1
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Zhou Z, Johnson MA, Wei Z, Bühringer MU, Garner MH, Tykwinski R, Petrukhina MA. Bending a Cumulene with Electrons: Stepwise Chemical Reduction and Structural Study of a Tetraaryl[4]Cumulene. Chemistry 2024:e202304145. [PMID: 38433113 DOI: 10.1002/chem.202304145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 03/02/2024] [Accepted: 03/03/2024] [Indexed: 03/05/2024]
Abstract
Chemical reduction of a [4]cumulene with cesium metal was explored, and the structural changes stemming from electron acquisition are detailed using X-ray crystallography. It is found that the [4]cumulene undergoes dramatic geometric changes upon stepwise reduction, including bending of the cumulenic core and twisting of the endgroups from orthogonal to planar. The structural deformation is consistent with early theoretical reports that suggest that the twisting should occur upon reduction of both even and odd [n]cumulenes. The current results, on the other hand, are inconsistent with a previous experimental study of a [3]cumulene in which the predicted twisting is not observed upon reduction. DFT calculations reveal that the barrier to deformation is an order of magnitude lower in a [3]cumulene than a [4]cumulene, allowing the barrier to be overcome in the solid-state.
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Affiliation(s)
- Zheng Zhou
- Department of Chemistry, University at Albany, State University of New York, Albany, NY-12222, USA
| | - Matthew A Johnson
- Department of Chemistry, University of Alberta, Edmonton, AB-T6G 2G2, Canada
| | - Zheng Wei
- Department of Chemistry, University at Albany, State University of New York, Albany, NY-12222, USA
| | - Martina U Bühringer
- Department of Chemistry and Pharmacy, University of Erlangen-Nuremberg, Nikolaus-Fiebiger Str. 10, 91058, Erlangen, Germany
| | - Marc H Garner
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Rik Tykwinski
- Department of Chemistry, University of Alberta, Edmonton, AB-T6G 2G2, Canada
| | - Marina A Petrukhina
- Department of Chemistry, University at Albany, State University of New York, Albany, NY-12222, USA
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2
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Garner MH, Blaskovits JT, Corminboeuf C. Enhanced inverted singlet-triplet gaps in azaphenalenes and non-alternant hydrocarbons. Chem Commun (Camb) 2024; 60:2070-2073. [PMID: 38291965 DOI: 10.1039/d3cc05747j] [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: 02/01/2024]
Abstract
Inverted singlet-triplet gaps may lead to novel molecular emitters if a rational design approach can be achieved. We uncover a substituent strategy that enables tuning of the gap and succeed in inducing inversion in near-gapless molecules. Based on known inverted-gap emitters, we design substituted analogs with even more negative singlet-triplet gaps than in the parent systems. The inversion is lost if the reverse substituent-strategy is used. We thus demonstrate a definite set of conceptual design rules for inverted gap molecules.
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Affiliation(s)
- Marc H Garner
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, École Polytechnique Fedéralé de Lausanne (EPFL), 1015 Lausanne, Switzerland.
| | - J Terence Blaskovits
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, École Polytechnique Fedéralé de Lausanne (EPFL), 1015 Lausanne, Switzerland.
| | - Clémence Corminboeuf
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, École Polytechnique Fedéralé de Lausanne (EPFL), 1015 Lausanne, Switzerland.
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3
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Garner MH, Blaskovits JT, Corminboeuf C. Double-bond delocalization in non-alternant hydrocarbons induces inverted singlet-triplet gaps. Chem Sci 2023; 14:10458-10466. [PMID: 37800005 PMCID: PMC10548509 DOI: 10.1039/d3sc03409g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 09/06/2023] [Indexed: 10/07/2023] Open
Abstract
Molecules where the first excited singlet state is lower in energy than the first excited triplet state have the potential to revolutionize OLEDs. This inverted singlet-triplet gap violates Hund's rule and currently there are only a few molecules which are known to have this property. Here, we screen the complete set of non-alternant hydrocarbons consisting of 5-, 6-, 7-membered rings fused into two-, three- and four-ring polycyclic systems. We identify several molecules where the symmetry of the ground-state structure is broken due to bond-length alternation. Through symmetry-constrained optimizations we identify several molecular cores where the singlet-triplet gap is inverted when the structure is in a higher symmetry, pentalene being a known example. We uncover a strategy to stabilize the molecular cores into their higher-symmetry structures with electron donors or acceptors. We design several substituted pentalenes, s-indacenes, and indeno[1,2,3-ef]heptalenes with inverted gaps, among which there are several synthetically known examples. In contrast to known inverted gap emitters, we identify the double-bond delocalized structure of their conjugated cores as the necessary condition to achieve the inverted gap. This strategy enables chemical tuning and paves the way for the rational design of polycyclic hydrocarbons with inverted singlet-triplet gaps. These molecules are prospective emitters if their properties can be optimized for use in OLEDs.
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Affiliation(s)
- Marc H Garner
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, École Polytechnique Fedéralé de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - J Terence Blaskovits
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, École Polytechnique Fedéralé de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Clémence Corminboeuf
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, École Polytechnique Fedéralé de Lausanne (EPFL) 1015 Lausanne Switzerland
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4
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Garner MH, Corminboeuf C. The fundamental relation between electrohelicity and molecular optical activity. Phys Chem Chem Phys 2023. [PMID: 37232016 DOI: 10.1039/d3cp01343j] [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: 05/27/2023]
Abstract
Electrohelicity arises in molecules such as allene and spiropentadiene when their symmetry is reduced and helical frontier molecular orbitals (MOs) appear. Such molecules are optically active and electrohelicity has been suggested as a possible design principle for increasing the chiroptical response. Here we examine the fundamental link between electrohelicity and optical activity by studying the origin of the electric and magnetic transition dipole moments of the π-π* transitions. We show that the helical character of the MOs drives the optical activity in allene, and we use this knowledge to design allenic molecules with increased chiroptical response. We further examine longer carbyne-like molecules. While the MO helicity also contributes to the optical activity in non-planar butatriene, the simplest cumulene, we show there is no relation between the chiroptical response and the helical π-MOs of tolane, a simple polyyne. Finally, we demonstrate that the optical activity of spiropentadiene is inherently linked to mixing of its two π-systems rather than the helical shape of its occupied π-MOs. We thus find that the fundamental connection between electrohelicity and optical activity is very molecule dependent. Although electrohelicity is not the underlying principle, we show that the chiroptical response can be enhanced through insight into the helical nature of electronic transitions.
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Affiliation(s)
- Marc H Garner
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, Ecole Polytechnique federale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
| | - Clemence Corminboeuf
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, Ecole Polytechnique federale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
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5
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Terence Blaskovits J, Garner MH, Corminboeuf C. Symmetry-Induced Singlet-Triplet Inversions in Non-Alternant Hydrocarbons. Angew Chem Int Ed Engl 2023; 62:e202218156. [PMID: 36786076 DOI: 10.1002/anie.202218156] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [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: 12/08/2022] [Revised: 02/09/2023] [Accepted: 02/13/2023] [Indexed: 02/15/2023]
Abstract
Molecules with inversion of the singlet and triplet excited-state energies are highly promising for the development of organic light-emitting diodes (OLEDs). To date, azaphenalenes are the only class of molecules where these inversions have been identified. Here, we screen a curated database of organic crystal structures to identify existing compounds for violations of Hund's rule in the lowest excited states. We identify two further classes with this behavior. The first, a class of zwitterions, has limited relevance to molecular emitters as the singlet-triplet inversions occur in the third excited singlet state. The second class consists of two D2h -symmetry non-alternant hydrocarbons, a fused azulene dimer and a bicalicene, whose lowest excited singlet states violate Hund's rule. Due to the connectivity of the polycyclic structure, they achieve this symmetry through aromatic stabilization. These hydrocarbons show promise as the next generation of building blocks for OLED emitters.
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Affiliation(s)
- J Terence Blaskovits
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, École Polytechnique Fedéralé de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Marc H Garner
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, École Polytechnique Fedéralé de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Clémence Corminboeuf
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, École Polytechnique Fedéralé de Lausanne (EPFL), 1015, Lausanne, Switzerland
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6
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Blaskovits JT, Garner MH, Corminboeuf C. Symmetry‐Induced Singlet‐Triplet Inversions in Non‐Alternant Hydrocarbons. Angew Chem Int Ed Engl 2023. [DOI: 10.1002/ange.202218156] [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: 02/16/2023]
Affiliation(s)
- J. Terence Blaskovits
- EPFL: Ecole Polytechnique Federale de Lausanne Institut des sciences et ingénierie chimiques EPFL SB ISIC LCMDBCH 5312 (Bât. BCH) CH-1015 Lausanne SWITZERLAND
| | - Marc H. Garner
- EPFL: Ecole Polytechnique Federale de Lausanne Institute of Chemical Sciences and Engineering SWITZERLAND
| | - Clemence Corminboeuf
- Ecole Polytechnique Federale de Lausanne Institute of Chemical Sciences and Engineering EPFL SB ISIC LCMDBCH 5312 10015 Lausanne SWITZERLAND
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7
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Garner MH, Koerstz M, Jensen JH, Solomon GC. Substituent Control of σ-Interference Effects in the Transmission of Saturated Molecules. ACS Phys Chem Au 2022; 2:282-288. [PMID: 36855417 PMCID: PMC9955259 DOI: 10.1021/acsphyschemau.2c00016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The single-molecule conductance of saturated molecules can potentially be fully suppressed by destructive quantum interference in their σ-system. However, only few molecules with σ-interference have been identified, and the structure-property relationship remains to be elucidated. Here, we explore the role of substituents in modulating the electronic transmission of saturated molecules. In functionalized bicyclo[2.2.2]octanes, the transmission is suppressed by σ-interference when fluorine substituents are applied. For bicyclo[2.2.2]octasilane and -octagermanes, the transmission is suppressed when carbon-based substituents are used, and such molecules are likely to be highly insulating. For the carbon-based substituents, we find a strong correlation between the appropriate Hammett constants and the transmission. The substituent effect enables systematic optimization of the insulating properties of saturated molecular cores.
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Affiliation(s)
- Marc H. Garner
- Nano-Science
Center, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark,Department
of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Mads Koerstz
- Department
of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Jan H. Jensen
- Department
of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Gemma C. Solomon
- Nano-Science
Center, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark,Department
of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark,
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8
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Garner MH, Laplaza R, Corminboeuf C. Helical versus linear Jahn–Teller distortions in allene and spiropentadiene radical cations. Phys Chem Chem Phys 2022; 24:26134-26143. [DOI: 10.1039/d2cp03544h] [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: 02/18/2023]
Abstract
The allene radical cation can be stabilized both by Jahn–Teller distortion of the bond lengths and by torsion of the end-groups.
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Affiliation(s)
- Marc H. Garner
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, Ecole Polytechnique federale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Ruben Laplaza
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, Ecole Polytechnique federale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Clemence Corminboeuf
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, Ecole Polytechnique federale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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9
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Abstract
The frontier molecular orbital (MO) topology of linear carbon molecules, such as polyynes, can be visually identified as helices. However, there is no clear way to quantify the helical curvature of these π-MOs, and it is thus challenging to quantify correlations between the helical curvature and molecular properties. In this paper, we develop a method that enables us to compute the helical curvature of MOs based on their nodal planes. Using this method, we define a robust way of quantifying the helical nature of MOs (helicality) by their deviation from a perfect helix. We explore several limiting cases, including polyynes, metallacumulenes, cyclic allenes, and spiroconjugated systems, where the change in helical curvature is subtle yet clearly highlighted with this method. For example, we show that strain only has a minor effect on the helicality of the frontier orbitals of cycloallenes and that the MOs of spiroconjugated systems are close to perfect helices around the spiro-carbon. Our work provides a well-defined method for assessing orbital helicality beyond visual inspection of MO isosurfaces, thus paving the way for future studies of how the helicality of π-MOs affects molecular properties.
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Affiliation(s)
- William Bro-Jørgensen
- Department of Chemistry and Nano-Science Center, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Marc H Garner
- Department of Chemistry and Nano-Science Center, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Gemma C Solomon
- Department of Chemistry and Nano-Science Center, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
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10
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Zhang B, Garner MH, Li L, Campos LM, Solomon GC, Venkataraman L. Destructive quantum interference in heterocyclic alkanes: the search for ultra-short molecular insulators. Chem Sci 2021; 12:10299-10305. [PMID: 34476051 PMCID: PMC8386164 DOI: 10.1039/d1sc02287c] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [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: 04/23/2021] [Accepted: 06/25/2021] [Indexed: 11/21/2022] Open
Abstract
Designing highly insulating sub-nanometer molecules is difficult because tunneling conductance increases exponentially with decreasing molecular length. This challenge is further enhanced by the fact that most molecules cannot achieve full conductance suppression with destructive quantum interference. Here, we present results for a series of small saturated heterocyclic alkanes where we show that conductance is suppressed due to destructive interference. Using the STM-BJ technique and density functional theory calculations, we confirm that their single-molecule junction conductance is lower than analogous alkanes of similar length. We rationalize the suppression of conductance in the junctions through analysis of the computed ballistic current density. We find there are highly symmetric ring currents, which reverse direction at the antiresonance in the Landauer transmission near the Fermi energy. This pattern has not been seen in earlier studies of larger bicyclic systems exhibiting interference effects and constitutes clear-cut evidence of destructive σ-interference. The finding of heterocyclic alkanes with destructive quantum interference charts a pathway for chemical design of short molecular insulators using organic molecules.
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Affiliation(s)
- Boyuan Zhang
- Department of Applied Physics and Applied Mathematics, Columbia University, New York New York 10027 USA
| | - Marc H Garner
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5 2100 Copenhagen Ø Denmark
| | - Liang Li
- Department of Chemistry, Columbia University, New York New York 10027 USA
| | - Luis M Campos
- Department of Chemistry, Columbia University, New York New York 10027 USA
| | - Gemma C Solomon
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5 2100 Copenhagen Ø Denmark
| | - Latha Venkataraman
- Department of Applied Physics and Applied Mathematics, Columbia University, New York New York 10027 USA .,Department of Chemistry, Columbia University, New York New York 10027 USA
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11
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Zang Y, Fung ED, Fu T, Ray S, Garner MH, Borges A, Steigerwald ML, Patil S, Solomon G, Venkataraman L. Voltage-Induced Single-Molecule Junction Planarization. Nano Lett 2021; 21:673-679. [PMID: 33337876 DOI: 10.1021/acs.nanolett.0c04260] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Probing structural changes of a molecule induced by charge transfer is important for understanding the physicochemical properties of molecules and developing new electronic devices. Here, we interrogate the structural changes of a single diketopyrrolopyrrole (DPP) molecule induced by charge transport at a high bias using scanning tunneling microscope break junction (STM-BJ) techniques. Specifically, we demonstrate that application of a high bias increases the average nonresonant conductance of single Au-DPP-Au junctions. We infer from the increased conductance that resonant charge transport induces planarization of the molecular backbone. We further show that this conformational planarization is assisted by thermally activated junction reorganization. The planarization only occurs under specific electronic conditions, which we rationalize by ab initio calculations. These results emphasize the need for a comprehensive view of single-molecule junctions which includes both the electronic properties and structure of the molecules and the electrodes when designing electrically driven single-molecule motors.
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Affiliation(s)
- Yaping Zang
- Department of Applied Physics, Columbia University, New York, New York 10027, United States
| | - E-Dean Fung
- Department of Applied Physics, Columbia University, New York, New York 10027, United States
| | - Tianren Fu
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Suman Ray
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Marc H Garner
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Copenhagen Ø DK-2100, Denmark
| | - Anders Borges
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Copenhagen Ø DK-2100, Denmark
| | - Michael L Steigerwald
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Satish Patil
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Gemma Solomon
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Copenhagen Ø DK-2100, Denmark
| | - Latha Venkataraman
- Department of Applied Physics, Columbia University, New York, New York 10027, United States
- Department of Chemistry, Columbia University, New York, New York 10027, United States
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12
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Abstract
The π–π* transitions of disubstituted spiropentadiene become helical due to mixing of its two perpendicular π-systems. The helicity is symmetry-protected and gives rise to experimentally observable effects, such as optical activity.
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Affiliation(s)
- Marc H. Garner
- Laboratory for Computational Molecular Design
- Institute of Chemical Sciences and Engineering
- Ecole Polytechnique Federale de Lausanne (EPFL)
- Lausanne 1015
- Switzerland
| | - Clemence Corminboeuf
- Laboratory for Computational Molecular Design
- Institute of Chemical Sciences and Engineering
- Ecole Polytechnique Federale de Lausanne (EPFL)
- Lausanne 1015
- Switzerland
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13
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Affiliation(s)
- Marc H. Garner
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Clemence Corminboeuf
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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14
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Abstract
Molecular dielectric materials require ostensibly conflicting requirements of high polarizability and low conductivity. As previous efforts toward molecular insulators focused on saturated molecules, it remains an open question whether π- and σ-transport can be simultaneously suppressed in conjugated systems. Here, we demonstrate that there are conjugated molecules where the σ-transmission is suppressed by destructive σ-interference, while the π-transmission can be suppressed by a localized disruption of conjugation. Using density functional theory, we study the Landauer transmission and ballistic current density, which allow us to determine how the transmission is affected by various structural changes in the molecule. We find that in para-linked oligophenyl rings the σ-transmission can be suppressed by changing the remaining hydrogens to methyl groups due to the inherent gauche-like structure of the carbon backbone within a benzene ring, similar to what was previously seen in saturated systems. At the same time, the methyl groups fulfill a dual purpose as they modulate the twist angle between neighboring phenyl rings. When neighboring rings are orthogonal to each other, the transmission through both π- and σ-systems is effectively suppressed. Alternatively, breaking conjugation in a single phenyl ring by saturating two carbons atoms with two methyl substituents on each carbon, results in suppressed π- and σ-transport independent of dihedral angle. These two strategies demonstrate that methyl-substituted oligophenyls are promising candidates for the development of molecular dielectric materials.
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Affiliation(s)
- Marc H Garner
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | - Gemma C Solomon
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
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15
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Abstract
Correction for ‘Helical orbitals and circular currents in linear carbon wires’ by Marc H. Garner et al., Chem. Sci., 2019, 10, 4598–4608.
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Affiliation(s)
- Marc H. Garner
- Department of Chemistry
- Nano-Science Center
- University of Copenhagen
- Copenhagen Ø
- Denmark
| | - Anders Jensen
- Department of Chemistry
- Nano-Science Center
- University of Copenhagen
- Copenhagen Ø
- Denmark
| | | | - Gemma C. Solomon
- Department of Chemistry
- Nano-Science Center
- University of Copenhagen
- Copenhagen Ø
- Denmark
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16
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Garner MH, Li H, Neupane M, Zou Q, Liu T, Su TA, Shangguan Z, Paley DW, Ng F, Xiao S, Nuckolls C, Venkataraman L, Solomon GC. Permethylation Introduces Destructive Quantum Interference in Saturated Silanes. J Am Chem Soc 2019; 141:15471-15476. [PMID: 31500410 DOI: 10.1021/jacs.9b06965] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The single-molecule conductance of silanes is suppressed due to destructive quantum interference in conformations with cisoid dihedral angles along the molecular backbone. Yet, despite the structural similarity, σ-interference effects have not been observed in alkanes. Here we report that the methyl substituents used in silanes are a prerequisite for σ-interference in these systems. Through density functional theory calculations, we find that the destructive interference is not evident to the same extent in nonmethylated silanes. We find the same is true in alkanes as the transmission is significantly suppressed in permethylated cyclic and bicyclic alkanes. Using scanning tunneling microscope break-junction method we determine the single-molecule conductance of functionalized cyclohexane and bicyclo[2.2.2]octane that are found to be higher than that of equivalent permethylated silanes. Rather than the difference between carbon and silicon atoms in the molecular backbones, our calculations reveal that it is primarily the difference between hydrogen and methyl substituents that result in the different electron transport properties of nonmethylated alkanes and permethylated silanes. Chemical substituents play an important role in determining the single-molecule conductance of saturated molecules, and this must be considered when we improve and expand the chemical design of insulating organic molecules.
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Affiliation(s)
- Marc H Garner
- Nano-Science Center and Department of Chemistry , University of Copenhagen , Universitetsparken 5, 2100 Copenhagen Ø , Denmark
| | - Haixing Li
- Department of Applied Physics and Applied Mathematics , Columbia University , New York , New York 10027 , United States
| | - Madhav Neupane
- Department of Chemistry , Columbia University , New York , New York 10027 , United States
| | - Qi Zou
- Department of Chemistry , Columbia University , New York , New York 10027 , United States
| | - Taifeng Liu
- Department of Chemistry , Columbia University , New York , New York 10027 , United States.,The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Optoelectronic Nano Materials and Devices Institute, Department of Chemistry , Shanghai Normal University , Shanghai 200234 , China
| | - Timothy A Su
- Department of Chemistry , Columbia University , New York , New York 10027 , United States
| | - Zhichun Shangguan
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Optoelectronic Nano Materials and Devices Institute, Department of Chemistry , Shanghai Normal University , Shanghai 200234 , China
| | - Daniel W Paley
- Department of Chemistry , Columbia University , New York , New York 10027 , United States
| | - Fay Ng
- Department of Chemistry , Columbia University , New York , New York 10027 , United States
| | - Shengxiong Xiao
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Optoelectronic Nano Materials and Devices Institute, Department of Chemistry , Shanghai Normal University , Shanghai 200234 , China
| | - Colin Nuckolls
- Department of Chemistry , Columbia University , New York , New York 10027 , United States
| | - Latha Venkataraman
- Department of Applied Physics and Applied Mathematics , Columbia University , New York , New York 10027 , United States.,Department of Chemistry , Columbia University , New York , New York 10027 , United States
| | - Gemma C Solomon
- Nano-Science Center and Department of Chemistry , University of Copenhagen , Universitetsparken 5, 2100 Copenhagen Ø , Denmark
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17
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Abstract
The tools commonly used to understand structure-property relationships in molecular conductance, inter-atomic currents and conductance eigenchannels, generally give us a sense of familiarity, with the chemical bonding framework and molecular orbitals reflected in the current. Here we show that while this picture is true for conjugated molecules, it breaks down in saturated systems. We investigate the current density in saturated chains of alkanes, silanes and germanes and show that the current density does not follow the bonds, but rather the nuclei define the diameter of a pipe through which the current flows. We discuss how this picture of current density can be used to understand details about the electron transport properties of these molecules. Understanding the spatial distribution of current through molecules, rather than simply the magnitude, provides a powerful tool for chemical insight into physical properties of molecules that are related to current flow. Our work emphasizes that the spatial understanding of coherent electron transport must be derived from current density, rather than other spatial representations, to ensure that accurate conclusions are drawn.
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18
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Garner MH, Jensen A, Hyllested LOH, Solomon GC. Helical orbitals and circular currents in linear carbon wires. Chem Sci 2019; 10:4598-4608. [PMID: 31123570 PMCID: PMC6496982 DOI: 10.1039/c8sc05464a] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [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: 12/06/2018] [Accepted: 03/14/2019] [Indexed: 01/07/2023] Open
Abstract
Disubstituted odd-carbon cumulenes are linear carbon wires with helical π-orbitals, which results in circular current around the wire.
Disubstituted odd-carbon cumulenes are linear carbon wires with near-degenerate helical π-orbitals. Such cumulenes are chiral molecules but their electronic structure consists of helical orbitals of both chiralities. For these helical molecular orbitals to give rise to experimentally observable effects, the near-degenerate orbitals of opposite helicities must be split. Here we show how pyramidalized single-faced π-donors, such as the amine substituent, provide a strategy for splitting the helical molecular orbitals. The chirality induced by the amine substituents allow for systematic control of the helicity of the frontier orbitals. We examine how the helical orbitals in odd-carbon cumulenes control the coherent electron transport properties, and we explicitly predict two modes in the experimental single-molecule conductance for these molecules. We also show that the current density through these linear wires exhibits strong circular currents. The direction of the circular currents is systematically controlled by the helicity of the frontier molecular orbitals, and is therefore altered by changing between the conformations of the molecule. Furthermore, the circular currents are subject to a full ring-reversal around antiresonances in the Landauer transmission, emphasizing the relation to destructive quantum interference. With circular currents present around truly linear carbon wires, cumulenes are promising candidates for novel applications in molecular electronics.
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Affiliation(s)
- Marc H Garner
- Department of Chemistry , Nano-Science Center , University of Copenhagen , Universitetsparken 5 , DK-2100 , Copenhagen Ø , Denmark . ;
| | - Anders Jensen
- Department of Chemistry , Nano-Science Center , University of Copenhagen , Universitetsparken 5 , DK-2100 , Copenhagen Ø , Denmark . ;
| | - Louise O H Hyllested
- Department of Chemistry , Nano-Science Center , University of Copenhagen , Universitetsparken 5 , DK-2100 , Copenhagen Ø , Denmark . ;
| | - Gemma C Solomon
- Department of Chemistry , Nano-Science Center , University of Copenhagen , Universitetsparken 5 , DK-2100 , Copenhagen Ø , Denmark . ;
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19
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Garner MH, Koerstz M, Jensen JH, Solomon GC. The Bicyclo[2.2.2]octane Motif: A Class of Saturated Group 14 Quantum Interference Based Single-Molecule Insulators. J Phys Chem Lett 2018; 9:6941-6947. [PMID: 30484655 DOI: 10.1021/acs.jpclett.8b03432] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The electronic transmission through σ-conjugated molecules can be fully suppressed by destructive quantum interference, which makes them potential candidates for single-molecule insulators. The first molecule with clear suppression of the single-molecule conductance due to σ-interference was recently found in the form of a functionalized bicyclo[2.2.2]octasilane. Here we continue the search for potential single-molecule insulators based on saturated group 14 molecules. Using a high-throughput screening approach, we assess the electron transport properties of the bicyclo[2.2.2]octane class by systematically varying the constituent atoms between carbon, silicon, and germanium, thus exploring the full chemical space of 771 different molecules. The majority of the molecules in the bicyclo[2.2.2]octane class are found to be highly insulating molecules. Though the all-silicon molecule is a clear-cut case of σ-interference, it is not unique within its class and there are many potential molecules that we predict to be more insulating. The finding of this class of quantum interference based single-molecule insulators indicates that a broad range of highly insulating saturated group 14 molecules are likely to exist.
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20
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Li H, Garner MH, Shangguan Z, Chen Y, Zheng Q, Su TA, Neupane M, Liu T, Steigerwald ML, Ng F, Nuckolls C, Xiao S, Solomon GC, Venkataraman L. Large Variations in the Single-Molecule Conductance of Cyclic and Bicyclic Silanes. J Am Chem Soc 2018; 140:15080-15088. [DOI: 10.1021/jacs.8b10296] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
| | - Marc H. Garner
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
| | - Zhichun Shangguan
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Optoelectronic Nano Materials and Devices Institute, Department of Chemistry, Shanghai Normal University, Shanghai 200234, China
| | - Yan Chen
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Optoelectronic Nano Materials and Devices Institute, Department of Chemistry, Shanghai Normal University, Shanghai 200234, China
| | - Qianwen Zheng
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Optoelectronic Nano Materials and Devices Institute, Department of Chemistry, Shanghai Normal University, Shanghai 200234, China
| | | | | | - Taifeng Liu
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Optoelectronic Nano Materials and Devices Institute, Department of Chemistry, Shanghai Normal University, Shanghai 200234, China
| | | | | | | | - Shengxiong Xiao
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Optoelectronic Nano Materials and Devices Institute, Department of Chemistry, Shanghai Normal University, Shanghai 200234, China
| | - Gemma C. Solomon
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
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21
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Zang Y, Ray S, Fung ED, Borges A, Garner MH, Steigerwald ML, Solomon GC, Patil S, Venkataraman L. Resonant Transport in Single Diketopyrrolopyrrole Junctions. J Am Chem Soc 2018; 140:13167-13170. [DOI: 10.1021/jacs.8b06964] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [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)
- Yaping Zang
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Suman Ray
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - E-Dean Fung
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Anders Borges
- Nano-Science Center and Department of Chemistry, University of Copenhagen, 1165 Copenhagen Ø, Denmark
| | - Marc H. Garner
- Nano-Science Center and Department of Chemistry, University of Copenhagen, 1165 Copenhagen Ø, Denmark
| | | | - Gemma C. Solomon
- Nano-Science Center and Department of Chemistry, University of Copenhagen, 1165 Copenhagen Ø, Denmark
| | - Satish Patil
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Latha Venkataraman
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
- Department of Chemistry, Columbia University, New York, New York 10027, United States
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22
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Garner MH, Hoffmann R, Rettrup S, Solomon GC. Coarctate and Möbius: The Helical Orbitals of Allene and Other Cumulenes. ACS Cent Sci 2018; 4:688-700. [PMID: 29974064 PMCID: PMC6026781 DOI: 10.1021/acscentsci.8b00086] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Indexed: 05/24/2023]
Abstract
As brought to the attention of the community by Hendon et al. and noted by previous workers, the π orbitals of the equilibrium geometry odd-carbon (even number of double bonds = n) [n]cumulenes may be written in either rectilinear or helical form. We trace the origins and detailed composition of the helical orbitals of cumulenes, which emerge in the simplest Hückel model and are not much modified in advanced computations. For the α,ω-disubstituted even [n]cumulenes, the helical representation is obligatory as the symmetry is reduced from D2d to C2. A relationship is apparent between these helical orbitals of the even [n]cumulenes, seen as a Herges coarctate system, and the corresponding Möbius cyclic polyene orbitals. The twist of the orbitals varies in interesting ways along the helix, and so does the contribution of the component atomic orbitals. Though the electronic structures of even [n]cumulenes and Möbius cyclopolyenes are closely related, they differ for higher n in intriguing ways; these are linked to the constrained rotation of the basis orbitals along the helical twist itinerary. Relations are constructed between the level patterns of the π-systems of even [n]cumulenes and ideas of Hückel and Möbius aromaticity.
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Affiliation(s)
- Marc H. Garner
- Department of Chemistry and Nano-Science Center, University
of Copenhagen, Universitetsparken
5, DK-2100, Copenhagen
Ø, Denmark
- Department
of Chemistry and Chemical Biology, Cornell
University, Ithaca, New York 4850, United
States
| | - Roald Hoffmann
- Department
of Chemistry and Chemical Biology, Cornell
University, Ithaca, New York 4850, United
States
| | - Sten Rettrup
- Department of Chemistry and Nano-Science Center, University
of Copenhagen, Universitetsparken
5, DK-2100, Copenhagen
Ø, Denmark
| | - Gemma C. Solomon
- Department of Chemistry and Nano-Science Center, University
of Copenhagen, Universitetsparken
5, DK-2100, Copenhagen
Ø, Denmark
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23
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Li H, Garner MH, Su TA, Jensen A, Inkpen MS, Steigerwald ML, Venkataraman L, Solomon GC, Nuckolls C. Extreme Conductance Suppression in Molecular Siloxanes. J Am Chem Soc 2017; 139:10212-10215. [DOI: 10.1021/jacs.7b05599] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Haixing Li
- Department
of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Marc H. Garner
- Nano-Science
Center and Department of Chemistry, University of Copenhagen, Universitetsparken
5, 2100 Copenhagen
Ø, Denmark
| | - Timothy A. Su
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Anders Jensen
- Nano-Science
Center and Department of Chemistry, University of Copenhagen, Universitetsparken
5, 2100 Copenhagen
Ø, Denmark
| | - Michael S. Inkpen
- Department
of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | | | - Latha Venkataraman
- Department
of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Gemma C. Solomon
- Nano-Science
Center and Department of Chemistry, University of Copenhagen, Universitetsparken
5, 2100 Copenhagen
Ø, Denmark
| | - Colin Nuckolls
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
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24
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Li H, Garner MH, Shangguan Z, Zheng Q, Su TA, Neupane M, Li P, Velian A, Steigerwald ML, Xiao S, Nuckolls C, Solomon GC, Venkataraman L. Conformations of cyclopentasilane stereoisomers control molecular junction conductance. Chem Sci 2016; 7:5657-5662. [PMID: 30034703 PMCID: PMC6022008 DOI: 10.1039/c6sc01360k] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [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: 03/27/2016] [Accepted: 05/27/2016] [Indexed: 01/02/2023] Open
Abstract
Here we examine the impact of ring conformation on the charge transport characteristics of cyclic pentasilane structures bound to gold electrodes in single molecule junctions. We investigate the conductance properties of alkylated cyclopentasilane cis and trans stereoisomers substituted in the 1,3-position with methylthiomethyl electrode binding groups using both the scanning tunneling microscope-based break junction technique and density functional theory based ab initio calculations. In contrast with the linear ones, these cyclic silanes yield lower conductance values; calculations reveal that the constrained dihedral geometries occurring within the ring are suboptimal for σ-orbital delocalization, and therefore, conductance. Theoretical calculations reproduce the measured conductance trends for both cis and trans isomers and find several distinct conformations that are likely to form stable molecular junctions at room temperature. Due to the weakened σ-conjugation in the molecule, through-space interactions are found to contribute significantly to the conductance. This manuscript details the vast conformational flexibility in cyclopentasilanes and the tremendous impact it has on controlling conductance.
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Affiliation(s)
- Haixing Li
- Department of Applied Physics and Applied Mathematics , Columbia University , New York 10027 , USA .
| | - Marc H Garner
- Nano-Science Center and Department of Chemistry , University of Copenhagen , Universitetsparken 5 , 2100 Copenhagen Ø , Denmark .
| | - Zhichun Shangguan
- The Education Ministry Key Lab of Resource Chemistry , Shanghai Key Laboratory of Rare Earth Functional Materials , Optoelectronic Nano Materials and Devices Institute , Department of Chemistry , Shanghai Normal University , Shanghai 200234 , China .
| | - Qianwen Zheng
- The Education Ministry Key Lab of Resource Chemistry , Shanghai Key Laboratory of Rare Earth Functional Materials , Optoelectronic Nano Materials and Devices Institute , Department of Chemistry , Shanghai Normal University , Shanghai 200234 , China .
| | - Timothy A Su
- Department of Chemistry , Columbia University , New York 10027 , USA .
| | - Madhav Neupane
- Department of Chemistry , Columbia University , New York 10027 , USA .
| | - Panpan Li
- The Education Ministry Key Lab of Resource Chemistry , Shanghai Key Laboratory of Rare Earth Functional Materials , Optoelectronic Nano Materials and Devices Institute , Department of Chemistry , Shanghai Normal University , Shanghai 200234 , China .
| | - Alexandra Velian
- Department of Chemistry , Columbia University , New York 10027 , USA .
| | | | - Shengxiong Xiao
- The Education Ministry Key Lab of Resource Chemistry , Shanghai Key Laboratory of Rare Earth Functional Materials , Optoelectronic Nano Materials and Devices Institute , Department of Chemistry , Shanghai Normal University , Shanghai 200234 , China .
| | - Colin Nuckolls
- The Education Ministry Key Lab of Resource Chemistry , Shanghai Key Laboratory of Rare Earth Functional Materials , Optoelectronic Nano Materials and Devices Institute , Department of Chemistry , Shanghai Normal University , Shanghai 200234 , China .
- Department of Chemistry , Columbia University , New York 10027 , USA .
| | - Gemma C Solomon
- Nano-Science Center and Department of Chemistry , University of Copenhagen , Universitetsparken 5 , 2100 Copenhagen Ø , Denmark .
| | - Latha Venkataraman
- Department of Applied Physics and Applied Mathematics , Columbia University , New York 10027 , USA .
- Department of Chemistry , Columbia University , New York 10027 , USA .
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25
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Abstract
Evidence is emerging that the nuclear envelope itself is responsible for transport and signaling activities quite distinct from those associated with the nuclear pore. For example, the envelope has a Ca2+-signaling pathway that, among other things, regulates meiosis in oocytes. The nuclear envelope's outer membrane also contains K+ channels. Here we show that Na+/K+ gradients exist between the nuclear envelope lumen and both cytoplasm and nucleoplasm in hepatocyte nuclei. The gradients are formed by Na,K-ATPases in the envelope's inner membrane, oriented with the ATP hydrolysis site in the nucleoplasm. We further demonstrate nucleoplasm/cytoplasm Na+ and K+ gradients, of which only the Na+ gradient is dissipated directly by Na,K-ATPase inhibition with ouabain. Finally, our results demonstrate that nuclear pores are not freely permeable to sodium and potassium. Based on these results and numerous in vitro studies, nuclear monovalent cation transporters and channels are likely to play a role in modulation of chromatin structure and gene expression.
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Affiliation(s)
- M H Garner
- Department of Pathology and Anatomy, UNT Health Science Center, 3500 Camp Bowie Blvd., Fort Worth, TX 76107, USA.
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26
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Garner MH. Lens sphingomyelinases. Exp Eye Res 2000; 71:103-7. [PMID: 10880281 DOI: 10.1006/exer.2000.0851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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27
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Garner MH, Kong Y. Lens epithelium and fiber Na,K-ATPases: distribution and localization by immunocytochemistry. Invest Ophthalmol Vis Sci 1999; 40:2291-8. [PMID: 10476795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023] Open
Abstract
PURPOSE To use immunofluorescence and immunogold techniques to identify the catalytic subunits of the Na,K-ATPases of the lens and to determine their location in the cells of the epithelium and cortex of bovine and human lenses. METHODS Frozen sections of capsulated and decapsulated bovine and human lenses were prepared, blocked, and treated with affinity-purified polyclonal rabbit antibodies to the Na,K-ATPase catalytic subunit isoforms with subsequent treatment with fluorescein isothiocyanate-labeled goat anti-rabbit IgG and visualization of the fluorescence by light microscopy. An immunogold-labeled goat anti-rabbit IgG was used to detect, by electron microscopy, the binding of the same affinity-purified polyclonal antibodies to thin sections of decapsulated lenses that had been fixed and embedded in Lowicryl K4M. The results were confirmed by staining of western blot analysis of sodium dodecyl sulfate-polyacrylamide gel separations of enriched membrane preparations from bovine and human lenses. RESULTS The three common catalytic subunits of the Na,K-ATPases are present in the plasma membranes of lens epithelium, lens fibers, or both. The data indicate a polarized distribution of the alpha1 and alpha3 catalytic subunit isoforms in central epithelium. In the cortical fibers, the alpha2 isoform is present around the interdigitations. The alpha3 isoform is found in the interdigitation-free regions of human cortical fibers. CONCLUSIONS This unique distribution of Na,K-ATPases precludes the popular pump-leak model for lens monovalent cation homeostasis. The functional significance of the distribution of Na,K-ATPases in the lens epithelium and superficial fibers is currently under investigation.
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Affiliation(s)
- M H Garner
- University of North Texas Health Science Center, Department of Anatomy and Cell Biology, Fort Worth 76107, USA
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28
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Abstract
The concentration of Na,K-adenosine triphosphatase (ATPase) and Na,K-ATPase-dependent adenosine triphosphate (ATP) turnover was measured in fasting blood samples of 20 subjects with insulin-dependent diabetes mellitus (IDDM), 22 subjects with non-insulin-dependent diabetes mellitus (NIDDM), and 20 nondiabetic subjects. [3H]ouabain binding was used to determine Na,K-ATPase concentration. There were 471 +/- 70 (mean +/- SD) ouabain binding sites per erythrocyte, normally distributed in the nondiabetic subjects. The number of ouabain sites per cell was lognormally distributed in the two populations of diabetic subjects. The mean of lognormal distributions of ouabain sites per cell was significantly lower in the IDDM group. The mean of the lognormal distribution for the NIDDM group was not significantly different from that of the nondiabetic subjects. Na,K-ATPase-dependent ATP turnover (molar activity) was 9,580 +/- 742 mol/mol minute (mean +/- SD) normally distributed in the nondiabetic population. A lognormal distribution was observed in the diabetic population. Means of the lognormal distributions were significantly different: 3.98 +/- 0.05 for the nondiabetic population and 3.13 +/- 0.48 for both diabetic populations. Changes in the concentration of Na,K-ATPase (ouabain sites per cell) and Na,K-ATPase-dependent ATP turnover did not correlate with hemoglobin A1C (HbA1C) or with blood glucose. This would suggest that elevated glucose concentrations do not directly cause decreased Na,K-ATPase function in the diabetic erythrocyte.
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Affiliation(s)
- M H Garner
- Department of Anatomy and Cell Biology, University of North Texas Health Science Center at Fort Worth 76107-2699, USA
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29
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Abstract
The cellular events underlying various retinopathies are poorly understood but likely involve perturbation of retinal glucose metabolism. Current methods for assessing this metabolism are destructive, thus limiting longitudinal studies. We hypothesize that following an intravitreous injection, the clearance rate of a glucose analogue will be a nondestructive index of retinal glucose transport and metabolism in vivo. First, radiolabeled glucose analogues were injected into the vitreous. After 40 min, the dominant clearance path was posterior via the retina and was consistent with a facilitated transport mechanism. Next, either [6,6-2H2]glucose or 3-deoxy-3-fluoro-D-glucose was injected into the vitreous of rabbit eyes, and the clearance rate of each analogue was determined over 40 min using, respectively, 2H or 19F NMR. These rates were interpreted as a function of the retinal glucose transport and consumption. From the NMR data, the rate of retinal glucose consumption was approximately 16 times slower than the transport of glucose. These data demonstrate that NMR measurements of glucose analogue clearance rate from the vitreous can provide a nondestructive index of retinal glucose transport and consumption in vivo.
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Affiliation(s)
- B A Berkowitz
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas 75235-8592, USA
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30
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Abstract
Previous studies suggest that an alpha 2-related isoform of the catalytic subunit is predominant in the lens fiber cells. The alpha 1 isoform is predominant in the lens epithelium (Garner, Horwitz and Enomoto, 1992). Data are presented to show that strophanthidin-sensitive K+ transport is sustained by both of these lens Na,K-ATPases. The K50 for strophanthidin inhibition of K+ transport was 1.4 +/- 0.5 x 10(-6) M for the alpha 1 isoform of the epithelium, 1.3 +/- 0.6 x 10(-7) M for the alpha 2-related isoform of the lens fiber cells. Na+ accumulation in cultured bovine lenses was strophanthidin sensitive. The K50 values for strophanthidin-sensitive Na+ accumulation were similar to those obtained for K+ transport. ARP turnover by the lens fiber cell Na,K-ATPase (1700 +/- 600 min-1) was lower than ATP turnover by the lens epithelium Na,K-ATPase (8000 +/0 1000 min-1). Both lens Na,K-ATPases form the (ouabain + Mg(2+) + phosphate)-dependent phosphoenzyme. Both lens Na,K-ATPases form the (ATP + Na(+) + Mg2+)-dependent phosphorylated intermediate. K+ does not effectively dephosphorylate the Na,K-ATPase of the lens fibers. K+ does cause dephosphorylation of the Na,K-ATPase of the lens epithelium. Interaction of the Na,K-ATPase with Mg2+ would appear to cause the monovalent cation insensitivity. The lens fiber cell Na,K-ATPase, like the lens epithelium Na,K-ATPase occludes two K+ ions. However, between the two major Na,K-ATPases of the lens, there would appear to be differences in the ATP dissolution of the K-occluded state.
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Affiliation(s)
- M H Garner
- University of Texas Southwestern Medical Center at Dallas, Department of Ophthalmology 75235-8592
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31
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Abstract
To identify the Na,K-ATPase isoforms present in the mammalian lens, seven antisera were prepared to selected peptide sequences of the catalytic (alpha) subunit. Three antisera were prepared to peptide sequences at the N-terminus of the three sequenced rat alpha isoforms. There is < 53% sequence homology among the isoforms in this region. Three antisera were prepared to peptide sequences at the ouabain binding site in the extracellular loop between membrane spanning sequences 1 and 2 of the sequenced rat alpha isoforms; sequence homology among the isoforms in this region is < 69%. An antiserum was also prepared to the carboxyl terminal region of the alpha 2 rat isoform. The sequenced isoforms (rat and human) in this region are > 94% homologous. The results from stains of Western blots of SDS-PAGE separations of lens membranes are presented. Alpha 1 is the predominant isoform of the epithelium. It is not found in cells of the central epithelium but is present in cells located more toward the equator. Alpha 3 is the catalytic subunit of the central 43% of the epithelium. The lens fiber cell membranes have a catalytic subunit that is related to the alpha 2 isoform. In the fiber cell a 98-100 kDa band stains with the antiserum to the alpha 2 N-terminus and the antiserum to the alpha 2 ouabain site. The antiserum to the alpha 2 C-terminus does not stain the 98-100 kDa band. (Preliminary reports of these results were presented at the 1992 and 1993 meetings of the Association for Research in Vision and Ophthalmology).
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Affiliation(s)
- M H Garner
- Jules Stein Eye Institute, University of California, Los Angeles School of Medicine 90024
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32
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Garner MH, Kuszak JR. Cations, oxidants, light as causative agents in senile cataracts. P R Health Sci J 1993; 12:115-22. [PMID: 8210282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Lens transparency is a function of regular cell shape, regular cell volume, minimal extracellular space, and minimal scatter elements. The cellular structure and molecular structure of the lens is reviewed. The importance of the cytoarchitecture especially the sutures, is discussed. The high cholesterol: phospholipid ratio of the lens fiber cell membranes is related to the functions of low permeability, low fluidity, and mechanical stability. Also reviewed are the contributions of the lens crystallins to lens clarity and to lens refractive index. The importance of intracellular and extracellular cation and water concentrations are reviewed. Finally the effects of systemic diseases, oxidation, and light on lens clarity are discussed relative to changes in lens fiber cell cation concentrations.
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Affiliation(s)
- M H Garner
- Department of Ophthalmology, University of Texas Southwestern, Medical Center, Dallas
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33
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Abstract
Na,K-ATPase, an enzyme intrinsic to the membrane of most cells, is inhibited in cataract. Na,K-ATPase, activity in clear non-cataractous lenses is found predominantly in the lens epithelium. The lens fiber cells would appear to be unique, among mammalian cells in that Na,K-ATPase activity is low if not absent. The study presented here indicates that Na,K-ATPase is present, often in high concentration, but progressively more functionally compromised as the fiber cells mature. The membrane lipid environment as causative agent in the loss of normal function of Na,K-ATPase, is considered in this study. The data indicate a correlation between increasing cholesterol/phospholipid ratio, increasing phospholipase A2 activity and decreasing Na,K-ATPase activity in normal clear lenses. The phospholipase A2 activity is higher in cortex and nucleus than in the epithelium of normal bovine and human lenses. The phospholipase A2 is Ca2+ dependent and may be membrane associated.
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Affiliation(s)
- S Baghieri
- University of Texas Southwestern Medical Center, Department of Ophthalmology, Dallas 75235-8592
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34
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Abstract
Na,K-ATPase function was studied in cultured bovine lens epithelial cells under confluent and non-confluent conditions. The affinity of the Na,K-ATPase for the cardiac glycoside, ouabain, differs between the confluent and non-confluent cultures. The confluent cells have a higher affinity for ouabain than do the non-confluent cells. The ouabain affinity of the confluent cells is similar to that for the Na,K-ATPase isolated from the bovine axolemma and the bovine lens cortex. The ouabain affinity of the non-confluent cells is similar to that for the Na,K-ATPase of the renal medulla and bovine lens epithelium. Similar results are not found with confluent and non-confluent MDCK cells. H2O2 treatment of confluent and non-confluent lens epithelial cell cultures has differing effects on the Na,K-ATPase function. In the confluent cell preparations, H2O2 affects K(+)-dependent dephosphorylation of the intermediate phosphoenzyme. In the non-confluent preparations. H2O2 appears to inhibit K(+)-occlusion.
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Affiliation(s)
- M H Garner
- Department of Ophthalmology, University of California, Irvine 92715
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35
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Abstract
This study showed that steady-state kinetics of ATP hydrolysis by Na(+)-K(+)-ATPase are altered in the BB Wistar diabetic rat and experimental galactosemia. Four days after onset, this change was not evident if NaCNBH3 was omitted during enzyme preparations (indicating reversibility). Ninety days after onset, NaCNBH3 reduction was not necessary to see the change in ATP hydrolysis kinetics (indicating nonreversibility). The change in steady-state ATP hydrolysis was similar to that reported earlier for Na(+)-K(+)-ATPase of the lens epithelium and kidney medulla of diabetic individuals and for two in vitro glycosylation models. Our study also showed that the affinities of Na(+)-K(+)-ATPase for K+ are altered, and Na(+)-K(+)-ATPase-dependent K+ occlusion is inhibited in diabetic and galactosemic animals. Because K+ occlusion is required for efficient K+ transport, this finding supports previous in vitro studies that indicated that glycosylation inhibits pump-dependent K+ transport. Furthermore, our study suggested an irreversible impairment of Na(+)-K(+)-ATPase function in the diabetic BB Wistar rat as early as 15 days after onset, even when blood glucose was maintained at 6.7 mM by daily insulin injection.
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Affiliation(s)
- S T Tehrani
- Department of Ophthalmology, California College of Medicine, University of California, Irvine 92717
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Garner MH, Bahador A, Sachs G. Nonenzymatic glycation of Na,K-ATPase. Effects on ATP hydrolysis and K+ occlusion. J Biol Chem 1990; 265:15058-66. [PMID: 2168400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Glycation of the Na,K-ATPase in vitro (formation of Schiff base with glucose followed by reduction with NaCNBH3) shows the presence of three classes of reactive amino groups that differentially affect catalysis and cation binding. Reaction in the absence of ATP results in irreversible inhibition of enzyme activity with a t1/2 of 53 min. This is due to modification of one class of amino groups that affect the catalytic domain of the enzyme. In the presence of ATP, glycation first results in a shift in the steady state kinetics of ATP hydrolysis from substrate activation to Michaelis-Menten kinetics accompanied by an increase in the apparent affinity for K+ in the p-nitrophenylphosphatase reaction. This change in kinetic properties occurs with a t1/2 of 9 min and results in the complete loss of K+ occlusion. Incorporation of glucose is into the catalytic subunit, remote from the N-terminal end. Apparent total inhibition of K+ occlusion occurs with a stoichiometry 0.8 mol of glucose incorporated per mol of enzyme. Therefore, there is a rapidly reacting amino group that affects the cation binding domain of the Na,K-ATPase. More slowly, with a t1/2 of 9 h, the ATP hydrolysis kinetics change from Michaelis-Menten to substrate inhibition without recovery of K+ occlusion, showing that, in the E1 conformation, there is a third, slower reacting class of amino groups in the Na,K-ATPase that affects low affinity nucleotide interaction with the catalytic subunit.
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Affiliation(s)
- M H Garner
- Department of Ophthalmology, California College of Medicine, University of California, Irvine 92717
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Abstract
The mammalian lens, like other ectodermal tissues, can regenerate itself given the proper environment. Endocapsular phacoemulsification of adult rabbit lenses was performed. A lens capsular bag with posterior and anterior lens capsule relatively intact was left in the eye. Regrowth of material in the capsular bag was followed by slit lamp biomicroscopy and photography over a 12-month period. Histopathology of the new material showed regions of relatively normal epithelial cells and lens fibers as well as regions where growth was irregular. All major lens crystallin classes were present in the regenerated lens. Several specific crystallin subunits, known to arise by post-translational modification of primary gene products, were absent or present in abnormally low concentrations.
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Affiliation(s)
- A Gwon
- Allergan Pharmaceuticals, Irvine, CA 92715
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Abstract
In diabetes, glucosylation of the Na,K-ATPase of the lens epithelium makes the pump inefficient. K+ transport and ATP hydrolysis (at near saturating ATP concentrations) are inhibited and the kinetics of ATP hydrolysis become substrate inhibition type. The AR inhibitor (AL1576, Alcon Laboratories) stimulates K+ transport and ATP hydrolysis by glucosylated bovine lens Na,K-ATPase. This inhibitor has a slight stimulatory effect upon the unmodified enzyme function also. The AR inhibitor is not able to prevent glucosylation of the pump in high-glucose-containing medium.
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Affiliation(s)
- M H Garner
- Department of Ophthalmology, California College of Medicine, University of California, Irvine 92717
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Abstract
In the presence of 10(-8) M concentrations of the aldose reductase inhibitor AL 1576, there is a 20-30% increase in the rate of hydrolysis of near-saturating concentrations of ATP by bovine renal Na+-K+-ATPase. When bovine renal Na+-K+-ATPase is reacted with glucose 6-phosphate in the presence of 10(-8) M concentrations of AL 1576 or 10(-6) M concentrations of a second aldose reductase inhibitor, sorbinil, glucosylation occurs. Whereas sorbinil has no effect on ATP hydrolysis by the glucosylated Na+-K+-ATPase, 10(-8) M AL 1576 causes a shift in the kinetics of hydrolysis of ATP from substrate inhibition to normal substrate activation. The aldose reductase inhibitors interact with the enzyme at the low-affinity ATP-binding site.
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Abstract
The steady-state kinetics of hydrolysis of Mg2+ ATP by the epithelial Na,K-ATPase of individual human lenses were determined. Among the cataract lens population, four distinct kinetic types were observed: negative kinetic co-operativity. Michaelis-Menten kinetics, positive kinetic co-operativity, and substrate inhibition kinetics. Negative kinetic co-operativity and Michaelis-Menten kinetics were also observed in a group of presumably clear lenses from non-diabetic individuals ages 16-42 years. Substrate inhibition kinetics were found to be prevalent in individuals with mature onset diabetes. Substrate inhibition kinetics were also observed for Na,K-ATPase isolated from lenses which had been incubated in high glucose. It would appear that this modification leads to an inhibition of Na,K-ATPase-dependent K+ influx into these cultured lenses.
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Garner MH, Garner WH, Spector A. H2O2-modification of Na,K-ATPase. Alterations in external Na+ and K+ stimulation of K+ influx. Invest Ophthalmol Vis Sci 1986; 27:103-7. [PMID: 3000974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Studies, at steady state, of the Na,K-ATPase dependent influx of K+ into bovine lenses in organ culture are used to characterize further the H2O2-modification of the Na+ pump. Control lenses display constants for interaction with external Na+ and K+ similar to those obtained for the erythrocyte. H2O2 treatment of the bovine lens leads to total loss of external Na+ stimulation and alteration of external K+ stimulation.
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Garner MH, Spector A. Glucose-6-phosphate modification of bovine renal Na,K-ATPase: a model for changes occurring in the human renal medulla in diabetes. Biochem Biophys Res Commun 1985; 131:1206-11. [PMID: 2996541 DOI: 10.1016/0006-291x(85)90219-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The kinetics of hydrolysis of ATP were determined for the renal Na,K-ATPase, in the K+ conformation, modified with glucose-6-phosphate. There was a shift in the ATP hydrolysis kinetics from negative kinetic co-operativity for the control enzyme preparations to substrate inhibition kinetics for the modified enzyme preparations. The effect was reversible and stabilized after NaBH4 reduction. Approximately 4 moles of glucose-6-phosphate were incorporated per mole of Na,K-ATPase (based on MW of 150,000 daltons). Similar substrate inhibition kinetics were observed for the renal Na,K-ATPase isolated from several human subjects with mature onset diabetes.
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Garner MH, Garner WH, Spector A. Kinetic cooperativity change after H2O2 modification of (Na,K)-ATPase. J Biol Chem 1984; 259:7712-8. [PMID: 6330074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The kinetics of hydrolysis of ATP and p-nitrophenylphosphate and the action of the allosteric effectors, Na+ and K+, upon the hydrolysis of these substrates were used to study the H2O2-modified, uncoupled (Na,K)-ATPase isolated from cultured bovine lenses ( Garner , W. H., Garner , M. H., and Spector , A. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 2044-2048). Pure bovine renal (Na,K)-ATPase was modified by H2O2 in 150 mM KCl and 20 mM MgCl2 to yield an enzyme with kinetic properties similar to the enzyme isolated from the H2O2-treated, cultured bovine lens. H2O2 modification changes the interaction of the ATP hydrolysis site from negative to positive kinetic cooperativity. H2O2 modification dramatically alters Na+ stimulation of ATP hydrolysis and Na+ inhibition of p-nitrophenylphosphate hydrolysis while having little effect upon K+ control of the hydrolysis of these two substrates.
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Abstract
A 1-hr exposure of bovine lenses in organ culture to H2O2 concentrations in the range found in the aqueous fluid of patients with cataracts inhibits 86Rb+ influx. At 1 mM H2O2, complete inhibition was observed and further investigated. Membrane permeability is slightly decreased. Although lactate concentrations increase 2-fold, lens ATP concentrations decrease approximately equal to 10%, suggesting that glycolysis may be stimulated but ATP production is not able to keep up with the demand for energy. Examination of epithelial cell Mg2+-stimulated Na+,K+-ATPase isolated from the cultured lenses indicates H2O2-induced modification. At 5 mM MgATP, ATP hydrolysis is accelerated 30%; at 3 mM MgATP, hydrolysis is normal; and at 0.75 mM MgATP, it is inhibited 75%. p-Nitrophenyl phosphate hydrolysis and eosin maleimide binding indicate that K+ control of the enzyme is modified. Thus, a very early effect of H2O2 upon the lens, well before the formation of opacity, appears to be the uncoupling of Na+ and K+ transport from ATP hydrolysis.
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Garner MH, Roy D, Rosenfeld L, Garner WH, Spector A. Biochemical evidence for membrane disintegration in human cataracts. Proc Natl Acad Sci U S A 1981; 78:1892-5. [PMID: 6785760 PMCID: PMC319241 DOI: 10.1073/pnas.78.3.1892] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Biochemical evidence is presented for the disintegration of the lens fiber plasma membrane in human cataracts. The intrinsic membrane proteins are found in both the water-soluble and water-insoluble nonmembrane fractions of the cataract lens but not in the normal tissue. Furthermore, in contrast to the normal lens, not all of the lipid found in the cataractous lens is isolated with the membrane fraction. In cataracts, both the membrane and membrane fragments are involved in covalent high molecular weight aggregates with an extrinsic membrane protein (43,000 daltons) and a cytoplasmic protein (gamma-crystallin).
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Farnsworth PN, Spector A, Lozier JR, Shyne SE, Garner MH, Garner WH. The localization of 43K polypeptide in normal and cataractous lenses by immunofluorescence. Exp Eye Res 1981; 32:257-64. [PMID: 7014233 DOI: 10.1016/0014-4835(81)90031-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Garner WH, Garner MH, Spector A. Gamma-crystallin, a major cytoplasmic polypeptide disulfide linked to membrane proteins in human cataract. Biochem Biophys Res Commun 1981; 98:439-47. [PMID: 6784722 DOI: 10.1016/0006-291x(81)90859-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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