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207. Cyclooctatetraene: A Bioactive Cubane Paradigm Complement

Author

Xing, Hui, primary, Houston, Sevan D., additional, Chen, Xuejie, additional, Ghassabian, Sussan, additional, Fahrenhorst‐Jones, Tyler, additional, Kuo, Andy, additional, Murray, Cody‐Ellen P., additional, Conn, Kyna‐Anne, additional, Jaeschke, Kara N., additional, Jin, Da‐Yun, additional, Pasay, Cielo, additional, Bernhardt, Paul V., additional, Burns, Jed M., additional, Tsanaktsidis, John, additional, Savage, G. Paul, additional, Boyle, Glen M., additional, De Voss, James J., additional, McCarthy, James, additional, Walter, Gimme H., additional, Burne, Thomas H. J., additional, Smith, Maree T., additional, Tie, Jian‐Ke, additional, and Williams, Craig M., additional

Published
2019
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210. The cubane paradigm in bioactive molecule discovery: further scope, limitations and the cyclooctatetraene complement

Author

Houston, Sevan D., primary, Fahrenhorst-Jones, Tyler, additional, Xing, Hui, additional, Chalmers, Benjamin A., additional, Sykes, Melissa L., additional, Stok, Jeanette E., additional, Farfan Soto, Clementina, additional, Burns, Jed M., additional, Bernhardt, Paul V., additional, De Voss, James J., additional, Boyle, Glen M., additional, Smith, Maree T., additional, Tsanaktsidis, John, additional, Savage, G. Paul, additional, Avery, Vicky M., additional, and Williams, Craig M., additional

Published
2019
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213. Phenethylammonium bismuth halides: from single crystals to bulky-organic cation promoted thin-film deposition for potential optoelectronic applications

Author

Ghasemi, Mehri, primary, Lyu, Miaoqiang, additional, Roknuzzaman, Md, additional, Yun, Jung-Ho, additional, Hao, Mengmeng, additional, He, Dongxu, additional, Bai, Yang, additional, Chen, Peng, additional, Bernhardt, Paul V., additional, Ostrikov, Kostya (Ken), additional, and Wang, Lianzhou, additional

Published
2019
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220. Molecular Approach to Alkali-Metal Encapsulation by a Prussian Blue Analogue FeII/CoIIICube in Aqueous Solution: A Kineticomechanistic Exchange Study

Author

Gonzálvez, Miguel A., Bernhardt, Paul V., Font-Bardia, Mercè, Gallen, Albert, Jover, Jesús, Ferrer, Montserrat, and Martínez, Manuel

Abstract

The preparation of a series of alkali-metal inclusion complexes of the molecular cube [{CoIII(Me3-tacn)}4{FeII(CN)6}4]4–(Me3-tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane), a mixed-valent Prussian Blue analogue bearing bridging cyanido ligands, has been achieved by following a redox-triggered self-assembly process. The molecular cubes are extremely robust and soluble in aqueous media ranging from 5 M [H+] to 2 M [OH–]. All the complexes have been characterized by the standard mass spectometry, UV–vis, inductively coupled plasma, multinuclear NMR spectroscopy, and electrochemistry. Furthermore, X-ray diffraction analysis of the sodium and lithium salts has also been achieved, and the inclusion of moieties of the form {M–OH2}+(M = Li, Na) is confirmed. These inclusion complexes in aqueous solution are rather inert to cation exchange and are characterized by a significant decrease in acidity of the confined water molecule due to hydrogen bonding inside the cubic cage. Exchange of the encapsulated cationic {M–OH2}+or M+units by other alkali metals has also been studied from a kineticomechanistic perspective at different concentrations, temperatures, ionic strengths, and pressures. In all cases, the thermal and pressure activation parameters obtained agree with a process that is dominated by differences in hydration of the cations entering and exiting the cage, although the size of the portal enabling the exchange also plays a determinant role, thus not allowing the large Cs+cation to enter. All the exchange substitutions studied follow a thermodynamic sequence that relates with the size and polarizing capability of the different alkali cations; even so, the process can be reversed, allowing the entry of {Li–OH2}+units upon adsorption of the cube on an anion exchange resin and subsequent washing with a Li+solution.

Published
2021
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221. Mesoionic 1,3-oxazinium olates: Rearrangement to acylketenes and 3-azabicyclo[3.1.1]heptanetriones

Author

Sheibani, Hassan, Bernhardt, Paul V., and Wentrup, Curt

Subjects
Molecular dynamics -- Research, Ketones -- Chemical properties, Ring formation (Chemistry) -- Research, Biological sciences, Chemistry
Abstract

Synthesis of 2-vinyl-1,3-oxazinium olates, their facile ring opening to ketenes is reported. Recyclization to 3-azabicyclo[3.1.1]heptanetriones in an intramolecular [2+2] criss-cross cycloaddition reaction is synthesized.

Published
2005

223. Biosynthetic insights provided by unusual sesterterpenes from the medicinal herb Aletris farinosa † †Dedicated to Prof. Sir Alan Battersby on the occasion of his 90th birthday. ‡ ‡Electronic supplementary information (ESI) available: Full computational details, 1H and 13C NMR spectra for 2–6 and experimental procedures Click here for additional data file. Click here for additional data file

Author

Challinor, Victoria L., Johnston, Ryne C., Bernhardt, Paul V., Lehmann, Reginald P., Krenske, Elizabeth H., and De Voss, James J.

Subjects
Chemistry
Abstract

Configuration of a single stereocenter determines if a key carbocation in sesterterpene biosynthesis undergoes simple elimination or a cascade of seven 1,2-methyl and hydride migrations., A series of novel sesterterpenes (2–6) have been isolated from the roots of Aletris farinosa and structurally characterized by MS, NMR, and X-ray crystallography in conjunction with computational modeling. Their structures provide new insights into the mechanisms of sesterterpene biosynthesis. Specifically, we propose with support from density functional theory computations that the configuration at a single stereocenter determines the fate of a key tetracyclic carbocationic intermediate, derived from an oxidogeranylfarnesol precursor. Whereas one epimer of the carbocation undergoes H+ elimination to give 6, the other undergoes a spectacular cascade of seven 1,2-methyl and hydride migrations leading to the previously unreported carbon skeleton of 5. Theoretical calculations suggest that the cascade is triggered by substrate preorganization in the enzyme active site.

Published
2015

225. Does H3O+Really Act as a Ligand in the Solid State?

Author

Blackman, Allan G., Jelley, Rebecca E., Krenske, Elizabeth H., Gahan, Lawrence R., and Bernhardt, Paul V.

Abstract

The evidence for the existence of metal complexes containing H3O+as a ligand in the solid state is examined. Each of the 68 examples in the Cambridge Structural Database in which H3O+is bound to a transition metal, lanthanoid, actinoid, or main group metal ion is detailed and critically appraised. It is concluded that none of the reported examples of complexes containing coordinated H3O+have been unequivocally characterized and that they result from either curation errors or misinterpretations of the crystallographic data. These conclusions are supported by computational techniques, which show that three purported H3O+complexes based on the 1,4,7,10,13,16,21,24-octa-azabicyclo(8.8.8)hexacosane azacryptand skeleton are better described as aqua complexes, with protonation occurring at the amine ligand.

Published
2021
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226. A supramolecular synthon for H-bonded transition metal arrays

Author

Bernhardt, Paul V.

Subjects
Copper compounds -- Research, Hydrogen bonding -- Research, Coordination compounds -- Research, Molecular structure -- Research, Chemistry
Abstract

The heterocycle melamine attached to a 14-membered polyazamacrocylic copper(II) complex ring can produce noncovalently linked arrays driven by H-bonding forces. The X-ray crystal structures of three different arrays of the macrocyclic transition metal complex are investigated. Results reveal both self-recognition and cocrystal formation with cyanuric and barbituric acid for the Cu(II) complex.

Published
1999

230. Cytochrome c Reductase is a Key Enzyme Involved in the Extracellular Electron Transfer Pathway towards Transition Metal Complexes in Pseudomonas Putida.

Author

Lai, Bin, Bernhardt, Paul V., and Krömer, Jens O.

Subjects
NADH dehydrogenase, TRANSITION metal complexes, CHARGE exchange, PSEUDOMONAS putida, CYTOCHROME oxidase, EXTRACELLULAR enzymes, CYTOCHROME c
Abstract

Mediator‐based extracellular electron transfer (EET) pathways can balance the redox metabolism of microbes. However, such electro‐biosynthesis processes are constrained by the unknown underlying EET mechanisms. In this paper, Pseudomonas putida was studied to systematically investigate its EET pathway to transition metal complexes (i. e., [Fe(CN)6]3−/4− and [Co(bpy)3]3+/2+; bpy=2,2′‐bipyridyl) under anaerobic conditions. Comparative proteomics showed the aerobic respiratory components were upregulated in a bioelectrochemical system without oxygen, suggesting their potential contribution to EET. Further tests found inhibiting cytochrome c oxidase activity by NaN3 and NADH dehydrogenase by rotenone did not significantly change the current output. However, the EET pathway was completely blocked, while cytochrome c reductase activity was inhibited by antimycin A. Although it cannot be excluded that cytochrome c and the periplasmic subunit of cytochrome c oxidase donate electrons to the transition metal complexes, these results strongly demonstrate that cytochrome c reductase is a key complex for the EET pathway. [ABSTRACT FROM AUTHOR]

Published
2020
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234. A spectroelectrochemical investigation of the heme‐based sensor DevS from Mycobacterium tuberculosis: a redox versus oxygen sensor.

Author

Barreto, Giamwemberg A., Carepo, Marta S. P., Gondim, Ana C. S., Guimarães, Wellinson G., Lopes, Luiz G. F., Bernhardt, Paul V., Paulo, Tércio F., Sousa, Eduardo H. S., and Diógenes, Izaura C. N.

Subjects
OXYGEN detectors, MYCOBACTERIUM tuberculosis, STANDARD hydrogen electrode, STRAIN sensors, DETECTORS, OXYGEN in the blood, OXYGEN carriers
Abstract

Tuberculosis is one of the oldest known infectious diseases, responsible for millions of deaths annually around the world. The ability of Mycobacterium tuberculosis (Mtb) to enter into a dormant state has been considered integral to the success of this bacterium as a human pathogen. One of the key systems involved in regulating the entrance into dormancy is the differentially expressed in virulent strain sensor protein (DevS) [(dormancy survival sensor protein (DosS)]. However, the physiological signal for DevS has remained unclear since it was first shown to be a heme‐based sensor with conflicting reports on whether it is a redox or an oxygen sensor. To address this question and provide a better understanding of the electronic properties of this protein, we present here, for the first time, a series of spectroelectrochemistry measurements of the full‐length holo DevS in anaerobic conditions as well as bound to CO, NO, imidazole (Imz), cyanide, and O2. An interesting feature of this protein is its ability to bind Imz even in the ferrous state, implying small‐molecule analogues could be designed as potential regulators. Nonetheless, a midpoint potential (Em) value of +10 mV [vs normal hydrogen electrode (NHE)] for DevS as measured under anaerobic conditions is much higher than the expected cytosolic potential for Mtb or even within stimulated macrophages (~ −270 mV vs NHE), indicating this sensor works in a reduced ferrous state. These data, along with the high oxygen affinity and very slow auto‐oxidation rate of DevS, provides evidence that it is not a redox sensor. Overall, this study validates the biological function of DevS as an oxygen sensor directly involved in the dormancy/latency of Mtb. [ABSTRACT FROM AUTHOR]

Published
2019
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236. Berichtigung: Validating Eaton's Hypothesis: Cubane as a Benzene Bioisostere

Author

Chalmers, Benjamin A., primary, Xing, Hui, additional, Houston, Sevan, additional, Clark, Charlotte, additional, Ghassabian, Sussan, additional, Kuo, Andy, additional, Cao, Benjamin, additional, Reitsma, Andrea, additional, Murray, Cody‐Ellen P., additional, Stok, Jeanette E., additional, Boyle, Glen M., additional, Pierce, Carly J., additional, Littler, Stuart W., additional, Winkler, David A., additional, Bernhardt, Paul V., additional, Pasay, Cielo, additional, De Voss, James J., additional, McCarthy, James, additional, Parsons, Peter G., additional, Walter, Gimme H., additional, Smith, Maree T., additional, Cooper, Helen M., additional, Nilsson, Susan K., additional, Tsanaktsidis, John, additional, Savage, G. Paul, additional, and Williams, Craig M., additional

Published
2018
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237. Corrigendum: Validating Eaton's Hypothesis: Cubane as a Benzene Bioisostere

Author

Chalmers, Benjamin A., primary, Xing, Hui, additional, Houston, Sevan, additional, Clark, Charlotte, additional, Ghassabian, Sussan, additional, Kuo, Andy, additional, Cao, Benjamin, additional, Reitsma, Andrea, additional, Murray, Cody‐Ellen P., additional, Stok, Jeanette E., additional, Boyle, Glen M., additional, Pierce, Carly J., additional, Littler, Stuart W., additional, Winkler, David A., additional, Bernhardt, Paul V., additional, Pasay, Cielo, additional, De Voss, James J., additional, McCarthy, James, additional, Parsons, Peter G., additional, Walter, Gimme H., additional, Smith, Maree T., additional, Cooper, Helen M., additional, Nilsson, Susan K., additional, Tsanaktsidis, John, additional, Savage, G. Paul, additional, and Williams, Craig M., additional

Published
2018
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240. Heteroatom-Interchanged Isomers of Lissoclinamide 5: Copper(II) Complexation, Halide Binding, and Biological Activity

Author

Xie, Sida, primary, Savchenko, Andrei I., additional, Kerscher, Marion, additional, Grange, Rebecca L., additional, Krenske, Elizabeth H., additional, Harmer, Jeffrey R., additional, Bauer, Michelle J., additional, Broit, Natasa, additional, Watters, Dianne J., additional, Boyle, Glen M., additional, Bernhardt, Paul V., additional, Parsons, Peter G., additional, Comba, Peter, additional, Gahan, Lawrence R., additional, and Williams, Craig M., additional

Published
2018
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246. The central active site arginine in sulfite oxidizing enzymes alters kinetic properties by controlling electron transfer and redox interactions

Author

Hsiao, Ju-Chun, primary, McGrath, Aaron P., additional, Kielmann, Linda, additional, Kalimuthu, Palraj, additional, Darain, Farzana, additional, Bernhardt, Paul V., additional, Harmer, Jeffrey, additional, Lee, Mihwa, additional, Meyers, Kimberley, additional, Maher, Megan J., additional, and Kappler, Ulrike, additional

Published
2018
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248. X-ray absorption and emission spectroscopy of N2S2 Cu(II)/(III) complexes.

Author

Geoghegan, Blaise L., Bilyj, Jessica K., Bernhardt, Paul V., DeBeer, Serena, and Cutsail, George E.

Subjects
*X-ray emission spectroscopy, *COPPER, *SCHIFF bases, *DENSITY functional theory, *OXIDATION states, *X-ray absorption near edge structure
Abstract

This study investigates the influence of ligand charge on transition energies in a series of CuN2S2 complexes based on dithiocarbazate Schiff base ligands using Cu K-edge X-ray absorption spectroscopy (XAS) and Kβ valence-to-core (VtC) X-ray emission spectroscopy (XES). By comparing the formally Cu(II) complexes [CuII(HL1)] (HL12− = dimethyl pentane-2,4-diylidenebis[carbonodithiohydrazonate]) and [CuII(HL2)] (HL22− = dibenzyl pentane-2,4-diylidenebis[carbonodithiohydrazonate]) and the formally Cu(III) complex [CuIII(L2)], distinct changes in transition energies are observed, primarily attributed to the metal oxidation state. Density functional theory (DFT) calculations demonstrate how an increased negative charge on the deprotonated L23− ligand stabilizes the Cu(III) center through enhanced charge donation, modulating the core transition energies. Overall, significant shifts to higher energies are noted upon metal oxidation, emphasizing the importance of scrutinizing ligand structure in XAS/VtC XES analysis. The data further support the redox-innocent role of the Schiff base ligands and underscore the criticality of ligand protonation levels in future spectroscopic studies, particularly for catalytic intermediates. The combined XAS-VtC XES methodology validates the Cu(III) oxidation state assignment while offering insights into ligand protonation effects on core-level spectroscopic transitions. [ABSTRACT FROM AUTHOR]

Published
2024
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249. Amaurones A–K: Polyketides from the Fish Gut-Derived Fungus Amauroascussp. CMB-F713

Author

Wu, Taizong, Salim, Angela A., Bernhardt, Paul V., and Capon, Robert J.

Abstract

Using a molecular networking guided strategy, chemical analysis of the Australian mullet fish gastrointestinal tract-derived fungus Amauroascussp. CMB-F713 yielded a family of polyketide pyrones, amaurones A–I (1–9), featuring an unprecedented carbon skeleton. Structures were assigned to 1–9by detailed spectroscopic analysis (including X-ray analysis of 1), biosynthetic considerations, and chemical interconversions. For example, the orthoacetate 5was unstable when stored dry at room temperature, transforming to the monoacetates 2and 3, while mild heating (40 °C) prompted quantitative conversion of 3to 2, via an intramolecular trans-acetylation. Likewise, during handling, the monoacetate 1was prone to intramolecular trans-acetylation, leading to an equilibrium mixture with the isomeric monoacetate amaurone J (10), confirmed when partial hydrolysis of the diacetate 2yielded the monoacetates 1and 10and the triol amaurone K (11).

Published
2021
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250. Mediated Catalytic Voltammetry of Holo and Heme-Free Human Sulfite Oxidases

Author

Kalimuthu, Palraj, Belaidi, Abdel A., Schwarz, Guenter, Bernhardt, Paul V., Kalimuthu, Palraj, Belaidi, Abdel A., Schwarz, Guenter, and Bernhardt, Paul V.

Abstract

Herein, we report the electrocatalytic voltammetry of holo and heme-free human sulfite oxidase (HSO) mediated by the synthetic iron complexes 1,2-bis(1,4,7-triaza-1-cyclononyl)ethane iron(III) bromide, ([Fe(dtne)]Br-3.3H(2)O), potassium ferricyanide (K-3[Fe(CN)(6)]), and ferrocene methanol (FM) at a 5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol (Hpyt) modified gold working electrode. Holo HSO contains two electroactive redox cofactors, comprising a mostly negatively charged cyt b(5) (heme) domain and a Mo cofactor (Moco) domain (the site of sulfite oxidation), where the surface near the active site is positively charged. We anticipated different catalytic voltammetry based on either repulsive or attractive electrostatic interactions between the holo or heme-free enzymes and the positively or negatively charged redox mediators. Both holo and heme-free HSO experimental catalytic voltammetry has been modeled by using electrochemical simulation across a range of sweep rates and concentrations of substrate and both positive and negatively charged electron acceptors ([Fe(dtne)](3+), [Fe(CN)(6)](3-) and FM+), which provides new insights into the kinetics of the HSO catalytic mechanism. These mediator complexes have almost the same redox potential (all lying in the range +415 to +430mV vs. NHE) and, thus, deliver the same driving force for electron transfer with the Mo cofactor. However, differences in the electrostatic affinities between HSO and the mediator have a significant influence on the electrocatalytic response.

Published
2017

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