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Kingston RL, Millane RP. A general method for directly phasing diffraction data from high-solvent-content protein crystals. IUCRJ 2022; 9:648-665. [PMID: 36071801 PMCID: PMC9438493 DOI: 10.1107/s2052252522006996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 07/08/2022] [Indexed: 06/15/2023]
Abstract
A procedure is described for direct phase determination in protein crystallography, applicable to crystals with high solvent content. The procedure requires only the diffraction data and an estimate of the solvent content as input. Direct phase determination is treated as a constraint satisfaction problem, in which an image is sought that is consistent with both the diffraction data and generic constraints on the density distribution in the crystal. The problem is solved using an iterative projection algorithm, the Difference Map algorithm, which has good global convergence properties, and can locate the correct solution without any initial phase information. Computational efficiency is improved by breaking the problem down into two stages; initial approximation of the molecular envelope at low resolution, followed by subsequent phase determination using all of the data. The molecular envelope is continually updated during the phase determination step. At both stages, the algorithm is initiated with many different and random phase sets, which are evolved subject to the constraints. A clustering procedure is used to identify consistent results across multiple runs, which are then averaged to generate consensus envelopes or phase sets. The emergence of highly consistent phase sets is diagnostic of success. The effectiveness of the procedure is demonstrated by application to 42 known structures of solvent fraction 0.60-0.85. The procedure works robustly at intermediate resolutions (1.9-3.5 Å) but is strongly dependent on crystal solvent content, only working routinely with solvent fractions greater than 0.70.
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Affiliation(s)
- Richard Lawrence Kingston
- School of Biological Sciences, University of Auckland, 3a Symonds St, Auckland City, Auckland 1010, New Zealand
| | - Rick P. Millane
- Computational Imaging Group, Department of Electrical and Computer Engineering, University of Canterbury, Christchurch, New Zealand
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2
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Valente M, Timm J, Castillo-Acosta VM, Ruiz-Pérez LM, Balzarini T, Nettleship JE, Bird LE, Rada H, Wilson KS, González-Pacanowska D. Cell cycle regulation and novel structural features of thymidine kinase, an essential enzyme in Trypanosoma brucei. Mol Microbiol 2016; 102:365-385. [PMID: 27426054 DOI: 10.1111/mmi.13467] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/17/2016] [Indexed: 11/28/2022]
Abstract
Thymidine kinase (TK) is a key enzyme in the pyrimidine salvage pathway which catalyzes the transfer of the γ-phosphate of ATP to 2'-deoxythymidine (dThd) forming thymidine monophosphate (dTMP). Unlike other type II TKs, the Trypanosoma brucei enzyme (TbTK) is a tandem protein with two TK homolog domains of which only the C-terminal one is active. In this study, we establish that TbTK is essential for parasite viability and cell cycle progression, independently of extracellular pyrimidine concentrations. We show that expression of TbTK is cell cycle regulated and that depletion of TbTK leads to strongly diminished dTTP pools and DNA damage indicating intracellular dThd to be an essential intermediate metabolite for the synthesis of thymine-derived nucleotides. In addition, we report the X-ray structure of the catalytically active domain of TbTK in complex with dThd and dTMP at resolutions up to 2.2 Å. In spite of the high conservation of the active site residues, the structures reveal a widened active site cavity near the nucleobase moiety compared to the human enzyme. Our findings strongly support TbTK as a crucial enzyme in dTTP homeostasis and identify structural differences within the active site that could be exploited in the process of rational drug design.
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Affiliation(s)
- Maria Valente
- Instituto de Parasitología y Biomedicina "López-Neyra", Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Jennifer Timm
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, YO10 5DD, UK
| | - Víctor M Castillo-Acosta
- Instituto de Parasitología y Biomedicina "López-Neyra", Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Luis M Ruiz-Pérez
- Instituto de Parasitología y Biomedicina "López-Neyra", Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Tom Balzarini
- Instituto de Parasitología y Biomedicina "López-Neyra", Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Joanne E Nettleship
- The Oxford Protein Production Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, R92 Harwell, Didcot, Oxfordshire, OX11 0FA, UK
| | - Louise E Bird
- The Oxford Protein Production Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, R92 Harwell, Didcot, Oxfordshire, OX11 0FA, UK
| | - Heather Rada
- The Oxford Protein Production Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, R92 Harwell, Didcot, Oxfordshire, OX11 0FA, UK
| | - Keith S Wilson
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, YO10 5DD, UK.
| | - Dolores González-Pacanowska
- Instituto de Parasitología y Biomedicina "López-Neyra", Consejo Superior de Investigaciones Científicas, Granada, Spain.
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3
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Agarwal HK, Khalil A, Ishita K, Yang W, Nakkula RJ, Wu LC, Ali T, Tiwari R, Byun Y, Barth RF, Tjarks W. Synthesis and evaluation of thymidine kinase 1-targeting carboranyl pyrimidine nucleoside analogs for boron neutron capture therapy of cancer. Eur J Med Chem 2015; 100:197-209. [PMID: 26087030 DOI: 10.1016/j.ejmech.2015.05.042] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 05/24/2015] [Accepted: 05/26/2015] [Indexed: 10/23/2022]
Abstract
A library of sixteen 2nd generation amino- and amido-substituted carboranyl pyrimidine nucleoside analogs, designed as substrates and inhibitors of thymidine kinase 1 (TK1) for potential use in boron neutron capture therapy (BNCT) of cancer, was synthesized and evaluated in enzyme kinetic-, enzyme inhibition-, metabolomic-, and biodistribution studies. One of these 2nd generation carboranyl pyrimidine nucleoside analogs (YB18A [3]), having an amino group directly attached to a meta-carborane cage tethered via ethylene spacer to the 3-position of thymidine, was approximately 3-4 times superior as a substrate and inhibitor of hTK1 than N5-2OH (2), a 1st generation carboranyl pyrimidine nucleoside analog. Both 2 and 3 appeared to be 5'-monophosphorylated in TK1(+) RG2 cells, both in vitro and in vivo. Biodistribution studies in rats bearing intracerebral RG2 glioma resulted in selective tumor uptake of 3 with an intratumoral concentration that was approximately 4 times higher than that of 2. The obtained results significantly advance the understanding of the binding interactions between TK1 and carboranyl pyrimidine nucleoside analogs and will profoundly impact future design strategies for these agents.
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Affiliation(s)
- Hitesh K Agarwal
- Division of Medicinal Chemistry & Pharmacognosy, The Ohio State University, Columbus, OH, USA
| | - Ahmed Khalil
- Division of Medicinal Chemistry & Pharmacognosy, The Ohio State University, Columbus, OH, USA
| | - Keisuke Ishita
- Division of Medicinal Chemistry & Pharmacognosy, The Ohio State University, Columbus, OH, USA
| | - Weilian Yang
- Department of Pathology, The Ohio State University, Columbus, OH, USA
| | - Robin J Nakkula
- Department of Pathology, The Ohio State University, Columbus, OH, USA
| | - Lai-Chu Wu
- Department of Internal Medicine, The Ohio State University, Columbus, OH, USA
| | - Tehane Ali
- Division of Medicinal Chemistry & Pharmacognosy, The Ohio State University, Columbus, OH, USA
| | - Rohit Tiwari
- Division of Medicinal Chemistry & Pharmacognosy, The Ohio State University, Columbus, OH, USA
| | - Youngjoo Byun
- College of Pharmacy, Korea University, Sejong, Republic of Korea
| | - Rolf F Barth
- Department of Pathology, The Ohio State University, Columbus, OH, USA
| | - Werner Tjarks
- Division of Medicinal Chemistry & Pharmacognosy, The Ohio State University, Columbus, OH, USA.
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4
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Structural and Kinetic Characterization of Thymidine Kinase from Leishmania major. PLoS Negl Trop Dis 2015; 9:e0003781. [PMID: 25978379 PMCID: PMC4433323 DOI: 10.1371/journal.pntd.0003781] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 04/23/2015] [Indexed: 01/17/2023] Open
Abstract
Leishmania spp. is a protozoan parasite and the causative agent of leishmaniasis. Thymidine kinase (TK) catalyses the transfer of the γ-phosphate of ATP to 2’-deoxythymidine (dThd) forming thymidine monophosphate (dTMP). L. major Type II TK (LmTK) has been previously shown to be important for infectivity of the parasite and therefore has potential as a drug target for anti-leishmanial therapy. In this study, we determined the enzymatic properties and the 3D structures of holo forms of the enzyme. LmTK efficiently phosphorylates dThd and dUrd and has high structural homology to TKs from other species. However, it significantly differs in its kinetic properties from Trypanosoma brucei TK since purines are not substrates of the enzyme and dNTPs such as dUTP inhibit LmTK. The enzyme had Km and kcat values for dThd of 1.1 μM and 2.62 s-1 and exhibits cooperative binding for ATP. Additionally, we show that the anti-retroviral prodrug zidovudine (3-azido-3-deoxythymidine, AZT) and 5’-modified dUrd can be readily phosphorylated by LmTK. The production of recombinant enzyme at a level suitable for structural studies was achieved by the construction of C-terminal truncated versions of the enzyme and the use of a baculoviral expression system. The structures of the catalytic core of LmTK in complex with dThd, the negative feedback regulator dTTP and the bi-substrate analogue AP5dT, were determined to 2.74, 3.00 and 2.40 Å, respectively, and provide the structural basis for exclusion of purines and dNTP inhibition. The results will aid the process of rational drug design with LmTK as a potential target for anti-leishmanial drugs. The DNA within the genome of an organism encodes all the information, firstly for reproduction and secondly for translation into proteins—the workhorses of a biological cell. Proteins carry out a host of essential biological activities within the cell. A full understanding of a protein now requires determination of a wide range of its properties in solution in the cell and in vitro in solution, but in addition, its 3D structure usually determined by X-ray crystallography. Leishmania species are a family of protozoan parasites of humans and the causative agent of leishmaniasis, a major health concern in the developing world. Selective inhibition of key enzymes in these parasites is a key route for combating these diseases. We have focused our work on thymidine kinase, an important enzyme from Leishmania major, and a potential target for the development of new drugs. We have carried out kinetic studies of the enzyme’s activity in solution and determined its 3D crystal structure, enabling rational drug design.
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Slot Christiansen L, Munch-Petersen B, Knecht W. Non-Viral Deoxyribonucleoside Kinases--Diversity and Practical Use. J Genet Genomics 2015; 42:235-48. [PMID: 26059771 DOI: 10.1016/j.jgg.2015.01.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 01/04/2015] [Accepted: 01/05/2015] [Indexed: 12/30/2022]
Abstract
Deoxyribonucleoside kinases (dNKs) phosphorylate deoxyribonucleosides to their corresponding monophosphate compounds. dNks also phosphorylate deoxyribonucleoside analogues that are used in the treatment of cancer or viral infections. The study of the mammalian dNKs has therefore always been of great medical interest. However, during the last 20 years, research on dNKs has gone into non-mammalian organisms. In this review, we focus on non-viral dNKs, in particular their diversity and their practical applications. The diversity of this enzyme family in different organisms has proven to be valuable in studying the evolution of enzymes. Some of these newly discovered enzymes have been useful in numerous practical applications in medicine and biotechnology, and have contributed to our understanding of the structural basis of nucleoside and nucleoside analogue activation.
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Affiliation(s)
| | - Birgitte Munch-Petersen
- Department of Biology, Lund University, Lund 22362, Sweden; Department of Science, Systems and Models, Roskilde University, Roskilde 4000, Denmark
| | - Wolfgang Knecht
- Department of Biology, Lund University, Lund 22362, Sweden; Lund Protein Production Platform, Lund University, Lund 22362, Sweden.
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Abstract
The compound class of 3-carboranyl thymidine analogues (3CTAs) are boron delivery agents for boron neutron capture therapy (BNCT), a binary treatment modality for cancer. Presumably, these compounds accumulate selectively in tumor cells via intracellular trapping, which is mediated by hTK1. Favorable in vivo biodistribution profiles of 3CTAs led to promising results in preclinical BNCT of rats with intracerebral brain tumors. This review presents an overview on the design, synthesis, and biological evaluation of first- and second-generation 3CTAs. Boronated nucleosides developed prior to 3CTAs for BNCT and non-boronated N3-substituted thymidine conjugates for other areas of cancer therapy and imaging are also described. In addition, basic features of carborane clusters, which are used as boron moieties in the design and synthesis of 3CTAs, and the biological and structural features of TK1-like enzymes, which are the molecular targets of 3CTAs, are discussed.
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Agarwal HK, McElroy CA, Sjuvarsson E, Eriksson S, Darby MV, Tjarks W. Synthesis of N3-substituted carboranyl thymidine bioconjugates and their evaluation as substrates of recombinant human thymidine kinase 1. Eur J Med Chem 2012; 60:456-68. [PMID: 23318906 DOI: 10.1016/j.ejmech.2012.11.041] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 11/23/2012] [Accepted: 11/29/2012] [Indexed: 01/19/2023]
Abstract
Four different libraries of overall twenty three N3-substituted thymidine (dThd) analogues, including eleven 3-carboranyl thymidine analogues (3CTAs), were synthesized. The latter are potential agents for Boron Neutron Capture Therapy (BNCT) of cancer. Linker between the dThd scaffold and the m-carborane cluster at the N3-position of the 3CTAs contained amidinyl-(3e and 3f), guanidyl-(7e-7g), tetrazolylmethyl-(9b1/2-9d1/2), or tetrazolyl groups (11b1/2-11d1/2) to improve human thymidine kinase 1 (hTK1) substrate characteristics and water solubilities compared with 1st generation 3CTAs, such as N5 and N5-2OH. The amidinyl- and guanidyl-type N3-substitued dThd analogues (3a-3f and 7a-7g) had hTK1 phosphorylation rates of <30% relative to that of dThd, the endogenous hTK1 substrate, whereas the tetrazolyl-type N3-substitued dThd analogues (9a, 9b1/2-9d1/2 and 11a, 11b1/2-11d1/2) had relative phosphorylation rates (rPRs) of >40%. Compounds 9a, 9b1/2-9d1/2 and 11a, 11b1/2-11d1/2 were subjected to in-depth enzyme kinetics studies and the obtained rk(cat)/K(m) (k(cat)/K(m) relative to that of dThd) ranged from 2.5 to 26%. The tetrazolyl-type N3-substitued dThd analogues 9b1/2 and 11d1/2 were the best substrates of hTK1 with rPRs of 52.4% and 42.5% and rk(cat)/K(m) values of 14.9% and 19.7% respectively. In comparison, the rPR and rk(cat)/K(m) values of N5-2OH in this specific study were 41.5% and 10.8%, respectively. Compounds 3e and 3f were >1900 and >1500 times, respectively, better soluble in PBS (pH 7.4) than N5-2OH whereas solubilities for 9b1/2-9d1/2 and 11b1/2-11d1/2 were only 1.3-13 times better.
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Affiliation(s)
- Hitesh K Agarwal
- Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA.
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Zander J, Hartenfeller M, Hähnke V, Proschak E, Besier S, Wichelhaus T, Schneider G. Multistep Virtual Screening for Rapid and Efficient Identification of Non-Nucleoside Bacterial Thymidine Kinase Inhibitors. Chemistry 2010; 16:9630-7. [DOI: 10.1002/chem.201001347] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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9
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Desbouis D, Struthers H, Spiwok V, Küster T, Schibli R. Synthesis, In Vitro, and In Silico Evaluation of Organometallic Technetium and Rhenium Thymidine Complexes with Retained Substrate Activity toward Human Thymidine Kinase Type 1. J Med Chem 2008; 51:6689-98. [PMID: 18837546 DOI: 10.1021/jm800530p] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dominique Desbouis
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland, Center for Radiopharmaceutical Science, ETH-PSI-USZ, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland, Department of Structure and Function of Saccharides, Institute of Chemistry, Slovak Academy of Sciences, Dubravska Cesta 9, 84538 Bratislava, Slovak Republic
| | - Harriet Struthers
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland, Center for Radiopharmaceutical Science, ETH-PSI-USZ, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland, Department of Structure and Function of Saccharides, Institute of Chemistry, Slovak Academy of Sciences, Dubravska Cesta 9, 84538 Bratislava, Slovak Republic
| | - Vojtech Spiwok
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland, Center for Radiopharmaceutical Science, ETH-PSI-USZ, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland, Department of Structure and Function of Saccharides, Institute of Chemistry, Slovak Academy of Sciences, Dubravska Cesta 9, 84538 Bratislava, Slovak Republic
| | - Tatiana Küster
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland, Center for Radiopharmaceutical Science, ETH-PSI-USZ, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland, Department of Structure and Function of Saccharides, Institute of Chemistry, Slovak Academy of Sciences, Dubravska Cesta 9, 84538 Bratislava, Slovak Republic
| | - Roger Schibli
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland, Center for Radiopharmaceutical Science, ETH-PSI-USZ, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland, Department of Structure and Function of Saccharides, Institute of Chemistry, Slovak Academy of Sciences, Dubravska Cesta 9, 84538 Bratislava, Slovak Republic
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Quaternary structure change as a mechanism for the regulation of thymidine kinase 1-like enzymes. Structure 2008; 15:1555-66. [PMID: 18073106 DOI: 10.1016/j.str.2007.09.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Revised: 09/18/2007] [Accepted: 09/19/2007] [Indexed: 11/21/2022]
Abstract
The human cytosolic thymidine kinase (TK) and structurally related TKs in prokaryotes play a crucial role in the synthesis and regulation of the cellular thymidine triphosphate pool. We report the crystal structures of the TK homotetramer from Thermotoga maritima in four different states: its apo-form, a binary complex with thymidine, as well as the ternary structures with the two substrates (thymidine/AppNHp) and the reaction products (TMP/ADP). In combination with fluorescence spectroscopy and mutagenesis experiments, our results demonstrate that ATP binding is linked to a substantial reorganization of the enzyme quaternary structure, leading to a transition from a closed, inactive conformation to an open, catalytic state. We hypothesize that these structural changes are relevant to enzyme function in situ as part of the catalytic cycle and serve an important role in regulating enzyme activity by amplifying the effects of feedback inhibitor binding.
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Lutz S, Lichter J, Liu L. Exploiting temperature-dependent substrate promiscuity for nucleoside analogue activation by thymidine kinase from Thermotoga maritima. J Am Chem Soc 2007; 129:8714-5. [PMID: 17592850 PMCID: PMC2085358 DOI: 10.1021/ja0734391] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Stefan Lutz
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, USA.
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12
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Tjarks W, Tiwari R, Byun Y, Narayanasamy S, Barth RF. Carboranyl thymidine analogues for neutron capture therapy. Chem Commun (Camb) 2007:4978-91. [DOI: 10.1039/b707257k] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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