1
|
Nguyen BX, VandeVen W, MacNeil GA, Zhou W, Paterson AR, Walsby CJ, Chiang L. High-Valent Ni and Cu Complexes of a Tetraanionic Bis(amidateanilido) Ligand. Inorg Chem 2023; 62:15180-15194. [PMID: 37676794 DOI: 10.1021/acs.inorgchem.3c02358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/09/2023]
Abstract
High-valent metal species are often invoked as intermediates during enzymatic and synthetic catalytic cycles. Anionic donors are often required to stabilize such high-valent states by forming strong bonds with the Lewis acidic metal centers while decreasing their oxidation potentials. In this report, we discuss the synthesis of two high-valent metal complexes [ML]+ in which the NiIII and CuIII centers are ligated by a new tetradentate, tetraanionic bis(amidateanilido) ligand. [ML]+, obtained via chemical oxidation of ML, exhibits UV-vis-NIR, EPR, and XANES spectra characteristic of square planar, high-valent MIII species, suggesting the locus of oxidation for both [ML]+ is predominantly metal-based. This is supported by theoretical analyses, which also support the observed visible transitions as ligand-to-metal charge transfer transitions characteristic of square planar, high-valent MIII species. Notably, [ML]+ can also be obtained via O2 oxidation of ML due to its remarkably negative oxidation potentials (CuL/[CuL]+: -1.16 V, NiL/[NiL]+: -1.01 V vs Fc/Fc+ in MeCN). This demonstrates the exceptionally strong donating nature of the tetraanionic bis(amidateanilido) ligation and its ability to stabilize high-valent metal centers..
Collapse
Affiliation(s)
- Bach X Nguyen
- Department of Chemistry, University of the Fraser Valley, Abbotsford, British Columbia V2S 7M8, Canada
- Department of Chemistry, Simon Fraser University, Burnaby, British Columba V5A 1S6, Canada
| | - Warren VandeVen
- Department of Chemistry, Simon Fraser University, Burnaby, British Columba V5A 1S6, Canada
| | - Gregory A MacNeil
- Department of Chemistry, Simon Fraser University, Burnaby, British Columba V5A 1S6, Canada
| | - Wen Zhou
- Department of Chemistry, Simon Fraser University, Burnaby, British Columba V5A 1S6, Canada
| | - Alisa R Paterson
- Canadian Light Source, 44 Innovation Boulevard, Saskatoon, Saskatchewan S7N 2 V3, Canada
| | - Charles J Walsby
- Department of Chemistry, Simon Fraser University, Burnaby, British Columba V5A 1S6, Canada
| | - Linus Chiang
- Department of Chemistry, University of the Fraser Valley, Abbotsford, British Columbia V2S 7M8, Canada
| |
Collapse
|
2
|
Gibbs C, Fedoretz-Maxwell BP, MacNeil GA, Walsby CJ, Warren JJ. Proximal Methionine Amino Acid Residue Affects the Properties of Redox-Active Tryptophan in an Artificial Model Protein. ACS Omega 2023; 8:19798-19806. [PMID: 37305310 PMCID: PMC10249128 DOI: 10.1021/acsomega.3c01589] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 05/11/2023] [Indexed: 06/13/2023]
Abstract
Redox-active amino acid residues are at the heart of biological electron-transfer reactions. They play important roles in natural protein functions and are implicated in disease states (e.g., oxidative-stress-associated disorders). Tryptophan (Trp) is one such redox-active amino acid residue, and it has long been known to serve a functional role in proteins. Broadly speaking, there is still much to learn about the local features that make some Trp redox active and others inactive. Herein, we describe a new protein model system where we investigate how a methionine (Met) residue proximal to a redox-active Trp affects its reactivity and spectroscopy. We use an artificial variant of azurin from Pseudomonas aeruginosa to produce these models. We employ a series of UV-visible spectroscopy, electrochemistry, electron paramagnetic resonance, and density functional theory experiments to demonstrate the effect that placing Met near Trp radicals has in the context of redox proteins. The introduction of Met proximal to Trp lowers its reduction potential by ca. 30 mV and causes clear shifts in the optical spectra of the corresponding radicals. While the effect may be small, it is significant enough to be a way for natural systems to tune Trp reactivity.
Collapse
|
3
|
MacNeil GA, Chang SW, Prosser KE, Ye E, Heroux D, Lewis AR, Bally M, Walsby CJ. Spatial characterization of redox processes and speciation of Ru(III) anticancer complexes by 19F magnetic resonance imaging. Chem Commun (Camb) 2023; 59:623-626. [PMID: 36537324 DOI: 10.1039/d2cc04830b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The application of CF3-labeled Ru(III) anticancer complexes to magnetic resonance (MR) imaging of tumour tissues is demonstrated. By combining anatomical chemical-shift selective (CHESS) imaging with 19F chemical-shift imaging (CSI) MR methods, we show that oxidation states and ligand-exchange processes of the complexes can be spatially encoded. Measurements on different tissue models, including a human breast adenocarcinoma tumour, validate the application of these complexes as MR theranostics for the sensing and targeting of hypoxia.
Collapse
Affiliation(s)
- Gregory A MacNeil
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| | - Stephanie W Chang
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| | - Kathleen E Prosser
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| | - Eric Ye
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| | - Devon Heroux
- BC Cancer Research Institute, 675 West 10th Ave., Vancouver, BC, V5Z 1L3, Canada
| | - Andrew R Lewis
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada. .,Callaghan Innovation, 69 Gracefield Rd, Lower Hutt, 5010, New Zealand
| | - Marcel Bally
- BC Cancer Research Institute, 675 West 10th Ave., Vancouver, BC, V5Z 1L3, Canada
| | - Charles J Walsby
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| |
Collapse
|
4
|
Briand GG, George T, MacLean BJ, MacNeil GA, Masuda JD, Mosher MW, Sandala GM, Srinivasan P, Stockli AH, Vanderkloet RL, Walsby CJ. Synthesis, Structure and Reactivity of Organoindium 1,2‐Benzenedithiolates and 2‐Amidobenzenethiolates. Eur J Inorg Chem 2022. [DOI: 10.1002/ejic.202200542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Glen Gerard Briand
- Mount Allison University Department of Chemistry and Biochemistry 63C York Street E4L1G8 Sackville CANADA
| | - Tanner George
- Saint Mary's University Department of Chemistry CANADA
| | - Brian J. MacLean
- StFX: Saint Francis Xavier University Department of Chemistry CANADA
| | | | | | | | - Gregory M. Sandala
- Mount Allison University Department of Chemistry and Biochemistry CANADA
| | | | | | | | | |
Collapse
|
5
|
Schrage BR, Zhou W, Harrison LA, Nevonen DE, Thompson JR, Prosser KE, Walsby CJ, Ziegler CJ, Leznoff DB, Nemykin VN. Resolving a Half-Century-Long Controversy between (Magneto)optical and EPR Spectra of Single-Electron-Reduced [PcFe] −, [PcFeL] −, and [PcFeX] 2– Complexes: Story of a Double Flip. Inorg Chem 2022; 61:20177-20199. [DOI: 10.1021/acs.inorgchem.2c03456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Briana R. Schrage
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee37996, United States
| | - Wen Zhou
- Department of Chemistry, Simon Fraser University, Burnaby, British ColumbiaV5A 1S6, Canada
| | - Laurel A. Harrison
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee37996, United States
| | - Dustin E. Nevonen
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee37996, United States
| | - John R. Thompson
- Department of Chemistry, Simon Fraser University, Burnaby, British ColumbiaV5A 1S6, Canada
| | - Kathleen E. Prosser
- Department of Chemistry, Simon Fraser University, Burnaby, British ColumbiaV5A 1S6, Canada
| | - Charles J. Walsby
- Department of Chemistry, Simon Fraser University, Burnaby, British ColumbiaV5A 1S6, Canada
| | | | - Daniel B. Leznoff
- Department of Chemistry, Simon Fraser University, Burnaby, British ColumbiaV5A 1S6, Canada
| | - Victor N. Nemykin
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee37996, United States
| |
Collapse
|
6
|
Houshmand A, Heroux D, Liu DY, Zhou W, Linington RG, Bally M, Warren JJ, Walsby CJ. Ferrocene-appended anthraquinone and coumarin as redox-active cytotoxins. Dalton Trans 2022; 51:11437-11447. [PMID: 35822497 DOI: 10.1039/d2dt01251k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Appending of ferrocene (Fc) to biologically-active organic backbones can generate novel multi-functional species for targeting bacteria and cancer. In this work Fc was linked to coumarin and anthraquinone with the goal of harnessing the redox-active Fc centre to generate new compounds that exhibit cytoxicity through the generation of toxic reactive oxygen species (ROS). A Cu(I)-catalyzed azide-alkyne cycloaddition "click" reaction was used to connect the organic and Fc components via a triazole linker. Cyclic voltammetry shows that the Fc potentials are suitable for oxidation by biological hydrogen peroxide to give reactive ferrocenium (Fc+) species, which can then generate hydroxyl radicals. The ability of the compounds to generate hydroxyl radicals in the presence of hydrogen peroxide was shown directly using EPR spin-trapping experiments. Furthermore, in vitro studies in MCF-7 breast cancer cells show significant increases in ROS following incubation with the Fc-functionalized compounds. Screening for antibacterial activity produced negative results for all of the Fc compounds, consitent with low levels of hydrogen peroxide typically found in bacteria. By contrast, Fc-coumarin showed cytotoxicity against A549 lung cancer and SKOV3 ovarian cancer cell lines, whereas the parent compound was inactive. This is consistent both with the cytoxic potential of the Fc group and the elevated hydrogen peroxide levels found in many cancers. Interestingly, the anthraquinone compounds showed the opposite effect with the parent compounds showing modest activity against A549 cells, but the Fc compounds being inactive. This demonstrates other potential negative impacts of including Fc, such as significantly increased lipophilicity.
Collapse
Affiliation(s)
- Aryan Houshmand
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| | - Devon Heroux
- BC Cancer Research Institute, 675 West 10th Ave., Vancouver, BC, V5Z 1L3, Canada
| | - Dennis Y Liu
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| | - Wen Zhou
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| | - Roger G Linington
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| | - Marcel Bally
- BC Cancer Research Institute, 675 West 10th Ave., Vancouver, BC, V5Z 1L3, Canada
| | - Jeffrey J Warren
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| | - Charles J Walsby
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
| |
Collapse
|
7
|
Fedoretz-Maxwell BP, Shin CH, MacNeil GA, Worrall LJ, Park R, Strynadka NCJ, Walsby CJ, Warren JJ. The Impact of Second Coordination Sphere Methionine-Aromatic Interactions in Copper Proteins. Inorg Chem 2022; 61:5563-5571. [DOI: 10.1021/acs.inorgchem.2c00030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Brooklyn P. Fedoretz-Maxwell
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Catherine H. Shin
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Gregory A. MacNeil
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Liam J. Worrall
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Rachel Park
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Natalie C. J. Strynadka
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Charles J. Walsby
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Jeffrey J. Warren
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| |
Collapse
|
8
|
Prosser KE, Xie D, Chu A, MacNeil GA, Varju BR, Kadakia RT, Que EL, Walsby CJ. Copper(II) Pyridyl Aminophenolates: Hypoxia-Selective, Nucleus-Targeting Cytotoxins, and Magnetic Resonance Probes. Chemistry 2021; 27:9839-9849. [PMID: 33878230 DOI: 10.1002/chem.202100603] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Indexed: 11/10/2022]
Abstract
Targeting the low-oxygen (hypoxic) environments found in many tumours by using redox-active metal complexes is a strategy that can enhance efficacy and reduce the side effects of chemotherapies. We have developed a series of CuII complexes with tridentate pyridine aminophenolate-based ligands for preferential activation in the reduction window provided by hypoxic tissues. Furthermore, ligand functionalization with a pendant CF3 group provides a 19 F spectroscopic handle for magnetic-resonance studies of redox processes at the metal centre and behaviour in cellular environments. The phenol group in the ligand backbone was substituted at the para position with H, Cl, and NO2 to modulate the reduction potential of the CuII centre, giving a range of values below the window expected for hypoxic tissues. The NO2 -substituted complex, which has the highest reduction potential, showed enhanced cytotoxic selectivity towards HeLa cells grown under hypoxic conditions. Cell death occurs by apoptosis, as determined by analysis of the cell morphology. A combination of 19 F NMR and ICP-OES indicates localization of the NO2 complex in HeLa cell nuclei and increased cellular accumulation under hypoxia. This correlates with DNA nuclease activity being the likely origin of cytotoxic activity, as demonstrated by cleavage of DNA plasmids in the presence of the CuII nitro complex and a reducing agent. Selective detection of the paramagnetic CuII complexes and their diamagnetic ligands by 19 F MRI suggests hypoxia-targeting theranostic applications by redox activation.
Collapse
Affiliation(s)
- Kathleen E Prosser
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada.,Department of Chemistry, The University of Texas at Austin, 105 E. 24th Street Stop A5300, Austin, TX 78712, USA
| | - Da Xie
- Department of Chemistry, The University of Texas at Austin, 105 E. 24th Street Stop A5300, Austin, TX 78712, USA
| | - Annica Chu
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
| | - Gregory A MacNeil
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
| | - Bryton R Varju
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
| | - Rahul T Kadakia
- Department of Chemistry, The University of Texas at Austin, 105 E. 24th Street Stop A5300, Austin, TX 78712, USA
| | - Emily L Que
- Department of Chemistry, The University of Texas at Austin, 105 E. 24th Street Stop A5300, Austin, TX 78712, USA
| | - Charles J Walsby
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada
| |
Collapse
|
9
|
Gomes LMF, Bataglioli JC, Jussila AJ, Smith JR, Walsby CJ, Storr T. Modification of Aβ Peptide Aggregation via Covalent Binding of a Series of Ru(III) Complexes. Front Chem 2019; 7:838. [PMID: 31921764 PMCID: PMC6915085 DOI: 10.3389/fchem.2019.00838] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 11/18/2019] [Indexed: 12/31/2022] Open
Abstract
Alzheimer's disease (AD) is the most common form of dementia, leading to loss of cognition, and eventually death. The disease is characterized by the formation of extracellular aggregates of the amyloid-beta (Aβ) peptide and neurofibrillary tangles of tau protein inside cells, and oxidative stress. In this study, we investigate a series of Ru(III) complexes (Ru-N) derived from NAMI-A in which the imidazole ligand has been substituted for pyridine derivatives, as potential therapeutics for AD. The ability of the Ru-N series to bind to Aβ was evaluated by NMR and ESI-MS, and their influence on the Aβ peptide aggregation process was investigated via electrophoresis gel/western blot, TEM, turbidity, and Bradford assays. The complexes were shown to bind covalently to the Aβ peptide, likely via a His residue. Upon binding, the complexes promote the formation of soluble high molecular weight aggregates, in comparison to peptide precipitation for peptide alone. In addition, TEM analysis supports both amorphous and fibrillar aggregate morphology for Ru-N treatments, while only large amorphous aggregates are observed for peptide alone. Overall, our results show that the Ru-N complexes modulate Aβ peptide aggregation, however, the change in the size of the pyridine ligand does not substantially alter the Aβ aggregation process.
Collapse
Affiliation(s)
- Luiza M F Gomes
- Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada
| | | | - Allison J Jussila
- Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Jason R Smith
- Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Charles J Walsby
- Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Tim Storr
- Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada
| |
Collapse
|
10
|
Safaei E, Balaghi SE, Chiang L, Clarke RM, Martelino D, Webb MI, Wong EWY, Savard D, Walsby CJ, Storr T. Stabilization of different redox levels of a tridentate benzoxazole amidophenoxide ligand when bound to Co(iii) or V(v). Dalton Trans 2019; 48:13326-13336. [DOI: 10.1039/c9dt02865j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The electronic structure of Co and V complexes of a tridentate benzoxazole-containing aminophenol ligand NNOH2 were characterized by both experimental and theoretical methods.
Collapse
Affiliation(s)
- Elham Safaei
- Department of Chemistry
- College of Science
- Shiraz University
- Shiraz
- Iran
| | | | - Linus Chiang
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Ryan M. Clarke
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Diego Martelino
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Michael I. Webb
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Edwin W. Y. Wong
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Didier Savard
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Charles J. Walsby
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| | - Tim Storr
- Department of Chemistry
- Simon Fraser University
- 8888 University Drive
- Burnaby
- Canada
| |
Collapse
|
11
|
Gomes LMF, Mahammed A, Prosser KE, Smith JR, Silverman MA, Walsby CJ, Gross Z, Storr T. A catalytic antioxidant for limiting amyloid-beta peptide aggregation and reactive oxygen species generation. Chem Sci 2018; 10:1634-1643. [PMID: 30842826 PMCID: PMC6369440 DOI: 10.1039/c8sc04660c] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 11/27/2018] [Indexed: 12/29/2022] Open
Abstract
Alzheimer's disease (AD) is a multifaceted disease that is characterized by increased oxidative stress, metal-ion dysregulation, and the formation of intracellular neurofibrillary tangles and extracellular amyloid-β (Aβ) aggregates. In this work we report the large affinity binding of the iron(iii) 2,17-bis-sulfonato-5,10,15-tris(pentafluorophenyl)corrole complex FeL1 to the Aβ peptide (K d ∼ 10-7) and the ability of the bound FeL1 to act as a catalytic antioxidant in both the presence and absence of Cu(ii) ions. Specific findings are that: (a) an Aβ histidine residue binds axially to FeL1; (b) that the resulting adduct is an efficient catalase; (c) this interaction restricts the formation of high molecular weight peptide aggregates. UV-Vis and electron paramagnetic resonance (EPR) studies show that although the binding of FeL1 does not influence the Aβ-Cu(ii) interaction (K d ∼ 10-10), bound FeL1 still acts as an antioxidant thereby significantly limiting reactive oxygen species (ROS) generation from Aβ-Cu. Overall, FeL1 is shown to bind to the Aβ peptide, and modulate peptide aggregation. In addition, FeL1 forms a ternary species with Aβ-Cu(ii) and impedes ROS generation, thus showing the promise of discrete metal complexes to limit the toxicity pathways of the Aβ peptide.
Collapse
Affiliation(s)
- Luiza M F Gomes
- Department of Chemistry , Simon Fraser University , V5A-1S6 , Burnaby , BC , Canada .
| | - Atif Mahammed
- Schulich Faculty of Chemistry , Technion-Israel Institute of Technology , Haifa , 32000 , Israel .
| | - Kathleen E Prosser
- Department of Chemistry , Simon Fraser University , V5A-1S6 , Burnaby , BC , Canada .
| | - Jason R Smith
- Department of Chemistry , Simon Fraser University , V5A-1S6 , Burnaby , BC , Canada .
| | - Michael A Silverman
- Department of Biological Sciences , Simon Fraser University , V5A-1S6 , Burnaby , BC , Canada
| | - Charles J Walsby
- Department of Chemistry , Simon Fraser University , V5A-1S6 , Burnaby , BC , Canada .
| | - Zeev Gross
- Schulich Faculty of Chemistry , Technion-Israel Institute of Technology , Haifa , 32000 , Israel .
| | - Tim Storr
- Department of Chemistry , Simon Fraser University , V5A-1S6 , Burnaby , BC , Canada .
| |
Collapse
|
12
|
Mu C, Prosser KE, Harrypersad S, MacNeil GA, Panchmatia R, Thompson JR, Sinha S, Warren JJ, Walsby CJ. Activation by Oxidation: Ferrocene-Functionalized Ru(II)-Arene Complexes with Anticancer, Antibacterial, and Antioxidant Properties. Inorg Chem 2018; 57:15247-15261. [PMID: 30495936 DOI: 10.1021/acs.inorgchem.8b02542] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Organometallic Ru(II)-cymene complexes linked to ferrocene (Fc) via nitrogen heterocycles have been synthesized and studied as cytotoxic agents. These compounds are analogues of Ru(II)-arene piano-stool anticancer complexes such as RAPTA-C. The Ru center was coordinated by pyridine, imidazole, and piperidine with 0-, 1-, or 2-carbon bridges to Fc to give six bimetallic, dinuclear compounds, and the properties of these complexes were compared with their non-Fc-functionalized parent compounds. Crystal structures for five of the compounds, their Ru-cymene parent compounds, and an unusual trinuclear compound were determined. Cyclic voltammetry was used to determine the formal MIII/II potentials of each metal center of the Ru-cymene-Fc complexes, with distinct one-electron waves observed in each case. The Fc-functionalized complexes were found to exhibit good cytotoxicity against HT29 human colon adenocarcinoma cells, whereas the parent compounds were inactive. Similarly, antibacterial activity from the Ru-cymene-Fc compounds was observed against Bacillus subtilis, but not from the unfunctionalized complexes. In both cases, the IC50 values correlated quantitatively with the Fc+/0 reduction potentials. This is consistent with more facile oxidation to give ferrocenium, and subsequent generation of toxic reactive oxygen species, leading to greater cytotoxicity. The antioxidant properties of the complexes were quantified by a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. EC50 values indicate that linking of the Ru and Fc centers promotes antioxidant activity.
Collapse
Affiliation(s)
- Changhua Mu
- Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby V5A 1S6 , British Columbia , Canada
| | - Kathleen E Prosser
- Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby V5A 1S6 , British Columbia , Canada
| | - Shane Harrypersad
- Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby V5A 1S6 , British Columbia , Canada
| | - Gregory A MacNeil
- Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby V5A 1S6 , British Columbia , Canada
| | - Rikesh Panchmatia
- Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby V5A 1S6 , British Columbia , Canada
| | - John R Thompson
- Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby V5A 1S6 , British Columbia , Canada
| | - Soumalya Sinha
- Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby V5A 1S6 , British Columbia , Canada
| | - Jeffrey J Warren
- Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby V5A 1S6 , British Columbia , Canada
| | - Charles J Walsby
- Department of Chemistry , Simon Fraser University , 8888 University Drive , Burnaby V5A 1S6 , British Columbia , Canada
| |
Collapse
|
13
|
Prosser KE, Leung AWY, Harrypersad S, Lewis AR, Bally MB, Walsby CJ. Transition Metal Ions Promote the Bioavailability of Hydrophobic Therapeutics: Cu and Zn Interactions with RNA Polymerase I Inhibitor CX5461. Chemistry 2018; 24:6334-6338. [PMID: 29490115 DOI: 10.1002/chem.201800289] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Indexed: 01/27/2023]
Abstract
Low aqueous solubility is a major barrier to the clinical application of otherwise promising drug candidates. We demonstrate that this issue can be resolved in medicinal molecules containing potential ligating groups, through the addition of labile transition-metal ions. Incubation of the chemotherapeutic CX5461 with Cu2+ or Zn2+ enables solubilization at neutral pH but does not affect intrinsic cytotoxicity. Spectroscopic and computational studies demonstrate that this arises from coordination to the pyrazine functionality of CX5461 and may involve bidentate coordination at physiological pH.
Collapse
Affiliation(s)
- Kathleen E Prosser
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada
| | - Ada W Y Leung
- Department of Experimental Therapeutics, British Columbia Cancer Agency, 675 West 10th Ave, Vancouver, BC, V5Z 4E6, Canada
| | - Shane Harrypersad
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada
| | - Andrew R Lewis
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada
| | - Marcel B Bally
- Department of Experimental Therapeutics, British Columbia Cancer Agency, 675 West 10th Ave, Vancouver, BC, V5Z 4E6, Canada
| | - Charles J Walsby
- Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada
| |
Collapse
|
14
|
Zhang C, Sutherland M, Herasymchuk K, Clarke RM, Thompson JR, Chiang L, Walsby CJ, Storr T. Octahedral Co(III) salen complexes: the role of peripheral ligand electronics on axial ligand release upon reduction. CAN J CHEM 2018. [DOI: 10.1139/cjc-2017-0277] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A series of octahedral CoIII salen complexes (where salen represents a N2O2 bis-Schiff-base bis-phenolate framework) were prepared with axial imidazole ligating groups. When using 1-methylimidazole (1-MeIm) axial ligands, the CoIII/CoII reduction potential could be altered by 220 mV via variation of the electron-donating ability of the para-ring substituents (R = H (1), OMe (2), tBu (3), Br (4), NO2 (5), and CF3 (6)). In addition, the irreversibility of the reduction process suggested substantial geometrical changes and axial ligand exchange upon reduction to the more labile CoII oxidation state. Installing an imidazole-coumarin conjugate as the axial ligands resulted in fluorescence quenching when bound to the CoIII centre (R = H (7), OMe (8), and CF3 (9)). The redox properties and fluorescence increase upon ligand release for 7–9 were studied under reducing conditions and in the presence of excess competing ligand (1-MeIm). It was determined that the Lewis acidity of the CoIII centre was the dominant factor in controlling axial ligand exchange for this series of complexes.
Collapse
Affiliation(s)
- Chen Zhang
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Mathew Sutherland
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Khrystyna Herasymchuk
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Ryan M. Clarke
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - John R. Thompson
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Linus Chiang
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Charles J. Walsby
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Tim Storr
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| |
Collapse
|
15
|
Stott LA, Prosser KE, Berdichevsky EK, Walsby CJ, Warren JJ. Lowering water oxidation overpotentials using the ionisable imidazole of copper(2-(2'-pyridyl)imidazole). Chem Commun (Camb) 2017; 53:651-654. [PMID: 27990513 DOI: 10.1039/c6cc09208j] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Rapid and low overpotential oxidation of water to dioxygen remains a key hurdle for storage of solar energy. Here, we address this issue by demonstrating that deprotonation of 2-(2'-pyridyl)-imidazole (pimH)-ligated copper complexes promotes water oxidation at low overpotential and low catalyst loading. This improves upon other work on homogeneous copper-based water oxidation catalysts, which are highly active, but limited by high overpotentials. EPR and UV-vis spectroscopic evaluation of catalyst speciation shows that at pH ≥ 12 coordinated pimH is deprotonated and a bis(hydroxide) Cu2+ active catalyst forms. Rapid electrochemical water oxidation (35 s-1, 0.85 V onset potential) was observed with 150 μM catalyst. These results demonstrate that catalytic water oxidation potentials can be shifted by hundreds of mV in homogeneous metal catalysts bearing an ionisable imidazole ligand.
Collapse
Affiliation(s)
- Leea A Stott
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Kathleen E Prosser
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Ellan K Berdichevsky
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Charles J Walsby
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada.
| | - Jeffrey J Warren
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby BC V5A 1S6, Canada. and Canadian Institute for Applied Research, CIFAR Azrieli Global Scholar and Bio-Inspired Solar Energy Programs, Toronto, ON M5G 1Z8, Canada
| |
Collapse
|
16
|
Prosser KE, Chang SW, Saraci F, Le PH, Walsby CJ. Anticancer copper pyridine benzimidazole complexes: ROS generation, biomolecule interactions, and cytotoxicity. J Inorg Biochem 2017; 167:89-99. [DOI: 10.1016/j.jinorgbio.2016.11.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 10/12/2016] [Accepted: 11/03/2016] [Indexed: 12/19/2022]
|
17
|
Affiliation(s)
- Kathleen E. Prosser
- Department of Chemistry; Simon Fraser University; 8888 University Dr. V5A 1S6 Burnaby BC Canada
| | - Charles J. Walsby
- Department of Chemistry; Simon Fraser University; 8888 University Dr. V5A 1S6 Burnaby BC Canada
| |
Collapse
|
18
|
Chang SW, Lewis AR, Prosser KE, Thompson JR, Gladkikh M, Bally MB, Warren JJ, Walsby CJ. CF3 Derivatives of the Anticancer Ru(III) Complexes KP1019, NKP-1339, and Their Imidazole and Pyridine Analogues Show Enhanced Lipophilicity, Albumin Interactions, and Cytotoxicity. Inorg Chem 2016; 55:4850-63. [DOI: 10.1021/acs.inorgchem.6b00359] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Stephanie. W. Chang
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC Canada, V5A 1S6
| | - Andrew R. Lewis
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC Canada, V5A 1S6
| | - Kathleen E. Prosser
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC Canada, V5A 1S6
| | - John R. Thompson
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC Canada, V5A 1S6
| | - Margarita Gladkikh
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC Canada, V5A 1S6
| | - Marcel B. Bally
- Department of Experimental Therapeutics, BC Cancer Agency, Vancouver, BC Canada, V5Z 4E6
| | - Jeffrey J. Warren
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC Canada, V5A 1S6
| | - Charles J. Walsby
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC Canada, V5A 1S6
| |
Collapse
|
19
|
Abstract
Herein we describe the synthesis, structure and electronic properties of an unusual redox-active ditopic ligand with a stable open-shell configuration. This stable phenoxyl radical features intense and very low energy electronic transitions in the near infrared (NIR) part of the spectrum and is structurally set up to strongly spin couple coordinated transition metal ions in [2 × 2] grid-type structures.
Collapse
Affiliation(s)
- N M Bonanno
- Department of Chemistry, Brandon University, Brandon, MB R7A 6A9, Canada.
| | | | | | | | | | | |
Collapse
|
20
|
Zhao J, Prosser KE, Chang SW, Zakharia SP, Walsby CJ. Combining a Ru(ii)-arene complex with a NO-releasing nitrate-ester ligand generates cytotoxic activity. Dalton Trans 2016; 45:18079-18083. [DOI: 10.1039/c6dt03661a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Synergy between a Ru(ii) arene complex and a 4-nitrooxymethylpyridine nitric-oxide donor ligand promotes cytotoxicity and selective activation by glutathione.
Collapse
Affiliation(s)
- Jian Zhao
- Department of Chemistry
- Simon Fraser University
- Burnaby
- Canada
| | | | | | | | | |
Collapse
|
21
|
Mu C, Chang SW, Prosser KE, Leung AWY, Santacruz S, Jang T, Thompson JR, Yapp DTT, Warren JJ, Bally MB, Beischlag TV, Walsby CJ. Induction of Cytotoxicity in Pyridine Analogues of the Anti-metastatic Ru(III) Complex NAMI-A by Ferrocene Functionalization. Inorg Chem 2015; 55:177-90. [PMID: 26652771 DOI: 10.1021/acs.inorgchem.5b02109] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of novel ferrocene (Fc) functionalized Ru(III) complexes was synthesized and characterized. These compounds are derivatives of the anti-metastatic Ru(III) complex imidazolium [trans-RuCl4(1H-imidazole) (DMSO-S)] (NAMI-A) and are derived from its pyridine analogue (NAMI-Pyr), with direct coupling of Fc to pyridine at the 4 or 3 positions, or at the 4 position via a two-carbon linker, which is either unsaturated (vinyl) or saturated (ethyl). Electron paramagnetic resonance (EPR) and UV-vis spectroscopic studies of the ligand exchange processes of the compounds in phosphate buffered saline (PBS) report similar solution behavior to NAMI-Pyr. However, the complex with Fc substitution at the 3 position of the coordinated pyridine shows greater solution stability, through resistance to the formation of oligomeric species. Further EPR studies of the complexes with human serum albumin (hsA) indicate that the Fc groups enhance noncoordinate interactions with the protein and help to inhibit the formation of protein-coordinated species, suggesting the potential for enhanced bioavailability. Cyclic voltammetry measurements demonstrate that the Fc groups modestly reduce the reduction potential of the Ru(III) center as compared to NAMI-Pyr, while the reduction potentials of the Fc moieties of the four compounds vary by 217 mV, with the longer linkers giving significantly lower values of E1/2. EPR spectra of the compounds with 2-carbon linkers show the formation of a high-spin Fe(III) species (S = 5/2) in PBS with a distinctive signal at g = 4.3, demonstrating oxidation of the Fe(II) ferrocene center and likely reflecting degradation products. Density functional theory calculations and paramagnetic (1)H NMR describe delocalization of spin density onto the ligands and indicate that the vinyl linker could be a potential pathway for electron transfer between the Ru and Fe centers. In the case of the ethyl linker, electron transfer is suggested to occur via an indirect mechanism enabled by the greater flexibility of the ligand. In vitro assays with the SW480 cell line reveal cytotoxicity induced by the ruthenium ferrocenylpyridine complexes that is at least an order of magnitude higher than the unfunctionalized complex, NAMI-Pyr. Furthermore, migration studies with LNCaP cells reveal that Fc functionalization does not reduce the ability of the compounds to inhibit cell motility. Overall, these studies demonstrate that NAMI-A-type compounds can be functionalized with redox-active ligands to produce both cytotoxic and anti-metastatic activity.
Collapse
Affiliation(s)
| | | | | | - Ada W Y Leung
- Department of Experimental Therapeutics, BC Cancer Agency , 675 West 10th Avenue, Vancouver, BC V5Z 4E6, Canada
| | | | | | | | - Donald T T Yapp
- Department of Experimental Therapeutics, BC Cancer Agency , 675 West 10th Avenue, Vancouver, BC V5Z 4E6, Canada
| | | | - Marcel B Bally
- Department of Experimental Therapeutics, BC Cancer Agency , 675 West 10th Avenue, Vancouver, BC V5Z 4E6, Canada
| | | | | |
Collapse
|
22
|
Webb MI, Walsby CJ. Albumin binding and ligand-exchange processes of the Ru(III) anticancer agent NAMI-A and its bis-DMSO analogue determined by ENDOR spectroscopy. Dalton Trans 2015; 44:17482-93. [PMID: 26174110 DOI: 10.1039/c5dt02021b] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The ruthenium anticancer compound NAMI-A, imidazolium [trans-RuCl4(1H-imidazole)(DMSO-S)], is currently undergoing advanced clinical evaluation. As with other Ru(iii) chemotherapeutic candidates, interactions with human serum albumin (HSA) have been identified as a key component of the speciation of NAMI-A following intravenous administration. To characterize coordination to HSA, we have performed electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopic analysis of deuterium-labelled isotopologues of both NAMI-A and its bis-DMSO analogue, [(DMSO)2H][trans-RuCl4(DMSO-S)2] (Ru-bis-DMSO). Samples were prepared using phosphate buffered saline, in the presence of HSA, and with the individual amino acids histidine, cysteine, and alanine. Analysis of (1)H ENDOR spectra shows characteristic hyperfine interactions from DMSO, water, and imidazole ligands. Furthermore, coordination of imidazole ligands was confirmed from diagnostic (14)N ENDOR signals. Combined with the EPR data from the complexes following incubation in the presence of histidine, the ENDOR data demonstrate that both complexes bind to HSA via histidine imidazoles. Furthermore, the protein-bound species are shown to have water ligands and, in the case of Ru-bis-DMSO, one species has a remaining coordinated DMSO.
Collapse
Affiliation(s)
- Michael I Webb
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada.
| | | |
Collapse
|
23
|
Jones MR, Mu C, Wang MCP, Webb MI, Walsby CJ, Storr T. Modulation of the Aβ peptide aggregation pathway by KP1019 limits Aβ-associated neurotoxicity. Metallomics 2014; 7:129-35. [PMID: 25387614 DOI: 10.1039/c4mt00252k] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Alzheimer's disease (AD) is a neurodegenerative disorder that is increasing worldwide due to increased life expectancy. AD is characterized by two pathological hallmarks in the brain: amyloid-β (Aβ) plaque deposits and neurofibrillary tangles. A focus of AD research has concentrated on either inhibiting Aβ peptide aggregation that leads to plaque formation or breaking down pre-formed Aβ peptide aggregates. An alternative approach is to modulate the Aβ aggregation profile by facilitating the formation of Aβ species that are off-pathway and non-toxic. Herein, we report the re-purposing of the widely studied Ru(iii) anti-cancer complex KP1019, towards regulating the aggregation profile of the Aβ peptide. Using electron paramagnetic resonance (EPR) spectroscopy, we conclude that KP1019 binds to histidine residues, located at the N-terminus of the peptide, in a rapid and robust fashion. Native gels and transmission electron microscopy (TEM) analyses have provided insight into the species and structures that are generated by KP1019-Aβ interactions. Finally, incubation in an in vitro human neuronal cell model has demonstrated that the formation of KP1019-Aβ species rescues cell viability from Aβ-associated neurotoxicity. Modulation of the Aβ aggregation pathway via covalent interactions with small molecules is thus a promising AD therapeutic strategy.
Collapse
Affiliation(s)
- Michael R Jones
- Department of Chemistry, Simon Fraser University, Burnaby, BC V5A1S6, Canada.
| | | | | | | | | | | |
Collapse
|
24
|
Lo SY, Säbel CE, Webb MI, Walsby CJ, Siemann S. High metal substitution tolerance of anthrax lethal factor and characterization of its active copper-substituted analogue. J Inorg Biochem 2014; 140:12-22. [DOI: 10.1016/j.jinorgbio.2014.06.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 05/27/2014] [Accepted: 06/16/2014] [Indexed: 01/19/2023]
|
25
|
Makins C, Whitelaw DA, Mu C, Walsby CJ, Wolthers KR. Isotope effects for deuterium transfer and mutagenesis of Tyr187 provide insight into controlled radical chemistry in adenosylcobalamin-dependent ornithine 4,5-aminomutase. Biochemistry 2014; 53:5432-43. [PMID: 25100213 DOI: 10.1021/bi5006706] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Adenosylcobalamin-dependent ornithine 4,5-aminomutase (OAM) from Clostridium sticklandii utilizes pyridoxal 5'-phosphate (PLP) to interconvert d-ornithine to 2,4-diaminopentanoate via a multistep mechanism that involves two hydrogen transfer steps. Herein, we uncover features of the OAM catalytic mechanism that differentiate it from its homologue, the more catalytically promiscuous lysine 5,6-aminomutase. Kinetic isotope effects (KIEs) with dl-ornithine-3,3,4,4,5,5-d6 revealed a diminished (D)kcat/Km of 2.5 ± 0.4 relative to a (D)kcat of 7.6 ± 0.5, suggesting slow release of the substrate from the active site. In contrast, a KIE was not observed on the rate constant associated with Co-C bond homolysis as this step is likely "gated" by the formation of the external aldimine. The role of tyrosine 187, which lies planar to the PLP pyridine ring, was also investigated via site-directed mutagenesis. The 25- and 1260-fold reduced kcat values for Y187F and Y187A, respectively, are attributed to a slower rate of external aldimine formation and a diminution of adenosylcobalamin Co-C bond homolysis. Notably, electron paramagnetic resonance studies of Y187F suggest that the integrity of the active site is maintained as cob(II)alamin and the PLP organic radical (even at lower concentrations) remain tightly exchange-coupled. Modeling of d-lysine and l-β-lysine into the 5,6-LAM active site reveals interactions between the substrate and protein are weaker than those in OAM and fewer in number. The combined data suggest that the level of protein-substrate interactions in aminomutases not only influences substrate specificity, but also controls radical chemistry.
Collapse
Affiliation(s)
- Caitlyn Makins
- Department of Chemistry, University of British Columbia , 3333 University Way, Kelowna, BC V1V 1V7, Canada
| | | | | | | | | |
Collapse
|
26
|
Webb MI, Wu B, Jang T, Chard RA, Wong EWY, Wong MQ, Yapp DTT, Walsby CJ. Increasing the Bioavailability of RuIIIAnticancer Complexes through Hydrophobic Albumin Interactions. Chemistry 2013; 19:17031-42. [DOI: 10.1002/chem.201302671] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Indexed: 11/08/2022]
|
27
|
|
28
|
Wong EWY, Miura A, Wright MD, He Q, Walsby CJ, Shimizu S, Kobayashi N, Leznoff DB. Inside Cover: Gold(II) Phthalocyanine Revisited: Synthesis and Spectroscopic Properties of Gold(III) Phthalocyanine and an Unprecedented Ring-Contracted Phthalocyanine Analogue (Chem. Eur. J. 39/2012). Chemistry 2012. [DOI: 10.1002/chem.201290168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
29
|
Wong EWY, Miura A, Wright MD, He Q, Walsby CJ, Shimizu S, Kobayashi N, Leznoff DB. Gold(II) Phthalocyanine Revisited: Synthesis and Spectroscopic Properties of Gold(III) Phthalocyanine and an Unprecedented Ring-Contracted Phthalocyanine Analogue. Chemistry 2012; 18:12404-10. [DOI: 10.1002/chem.201201701] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Indexed: 11/11/2022]
|
30
|
Simmons JM, Yildirim T, Hamaed A, Antonelli DM, Webb MI, Walsby CJ. Direct Observation of Activated Hydrogen Binding to a Supported Organometallic Compound at Room Temperature. Chemistry 2012; 18:4170-3. [DOI: 10.1002/chem.201102658] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 02/13/2012] [Indexed: 11/09/2022]
|
31
|
Webb MI, Chard RA, Al-Jobory YM, Jones MR, Wong EWY, Walsby CJ. Pyridine analogues of the antimetastatic Ru(III) complex NAMI-A targeting non-covalent interactions with albumin. Inorg Chem 2011; 51:954-66. [PMID: 22224431 DOI: 10.1021/ic202029e] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of pyridine-based derivatives of the antimetastatic Ru(III) complex imidazolium [trans-RuCl(4)(1H-imidazole)(DMSO-S)] (NAMI-A) have been synthesized along with their sodium-ion compensated analogues. These compounds have been characterized by X-ray crystallography, electron paramagnetic resonance (EPR), NMR, and electrochemistry, with the goal of probing their noncovalent interactions with human serum albumin (hsA). EPR studies show that the choice of imidazolium ligands and compensating ions does not strongly influence the rates of ligand exchange processes in aqueous buffer solutions. By contrast, the rate of formation and persistence of interactions of the complexes with hsA is found to be strongly dependent on the properties of the axial ligands. The stability of noncovalent binding is shown to correlate with the anticipated ability of the various pyridine ligands to interact with the hydrophobic binding domains of hsA. These interactions prevent the oligomerization of the complexes in solution and limit the rate of covalent binding to albumin amino acid side chains. Electrochemical studies demonstrate relatively high reduction potentials for these complexes, leading to the formation of Ru(II) species in aqueous solutions containing biological reducing agents, such as ascorbate. However, EPR measurements indicate that while noncovalent interactions with hsA do not prevent reduction, covalent binding produces persistent mononuclear Ru(III) species under these conditions.
Collapse
Affiliation(s)
- Michael I Webb
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | | | | | | | | | | |
Collapse
|
32
|
Sherren CN, Mu C, Webb MI, McKenzie I, McCollum BM, Brodovitch JC, Percival PW, Storr T, Seddon KR, Clyburne JAC, Walsby CJ. Merging the chemistry of electron-rich olefins with imidazolium ionic liquids: radicals and hydrogen-atom adducts. Chem Sci 2011. [DOI: 10.1039/c1sc00408e] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
|
33
|
Webb MI, Walsby CJ. Control of ligand-exchange processes and the oxidation state of the antimetastatic Ru(iii) complex NAMI-A by interactions with human serum albumin. Dalton Trans 2011; 40:1322-31. [DOI: 10.1039/c0dt01168a] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
34
|
Hoang TKA, Webb MI, Mai HV, Hamaed A, Walsby CJ, Trudeau M, Antonelli DM. Design and Synthesis of Vanadium Hydrazide Gels for Kubas-Type Hydrogen Adsorption: A New Class of Hydrogen Storage Materials. J Am Chem Soc 2010; 132:11792-8. [DOI: 10.1021/ja104926h] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Tuan K. A. Hoang
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada, Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada, Emerging Technologies, Hydro-Québec Institute, 1800 Boul. Lionel-Boulet, Varennes, Quebec J3X 1S1, Canada, and Sustainable Environment Research Center, University of Glamorgan, Pontypridd CF37 1DL, United Kingdom
| | - Michael I. Webb
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada, Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada, Emerging Technologies, Hydro-Québec Institute, 1800 Boul. Lionel-Boulet, Varennes, Quebec J3X 1S1, Canada, and Sustainable Environment Research Center, University of Glamorgan, Pontypridd CF37 1DL, United Kingdom
| | - Hung V. Mai
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada, Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada, Emerging Technologies, Hydro-Québec Institute, 1800 Boul. Lionel-Boulet, Varennes, Quebec J3X 1S1, Canada, and Sustainable Environment Research Center, University of Glamorgan, Pontypridd CF37 1DL, United Kingdom
| | - Ahmad Hamaed
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada, Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada, Emerging Technologies, Hydro-Québec Institute, 1800 Boul. Lionel-Boulet, Varennes, Quebec J3X 1S1, Canada, and Sustainable Environment Research Center, University of Glamorgan, Pontypridd CF37 1DL, United Kingdom
| | - Charles J. Walsby
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada, Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada, Emerging Technologies, Hydro-Québec Institute, 1800 Boul. Lionel-Boulet, Varennes, Quebec J3X 1S1, Canada, and Sustainable Environment Research Center, University of Glamorgan, Pontypridd CF37 1DL, United Kingdom
| | - Michel Trudeau
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada, Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada, Emerging Technologies, Hydro-Québec Institute, 1800 Boul. Lionel-Boulet, Varennes, Quebec J3X 1S1, Canada, and Sustainable Environment Research Center, University of Glamorgan, Pontypridd CF37 1DL, United Kingdom
| | - David M. Antonelli
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada, Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada, Emerging Technologies, Hydro-Québec Institute, 1800 Boul. Lionel-Boulet, Varennes, Quebec J3X 1S1, Canada, and Sustainable Environment Research Center, University of Glamorgan, Pontypridd CF37 1DL, United Kingdom
| |
Collapse
|
35
|
Wong EWY, Walsby CJ, Storr T, Leznoff DB. Phthalocyanine as a Chemically Inert, Redox-Active Ligand: Structural and Electronic Properties of a Nb(IV)-Oxo Complex Incorporating a Highly Reduced Phthalocyanine(4−) Anion. Inorg Chem 2010; 49:3343-50. [DOI: 10.1021/ic902409n] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
36
|
Ramnial T, Taylor SA, Bender ML, Gorodetsky B, Lee PTK, Dickie DA, McCollum BM, Pye CC, Walsby CJ, Clyburne JAC. Carbon-Centered Strong Bases in Phosphonium Ionic Liquids. J Org Chem 2008; 73:801-12. [DOI: 10.1021/jo701289d] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Taramatee Ramnial
- Department of Chemistry, Simon Fraser University, Burnaby BC, V5A 1S6, Canada, and Department of Chemistry, Saint Mary's University, Halifax NS, B3H 3C3, Canada
| | - Stephanie A. Taylor
- Department of Chemistry, Simon Fraser University, Burnaby BC, V5A 1S6, Canada, and Department of Chemistry, Saint Mary's University, Halifax NS, B3H 3C3, Canada
| | - Marissa L. Bender
- Department of Chemistry, Simon Fraser University, Burnaby BC, V5A 1S6, Canada, and Department of Chemistry, Saint Mary's University, Halifax NS, B3H 3C3, Canada
| | - Brian Gorodetsky
- Department of Chemistry, Simon Fraser University, Burnaby BC, V5A 1S6, Canada, and Department of Chemistry, Saint Mary's University, Halifax NS, B3H 3C3, Canada
| | - Peter T. K. Lee
- Department of Chemistry, Simon Fraser University, Burnaby BC, V5A 1S6, Canada, and Department of Chemistry, Saint Mary's University, Halifax NS, B3H 3C3, Canada
| | - Diane A. Dickie
- Department of Chemistry, Simon Fraser University, Burnaby BC, V5A 1S6, Canada, and Department of Chemistry, Saint Mary's University, Halifax NS, B3H 3C3, Canada
| | - Brett M. McCollum
- Department of Chemistry, Simon Fraser University, Burnaby BC, V5A 1S6, Canada, and Department of Chemistry, Saint Mary's University, Halifax NS, B3H 3C3, Canada
| | - Cory C. Pye
- Department of Chemistry, Simon Fraser University, Burnaby BC, V5A 1S6, Canada, and Department of Chemistry, Saint Mary's University, Halifax NS, B3H 3C3, Canada
| | - Charles J. Walsby
- Department of Chemistry, Simon Fraser University, Burnaby BC, V5A 1S6, Canada, and Department of Chemistry, Saint Mary's University, Halifax NS, B3H 3C3, Canada
| | - Jason A. C. Clyburne
- Department of Chemistry, Simon Fraser University, Burnaby BC, V5A 1S6, Canada, and Department of Chemistry, Saint Mary's University, Halifax NS, B3H 3C3, Canada
| |
Collapse
|
37
|
Dickie DA, MacIntosh IS, Ino DD, He Q, Labeodan OA, Jennings MC, Schatte G, Walsby CJ, Clyburne JA. Synthesis of the bulkym-terphenyl phenol Ar*OH (Ar* = C6H3-2,6-Mes2, Mes = 2,4,6-trimethylphenyl) and the preparation and structural characterization of several of its metal complexes. CAN J CHEM 2008. [DOI: 10.1139/v07-131] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The bulky m-terphenyl phenol Ar*OH 1 (Ar* = C6H3-2,6-Mes2, Mes = 2,4,6-trimethylphenyl) was synthesized via the treatment of Ar*Li with nitrobenzene. The phenol 1 is prepared in modest to good yield using this method. Attempts were also made to prepare 1 through oxidation of the bulky boronic acid Ar*B(OH)2with Oxone®, but this reaction was not suitable for preparative-scale reactions. Side products of the reaction between Ar*Li and nitrobenzene were identified as Ar*[N(O)Ph] and [C6H5N(O)]2and were characterized by X-ray crystallography and EPR spectroscopy. A variety of main-group and transition-metal complexes of Ar*OH were prepared, namely Sn(OAr*)2, Ge(OAr*)2, [N(SiMe3)2]Ge(OAr*), [Me2Al(OAr*)]2, and Ti(NMe2)(OAr*)2. All compounds were characterized spectroscopically and most were studied by single-crystal X-ray diffraction as well.Key words: m-terphenyl, main-group compounds, X-ray crystallography, multinuclear NMR spectroscopy, EPR spectroscopy.
Collapse
|
38
|
Ramnial T, Taylor SA, Clyburne JAC, Walsby CJ. Grignard reagents in ionic solvents: electron transfer reactions and evidence for facile Br-Mg exchange. Chem Commun (Camb) 2007:2066-8. [PMID: 17713080 DOI: 10.1039/b617861h] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Grignard reagents form persistent solutions in phosphonium ionic liquids possessing O-donor anions and these solutions are excellent reaction media for electron transfer processes and transmetallation reactions.
Collapse
Affiliation(s)
- Taramatee Ramnial
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada
| | | | | | | |
Collapse
|
39
|
Lees NS, Chen D, Walsby CJ, Behshad E, Frey PA, Hoffman BM. How an Enzyme Tames Reactive Intermediates: Positioning of the Active-Site Components of Lysine 2,3-Aminomutase during Enzymatic Turnover As Determined by ENDOR Spectroscopy. J Am Chem Soc 2006; 128:10145-54. [PMID: 16881644 DOI: 10.1021/ja061282r] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Lysine 2,3-aminomutase (LAM) utilizes a [4Fe-4S] cluster, S-adenosyl-L-methionine (SAM), and pyridoxal 5'-phosphate (PLP) to isomerize L-alpha-lysine to L-beta-lysine. LAM is a member of the radical-SAM enzyme superfamily in which a [4Fe-4S]+ cluster reductively cleaves SAM to produce the 5'-deoxyadenosyl radical, which abstracts an H-atom from substrate to form 5'-deoxyadenosine (5'-Ado) and the alpha-Lys* radical (state 3 (Lys*)). This radical isomerizes to the beta-Lys* radical (state 4(Lys*)), which then abstracts an H-atom from 5'-Ado to form beta-lysine and the 5'-deoxyadenosyl radical; the latter then regenerates SAM. We use 13C, 1,2H, 31P, and 14N ENDOR to characterize the active site of LAM in intermediate states that contain the isomeric substrate radicals or analogues. With L-alpha-lysine as substrate, we monitor the state with beta-Lys*. In parallel, we use two substrate analogues that generate stable analogues of the alpha-Lys* radical: trans-4,5-dehydro-L-lysine (DHLys) and 4-thia-L-lysine (SLys). This first glimpse of the motions of active-site components during catalytic turnover suggests a possible major movement of PLP during catalysis. However, the principal focus of this work is on the relative positions of the carbons involved in H-atom transfer. We conclude that the active site facilitates hydrogen atom transfer by enforcing van der Waals contact between radicals and their reacting partners. This constraint enables the enzyme to minimize and even eliminate side reactions of highly reactive species such as the 5'-deoxyadensosyl radical.
Collapse
Affiliation(s)
- Nicholas S Lees
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
| | | | | | | | | | | |
Collapse
|
40
|
Veerapen N, Taylor SA, Walsby CJ, Pinto BM. A Mild Pummerer-Like Reaction of Carbohydrate-Based Selenoethers and Thioethers Involving Linear Ozonide Acetates as Putative Intermediates. J Am Chem Soc 2005; 128:227-39. [PMID: 16390151 DOI: 10.1021/ja0557029] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pummerer-like rearrangements of carbohydrate-based heterocycles containing selenium and sulfur were investigated. To the best of our knowledge, this is the first report on the Pummerer rearrangement in selenoheterocycles. Ozonization of 1,4-anhydro-D-galactitol or 1,5-anhydroxylitol derivatives containing sulfur or selenium as the ring heteroatom gave unstable intermediates that were attributed to ozonides. These intermediates decomposed upon warming to give selenoxides or sulfoxides. Significantly, addition of acetic anhydride at low temperature to the ozonization reaction mixtures gave Pummerer-rearrangement products after warming to ambient temperature. However, when the isolated selenoxides or sulfoxides were treated with acetic anhydride, Pummerer rearrangement occurred but the sulfoxides required much higher reaction temperatures. The latter results are at variance with the former and are interpreted in terms of the rearrangement of the ozonide acetate intermediates in the former cases. To probe whether the rearrangement proceeded heterolytically via extrusion of singlet oxygen or homolytically via the generation of radical species, trapping experiments with rubrene and electron paramagnetic resonance (EPR) studies with the radical trap DMPO were performed. The results of these experiments are consistent with the intermediacy of radical species and suggest a new and milder synthetic method to generate Pummerer-type products.
Collapse
Affiliation(s)
- Natacha Veerapen
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | | | | | | |
Collapse
|
41
|
Walsby CJ, Ortillo D, Yang J, Nnyepi MR, Broderick WE, Hoffman BM, Broderick JB. Spectroscopic approaches to elucidating novel iron-sulfur chemistry in the "radical-Sam" protein superfamily. Inorg Chem 2005; 44:727-41. [PMID: 15859242 DOI: 10.1021/ic0484811] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), and Mössbauer spectroscopies and other physical methods have provided important new insights into the radical-SAM superfamily of proteins, which use iron-sulfur clusters and S-adenosylmethionine to initiate H atom abstraction reactions. This remarkable chemistry involves the generation of the extremely reactive 5'-deoxyadenosyl radical, the same radical intermediate utilized in B12-dependent reactions. Although early speculation focused on the possibility of an organometallic intermediate in radical-SAM reactions, current evidence points to novel chemistry involving a site-differentiated [4Fe-4S] cluster. The focus of this forum article is on one member of the radical-SAM superfamily, pyruvate formate-lyase activating enzyme, and how physical methods, primarily EPR and ENDOR spectroscopies, are contributing to our understanding of its structure and mechanism. New ENDOR data supporting coordination of the methionine moiety of SAM to the unique site of the [4Fe-4S]2+/+ cluster are presented.
Collapse
Affiliation(s)
- Charles J Walsby
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | | | | | | | | | | | | |
Collapse
|
42
|
Walsby CJ, Telser J, Rigsby RE, Armstrong RN, Hoffman BM. Enzyme Control of Small-Molecule Coordination in FosA as Revealed by 31P Pulsed ENDOR and ESE-EPR. J Am Chem Soc 2005; 127:8310-9. [PMID: 15941264 DOI: 10.1021/ja044094e] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
FosA is a manganese metalloglutathione transferase that confers resistance to the broad-spectrum antibiotic fosfomycin, which contains a phosphonate group. The active site of this enzyme consists of a high-spin Mn(2+) ion coordinated by endogenous ligands (a glutamate and two histidine residues) and by exogenous ligands, such as substrate fosfomycin. To study the Mn(2+) coordination environment of FosA in the presence of substrate and the inhibitors phosphonoformate and phosphate, we have used (31)P pulsed electron-nuclear double resonance (ENDOR) at 35 GHz to obtain metrical information from (31)P-Mn(2+) interactions. We have found that continuous wave (CW) (31)P ENDOR is not successful in the study of phosphates and phosphonates coordinated to Mn(2+). Parallel studies of phosph(on)ate binding to the Mn(2+) of FosA and to aqueous Mn(2+) ion disclose how the enzyme modifies the coordination of these molecules to the active site Mn(2+). Through analysis of (31)P hyperfine parameters derived from simulations of the ENDOR spectra we have determined the binding modes of the phosph(on)ates in each sample and discerned details of the geometric and electronic structure of the metal center. The (31)P ENDOR studies of the protein samples agree with, or improve on, the Mn-P distances determined from crystal structures and provide Mn-phosph(on)ate bonding information not available from these studies. Electron spin echo electron paramagnetic resonance (ESE-EPR) spectra have also been recorded. Simulation of these spectra yield the axial and rhombic components of the Mn(2+) (S = (5)/(2)) zero-field splitting (zfs) tensor. Comparison of structural inferences based on these zfs parameters both with the known enzyme structures and the (31)P ENDOR results establishes that the time-honored procedure of analyzing Mn(2+) zfs parameters to describe the coordination environment of the metal ion is not valid or productive.
Collapse
Affiliation(s)
- Charles J Walsby
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
| | | | | | | | | |
Collapse
|
43
|
Petering DH, Krepkiy D, Forsterling H, Walsby CJ, Hoffman B. Structure, DNA binding, and comparative properties of zinc, cadmium, lead, and cobalt finger-3 peptides from Xenopus laevis transcription factor IIIA. J Inorg Biochem 2003. [DOI: 10.1016/s0162-0134(03)80527-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
44
|
Broderick JB, Ortillo D, Broderick WE, Hong W, Walsby CJ, Hoffman BM, Krebs C, Hanh B. Poised for radical generation: Interaction of S-adenosylmethionine with a [4Fe4S] cluster. J Inorg Biochem 2003. [DOI: 10.1016/s0162-0134(03)80571-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
45
|
Walsby CJ, Krepkiy D, Petering DH, Hoffman BM. Cobalt-substituted zinc finger 3 of transcription factor IIIA: interactions with cognate DNA detected by (31)P ENDOR spectroscopy. J Am Chem Soc 2003; 125:7502-3. [PMID: 12812475 DOI: 10.1021/ja034589o] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We show the first ENDOR study of the coordination environment of high-spin Co(II) in a biological system with a study of DNA binding to the Co-substituted Cys2/His2 single Zn-finger domain, Finger 3 (F3), from the prototypical zinc finger protein, transcription factor IIIA (TFIIIA) from Xenopus laevis. High covalency to cysteine and histidine is implied by ENDOR-derived 1H couplings to protons of cysteinyl ligands and 14N couplings to histidyl nitrogens, results which support the expectation that Zn(II) and Co(II) bind to F3 in a very similar manner. No changes in either 1H or 14N ENDOR were detected upon binding Co(II)-F3 to C-block DNA. Of particular importance to the use of Co(II) substitution for Zn(II), the ENDOR method shows that Co(II)-F3 undergoes sequence-specific binding to the cognate DNA for Zn(II)-F3, the internal control region (ICR) of the 5S rRNA (C-block). 31P ENDOR measurements yield a Co-31P distance of rCo-P = 8.1(3) A to the nearest backbone phosphodiester of the C-block. Interestingly, a 31P ENDOR doublet observed for Co(II)-F3 in phosphate buffer indicates that inorganic phosphate (Pi) binds at a comparable distance from Co as does the nearest phosphate of DNA, presumably at the same site.
Collapse
Affiliation(s)
- Charles J Walsby
- Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA
| | | | | | | |
Collapse
|
46
|
Walsby CJ, Ortillo D, Broderick WE, Broderick JB, Hoffman BM. An anchoring role for FeS clusters: chelation of the amino acid moiety of S-adenosylmethionine to the unique iron site of the [4Fe-4S] cluster of pyruvate formate-lyase activating enzyme. J Am Chem Soc 2002; 124:11270-1. [PMID: 12236732 DOI: 10.1021/ja027078v] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pyruvate formate-lyase activating enzyme (PFL-AE) generates the catalytically essential glycyl radical on pyruvate formate-lyase via the interaction of the catalytically active [4Fe-4S]+ cluster with S-adenosylmethionine (AdoMet). Like other members of the Fe-S/AdoMet family of enzymes, PFL-AE is thought to function via generation of an AdoMet-derived 5'-deoxyadenosyl radical intermediate; however, the mechanistic steps by which this radical is generated remain to be elucidated. While all of the members of the Fe-S/AdoMet family of enzymes appear to have a unique iron site in the [4Fe-4S] cluster, based on the presence of a conserved three-cysteine cluster binding motif, the role of this unique site has been elusive. Here we utilize 35-GHz pulsed electron nuclear double resonance (ENDOR) studies of the [4Fe-4S]+ cluster of PFL-AE in complex with isotopically labeled AdoMet (denoted [1+/AdoMet]) to show that the unique iron serves to anchor the AdoMet for catalysis. AdoMet labeled with 17O at the carboxylate shows a coupling of A = 12.2 MHz, consistent with direct coordination of the carboxylate to the unique iron of the cluster. This is supported by 13C-ENDOR with the carboxylato carbon labeled with 13C, which shows a hyperfine coupling of 0.71 MHz. AdoMet enriched with 15N at the amino position gives rise to a spectrum with A(15N) = 5.8 MHz, consistent with direct coordination of the amino group to a unique iron of the cluster. Together, the results demonstrate that the unique iron of the [4Fe-4S] cluster anchors AdoMet by forming a classical N/O chelate with the amino and carboxylato groups of the methionine fragment.
Collapse
Affiliation(s)
- Charles J Walsby
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA
| | | | | | | | | |
Collapse
|
47
|
Walsby CJ, Hong W, Broderick WE, Cheek J, Ortillo D, Broderick JB, Hoffman BM. Electron-nuclear double resonance spectroscopic evidence that S-adenosylmethionine binds in contact with the catalytically active [4Fe-4S](+) cluster of pyruvate formate-lyase activating enzyme. J Am Chem Soc 2002; 124:3143-51. [PMID: 11902903 DOI: 10.1021/ja012034s] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pyruvate formate-lyase activating enzyme (PFL-AE) is a representative member of an emerging family of enzymes that utilize iron-sulfur clusters and S-adenosylmethionine (AdoMet) to initiate radical catalysis. Although these enzymes have diverse functions, evidence is emerging that they operate by a common mechanism in which a [4Fe-4S](+) interacts with AdoMet to generate a 5'-deoxyadenosyl radical intermediate. To date, however, it has been unclear whether the iron-sulfur cluster is a simple electron-transfer center or whether it participates directly in the radical generation chemistry. Here we utilize electron paramagnetic resonance (EPR) and pulsed 35 GHz electron-nuclear double resonance (ENDOR) spectroscopy to address this question. EPR spectroscopy reveals a dramatic effect of AdoMet on the EPR spectrum of the [4Fe-4S](+) of PFL-AE, changing it from rhombic (g = 2.02, 1.94, 1.88) to nearly axial (g = 2.01, 1.88, 1.87). (2)H and (13)C ENDOR spectroscopy was performed on [4Fe-4S](+)-PFL-AE (S = (1)/(2)) in the presence of AdoMet labeled at the methyl position with either (2)H or (13)C (denoted [1+/AdoMet]). The observation of a substantial (2)H coupling of approximately 1 MHz ( approximately 6-7 MHz for (1)H), as well as hyperfine-split signals from the (13)C, manifestly require that AdoMet lie close to the cluster. (2)H and (13)C ENDOR data were also obtained for the interaction of AdoMet with the diamagnetic [4Fe-4S](2+) state of PFL-AE, which is visualized through cryoreduction of the frozen [4Fe-4S](2+)/AdoMet complex to form the reduced state (denoted [2+/AdoMet](red)) trapped in the structure of the oxidized state. (2)H and (13)C ENDOR spectra for [2+/AdoMet](red) are essentially identical to those obtained for the [1+/AdoMet] samples, showing that the cofactor binds in the same geometry to both the 1+ and 2+ states of PFL-AE. Analysis of 2D field-frequency (13)C ENDOR data reveals an isotropic hyperfine contribution, which requires that AdoMet lie in contact with the cluster, weakly interacting with it through an incipient bond/antibond. From the anisotropic hyperfine contributions for the (2)H and (13)C ENDOR, we have estimated the distance from the closest methyl proton of AdoMet to the closest iron of the cluster to be approximately 3.0-3.8 A, while the distance from the methyl carbon to the nearest iron is approximately 4-5 A. We have used this information to construct a model for the interaction of AdoMet with the [4Fe-4S](2+/+) cluster of PFL-AE and have proposed a mechanism for radical generation that is consistent with these results.
Collapse
Affiliation(s)
- Charles J Walsby
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA
| | | | | | | | | | | | | |
Collapse
|