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Wolf S, Domes R, Domes C, Frosch T. Spectrally Resolved and Highly Parallelized Raman Difference Spectroscopy for the Analysis of Drug-Target Interactions between the Antimalarial Drug Chloroquine and Hematin. Anal Chem 2024; 96:3345-3353. [PMID: 38301154 PMCID: PMC10902819 DOI: 10.1021/acs.analchem.3c04231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Abstract
Malaria is a severe disease caused by cytozoic parasites of the genus Plasmodium, which infiltrate and infect red blood cells. Several drugs have been developed to combat the devastating effects of malaria. Antimalarials based on quinolines inhibit the crystallization of hematin into hemozoin within the parasite, ultimately leading to its demise. Despite the frequent use of these agents, there are unanswered questions about their mechanisms of action. In the present study, the quinoline chloroquine and its interaction with the target structure hematin was investigated using an advanced, highly parallelized Raman difference spectroscopy (RDS) setup. Simultaneous recording of the spectra of hematin and chloroquine mixtures with varying compositions enabled the observation of changes in peak heights and positions based on the altered molecular structure resulting from their interaction. A shift of (-1.12 ± 0.05) cm-1 was observed in the core-size marker band ν(CαCm)asym peak position of the 1:1 chloroquine-hematin mixture compared to pure hematin. The oxidation-state marker band ν(pyrrole half-ring)sym exhibited a shift by (+0.93 ± 0.13) cm-1. These results were supported by density functional theory (DFT) calculations, indicating a hydrogen bond between the quinolinyl moiety of chloroquine and the oxygen atom of ferric protoporphyrin IX hydroxide (Fe(III)PPIX-OH). The consequence is a reduced electron density within the porphyrin moiety and an increase in its core size. This hypothesis provided further insights into the mechanism of hemozoin inhibition, suggesting chloroquine binding to the monomeric form of hematin, thereby preventing its further crystallization to hemozoin.
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Affiliation(s)
- Sebastian Wolf
- Leibniz Institute of Photonic Technology, 07745 Jena, Germany
| | - Robert Domes
- Leibniz Institute of Photonic Technology, 07745 Jena, Germany
| | - Christian Domes
- Leibniz Institute of Photonic Technology, 07745 Jena, Germany
| | - Torsten Frosch
- Biophotonics and Biomedical Engineering Group, Technical University Darmstadt, Merckstr. 25, 64283 Darmstadt, Germany
- Leibniz Institute of Photonic Technology, 07745 Jena, Germany
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Abstract
Ferric heme b (= ferric protoporphyrin IX = hemin) is an important prosthetic group of different types of enzymes, including the intensively investigated and widely applied horseradish peroxidase (HRP). In HRP, hemin is present in monomeric form in a hydrophobic pocket containing among other amino acid side chains the two imidazoyl groups of His170 and His42. Both amino acids are important for the peroxidase activity of HRP as an axial ligand of hemin (proximal His170) and as an acid/base catalyst (distal His42). A key feature of the peroxidase mechanism of HRP is the initial formation of compound I under heterolytic cleavage of added hydrogen peroxide as a terminal oxidant. Investigations of free hemin dispersed in aqueous solution showed that different types of hemin dimers can form, depending on the experimental conditions, possibly resulting in hemin crystallization. Although it has been recognized already in the 1970s that hemin aggregation can be prevented in aqueous solution by using micelle-forming amphiphiles, it remains a challenge to prepare hemin-containing micellar and vesicular systems with peroxidase-like activities. Such systems are of interest as cheap HRP-mimicking catalysts for analytical and synthetic applications. Some of the key concepts on which research in this fascinating and interdisciplinary field is based are summarized, along with major accomplishments and possible directions for further improvement. A systematic analysis of the physico-chemical properties of hemin in aqueous micellar solutions and vesicular dispersions must be combined with a reliable evaluation of its catalytic activity. Future studies should show how well the molecular complexity around hemin in HRP can be mimicked by using micelles or vesicles. Because of the importance of heme b in virtually all biological systems and the fact that porphyrins and hemes can be obtained under potentially prebiotic conditions, ideas exist about the possible role of heme-containing micellar and vesicular systems in prebiotic times.
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Márquez I, Olloqui-Sariego JL, Molero M, Andreu R, Roldán E, Calvente JJ. Active Role of the Buffer in the Proton-Coupled Electron Transfer of Immobilized Iron Porphyrins. Inorg Chem 2021; 60:42-54. [PMID: 32568550 DOI: 10.1021/acs.inorgchem.0c01091] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Evaluation of the proton-coupled electron transfer thermodynamics of immobilized hemin is challenging due to the disparity of its electrochemical titration curves reported in the literature. Deviations from the one-electron, one-proton transfer at circumneutral pHs have been commonly ascribed to either the formation of dimeric species or the ionization of a second iron-bound water molecule. Herein, however, we report on non-idealities in the more acidic region, whose onset and extent vary with the nature and concentration of the commonly used phosphate and acetate buffers. It is shown that these deviations originate in the ligand-exchange binding between the oxidized aquo-hemin complex and the anionic components of the buffer, so that they are restricted to the pH interval where these forms coexist. A stepwise approach was developed to quantify unambiguously the apparent and intrinsic binding equilibrium constants. The apparent binding equilibrium constant exhibits a peak-shaped pH dependence, whose maximum is located at approximately the midpoint between the pKa of the iron-bound water and the first pKa of the buffer, and its magnitude is greater for the phosphate than for the acetate buffer. But strikingly, the opposite trend was found for the magnitude of the intrinsic binding equilibrium constants determined from the apparent ones, due to the different relative locations of the phosphoric and acetic pKa values with respect to that of the oxidized aquo-hemin. To probe the role of the heme propionic residues, a similar study was carried out with a propionic-free iron porphyrin containing eight ethyl residues. These substituents decrease the acidity of the iron-bound water, strengthen the iron(III)-acetate binding, weaken the iron(III)-dihydrogen phosphate binding, and enable the binding between iron(III) and monohydrogen phosphate, which was hampered in hemin by the presence of the negatively charged propionate residues. Overall, this work provides a more complete speciation of immobilized iron porphyrins under acidic conditions than previously considered, showing the substitutional lability of the aqua ligand in the oxidized state of the iron center and the reluctance of its hydroxyl counterpart to anion exchange. Knowledge of these redox- and pH-dependent bindings with the buffer components is crucial for a rigorous quantification of the proton-coupled electron transfer and the electrocatalytic activity of iron porphyrins.
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Affiliation(s)
- Inmaculada Márquez
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
| | - José Luis Olloqui-Sariego
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
| | - Miguel Molero
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
| | - Rafael Andreu
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
| | - Emilio Roldán
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
| | - Juan José Calvente
- Departamento de Quı́mica Fı́sica, Universidad de Sevilla, C/Profesor Garcı́a Conzález, 1, 41012 Sevilla, Spain
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Rossier J, Nasiri Sovari S, Pavic A, Vojnovic S, Stringer T, Bättig S, Smith GS, Nikodinovic-Runic J, Zobi F. Antiplasmodial Activity and In Vivo Bio-Distribution of Chloroquine Molecules Released with a 4-(4-Ethynylphenyl)-Triazole Moiety from Organometallo-Cobalamins. Molecules 2019; 24:molecules24122310. [PMID: 31234469 PMCID: PMC6630517 DOI: 10.3390/molecules24122310] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 06/17/2019] [Accepted: 06/19/2019] [Indexed: 01/01/2023] Open
Abstract
We have explored the possibility of using organometallic derivatives of cobalamin as a scaffold for the delivery of the same antimalarial drug to both erythro- and hepatocytes. This hybrid molecule approach, intended as a possible tool for the development of multi-stage antimalarial agents, pivots on the preparation of azide-functionalized drugs which, after coupling to the vitamin, are released with a 4-(4-ethynylphenyl)-triazole functionality. Three chloroquine and one imidazolopiperazine derivative (based on the KAF156 structure) were selected as model drugs. One hybrid chloroquine conjugate was extensively studied via fluorescent labelling for in vitro and in vivo bio-distribution studies and gave proof-of-concept for the design. It showed no toxicity in vivo (zebrafish model) as well as no hepatotoxicity, no cardiotoxicity or developmental toxicity of the embryos. All 4-(4-ethynylphenyl)-triazole derivatives of chloroquine were equally active against chloroquine-resistant (CQR) and chloroquine-sensitive (CQS) Plasmodium falciparum strains.
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Affiliation(s)
- Jeremie Rossier
- Department of Chemistry, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland.
| | - Sara Nasiri Sovari
- Department of Chemistry, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland.
| | - Aleksandar Pavic
- Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444a, 11000 Belgrade, Republic of Serbia.
| | - Sandra Vojnovic
- Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444a, 11000 Belgrade, Republic of Serbia.
| | - Tameryn Stringer
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa.
| | - Sarah Bättig
- Department of Chemistry, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland.
| | - Gregory S Smith
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa.
| | - Jasmina Nikodinovic-Runic
- Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444a, 11000 Belgrade, Republic of Serbia.
| | - Fabio Zobi
- Department of Chemistry, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland.
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Dilanian RA, Streltsov V, Coughlan HD, Quiney HM, Martin AV, Klonis N, Dogovski C, Boutet S, Messerschmidt M, Williams GJ, Williams S, Phillips NW, Nugent KA, Tilley L, Abbey B. Nanocrystallography measurements of early stage synthetic malaria pigment. J Appl Crystallogr 2017; 50:1533-1540. [PMID: 29021736 PMCID: PMC5627683 DOI: 10.1107/s1600576717012663] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 09/04/2017] [Indexed: 11/10/2022] Open
Abstract
The recent availability of extremely intense, femtosecond X-ray free-electron laser (XFEL) sources has spurred the development of serial femtosecond nanocrystallography (SFX). Here, SFX is used to analyze nanoscale crystals of β-hematin, the synthetic form of hemozoin which is a waste by-product of the malaria parasite. This analysis reveals significant differences in β-hematin data collected during SFX and synchrotron crystallography experiments. To interpret these differences two possibilities are considered: structural differences between the nanocrystal and larger crystalline forms of β-hematin, and radiation damage. Simulation studies show that structural inhomogeneity appears at present to provide a better fit to the experimental data. If confirmed, these observations will have implications for designing compounds that inhibit hemozoin formation and suggest that, for some systems at least, additional information may be gained by comparing structures obtained from nanocrystals and macroscopic crystals of the same molecule.
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Affiliation(s)
- Ruben A. Dilanian
- ARC Centre of Excellence in Advanced Molecular Imaging, School of Physics, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | | | - Hannah D. Coughlan
- ARC Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
- CSIRO Manufacturing Flagship, Parkville, Victoria, Australia
| | - Harry M. Quiney
- ARC Centre of Excellence in Advanced Molecular Imaging, School of Physics, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Andrew V. Martin
- ARC Centre of Excellence in Advanced Molecular Imaging, School of Physics, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Nectarios Klonis
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Con Dogovski
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Sébastien Boutet
- LiNAC Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | | | - Garth J. Williams
- Brookhaven National Laboratory, PO Box 5000, Upton, NY 11973-5000, USA
| | - Sophie Williams
- ARC Centre of Excellence in Advanced Molecular Imaging, School of Physics, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Nicholas W. Phillips
- CSIRO, Parkville, Victoria 3052, Australia
- ARC Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
| | - Keith A. Nugent
- ARC Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
| | - Leann Tilley
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Brian Abbey
- ARC Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
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Kuter D, Streltsov V, Davydova N, Venter GA, Naidoo KJ, Egan TJ. Molecular structures and solvation of free monomeric and dimeric ferriheme in aqueous solution: insights from molecular dynamics simulations and extended X-ray absorption fine structure spectroscopy. Inorg Chem 2014; 53:10811-24. [PMID: 25275882 DOI: 10.1021/ic500454d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
CHARMM force field parameters have been developed to model nonprotein bound five-coordinate ferriheme (ferriprotoporphyrin IX) species in aqueous solution. Structures and solvation were determined from molecular dynamics (MD) simulations at 298 K of monomeric [HO-ferriheme](2-), [H2O-ferriheme](-), and [H2O-ferriheme](0); π-π dimeric [(HO-ferriheme)2](4-), [(H2O-ferriheme)(HO-ferriheme)](3-), [(H2O-ferriheme)2](2-), and [(H2O-ferriheme)2](0); and μ-oxo dimeric [μ-(ferriheme)2O](4-). Solvation of monomeric species predominated around the axial ligand, meso-hydrogen atoms of the porphyrin ring (Hmeso), and the unligated face. Existence of π-π ferriheme dimers in aqueous solution was supported by MD calculations where such dimers remained associated over the course of the simulation. Porphyrin rings were essentially coplanar. In these dimers major and minor solvation was observed around the axial ligand and Hmeso positions, respectively. In μ-oxo ferriheme, strong solvation of the unligated face and bridging oxide ligand was observed. The solution structure of the μ-oxo dimer was investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy. The EXAFS spectrum obtained from frozen solution was markedly different from that recorded on dried μ-oxo ferriheme solid. Inclusion of five solvent molecules obtained from spatial distribution functions in the structure generated from MD simulation was required to produce acceptable fits to the EXAFS spectra of the dimer in solution, while the solid was suitably fitted using the crystal structure of μ-oxo ferriheme dimethyl ester which included no solvent molecules.
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Affiliation(s)
- David Kuter
- Scientific Computing Research Unit, †Department of Chemistry, University of Cape Town , Private Bag, Rondebosch 7701, South Africa
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Kuter D, Benjamin SJ, Egan TJ. Multiple spectroscopic and magnetic techniques show that chloroquine induces formation of the μ-oxo dimer of ferriprotoporphyrin IX. J Inorg Biochem 2014; 133:40-9. [PMID: 24480793 DOI: 10.1016/j.jinorgbio.2014.01.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 01/03/2014] [Accepted: 01/07/2014] [Indexed: 11/28/2022]
Abstract
Interaction of the antimalarial chloroquine (CQ) with ferriprotoporphyrin IX, Fe(III)PPIX, was investigated in aqueous solution (pH7.4) and as a precipitate from aqueous medium at pH5.0. In solution, spectrophotometric titrations indicated strong association (logKobs 13.3±0.2) and a Job plot gave a stoichiometry of 1:2 CQ:Fe(III)PPIX. UV-visible absorbance and magnetic circular dichroism spectra of the complex were compared to various Fe(III)PPIX species. Close similarity to the spectra of the μ-oxo dimer, μ-[Fe(III)PPIX]2O, was revealed. The induction of this species by CQ was confirmed by magnetic susceptibility measurements using the Evans NMR method. The observed low-magnetic moment (2.25±0.02 μB) could only be attributed to antiferromagnetically coupled Fe(III) centers. The value was comparable to that of μ-[Fe(III)PPIX]2O (2.0±0.1 μB). In the solid-state, mass spectrometry confirmed the presence of CQ in the complex. Dissolution of this solid in aqueous solution (pH7.4) resulted in a solution with a UV-visible spectrum consistent with the same 1:2 stoichiometry observed in the Job plot. Magnetic susceptibility measurements made on the solid using an Evans balance produced a magnetic moment (2.3±0.1 μB) consistent with that in solution. Diffusion coefficients of CQ and its complex with Fe(III)PPIX were measured in aqueous solution (3.3±0.3 and 0.6±0.2×10(-10) m(2)·s(-1), respectively). The latter was used in conjunction with an empirical relationship between diffusion coefficient and molar volume to estimate the degree of aggregation. The findings suggest the formation of a 2:4 CQ:Fe(III)PPIX complex in aqueous solution at pH7.4.
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Affiliation(s)
- David Kuter
- Department of Chemistry, University of Cape Town, Private Bag, Rondebosch 7701, South Africa
| | - Stefan J Benjamin
- Department of Chemistry, University of Cape Town, Private Bag, Rondebosch 7701, South Africa
| | - Timothy J Egan
- Department of Chemistry, University of Cape Town, Private Bag, Rondebosch 7701, South Africa.
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Klonis N, Creek DJ, Tilley L. Iron and heme metabolism in Plasmodium falciparum and the mechanism of action of artemisinins. Curr Opin Microbiol 2013; 16:722-7. [PMID: 23932203 DOI: 10.1016/j.mib.2013.07.005] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 07/04/2013] [Indexed: 11/17/2022]
Abstract
During the asexual blood stage of its lifecycle, the malaria parasite Plasmodium falciparum grows and multiplies in the hemoglobin-rich environment of the human erythrocyte. Although the parasite has evolved unique strategies to survive in this environment, its interaction with iron represents an Achilles' heel that is exploited by many antimalarial drugs. Recent work has shed new light on how the parasite deals with hemoglobin breakdown products and on the role of iron as a mediator of the action of the antimalarial drug, artemisinin.
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Affiliation(s)
- Nectarios Klonis
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, and ARC Centre of Excellence for Coherent X-ray Science, 30 Flemington Road, University of Melbourne, Parkville, VIC 3010, Australia
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Teguh SC, Klonis N, Duffy S, Lucantoni L, Avery VM, Hutton CA, Baell JB, Tilley L. Novel Conjugated Quinoline–Indoles Compromise Plasmodium falciparum Mitochondrial Function and Show Promising Antimalarial Activity. J Med Chem 2013; 56:6200-15. [DOI: 10.1021/jm400656s] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | - Sandra Duffy
- Eskitis Institute for Drug Discovery, Brisbane Innovation Park, Griffith University,
Nathan QLD 4111, Australia
| | - Leonardo Lucantoni
- Eskitis Institute for Drug Discovery, Brisbane Innovation Park, Griffith University,
Nathan QLD 4111, Australia
| | - Vicky M. Avery
- Eskitis Institute for Drug Discovery, Brisbane Innovation Park, Griffith University,
Nathan QLD 4111, Australia
| | | | - Jonathan B. Baell
- Medicinal
Chemistry, Monash Institute of Pharmaceutical Science, Parkville
VIC 3052, Australia
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Kuter D, Venter GA, Naidoo KJ, Egan TJ. Experimental and time-dependent density functional theory characterization of the UV-visible spectra of monomeric and μ-oxo dimeric ferriprotoporphyrin IX. Inorg Chem 2012; 51:10233-50. [PMID: 22963249 DOI: 10.1021/ic301154e] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Speciation of ferriprotoporphyrin IX, Fe(III)PPIX, in aqueous solution is complex. Despite the use of its characteristic spectroscopic features for identification, the theoretical basis of the unique UV-visible absorbance spectrum of μ-[Fe(III)PPIX](2)O has not been explored. To investigate this and to establish a structural and spectroscopic model for Fe(III)PPIX species, density functional theory (DFT) calculations were undertaken for H(2)O-Fe(III)PPIX and μ-[Fe(III)PPIX](2)O. The models agreed with related Fe(III)porphyrin crystal structures and reproduced vibrational spectra well. The UV-visible absorbance spectra of H(2)O-Fe(III)PPIX and μ-[Fe(III)PPIX](2)O were calculated using time-dependent DFT and reproduced major features of the experimental spectra of both. Transitions contributing to calculated excitations have been identified. The features of the electronic spectrum calculated for μ-[Fe(III)PPIX](2)O were attributed to delocalization of electron density between the two porphyrin rings of the dimer, the weaker ligand field of the axial ligand, and antiferromagnetic coupling of the Fe(III) centers. Room temperature magnetic circular dichroism (MCD) spectra have been recorded and are shown to be useful in distinguishing between these two Fe(III)PPIX species. Bands underlying major spectroscopic features were identified through simultaneous deconvolution of UV-visible and MCD spectra. Computed UV-visible spectra were compared to deconvoluted spectra. Interpretation of the prominent bands of H(2)O-Fe(III)PPIX largely conforms to previous literature. Owing to the weak paramagnetism of μ-[Fe(III)PPIX](2)O at room temperature and the larger number of underlying excitations, interpretation of its experimental UV-visible spectrum was necessarily tentative. Nonetheless, comparison with the calculated spectra of antiferromagnetically coupled and paramagnetic forms of the μ-oxo dimer of Fe(III)porphine suggested that the composition of the Soret band involves a mixture of π→π* and π→d(π) charge transfer transitions. The Q-band and charge transfer bands appear to amalgamate into a mixed low energy envelope consisting of excitations with heavily admixed π→π* and charge transfer transitions.
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Affiliation(s)
- David Kuter
- Department of Chemistry, Department of Chemistry, University of Cape Town, Private Bag, Rondebosch 7701 South Africa
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11
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Blank O, Davioud-Charvet E, Elhabiri M. Interactions of the antimalarial drug methylene blue with methemoglobin and heme targets in Plasmodium falciparum: a physico-biochemical study. Antioxid Redox Signal 2012; 17:544-54. [PMID: 22256987 DOI: 10.1089/ars.2011.4239] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AIMS Resistance of Plasmodium falciparum to drugs has led to renewed interest of redox-active methylene blue (MB) for which no resistance has been reported so far. Moreover, MB displays unique interactions with glutathione reductase (GR). However, the mechanisms of action/interaction with potential targets of MB are yet to be elucidated. Our physico-biochemical study on MB and relevant hematin-containing targets was performed under quasi-physiological conditions. RESULTS The water deprotonation of the Fe(III)protoporphyrin dimer, the major building block of β-hematin, was studied. At pH 6, the predominant dimer possesses water coordinated to both metals. Below pH 6, spontaneous precipitation of β-hematin occurred reminiscent of hemozoin biomineralization at pH 5.0-5.5 in the food vacuole of the malarial parasite. MB also forms dimers (K(Dim)=6800 M(-1)) and firmly binds to hematin in a 2:1 hematin:MB sandwich complex (K(D)=3.16 μM). MB bioactivation catalyzed by GR induces efficient methemoglobin(Fe(III)) [metHb(Fe(III))] reduction to hemoglobin(Fe(II)). The reduction rate, mediated by leucomethylene blue (LMB), was determined (k(metHb)(red)=991 M(-1)·s(-1)) in an assay coupled to the GR/reduced form of nicotinamide adenine dinucleotide phosphate system. INNOVATION AND CONCLUSION Our work provides new insights into the understanding of (i) how MB interacts with hematin-containing targets, (ii) other relevant MB properties in corroboration with the distribution of the three major LMB species as a function of pH, and (iii) how this redox-active cycler induces efficient catalytic reduction of metHb(Fe(III)) to hemoglobin(Fe(II)) mediated by oxidoreductases. These physico-biochemical parameters of MB open promising perspectives for the interpretation of the pharmacology and pathophysiology of malaria and possibly new routes for antimalarial drug development.
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Affiliation(s)
- Olga Blank
- Laboratoire de Chimie Bioorganique et Médicinale, European School of Chemistry, Polymers and Materials (ECPM), University of Strasbourg and Centre National de la Recherche Scientifique, Strasbourg, France
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12
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Interaction of quinoline antimalarial drugs with ferriprotoporphyrin IX, a solid state spectroscopy study. J Inorg Biochem 2011; 105:1662-9. [DOI: 10.1016/j.jinorgbio.2011.08.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 08/05/2011] [Accepted: 08/05/2011] [Indexed: 11/21/2022]
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Alumasa JN, Gorka AP, Casabianca LB, Comstock E, de Dios AC, Roepe PD. The hydroxyl functionality and a rigid proximal N are required for forming a novel non-covalent quinine-heme complex. J Inorg Biochem 2011; 105:467-75. [PMID: 20864177 PMCID: PMC3010338 DOI: 10.1016/j.jinorgbio.2010.08.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 08/17/2010] [Accepted: 08/18/2010] [Indexed: 11/28/2022]
Abstract
Quinoline antimalarial drugs bind both monomeric and dimeric forms of free heme, with distinct preferences depending on the chemical environment. Under biological conditions, chloroquine (CQ) appears to prefer to bind to μ-oxo dimeric heme, while quinine (QN) preferentially binds monomer. To further explore this important distinction, we study three newly synthesized and several commercially available QN analogues lacking various functional groups. We find that removal of the QN hydroxyl lowers heme affinity, hemozoin (Hz) inhibition efficiency, and antiplasmodial activity. Elimination of the rigid quinuclidyl ring has similar effects, but elimination of either the vinyl or methoxy group does not. Replacing the quinuclidyl N with a less rigid tertiary aliphatic N only partially restores activity. To further study these trends, we probe drug-heme interactions via NMR studies with both Fe and Zn protoporphyrin IX (FPIX, ZnPIX) for QN, dehydroxyQN (DHQN), dequinuclidylQN (DQQN), and deamino-dequinuclidylQN (DADQQN). Magnetic susceptibility measurements in the presence of FPIX demonstrate that these compounds differentially perturb FPIX monomer-dimer equilibrium. We also isolate the QN-FPIX complex formed under mild aqueous conditions and analyze it by mass spectrometry, as well as fluorescence, vibrational, and solid-state NMR spectroscopies. The data elucidate key features of QN pharmacology and allow us to propose a refined model for the preferred binding of QN to monomeric FPIX under biologically relevant conditions. With this model in hand, we also propose how QN, CQ, and amodiaquine (AQ) differ in their ability to inhibit Hz formation.
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Affiliation(s)
- John N. Alumasa
- Department of Chemistry, Georgetown University, 37 and O Streets, NW Washington, D.C. 20057
| | - Alexander P. Gorka
- Department of Chemistry, Georgetown University, 37 and O Streets, NW Washington, D.C. 20057
| | | | | | - Angel C. de Dios
- Department of Chemistry, Georgetown University, 37 and O Streets, NW Washington, D.C. 20057
- Center for Infectious Diseases, Georgetown University, 37 and O Streets, NW Washington, D.C. 20057
| | - Paul D. Roepe
- Department of Chemistry, Georgetown University, 37 and O Streets, NW Washington, D.C. 20057
- Department of Biochemistry and Molecular Biology & Cellular Biology, Georgetown University, 37 and O Streets, NW Washington, D.C. 20057
- Center for Infectious Diseases, Georgetown University, 37 and O Streets, NW Washington, D.C. 20057
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Abstract
A wide range of drug transport studies using intact infected red blood cells, isolated malarial parasites, heterologous expression systems, and purified protein, combined with elegant genetic experiments, have suggested that chloroquine transport by the Plasmodium falciparum chloroquine resistance transporter (PfCRT) is a key aspect of the molecular mechanism of quinoline antimalarial drug resistance. However, many questions remain. This short review summarizes data that have led to drug channel versus drug pump hypotheses for PfCRT and suggests ways in which recent contrasting interpretations might be reconciled.
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Affiliation(s)
- Paul D Roepe
- Department of Chemistry, Department of Biochemistry and Cellular and Molecular Biology, Georgetown University, Washington, DC 20057, United States.
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