaging, enable earlier and more accurate diagnosis of cancer and cardiovascular diseases. New possibilities for noninvasive molecular imaging in vivo have emerged with advances in bioorthogonal chemistry. For example, tetrazine-related Inverse Electron Demand Diels-Alder (IEDDA) reactions can rapidly generate short-lived radioisotope probes in vivo that provide strong contrast for SPECT and PET. Here, we review pretargeting strategies for molecular imaging and novel radiotracers synthesized via tetrazine bioorthogonal chemistry. We systematically describe advances in direct radiolabeling and pretargeting approaches in SPECT and PET using metal and nonmetal radioisotopes based on tetrazine bioorthogonal reactions, and we discuss prospects for the future of such contrast agents.
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Affiliation(s)
- Ping Dong
- Department of Nuclear Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Xueyi Wang
- West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu, Sichuan 610041, China
| | - Junwei Zheng
- West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu, Sichuan 610041, China
| | - Xiaoyang Zhang
- Department of Nuclear Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Yiwen Li
- College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, Sichuan, 610065, China
| | - Haoxing Wu
- Huaxi MR Research Center, Department of Radiology, West China Hospital and West China School of Medicine, Sichuan University, Chengdu, Sichuan 610041, China
| | - Lin Li
- Department of Nuclear Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
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8
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Baalmann M, Ziegler MJ, Werther P, Wilhelm J, Wombacher R. Enzymatic and Site-Specific Ligation of Minimal-Size Tetrazines and Triazines to Proteins for Bioconjugation and Live-Cell Imaging. Bioconjug Chem 2019; 30:1405-1414. [PMID: 30883100 DOI: 10.1021/acs.bioconjchem.9b00157] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Diels-Alder reactions with inverse electron demand (DAinv) have emerged as an indispensable tool for bioorthogonal labeling and the manipulation of biomolecules. In this context, reactions between tetrazines and strained dienophiles have received attention because of high reaction rates. Current methods for the DAinv-mediated functionalization of proteins suffer from slow reactivity, impaired stability, isomerization, or elimination of the incorporated strained dienophiles. We report here a versatile platform for the posttranslational, highly selective, and quantitative modification of proteins with stable dienes. New synthetic access to minimal size tetrazine and triazine derivatives enabled us to synthesize tailored diene substrates for the lipoic acid protein ligase A (LplA) from Escherichia coli, which we employ for the rapid, mild, and quantitative bioconjugation of proteins by DAinv. The presented method benefits from the minimal tag size for LplA recognition and can be applied to proteins from any source organism. We demonstrate its broad suitability by site-specific in vitro protein labeling and live cell labeling for fluorescence microscopy. With this work we expand the scope of DAinv bioorthogonal chemistry for site-specific protein labeling, providing additional experimental flexibility for preparing well-defined bioconjugates and addressing biological questions in complex biological environments.
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Affiliation(s)
- Mathis Baalmann
- Institute of Pharmacy and Molecular Biotechnology , Heidelberg University , Im Neuenheimer Feld 364 , 69120 Heidelberg , Germany
| | - Michael J Ziegler
- Institute of Pharmacy and Molecular Biotechnology , Heidelberg University , Im Neuenheimer Feld 364 , 69120 Heidelberg , Germany
| | - Philipp Werther
- Institute of Pharmacy and Molecular Biotechnology , Heidelberg University , Im Neuenheimer Feld 364 , 69120 Heidelberg , Germany
| | - Jonas Wilhelm
- Institute of Pharmacy and Molecular Biotechnology , Heidelberg University , Im Neuenheimer Feld 364 , 69120 Heidelberg , Germany
| | - Richard Wombacher
- Institute of Pharmacy and Molecular Biotechnology , Heidelberg University , Im Neuenheimer Feld 364 , 69120 Heidelberg , Germany
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9
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Pagel M. Inverse electron demand Diels-Alder (IEDDA) reactions in peptide chemistry. J Pept Sci 2019; 25:e3141. [PMID: 30585397 DOI: 10.1002/psc.3141] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 11/22/2018] [Accepted: 11/23/2018] [Indexed: 01/05/2023]
Abstract
Click chemistry is applied to selectively modify, lable and ligate peptides for their use as therapeutics, in biomaterials or analytical investigations. The inverse electron demand Diels-Alder (IEDDA) reaction is a catalyst-free click reaction with pronounced chemoselectivity and fast reaction rates. Applications and achievements of the IEDDA reaction in peptide chemistry since 2008 are described in this review.
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Affiliation(s)
- Mareen Pagel
- Institute of Biochemistry, Faculty of Biosciences, Pharmacy and Psychology, Leipzig University, Leipzig, Germany
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10
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An efficient metal catalyst free approach to synthesize 5-(4-(1,2,4,5 tetrazin-3-yl)benzylamino)-5-oxopentanoic acid. Tetrahedron Lett 2018. [DOI: 10.1016/j.tetlet.2018.06.071] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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11
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Oliveira BL, Guo Z, Bernardes GJL. Inverse electron demand Diels-Alder reactions in chemical biology. Chem Soc Rev 2018; 46:4895-4950. [PMID: 28660957 DOI: 10.1039/c7cs00184c] [Citation(s) in RCA: 644] [Impact Index Per Article: 107.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The emerging inverse electron demand Diels-Alder (IEDDA) reaction stands out from other bioorthogonal reactions by virtue of its unmatchable kinetics, excellent orthogonality and biocompatibility. With the recent discovery of novel dienophiles and optimal tetrazine coupling partners, attention has now been turned to the use of IEDDA approaches in basic biology, imaging and therapeutics. Here we review this bioorthogonal reaction and its promising applications for live cell and animal studies. We first discuss the key factors that contribute to the fast IEDDA kinetics and describe the most recent advances in the synthesis of tetrazine and dienophile coupling partners. Both coupling partners have been incorporated into proteins for tracking and imaging by use of fluorogenic tetrazines that become strongly fluorescent upon reaction. Selected notable examples of such applications are presented. The exceptional fast kinetics of this catalyst-free reaction, even using low concentrations of coupling partners, make it amenable for in vivo radiolabelling using pretargeting methodologies, which are also discussed. Finally, IEDDA reactions have recently found use in bioorthogonal decaging to activate proteins or drugs in gain-of-function strategies. We conclude by showing applications of the IEDDA reaction in the construction of biomaterials that are used for drug delivery and multimodal imaging, among others. The use and utility of the IEDDA reaction is interdisciplinary and promises to revolutionize chemical biology, radiochemistry and materials science.
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Affiliation(s)
- B L Oliveira
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
| | - Z Guo
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
| | - G J L Bernardes
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK. and Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, Lisboa, 1649-028, Portugal.
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12
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Abstract
The interest in zirconium-89 (89Zr) as a positron-emitting radionuclide has grown considerably over the last decade due to its standardized production, long half-life of 78.2 h, favorable decay characteristics for positron emission tomography (PET) imaging and its successful use in a variety of clinical and preclinical applications. However, to be utilized effectively in PET applications it must be stably bound to a targeting ligand, and the most successfully used 89Zr chelator is desferrioxamine B (DFO), which is commercially available as the iron chelator Desferal®. Despite the prevalence of DFO in 89Zr-immuno-PET applications, the development of new ligands for this radiometal is an active area of research. This review focuses on recent advances in zirconium-89 chelation chemistry and will highlight the rapidly expanding ligand classes that are under investigation as DFO alternatives.
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Affiliation(s)
- Nikunj B Bhatt
- Department of Cancer Biology, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA.
| | - Darpan N Pandya
- Department of Cancer Biology, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA.
| | - Thaddeus J Wadas
- Department of Cancer Biology, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA.
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13
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Baalmann M, Best M, Wombacher R. Site-Specific Protein Labeling Utilizing Lipoic Acid Ligase (LplA) and Bioorthogonal Inverse Electron Demand Diels-Alder Reaction. Methods Mol Biol 2018; 1728:365-387. [PMID: 29405010 DOI: 10.1007/978-1-4939-7574-7_23] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Here, we describe a two-step protocol for selective protein labeling based on enzyme-mediated peptide labeling utilizing lipoic acid ligase (LplA) and bioorthogonal chemistry. The method can be applied to purified proteins, protein in cell lysates, as well as living cells. In a first step a W37V mutant of the lipoic acid ligase (LplAW37V) from Escherichia coli is utilized to ligate a synthetic chemical handle site-specifically to a lysine residue in a 13 amino acid peptide motif-a short sequence that can be genetically expressed as a fusion with any protein of interest. In a second step, a molecular probe can be attached to the chemical handle in a bioorthogonal Diels-Alder reaction with inverse electron demand (DAinv). This method is a complementary approach to protein labeling using genetic code expansion and circumvents larger protein tags while maintaining label specificity, providing experimental flexibility and straightforwardness.
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Affiliation(s)
- Mathis Baalmann
- Institute of Pharmacy and Molecular Biotechnology, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
| | - Marcel Best
- Institute of Pharmacy and Molecular Biotechnology, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
| | - Richard Wombacher
- Institute of Pharmacy and Molecular Biotechnology, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany.
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14
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Meyer JP, Kozlowski P, Jackson J, Cunanan KM, Adumeau P, Dilling TR, Zeglis BM, Lewis JS. Exploring Structural Parameters for Pretargeting Radioligand Optimization. J Med Chem 2017; 60:8201-8217. [PMID: 28857566 DOI: 10.1021/acs.jmedchem.7b01108] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Pretargeting offers a way to enhance target specificity while reducing off-target radiation dose to healthy tissue during payload delivery. We recently reported the development of an 18F-based pretargeting strategy predicated on the inverse electron demand Diels-Alder reaction as well as the use of this approach to visualize pancreatic tumor tissue in vivo as early as 1 h postinjection. Herein, we report a comprehensive structure: pharmacokinetic relationship study of a library of 25 novel radioligands that aims to identify radiotracers with optimal pharmacokinetic and dosimetric properties. This investigation revealed key relationships between molecular structure and in vivo behavior and produced two lead candidates exhibiting rapid tumor targeting with high target-to-background activity concentration ratios at early time points. We believe this knowledge to be of high value for the design and clinical translation of next-generation pretargeting agents for the diagnosis and treatment of disease.
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Affiliation(s)
- Jan-Philip Meyer
- Department of Radiology, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States
| | - Paul Kozlowski
- Department of Radiology, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States
| | - James Jackson
- Department of Radiology, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States
| | - Kristen M Cunanan
- Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States
| | - Pierre Adumeau
- Department of Chemistry, Hunter College of the City University of New York , New York, New York 10065, United States
| | - Thomas R Dilling
- Department of Radiology, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States
| | - Brian M Zeglis
- Department of Radiology, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.,Department of Chemistry, Hunter College of the City University of New York , New York, New York 10065, United States.,Ph.D. Program in Chemistry, Graduate Center of the City University of New York , New York, New York 10016, United States.,Departments of Radiology and Pharmacology, Weill Cornell Medical College , New York, New York 10065, United States
| | - Jason S Lewis
- Department of Radiology, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.,Program in Molecular Pharmacology, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.,Departments of Radiology and Pharmacology, Weill Cornell Medical College , New York, New York 10065, United States
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15
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Heskamp S, Raavé R, Boerman O, Rijpkema M, Goncalves V, Denat F. 89Zr-Immuno-Positron Emission Tomography in Oncology: State-of-the-Art 89Zr Radiochemistry. Bioconjug Chem 2017; 28:2211-2223. [PMID: 28767228 PMCID: PMC5609224 DOI: 10.1021/acs.bioconjchem.7b00325] [Citation(s) in RCA: 132] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Immuno-positron
emission tomography (immunoPET) with 89Zr-labeled antibodies
has shown great potential in cancer imaging.
It can provide important information about the pharmacokinetics and
tumor-targeting properties of monoclonal antibodies and may help in
anticipating on toxicity. Furthermore, it allows accurate dose planning
for individualized radioimmunotherapy and may aid in patient selection
and early-response monitoring for targeted therapies. The most commonly
used chelator for 89Zr is desferrioxamine (DFO). Preclinical
studies have shown that DFO is not an ideal chelator because the 89Zr–DFO complex is partly unstable in vivo, which results
in the release of 89Zr from the chelator and the subsequent
accumulation of 89Zr in bone. This bone accumulation interferes
with accurate interpretation and quantification of bone uptake on
PET images. Therefore, there is a need for novel chelators that allow
more stable complexation of 89Zr. In this Review, we will
describe the most recent developments in 89Zr radiochemistry,
including novel chelators and site-specific conjugation methods.
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Affiliation(s)
- Sandra Heskamp
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center , Geert Grooteplein-Zuid 10, 6525 HP Nijmegen, The Netherlands
| | - René Raavé
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center , Geert Grooteplein-Zuid 10, 6525 HP Nijmegen, The Netherlands
| | - Otto Boerman
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center , Geert Grooteplein-Zuid 10, 6525 HP Nijmegen, The Netherlands
| | - Mark Rijpkema
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center , Geert Grooteplein-Zuid 10, 6525 HP Nijmegen, The Netherlands
| | - Victor Goncalves
- Institut de Chimie Moléculaire de l'Université de Bourgogne, UMR6302, CNRS, Université Bourgogne Franche-Comté , F-21000 Dijon, France
| | - Franck Denat
- Institut de Chimie Moléculaire de l'Université de Bourgogne, UMR6302, CNRS, Université Bourgogne Franche-Comté , F-21000 Dijon, France
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16
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Pandya DN, Bhatt N, Yuan H, Day CS, Ehrmann BM, Wright M, Bierbach U, Wadas TJ. Zirconium tetraazamacrocycle complexes display extraordinary stability and provide a new strategy for zirconium-89-based radiopharmaceutical development. Chem Sci 2017; 8:2309-2314. [PMID: 28451334 PMCID: PMC5363373 DOI: 10.1039/c6sc04128k] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 12/12/2016] [Indexed: 11/21/2022] Open
Abstract
We report our initial investigations into the use of tetraazamacrocycles as zirconium-89 chelators. We describe the synthesis and complete characterization of several Zr tetraazamacrocycle complexes, and definitively describe the first crystal structure of zirconium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (Zr-DOTA) using single crystal X-ray diffraction analysis. After evaluating several radioactive analogs, we found that 89Zr-DOTA is superior to 89Zr-DFO, the only 89Zr-complex to be used clinically in 89Zr-radiopharmaceutical applications. Finally, we provide a rationale for the unanticipated and extraordinary stability of these complexes in vitro and in vivo. These results may inform the development of safer and more robust immuno-PET agents for precision medicine applications.
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Affiliation(s)
- Darpan N Pandya
- Department of Cancer Biology , Wake Forest School of Medicine , Winston-Salem , NC 27157 , USA . ;
| | - Nikunj Bhatt
- Department of Cancer Biology , Wake Forest School of Medicine , Winston-Salem , NC 27157 , USA . ;
| | - Hong Yuan
- Department of Radiology , University of North Carolina at Chapel Hill , Chapel Hill , NC 27599 , USA
| | - Cynthia S Day
- Department of Chemistry , Wake Forest University , Winston-Salem , NC 27109 , USA
| | - Brandie M Ehrmann
- Department of Chemistry , University of North Carolina at Chapel Hill , Chapel Hill , NC 27599 , USA
| | - Marcus Wright
- Department of Chemistry , Wake Forest University , Winston-Salem , NC 27109 , USA
| | - Ulrich Bierbach
- Department of Chemistry , Wake Forest University , Winston-Salem , NC 27109 , USA
| | - Thaddeus J Wadas
- Department of Cancer Biology , Wake Forest School of Medicine , Winston-Salem , NC 27157 , USA . ;
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17
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Wang M, Svatunek D, Rohlfing K, Liu Y, Wang H, Giglio B, Yuan H, Wu Z, Li Z, Fox J. Conformationally Strained trans-Cyclooctene (sTCO) Enables the Rapid Construction of (18)F-PET Probes via Tetrazine Ligation. Theranostics 2016; 6:887-95. [PMID: 27162558 PMCID: PMC4860896 DOI: 10.7150/thno.14742] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 03/10/2016] [Indexed: 11/27/2022] Open
Abstract
The bioorthogonal reaction between tetrazines and trans-cyclooctenes is a method for the rapid construction of F-18 probes for PET imaging. Described here is a second generation 18F-labeling system based on a conformationally strained trans-cyclooctene (sTCO)—a dienophile that is approximately 2 orders of magnitude more reactive than conventional TCO dienophiles. Starting from a readily prepared tosylate precursor, an 18F labeled sTCO derivative (18F-sTCO) could be synthesized in 29.3 +/- 5.1% isolated yield and with high specific activity. Tetrazine ligation was carried out with a cyclic RGD-conjugate of a diphenyl-s-tetrazine analogue (RGD-Tz) chosen from a diene class with an excellent combination of fast reactivity and stability both for the diene as well as the Diels-Alder adduct. For both the tetrazine and the sTCO, mini-PEG spacers were included to enhance solubility and improve the in vivo distribution profile of the resulting probe. Extremely fast reactivity (up to 2.86 x 105 M-1s-1 at 25 °C in water) has been observed in kinetic studies in the reaction of sTCO with diphenyl-s-tetrazine derivatives. A kinetic study on sTCO diastereomers in 55:45 MeOH:water showed that the syn-diastereomer displayed slightly faster reactivity than the anti-diastereomer. An 18F-sTCO conjugate with RGD-Tz demonstrated prominent and persistent tumor uptake in vivo with good tumor-to-background contrast. Unlike most radiolabeled RGD peptides, the tumor uptake of this PET agent increased from 5.3 +/- 0.2% ID/g at 1 h post injection (p.i.), to 8.9 +/- 0.5% ID/g at 4 h p.i., providing evidence for prolonged blood circulation. These findings suggest that tetrazine ligations employing 18F-sTCO should serve as a powerful and general platform for the rapid construction of peptide or protein derived PET agents.
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18
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Meyer JP, Houghton J, Kozlowski P, Abdel-Atti D, Reiner T, Pillarsetty NVK, Scholz WW, Zeglis BM, Lewis JS. (18)F-Based Pretargeted PET Imaging Based on Bioorthogonal Diels-Alder Click Chemistry. Bioconjug Chem 2016; 27:298-301. [PMID: 26479967 PMCID: PMC4759614 DOI: 10.1021/acs.bioconjchem.5b00504] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 10/16/2015] [Indexed: 01/03/2023]
Abstract
A first-of-its-kind (18)F pretargeted PET imaging approach based on the bioorthogonal inverse electron demand Diels-Alder (IEDDA) reaction between tetrazine (Tz) and trans-cyclooctene (TCO) is presented. As proof-of-principle, a TCO-bearing immunoconjugate of the anti-CA19.9 antibody 5B1 and an Al[(18)F]NOTA-labeled tetrazine radioligand were harnessed for the visualization of CA19.9-expressing BxPC3 pancreatic cancer xenografts. Biodistribution and (18)F-PET imaging data clearly demonstrate that this methodology effectively delineates tumor mass with activity concentrations up to 6.4 %ID/g at 4 h after injection of the radioligand.
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Affiliation(s)
- Jan-Philip Meyer
- Department
of Radiology, Memorial Sloan Kettering Cancer
Center, 1275 York Avenue, New York, New York 10065, United States
| | - Jacob
L. Houghton
- Department
of Radiology, Memorial Sloan Kettering Cancer
Center, 1275 York Avenue, New York, New York 10065, United States
| | - Paul Kozlowski
- Department
of Radiology, Memorial Sloan Kettering Cancer
Center, 1275 York Avenue, New York, New York 10065, United States
| | - Dalya Abdel-Atti
- Department
of Radiology, Memorial Sloan Kettering Cancer
Center, 1275 York Avenue, New York, New York 10065, United States
| | - Thomas Reiner
- Department
of Radiology, Memorial Sloan Kettering Cancer
Center, 1275 York Avenue, New York, New York 10065, United States
| | - Naga Vara Kishore Pillarsetty
- Department
of Radiology, Memorial Sloan Kettering Cancer
Center, 1275 York Avenue, New York, New York 10065, United States
| | - Wolfgang W. Scholz
- MabVax
Therapeutics, 11588 Sorrento
Valley Road Suite 20, San Diego, California 92121, United States
| | - Brian M. Zeglis
- Department
of Chemistry, Hunter College of the City
University of New York, 695 Park Avenue, New York, New York 10065, United
States
- The
Graduate Center, City University of New York, 365 Fifth Avenue, New York, New York 10016, United States
| | - Jason S. Lewis
- Department
of Radiology, Memorial Sloan Kettering Cancer
Center, 1275 York Avenue, New York, New York 10065, United States
- Molecular
Pharmacology Program, Memorial Sloan Kettering
Cancer Center, 1275 York
Avenue, New York, New York 10065, United States
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19
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Pagel M, Meier R, Braun K, Wiessler M, Beck-Sickinger AG. On-resin Diels–Alder reaction with inverse electron demand: an efficient ligation method for complex peptides with a varying spacer to optimize cell adhesion. Org Biomol Chem 2016; 14:4809-16. [DOI: 10.1039/c6ob00314a] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The DARinvon resin is a new orthogonal reaction in peptide synthesis and the benefits for cell adhesion are discussed.
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Affiliation(s)
- Mareen Pagel
- Institute of Biochemistry
- Faculty of Biosciences
- Pharmacy and Psychology
- Leipzig
- Germany
| | - René Meier
- Institute of Biochemistry
- Faculty of Biosciences
- Pharmacy and Psychology
- Leipzig
- Germany
| | - Klaus Braun
- Deutsches Krebsforschungszentrum
- 69120 Heidelberg
- Germany
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20
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Zeglis BM, Brand C, Abdel-Atti D, Carnazza KE, Cook BE, Carlin S, Reiner T, Lewis JS. Optimization of a Pretargeted Strategy for the PET Imaging of Colorectal Carcinoma via the Modulation of Radioligand Pharmacokinetics. Mol Pharm 2015; 12:3575-87. [PMID: 26287993 PMCID: PMC4696756 DOI: 10.1021/acs.molpharmaceut.5b00294] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Pretargeted PET imaging has emerged as an effective strategy for merging the exquisite selectivity of antibody-based targeting vectors with the rapid pharmacokinetics of radiolabeled small molecules. We previously reported the development of a strategy for the pretargeted PET imaging of colorectal cancer based on the bioorthogonal inverse electron demand Diels-Alder reaction between a tetrazine-bearing radioligand and a transcyclooctene-modified huA33 immunoconjugate. Although this method effectively delineated tumor tissue, its clinical potential was limited by the somewhat sluggish clearance of the radioligand through the gastrointestinal tract. Herein, we report the development and in vivo validation of a pretargeted strategy for the PET imaging of colorectal carcinoma with dramatically improved pharmacokinetics. Two novel tetrazine constructs, Tz-PEG7-NOTA and Tz-SarAr, were synthesized, characterized, and radiolabeled with (64)Cu in high yield (>90%) and radiochemical purity (>99%). PET imaging and biodistribution experiments in healthy mice revealed that although (64)Cu-Tz-PEG7-NOTA is cleared via both the gastrointestinal and urinary tracts, (64)Cu-Tz-SarAr is rapidly excreted by the renal system alone. On this basis, (64)Cu-Tz-SarAr was selected for further in vivo evaluation. To this end, mice bearing A33 antigen-expressing SW1222 human colorectal carcinoma xenografts were administered huA33-TCO, and the immunoconjugate was given 24 h to accumulate at the tumor and clear from the blood, after which (64)Cu-Tz-SarAr was administered via intravenous tail vein injection. PET imaging and biodistribution experiments revealed specific uptake of the radiotracer in the tumor at early time points (5.6 ± 0.7 %ID/g at 1 h p.i.), high tumor-to-background activity ratios, and rapid elimination of unclicked radioligand. Importantly, experiments with longer antibody accumulation intervals (48 and 120 h) yielded slight decreases in tumoral uptake but also concomitant increases in tumor-to-blood activity concentration ratios. This new strategy offers dosimetric benefits as well, yielding a total effective dose of 0.041 rem/mCi, far below the doses produced by directly labeled (64)Cu-NOTA-huA33 (0.133 rem/mCi) and (89)Zr-DFO-huA33 (1.54 rem/mCi). Ultimately, this pretargeted PET imaging strategy boasts a dramatically improved pharmacokinetic profile compared to our first generation system and is capable of clearly delineating tumor tissue with high image contrast at only a fraction of the radiation dose created by directly labeled radioimmunoconjugates.
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Affiliation(s)
- Brian M. Zeglis
- Department of Chemistry and Biochemistry, Hunter College and the Graduate Center of the City University of New York, New York, New York 10021, United States
| | - Christian Brand
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Dalya Abdel-Atti
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Kathryn E. Carnazza
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Brendon E. Cook
- Department of Chemistry and Biochemistry, Hunter College and the Graduate Center of the City University of New York, New York, New York 10021, United States
| | - Sean Carlin
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Thomas Reiner
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
| | - Jason S. Lewis
- Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
- Program in Molecular Pharmacology and Chemistry, Memorial Sloan Kettering Cancer Center, New York, New York 10065, United States
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21
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Hörner S, Uth C, Avrutina O, Frauendorf H, Wiessler M, Kolmar H. Combination of inverse electron-demand Diels–Alder reaction with highly efficient oxime ligation expands the toolbox of site-selective peptide conjugations. Chem Commun (Camb) 2015; 51:11130-3. [DOI: 10.1039/c5cc03434e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A modular bioconjugation strategy based on stepwise oxime ligation and inverse electron-demand Diels–Alder reaction.
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Affiliation(s)
- S. Hörner
- Technische Universität Darmstadt
- Clemens-Schöpf-Institut für Organische Chemie und Biochemie
- 64287 Darmstadt
- Germany
| | - C. Uth
- Technische Universität Darmstadt
- Clemens-Schöpf-Institut für Organische Chemie und Biochemie
- 64287 Darmstadt
- Germany
| | - O. Avrutina
- Technische Universität Darmstadt
- Clemens-Schöpf-Institut für Organische Chemie und Biochemie
- 64287 Darmstadt
- Germany
| | - H. Frauendorf
- Georg-August-Universität Göttingen
- Institut für Organische und Biomolekulare Chemie
- Zentrale Analytik/Massenspektrometrie
- 37077 Göttingen
- Germany
| | - M. Wiessler
- Deutsches Krebsforschungszentrum
- Medizinische Physik in der Radiologie
- 69120 Heidelberg
- Germany
| | - H. Kolmar
- Technische Universität Darmstadt
- Clemens-Schöpf-Institut für Organische Chemie und Biochemie
- 64287 Darmstadt
- Germany
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