1
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Stockhammer L, Radetzky M, Khatoon SS, Bechmann M, Waser M. Chiral Lewis Base-Catalysed Asymmetric Syntheses of Benzo-fused ϵ-Lactones. European J Org Chem 2023; 26:e202300704. [PMID: 38601860 PMCID: PMC11005097 DOI: 10.1002/ejoc.202300704] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 08/24/2023] [Indexed: 04/12/2024]
Abstract
We herein report a two-step protocol for the asymmetric synthesis of novel chiral benzofused ϵ-lactones starting from O-protected hydroxymethyl-para-quinone methides and activated aryl esters. By using chiral isothiourea Lewis base catalysts a broad variety of differently substituted products could be obtained in yields of around 50 % over both steps with high levels of enantioselectivities, albeit low diastereoselectivities only.
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Affiliation(s)
- Lotte Stockhammer
- Institute of Organic ChemistryJohannes Kepler University LinzAltenbergerstrasse 694040LinzAustria
| | - Maximilian Radetzky
- Institute of Organic ChemistryJohannes Kepler University LinzAltenbergerstrasse 694040LinzAustria
| | - Syeda Sadia Khatoon
- Institute of Organic ChemistryJohannes Kepler University LinzAltenbergerstrasse 694040LinzAustria
| | - Matthias Bechmann
- Institute of Organic ChemistryJohannes Kepler University LinzAltenbergerstrasse 694040LinzAustria
| | - Mario Waser
- Institute of Organic ChemistryJohannes Kepler University LinzAltenbergerstrasse 694040LinzAustria
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2
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Aljabour A, Awada H, Song L, Sun H, Offenthaler S, Yari F, Bechmann M, Scharber MC, Schöfberger W. A Bifunctional Electrocatalyst for OER and ORR based on a Cobalt(II) Triazole Pyridine Bis-[Cobalt(III) Corrole] Complex. Angew Chem Weinheim Bergstr Ger 2023; 135:e202302208. [PMID: 38516328 PMCID: PMC10952570 DOI: 10.1002/ange.202302208] [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] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Indexed: 02/25/2023]
Abstract
As alternative energy sources are essential to reach a climate-neutral economy, hydrogen peroxide (H2O2) as futuristic energy carrier gains enormous awareness. However, seeking for stable and electrochemically selective H2O2 ORR electrocatalyst is yet a challenge, making the design of-ideally-bifunctional catalysts extremely important and outmost of interest. In this study, we explore the application of a trimetallic cobalt(II) triazole pyridine bis-[cobalt(III) corrole] complex CoIITP[CoIIIC]2 3 in OER and ORR catalysis due to its remarkable physicochemical properties, fast charge transfer kinetics, electrochemical reversibility, and durability. With nearly 100 % selective catalytic activity towards the two-electron transfer generated H2O2, an ORR onset potential of 0.8 V vs RHE and a cycling stability of 50 000 cycles are detected. Similarly, promising results are obtained when applied in OER catalysis. A relatively low overpotential at 10 mA cm-2 of 412 mV, Faraday efficiency 98 % for oxygen, an outstanding Tafel slope of 64 mV dec-1 combined with superior stability.
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Affiliation(s)
- Abdalaziz Aljabour
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - Houssein Awada
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - Luyang Song
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - He Sun
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - Simon Offenthaler
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
- Institute of Applied ChemistryDepartment of Science and TechnologyIMC University of Applied Sciences Krems WienPiaristengasse 13500KremsAustria
| | - Farzaneh Yari
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - Matthias Bechmann
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - Markus Clark Scharber
- Institute of Physical Chemistry and Linz Institute of Organic Solar CellsJohannes Kepler University LinzAltenberger Straße 694040LinzAustria
| | - Wolfgang Schöfberger
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
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3
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Aljabour A, Awada H, Song L, Sun H, Offenthaler S, Yari F, Bechmann M, Scharber MC, Schöfberger W. A Bifunctional Electrocatalyst for OER and ORR based on a Cobalt(II) Triazole Pyridine Bis-[Cobalt(III) Corrole] Complex. Angew Chem Int Ed Engl 2023; 62:e202302208. [PMID: 36821699 PMCID: PMC10947295 DOI: 10.1002/anie.202302208] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [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: 02/13/2023] [Revised: 02/23/2023] [Accepted: 02/23/2023] [Indexed: 02/25/2023]
Abstract
As alternative energy sources are essential to reach a climate-neutral economy, hydrogen peroxide (H2 O2 ) as futuristic energy carrier gains enormous awareness. However, seeking for stable and electrochemically selective H2 O2 ORR electrocatalyst is yet a challenge, making the design of-ideally-bifunctional catalysts extremely important and outmost of interest. In this study, we explore the application of a trimetallic cobalt(II) triazole pyridine bis-[cobalt(III) corrole] complex CoII TP[CoIII C]2 3 in OER and ORR catalysis due to its remarkable physicochemical properties, fast charge transfer kinetics, electrochemical reversibility, and durability. With nearly 100 % selective catalytic activity towards the two-electron transfer generated H2 O2 , an ORR onset potential of 0.8 V vs RHE and a cycling stability of 50 000 cycles are detected. Similarly, promising results are obtained when applied in OER catalysis. A relatively low overpotential at 10 mA cm-2 of 412 mV, Faraday efficiency 98 % for oxygen, an outstanding Tafel slope of 64 mV dec-1 combined with superior stability.
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Affiliation(s)
- Abdalaziz Aljabour
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - Houssein Awada
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - Luyang Song
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - He Sun
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - Simon Offenthaler
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
- Institute of Applied ChemistryDepartment of Science and TechnologyIMC University of Applied Sciences Krems WienPiaristengasse 13500KremsAustria
| | - Farzaneh Yari
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - Matthias Bechmann
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
| | - Markus Clark Scharber
- Institute of Physical Chemistry and Linz Institute of Organic Solar CellsJohannes Kepler University LinzAltenberger Straße 694040LinzAustria
| | - Wolfgang Schöfberger
- Institute of Organic ChemistryLaboratory for Sustainable Chemistry and Catalysis (LSusCat)Johannes Kepler University (JKU)Altenberger Straße 694040LinzAustria
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4
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Röser K, Scheucher A, Mairhofer C, Bechmann M, Waser M. Oxidative decarboxylative ammonium hypoiodite-catalysed dihydrobenzofuran synthesis. Org Biomol Chem 2022; 20:3273-3276. [PMID: 35363244 DOI: 10.1039/d2ob00463a] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The catalytic use of quaternary ammonium iodides under oxidative conditions allows for the direct conversion of readily available β-ketolactones into dihydrobenzofurans via a decarboxylative oxidative cycloetherification sequence facilitated by an in situ formed ammonium hypoiodite species.
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Affiliation(s)
- Katharina Röser
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, Linz 4040, Austria.
| | - Anna Scheucher
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, Linz 4040, Austria.
| | - Christopher Mairhofer
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, Linz 4040, Austria.
| | - Matthias Bechmann
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, Linz 4040, Austria.
| | - Mario Waser
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, Linz 4040, Austria.
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5
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Schaumüller S, Cristurean D, Haudum S, Pappas GS, Himmelsbach M, Bechmann M, Brüggemann O, Teasdale I. Post‐polymerization
modification of aromatic polyimides via Diels‐Alder cycloaddition. Journal of Polymer Science 2021. [DOI: 10.1002/pol.20210711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
| | - Doris Cristurean
- Institute of Polymer Chemistry Johannes Kepler University Linz Linz Austria
| | - Stephan Haudum
- Institute of Polymer Chemistry Johannes Kepler University Linz Linz Austria
| | - George S. Pappas
- Institute of Polymer Chemistry Johannes Kepler University Linz Linz Austria
| | - Markus Himmelsbach
- Institute of Analytical Chemistry Johannes Kepler University Linz Linz Austria
| | - Matthias Bechmann
- Institute of Organic Chemistry Johannes Kepler University Linz Linz Austria
| | - Oliver Brüggemann
- Institute of Polymer Chemistry Johannes Kepler University Linz Linz Austria
| | - Ian Teasdale
- Institute of Polymer Chemistry Johannes Kepler University Linz Linz Austria
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6
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Rodin V, Ginthör S, Bechmann M, Desvaux H, Müller N. Spin noise gradient echoes. Magn Reson (Gott) 2021; 2:827-834. [PMID: 37905214 PMCID: PMC10539801 DOI: 10.5194/mr-2-827-2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 10/11/2021] [Indexed: 11/01/2023]
Abstract
Nuclear spin noise spectroscopy in the absence of radio frequency pulses was studied under the influence of pulsed field gradients (PFGs) on pure and mixed liquids. Under conditions where the radiation-damping-induced line broadening is smaller than the gradient-dependent inhomogeneous broadening, echo responses can be observed in difference spectra between experiments employing pulsed field gradient pairs of the same and opposite signs. These observed spin noise gradient echoes (SNGEs) were analyzed through a simple model to describe the effects of transient phenomena. Experiments performed on high-resolution nuclear magnetic resonance (NMR) probes demonstrate how refocused spin noise behaves and how it can be exploited to determine sample properties. In bulk liquids and their mixtures, transverse relaxation times and translational diffusion constants can be determined from SNGE spectra recorded following tailored sequences of magnetic field gradient pulses.
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Affiliation(s)
- Victor V. Rodin
- Institute of Organic Chemistry, Johannes Kepler University Linz,
Altenbergerstraße 69, 4040 Linz, Austria
| | - Stephan J. Ginthör
- Institute of Organic Chemistry, Johannes Kepler University Linz,
Altenbergerstraße 69, 4040 Linz, Austria
| | - Matthias Bechmann
- Institute of Organic Chemistry, Johannes Kepler University Linz,
Altenbergerstraße 69, 4040 Linz, Austria
| | - Hervé Desvaux
- NIMBE, CEA, CNRS, Université Paris-Saclay, CEA/Saclay, 91191
Gif-sur-Yvette, France
| | - Norbert Müller
- Institute of Organic Chemistry, Johannes Kepler University Linz,
Altenbergerstraße 69, 4040 Linz, Austria
- Faculty of Science, University of South Bohemia in České
Budějovice, Branišovská 1645/31a, 370 05 České Budějovice, Czech Republic
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7
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Wielend D, Salinas Y, Mayr F, Bechmann M, Yumusak C, Neugebauer H, Brüggemann O, Sariciftci NS. Immobilized Poly(anthraquinones) for Electrochemical Energy Storage Applications: Structure‐Property Relations. ChemElectroChem 2021. [DOI: 10.1002/celc.202101315] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Dominik Wielend
- Linz Institute for Organic Solar Cells (LIOS) Institute of Physical Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Yolanda Salinas
- Institute of Polymer Chemistry (ICP) Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Felix Mayr
- Linz Institute for Organic Solar Cells (LIOS) Institute of Physical Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
- Institute of Applied Physics Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Matthias Bechmann
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Cigdem Yumusak
- Linz Institute for Organic Solar Cells (LIOS) Institute of Physical Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
- Materials Research Centre Faculty of Chemistry Brno University of Technology Purkyňova 118 612 00 Brno Czech Republic
| | - Helmut Neugebauer
- Linz Institute for Organic Solar Cells (LIOS) Institute of Physical Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Oliver Brüggemann
- Institute of Polymer Chemistry (ICP) Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Niyazi Serdar Sariciftci
- Linz Institute for Organic Solar Cells (LIOS) Institute of Physical Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
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8
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Haas M, Krisch D, Gonglach S, Bechmann M, Scharber MC, Ertl M, Monkowius U, Schöfberger W. Front Cover: Gallium(III) Corrole Complexes as Near‐Infrared Emitter – Synthesis, Computational and Photophysical Study (Eur. J. Org. Chem. 10/2021). European J Org Chem 2021. [DOI: 10.1002/ejoc.202100222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Michael Haas
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Dominik Krisch
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Sabrina Gonglach
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Matthias Bechmann
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Markus C. Scharber
- Institute of Physical Chemistry and Linz Institute of Organic Solar Cells Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Martin Ertl
- Linz School of Education Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Uwe Monkowius
- Linz School of Education Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Wolfgang Schöfberger
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
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9
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Haas M, Krisch D, Gonglach S, Bechmann M, Scharber MC, Ertl M, Monkowius U, Schöfberger W. Gallium(III) Corrole Complexes as Near‐Infrared Emitter – Synthesis, Computational and Photophysical Study. European J Org Chem 2021. [DOI: 10.1002/ejoc.202100097] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Michael Haas
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Dominik Krisch
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Sabrina Gonglach
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Matthias Bechmann
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Markus C. Scharber
- Institute of Physical Chemistry and Linz Institute of Organic Solar Cells Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Martin Ertl
- Linz School of Education Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Uwe Monkowius
- Linz School of Education Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
| | - Wolfgang Schöfberger
- Institute of Organic Chemistry Johannes Kepler University Linz Altenberger Straße 69 4040 Linz Austria
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10
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Rathner P, Fahrner M, Cerofolini L, Grabmayr H, Horvath F, Krobath H, Gupta A, Ravera E, Fragai M, Bechmann M, Renger T, Luchinat C, Romanin C, Müller N. Interhelical interactions within the STIM1 CC1 domain modulate CRAC channel activation. Nat Chem Biol 2021; 17:196-204. [PMID: 33106661 PMCID: PMC7610458 DOI: 10.1038/s41589-020-00672-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 09/04/2020] [Accepted: 09/11/2020] [Indexed: 01/28/2023]
Abstract
The calcium release activated calcium channel is activated by the endoplasmic reticulum-resident calcium sensor protein STIM1. On activation, STIM1 C terminus changes from an inactive, tight to an active, extended conformation. A coiled-coil clamp involving the CC1 and CC3 domains is essential in controlling STIM1 activation, with CC1 as the key entity. The nuclear magnetic resonance-derived solution structure of the CC1 domain represents a three-helix bundle stabilized by interhelical contacts, which are absent in the Stormorken disease-related STIM1 R304W mutant. Two interhelical sites between the CC1α1 and CC1α2 helices are key in controlling STIM1 activation, affecting the balance between tight and extended conformations. Nuclear magnetic resonance-directed mutations within these interhelical interactions restore the physiological, store-dependent activation behavior of the gain-of-function STIM1 R304W mutant. This study reveals the functional impact of interhelical interactions within the CC1 domain for modifying the CC1-CC3 clamp strength to control the activation of STIM1.
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Affiliation(s)
- Petr Rathner
- Institute of Organic Chemistry, Johannes Kepler University Linz, Linz, Austria
- Institute of Inorganic Chemistry, Johannes Kepler University Linz, Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Linda Cerofolini
- Magnetic Resonance Center (CERM), University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metallo Proteine (CIRMMP), Sesto Fiorentino, Italy
| | - Herwig Grabmayr
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria
| | - Ferdinand Horvath
- Institute for Theoretical Physics, Johannes Kepler University Linz, Linz, Austria
| | - Heinrich Krobath
- Institute for Theoretical Physics, Johannes Kepler University Linz, Linz, Austria
| | - Agrim Gupta
- Institute of Organic Chemistry, Johannes Kepler University Linz, Linz, Austria
| | - Enrico Ravera
- Magnetic Resonance Center (CERM), University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metallo Proteine (CIRMMP), Sesto Fiorentino, Italy
- Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
| | - Marco Fragai
- Magnetic Resonance Center (CERM), University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metallo Proteine (CIRMMP), Sesto Fiorentino, Italy
- Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
| | - Matthias Bechmann
- Institute of Organic Chemistry, Johannes Kepler University Linz, Linz, Austria
| | - Thomas Renger
- Institute for Theoretical Physics, Johannes Kepler University Linz, Linz, Austria
| | - Claudio Luchinat
- Magnetic Resonance Center (CERM), University of Florence and Consorzio Interuniversitario Risonanze Magnetiche di Metallo Proteine (CIRMMP), Sesto Fiorentino, Italy
- Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University Linz, Linz, Austria.
| | - Norbert Müller
- Institute of Organic Chemistry, Johannes Kepler University Linz, Linz, Austria.
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.
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11
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Cristurean D, Schaumüller S, Strasser P, Haudum S, Himmelsbach M, Bechmann M, Brüggemann O, Teasdale I. Diels–Alder cycloaddition polymerization of highly aromatic polyimides and their multiblock copolymers. Polym Chem 2021. [DOI: 10.1039/d1py00314c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A novel route to highly aromatic polyimides is presented and is used to form multiblock copolymers which is inherently difficult to achieve via traditional routes for this important polymer family.
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Affiliation(s)
- Doris Cristurean
- Institute of Polymer Chemistry
- Johannes Kepler University Linz
- 4040 Linz
- Austria
| | - Stephan Schaumüller
- Institute of Polymer Chemistry
- Johannes Kepler University Linz
- 4040 Linz
- Austria
| | - Paul Strasser
- Institute of Polymer Chemistry
- Johannes Kepler University Linz
- 4040 Linz
- Austria
| | - Stephan Haudum
- Institute of Polymer Chemistry
- Johannes Kepler University Linz
- 4040 Linz
- Austria
| | - Markus Himmelsbach
- Institute of Analytical Chemistry
- Johannes Kepler University Linz
- 4040 Linz
- Austria
| | - Matthias Bechmann
- Institute of Organic Chemistry
- Johannes Kepler University Linz
- 4040 Linz
- Austria
| | - Oliver Brüggemann
- Institute of Polymer Chemistry
- Johannes Kepler University Linz
- 4040 Linz
- Austria
| | - Ian Teasdale
- Institute of Polymer Chemistry
- Johannes Kepler University Linz
- 4040 Linz
- Austria
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12
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Ginthör S, Schlagnitweit J, Bechmann M, Müller N. Nuclear spin noise tomography in three dimensions with iterative simultaneous algebraic reconstruction technique (SART) processing. Magn Reson (Gott) 2020; 1:165-173. [PMID: 37904820 PMCID: PMC10500707 DOI: 10.5194/mr-1-165-2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 07/17/2020] [Indexed: 11/01/2023]
Abstract
We report three-dimensional spin noise imaging (SNI) of nuclear spin density from spin noise data acquired by Faraday detection. Our approach substantially extends and improves the two-dimensional SNI method for excitation-less magnetic resonance tomography reported earlier (Müller and Jerschow, 2006). This proof of principle was achieved by taking advantage of the particular continuous nature of spin noise acquired in the presence of constant magnitude magnetic field gradients and recent advances in nuclear spin noise spectroscopy acquisition as well as novel processing techniques. In this type of projection-reconstruction-based spin noise imaging the trade-off between signal-to-noise ratio (or image contrast) and resolution can be adjusted a posteriori during processing of the original time-domain data by iterative image reconstruction in a unique way not possible in conventional rf-pulse-dependent magnetic resonance imaging (MRI). The 3D SNI is demonstrated as a proof of concept on a commercial 700 MHz high-resolution NMR spectrometer, using a 3D-printed polymeric phantom immersed in water.
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Affiliation(s)
- Stephan J. Ginthör
- Institute of Organic Chemistry, Johannes Kepler University Linz, 4040 Linz, Austria
| | - Judith Schlagnitweit
- Institute of Organic Chemistry, Johannes Kepler University Linz, 4040 Linz, Austria
- current address: Department of Medical Biochemistry and
Biophysics, Karolinska Institutet, Stockholm, 171 77, Sweden
| | - Matthias Bechmann
- Institute of Organic Chemistry, Johannes Kepler University Linz, 4040 Linz, Austria
| | - Norbert Müller
- Institute of Organic Chemistry, Johannes Kepler University Linz, 4040 Linz, Austria
- Faculty of Science, University of South Bohemia, České
Budějovice, 37005, Czech Republic
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13
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Ponzini E, Natalello A, Usai F, Bechmann M, Peri F, Müller N, Grandori R. Structural characterization of aerogels derived from enzymatically oxidized galactomannans of fenugreek, sesbania and guar gums. Carbohydr Polym 2019; 207:510-520. [DOI: 10.1016/j.carbpol.2018.11.100] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Revised: 11/29/2018] [Accepted: 11/30/2018] [Indexed: 10/27/2022]
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14
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Bieroza MZ, Heathwaite AL, Bechmann M, Kyllmar K, Jordan P. The concentration-discharge slope as a tool for water quality management. Sci Total Environ 2018; 630:738-749. [PMID: 29499532 DOI: 10.1016/j.scitotenv.2018.02.256] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 02/20/2018] [Accepted: 02/21/2018] [Indexed: 05/23/2023]
Abstract
Recent technological breakthroughs of optical sensors and analysers have enabled matching the water quality measurement interval to the time scales of stream flow changes and led to an improved understanding of spatially and temporally heterogeneous sources and delivery pathways for many solutes and particulates. This new ability to match the chemograph with the hydrograph has promoted renewed interest in the concentration-discharge (c-q) relationship and its value in characterizing catchment storage, time lags and legacy effects for both weathering products and anthropogenic pollutants. In this paper we evaluated the stream c-q relationships for a number of water quality determinands (phosphorus, suspended sediments, nitrogen) in intensively managed agricultural catchments based on both high-frequency (sub-hourly) and long-term low-frequency (fortnightly-monthly) routine monitoring data. We used resampled high-frequency data to test the uncertainty in water quality parameters (e.g. mean, 95th percentile and load) derived from low-frequency sub-datasets. We showed that the uncertainty in water quality parameters increases with reduced sampling frequency as a function of the c-q slope. We also showed that different sources and delivery pathways control c-q relationship for different solutes and particulates. Secondly, we evaluated the variation in c-q slopes derived from the long-term low-frequency data for different determinands and catchments and showed strong chemostatic behaviour for phosphorus and nitrogen due to saturation and agricultural legacy effects. The c-q slope analysis can provide an effective tool to evaluate the current monitoring networks and the effectiveness of water management interventions. This research highlights how improved understanding of solute and particulate dynamics obtained with optical sensors and analysers can be used to understand patterns in long-term water quality time series, reduce the uncertainty in the monitoring data and to manage eutrophication in agricultural catchments.
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Affiliation(s)
- M Z Bieroza
- Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, Box 7014, 750 07, Sweden.
| | - A L Heathwaite
- Lancaster Environment Centre, Library Avenue, Lancaster University, Lancaster LA1 4YQ, United Kingdom.
| | - M Bechmann
- Norwegian Institute of Bioeconomy Research, P.O. Box 115, NO-1431 Ås, Norway.
| | - K Kyllmar
- Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, Box 7014, 750 07, Sweden.
| | - P Jordan
- School of Geography & Environmental Sciences, Ulster University, Coleraine BT52 1SA, United Kingdom.
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Ginthör SJ, Chandra K, Bechmann M, Rodin VV, Müller N. Spin-Noise-Detected Two-Dimensional Nuclear Magnetic Resonance at Triple Sensitivity. Chemphyschem 2018; 19:907-912. [PMID: 29399935 PMCID: PMC5915744 DOI: 10.1002/cphc.201800008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Indexed: 11/11/2022]
Abstract
A major breakthrough in speed and sensitivity of 2 D spin-noise-detected NMR is achieved owing to a new acquisition and processing scheme called "double block usage" (DBU) that utilizes each recorded noise block in two independent cross-correlations. The mixing, evolution, and acquisition periods are repeated head-to-tail without any recovery delays and well-known building blocks of multidimensional NMR (constant-time evolution and quadrature detection in the indirect dimension as well as pulsed field gradients) provide further enhancement and artifact suppression. Modified timing of the receiver electronics eliminates spurious random excitation. We achieve a threefold sensitivity increase over the original snHMQC (spin-noise-detected heteronuclear multiple quantum correlation) experiment (K. Chandra et al., J. Phys. Chem. Lett. 2013, 4, 3853) and demonstrate the feasibility of spin-noise-detected long-range correlation.
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Affiliation(s)
- Stephan J Ginthör
- Institute of Organic Chemistry, Johannes Kepler, University Linz, Altenbergerstraße 69, 4040, Linz, Austria
| | - Kousik Chandra
- Institute of Organic Chemistry, Johannes Kepler, University Linz, Altenbergerstraße 69, 4040, Linz, Austria.,Present address: NMR Research Centre, Indian Institute of Science, Bangalore, 560012, India
| | - Matthias Bechmann
- Institute of Organic Chemistry, Johannes Kepler, University Linz, Altenbergerstraße 69, 4040, Linz, Austria
| | - Victor V Rodin
- Institute of Organic Chemistry, Johannes Kepler, University Linz, Altenbergerstraße 69, 4040, Linz, Austria
| | - Norbert Müller
- Institute of Organic Chemistry, Johannes Kepler, University Linz, Altenbergerstraße 69, 4040, Linz, Austria.,Faculty of Science, University of South Bohemia, Branišovská 1645/31A, 370 05, České Budějovice, Czech Republic
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Donau SS, Bechmann M, Müller N, Nielsen TT, Wimmer R. ( Z
), Not ( E
) - An End to a Century of Confusion about the Double-Bond Stereoisomers of 3-Amino-2-cyanoacrylates. European J Org Chem 2017. [DOI: 10.1002/ejoc.201701235] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Søren S. Donau
- Department of Chemistry and Bioscience; Aalborg University; Frederik Bajers Vej 7H 9220 Aalborg Ø Denmark
| | - Matthias Bechmann
- Institute of Organic Chemistry; Johannes Kepler University Linz; Altenbergerstr 69 4040 Linz Austria
| | - Norbert Müller
- Institute of Organic Chemistry; Johannes Kepler University Linz; Altenbergerstr 69 4040 Linz Austria
- Faculty of Science; University of South Bohemia; Branišovská 31 37005 České Budějovice Czech Republic
| | - Thorbjørn T. Nielsen
- Department of Chemistry and Bioscience; Aalborg University; Frederik Bajers Vej 7H 9220 Aalborg Ø Denmark
| | - Reinhard Wimmer
- Department of Chemistry and Bioscience; Aalborg University; Frederik Bajers Vej 7H 9220 Aalborg Ø Denmark
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Pöschko MT, Vuichoud B, Milani J, Bornet A, Bechmann M, Bodenhausen G, Jannin S, Müller N. Spin Noise Detection of Nuclear Hyperpolarization at 1.2 K. Chemphyschem 2015; 16:3859-64. [PMID: 26477605 PMCID: PMC4691331 DOI: 10.1002/cphc.201500805] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Indexed: 11/24/2022]
Abstract
We report proton spin noise spectra of a hyperpolarized solid sample of commonly used “DNP (dynamic nuclear polarization) juice” containing TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine N-oxide) and irradiated by a microwave field at a temperature of 1.2 K in a magnetic field of 6.7 T. The line shapes of the spin noise power spectra are sensitive to the variation of the microwave irradiation frequency and change from dip to bump, when the electron Larmor frequency is crossed, which is shown to be in good accordance with theory by simulations. Small but significant deviations from these predictions are observed, which can be related to spin noise and radiation damping phenomena that have been reported in thermally polarized systems. The non-linear dependence of the spin noise integral on nuclear polarization provides a means to monitor hyperpolarization semi-quantitatively without any perturbation of the spin system by radio frequency irradiation.
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Affiliation(s)
- Maria Theresia Pöschko
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040, Linz, Austria
| | - Basile Vuichoud
- Institut de Sciences et Ingénerie Chimiques, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland
| | - Jonas Milani
- Institut de Sciences et Ingénerie Chimiques, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland
| | - Aurélien Bornet
- Institut de Sciences et Ingénerie Chimiques, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland
| | - Matthias Bechmann
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040, Linz, Austria
| | - Geoffrey Bodenhausen
- Institut de Sciences et Ingénerie Chimiques, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland.,Département de Chimie, Ecole Normale Supérieure, PSL, 24 Rue Lhomond, 75231, Paris, Cedex 05, France.,Université Pierre-et-Marie Curie, 4 Place Jussieu, 75005, Paris (France.,UMR 7203, CNRS/UPMC/ENS, Ecole Normale Supérieure, Paris, France
| | - Sami Jannin
- Institut de Sciences et Ingénerie Chimiques, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland. .,Bruker BioSpin AG, Industriestrasse 26, 8117, Fällanden, Switzerland.
| | - Norbert Müller
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040, Linz, Austria. .,Faculty of Science, University of South Bohemia, Branišovská 1645/31A, 370 05, České Budějovice, Czech Republic.
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Bechmann M, Clark J, Sebald A. Genetic algorithms and solid state NMR pulse sequences. J Magn Reson 2013; 228:66-75. [PMID: 23357428 DOI: 10.1016/j.jmr.2012.12.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 12/17/2012] [Accepted: 12/21/2012] [Indexed: 06/01/2023]
Abstract
The use of genetic algorithms for the optimisation of magic angle spinning NMR pulse sequences is discussed. The discussion uses as an example the optimisation of the C7(2)(1) dipolar recoupling pulse sequence, aiming to achieve improved efficiency for spin systems characterised by large chemical shielding anisotropies and/or small dipolar coupling interactions. The optimised pulse sequence is found to be robust over a wide range of parameters, requires only minimal a priori knowledge of the spin system for experimental implementations with buildup rates being solely determined by the magnitude of the dipolar coupling interaction, but is found to be less broadbanded than the original C7(2)(1) pulse sequence. The optimised pulse sequence breaks the synchronicity between r.f. pulses and sample spinning.
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Kronvang B, Bechmann M, Lundekvam H, Behrendt H, Rubaek GH, Schoumans OF, Syversen N, Andersen HE, Hoffmann CC. Phosphorus losses from agricultural areas in river basins: effects and uncertainties of targeted mitigation measures. J Environ Qual 2005; 34:2129-44. [PMID: 16275713 DOI: 10.2134/jeq2004.0439] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
In this paper we show the quantitative and relative importance of phosphorus (P) losses from agricultural areas within European river basins and demonstrate the importance of P pathways, linking agricultural source areas to surface water at different scales. Agricultural P losses are increasingly important for the P concentration in most European rivers, lakes, and estuaries, even though the quantity of P lost from agricultural areas in European catchments varies at least one order of magnitude (<0.2 kg P ha(-1) to >2.1 kg P ha(-1)). We focus on the importance of P for the implementation of the EU Water Framework Directive and discuss the benefits, uncertainties, and side effects of the different targeted mitigation measures that can be adopted to combat P losses from agricultural areas in river basins. Experimental evidence of the effects of some of the main targeted mitigation measures hitherto implemented is demonstrated, including: (i) soil tillage changes, (ii) treatment of soils near ditches and streams with iron to reduce P transport from source areas to surface waters, (iii) establishment of buffer zones for retaining P from surface runoff, (iv) restoration of river-floodplain systems to allow natural inundation of riparian areas and deposition of P, and (v) inundation of riparian areas with tile drainage water for P retention. Furthermore, we show how river basin managers can map and analyze the extent and importance of P risk areas, exemplified by four catchments differing in size in Norway, Denmark, and the Netherlands. Finally, we discuss the factors and mechanisms that may delay and/or counteract the responses of mitigation measures for combating P losses from agricultural areas when monitored at the catchment scale.
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Affiliation(s)
- B Kronvang
- National Environmental Research Institute, Department of Freshwater Ecology, Silkeborg, Denmark.
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20
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Bechmann M, Dusold S, Geipel F, Sebald A, Sellmann D. Magnitudes and Orientations of 31P Chemical Shielding Tensors in Pt(II)−Phosphine Complexes and Other Four-Fold Coordinated Phosphorus Sites. J Phys Chem A 2005; 109:5275-80. [PMID: 16839050 DOI: 10.1021/jp045353p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
31P MAS and double-quantum filtered 31P MAS NMR experiments at and near the n = 0 rotational resonance condition, as well as off-magic angle spinning 31P NMR experiments on two polycrystalline samples of Pt(II)-phosphine thiolate complexes are reported. Numerical simulations yield complete descriptions of the two 31P spin pairs. 195Pt MAS NMR spectra are straightforward to obtain but sensitively reflect only some parameters of the 195Pt(31P)2 three-spin system. Based on the 31P NMR results obtained and in conjunction with a large body of literature data and irrespective of the chemical nature of the specimen, a unified picture of the dominating motif of 31P chemical shielding tensor orientations of phosphorus sites with 4-fold coordination is identified as a local (pseudo)plane rather than the directions of P element bond directions.
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Affiliation(s)
- Matthias Bechmann
- Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany, and Institut für Anorganische Chemie II, Universität Erlangen, Egerlandstr. 1, D-91058 Erlangen, Germany
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21
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Bechmann M, Foerster H, Maisel H, Sebald A. Double-quantum filtered 1H MAS NMR spectra. Solid State Nucl Magn Reson 2005; 27:174-179. [PMID: 15681134 DOI: 10.1016/j.ssnmr.2004.11.001] [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] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2004] [Indexed: 05/24/2023]
Abstract
It is shown that straightforward double-quantum filtered (1)H MAS NMR experiments yield spectral lineshapes that permit to estimate the minimum number of (1)H spins in a cluster. The approach may offer an alternative to multiple-quantum experiments for the characterisation of (1)H spin clusters of moderate size. The duration of the double-quantum excitation period has to be chosen suitably, it is necessary to find a practical compromise between optimum double-quantum filtration efficiency and optimum information content of the spectral lineshapes. Some (1)H MAS NMR experiments on partially deuterated maleic acid are reported as well as numerical simulations.
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Affiliation(s)
- Matthias Bechmann
- Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
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22
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Bechmann M, Sebald A. MAS NMR with and without double-quantum filtration at and near the n=0 rotational resonance condition. J Magn Reson 2005; 173:296-304. [PMID: 15780921 DOI: 10.1016/j.jmr.2004.12.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2004] [Revised: 12/20/2004] [Indexed: 05/24/2023]
Abstract
Spectral lineshapes of MAS NMR spectra of dipolar (re)coupled spin pairs exhibiting considerable chemical shielding anisotropies at and near the so-called n=0 rotational resonance (R2) condition are considered. The n=0 R2 condition is found to be not extremely sharp. Anisotropic interaction parameters such as chemical shielding tensor orientations and the magnitude of the dipolar coupling constant remain sensitively encoded in such lineshapes even when differences in isotropic chemical shielding values of up to 400 Hz (corresponding to ca. half the size of the dipolar coupling constant) are present. Additional double-quantum filtration (DQF) may enhance the sensitivity of spectral lineshapes to anisotropic interaction parameters for even larger differences in isotropic chemical shielding values. The dependence of the DQF efficiency on spin-system parameters as well as on external parameters (Larmor and MAS frequencies) is investigated. Away from R2 conditions a trend to lower DQF efficiencies is found whereas some spin-system parameters are more sensitively encoded in the corresponding spectral lineshapes. Our study is based on numerical simulations, with the known parameters of the 31P spin pair in Na4P2O7.10H2O representing our model case.
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Affiliation(s)
- Matthias Bechmann
- Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
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Rudolph G, Kalpadakis P, Bechmann M, Haritoglou C, Kampik A. Scanning laser ophthalmoscope-evoked multifocal ERG (SLO-mfERG) in patients with macular holes and normal individuals. Eye (Lond) 2003; 17:801-8. [PMID: 14528241 DOI: 10.1038/sj.eye.6700502] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
AIMS A scanning laser ophthalmoscope (SLO) has been used for multifocal electroretinography (mf ERG) measurements under simultaneous fundus monitoring. The aim of this study was to prove if the SLO-mfERG measurement reflects reliably the clinically registered underlying disease, and to demonstrate the importance of its main advantage, fixation monitoring. METHODS In all, 10 patients with macular hole stage II/III were included in the study, and 19 normal individuals served as the control group. The mf ERG device was combined with an SLO, which was used both as a stimulus and trigger unit as well as a fundus-monitoring system. Monitoring of the fundus was guaranteed by an infrared laser (780 nm). The stimulus matrix consisted of 61 hexagonal elements, covering 24 degrees of the posterior pole. We examined both, patients with macular holes and healthy individuals. RESULTS Compared to normal controls, patients with a macular hole (Gass stage III) showed a significant decrease in response density in the centre of the stimulus array, which correlated well with the morphological alteration observed by clinical examination. However, variation of response density of the central hexagonal area has been proved to be high. CONCLUSIONS SLO-mfERG is a feasible and reliable new technique to investigate macular function under simultaneous fundus control. The main advantage is that control of fixation can be used in order to obtain more reliable results that correlate well with visible fundus abnormalities such as in patients with macular holes. However, further investigations have to be performed in order to overcome sufficiently the problem of fixation instability.
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Affiliation(s)
- G Rudolph
- Eye Clinic, Ludwig-Maximilians-University Munich, Germany.
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24
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Bechmann M, Hain K, Marichal C, Sebald A. X-[1H, 19F] triple resonance with a X-[1H] CP MAS probe and characterisation of a 29Si-19F spin pair. Solid State Nucl Magn Reson 2003; 23:50-61. [PMID: 12633831 DOI: 10.1016/s0926-2040(02)00014-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
An economic approach for implementing X-[1H,19F] double-decoupling MAS NMR experiments with a conventional X-[1H] dual-channel CP MAS probe is demonstrated. The parameters characterising the isolated 29Si-19F spin pair in an organosilicon compound R(3)SiF (R = 9-anthryl) are determined. In addition, we discuss the optimum choice of experimental parameters for determining all 29Si-19F spin-pair parameters from straightforward 29Si MAS NMR spectra with only 1H decoupling applied during acquisition.
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Affiliation(s)
- Matthias Bechmann
- Bayerisches Geoinstitut, Universität Bayreuth, 95440 Bayreuth, Germany
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Bechmann M, Schaumberger M, Schönfeld CL, Ludwig K. [Relationship between lens power in refraction]. Ophthalmologe 2002; 99:709-12. [PMID: 12219260 DOI: 10.1007/s00347-001-0566-9] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND To achieve emmetropia, several components such as the cornea and lens power, and axial length have to be coordinated. Until now, not much is known about the influence of these factors on each other. METHODS A total of 66 healthy subjects were enrolled in this study. Ocular dimensions including anterior chamber depth, lens thickness, vitreous chamber depth, and axial length were measured by A-scan ultrasonography. Corneal radius and corneal refractive power were determined by ophthalmometry. The equivalent lens power was calculated by a method based on the Gullstrand schematic eye. RESULTS As expected, a good correlation was found to exist between refraction and axial length. Lens power was independent of refraction, but in emmetropic eyes a good correlation between lens power and axial length could be found. Higher axial length was related to lower values of lens power and vice versa. CONCLUSION In emmetropic eyes, deviation of axial length seems to be compensated by lens power and if this mechanism does not function, ametropia results.
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Affiliation(s)
- M Bechmann
- Augenklinik der Ludwig-Maximilians-Universität München.
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Abstract
BACKGROUND/PURPOSE Lamellar keratoplasty is an established therapy of corneal pathologies without endothelial involvement and the lack of endothelial rejection is one of the major advantages compared to penetrating keratoplasty. The major disadvantages of manually prepared lamellar corneal grafts are the limited mechanical and optical quality but the automated lamellar therapeutic keratoplasty system ALTK (MORIA) is intended to overcome these disadvantages. The purpose of this preliminary work is to investigate histologically and in clinical cases, if the ALTK system can achieve this aim. PATIENTS AND METHODS Corneas from two human donors were cut with a 300 microns trephine. After fixation, the stromal bed and the excised cup of one specimen were stained with PAS and examined by light microscopy and the other specimen was analyzed by scanning electron microscopy. In addition, follow-up data of two patients who received such a lamellar graft are reported for the first 9 and 7 months postoperation, respectively. RESULTS The lamellar cut of homogeneous depth revealed only minor stromal trauma. Both clinical cases demonstrated only minimal interface haze during follow-up. Despite a remarkably clear cornea, visual acuity improved only slowly because the precise lamellar cut tended to partially reproduce any preexisting irregular astigmatism. CONCLUSIONS The ALTK system simplifies and standardizes the trephination of lamellar corneal grafts but a longer follow up is necessary with respect to visual development and preservation of a clear graft.
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Affiliation(s)
- K Ludwig
- Augenklinik, Klinikum der Ludwig-Maximilians-Universität München, Innenstadt, Mathildenstrasse 8, 80336 München.
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Rudolph G, Kalpadakis P, Bechmann M, La Rocca G, Hörmann C, Berninger T. Scanning laser ophthalmoscope-evoked multifocal-ERG (SLO-m-ERG) by using short m-sequences. Eur J Ophthalmol 2002; 12:109-16. [PMID: 12022282 DOI: 10.1177/112067210201200206] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
PURPOSE To demonstrate the possibility of topographic mapping of retinal function under simultaneous control of fixation in humans, by scanning laser ophthalmoscope evoked multifocal electroretinography (SLO-m-ERG). METHODS A confocal scanning laser ophthalmoscope was used as a stimulator and trigger unit to take m-ERGs. Short m-sequences based on a modified algorithm were used, with the advantage that each measurement cycle can be evaluated separately. We examined 78 normal subjects; in 62 a distortion factor of 1:1 was applied, and a factor of 1:4 in 16. RESULTS The recorded amplitudes decreased with eccentricity, approximately following the decrease of retinal cone density. Amplitudes were higher in the central hexagonal element in the group with 1:4 distortion than in the group with the 1:1 distortion setting. CONCLUSIONS SLO-m-ERG is a reliable technique for topographic mapping of retinal function under simultaneous control of fixation.
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Affiliation(s)
- G Rudolph
- Eye Clinic, Ludwig-Maximilians-University, Munich, Germany.
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Neubauer AS, Priglinger S, Ullrich S, Bechmann M, Thiel MJ, Ulbig MW, Kampik A. Comparison of foveal thickness measured with the retinal thickness analyzer and optical coherence tomography. Retina 2002; 21:596-601. [PMID: 11756882 DOI: 10.1097/00006982-200112000-00006] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To assess and compare the reliability and reproducibility of retinal thickness measurements for the retinal thickness analyzer (RTA) and optical coherence tomography (OCT) in normal and edematous retina. METHODS The authors measured the foveal thickness of 21 normal eyes and 9 eyes with macular edema with both methods in random order. With the RTA, the fovea was measured 10 times; with the OCT, six scans (one horizontal and five vertical cross-sections) of the fovea were obtained. RESULTS Mean foveal thickness of normal eyes measured 153 microm with OCT and 181 microm with RTA (median for both methods 150 microm). Coefficients of variation (CV) within the same subjects were 10% (OCT) and 9% (RTA) reducing to 9% (OCT) and 7% (RTA) when scans were repeated only five times for both methods. The RTA, however, yielded an interpatient CV of 33% (OCT 17%), which was caused by several falsely high readings in normal individuals. In eyes with retinal thickening the OCT measured a mean of 324 microm with 15% intra- and 58% interpatient CV. The RTA yielded a mean of 403 microm with CV of 18% and 73%, respectively. CONCLUSION Both methods yield reproducible measurements of foveal thickness in normal individuals and individuals with macular edema. However, falsely high measurements may occur with the RTA, reducing its reliability as compared to the OCT.
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Affiliation(s)
- A S Neubauer
- Department of Ophthalmology, Ludwig-Maximilians-Universität, Munich, Germany.
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Bechmann M, Helluy X, Marichal C, Sebald A. Double-quantum filtered MAS NMR in the presence of chemical shielding anisotropies and direct dipolar and J couplings. Solid State Nucl Magn Reson 2002; 21:71-85. [PMID: 11949819 DOI: 10.1006/snmr.2001.0042] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Double-quantum filtered MAS NMR spectra of an isolated homonuclear spin-1/2 pair are considered, at and away from rotational resonance conditions. The pulse sequence used is the solid-state NMR equivalent of double-quantum filtered COSY, known from solution-state NMR. The 119Sn spin pair in [(chex3Sn)2S] is characterized by a difference in isotropic chemical shielding smaller than the two chemical shielding anisotropies and by direct dipolar and isotropic J-coupling constants of similar magnitudes. At rotational resonance, one-dimensional double-quantum filtered 119Sn lineshapes yield the relative orientation of the two 119Sn chemical shielding tensors. Good double-quantum filtration efficiencies are found at and away from rotational resonance conditions, despite the presence of large chemical shielding anisotropies. Numerical simulations illustrate the interplay of the direct dipolar and J-coupling pathways and identify the latter as the main pathway even at rotational resonance conditions.
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Deelstra J, Bechmann M, Kvaernø SH. SOIL and SOIL-NO at catchment scale--a case study for an agriculture-dominated catchment. Water Sci Technol 2002; 45:9-17. [PMID: 12079129] [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] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A one-dimensional model, SOIL/SOIL-NO, is used to simulate the water and nitrogen balance at catchment scale. The objective is to use the model in simulating the effects of best management practices on nitrogen runoff. The model was applied to individual farm fields in an agriculture dominated catchment and simulations were carried out for the period from 94-98. The results were promising. The simulated nitrogen runoff agreed quite well with the measured nitrogen loss at the main station. The effects of best management practices like optimal fertiliser application, catch crops and irrigation were simulated. For this particular catchment, the introduction of catch crops resulted in the best effect on reducing nitrogen runoff from agricultural dominated catchments.
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Affiliation(s)
- J Deelstra
- Jordforsk-Centre for Soil and Environmental Research, Aas, Norway
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Abstract
AIM Vitrectomies are performed either under general anesthesia (GA), local anesthesia (LA), or a combination of both. Postoperative pain is expected to be less in patients with LA because of prolonged action of the local anaesthetic. Pre-emptive analgesia is based on the idea that analgesia initiated before a nociceptive event will be more effective than analgesia commenced afterwards. The authors compared postoperative analgesia in patients with GA combined with preoperative or postoperative LA. METHODS 90 patients scheduled for vitrectomy without buckling were enrolled in the study. 60 patients underwent GA, 30 without LA, 15 with preoperative LA, and 15 with postoperative LA. 30 patients received LA alone. Subjective postoperative pain was determined using the visual analogue scale. RESULTS Postoperative pain was less under LA alone compared to GA alone (p < 0.0001). Additional preoperative application of LA resulted in less pain than additional postoperative application (p <0.05). Additional postoperative peribulbar aneasthesia did not differ from GA alone. CONCLUSION The authors conclude that LA alone or preoperatively in addition to GA provides the best comfort for the patient in vitreoretinal surgery.
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Affiliation(s)
- N Kristin
- Klinikum Innenstadt, Mathildenstrasse 8, D-80336 Munich, Germany.
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Bechmann M, Helluy X, Sebald A. Double-quantum-filtered rotational-resonance MAS NMR in the presence of large chemical shielding anisotropies. J Magn Reson 2001; 152:14-25. [PMID: 11531360 DOI: 10.1006/jmre.2001.2393] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Double-quantum filtration under rotational resonance MAS NMR conditions where the chemical shielding anisotropies involved exceed the differences in isotropic chemical shielding is considered by means of numerical simulations and (13)C MAS NMR experiments. The responses of two different pulse sequences, suitable for double-quantum filtration specifically under rotational resonance conditions, to large chemical shielding anisotropies are compared. In the presence of large chemical shielding anisotropies a very recently introduced pulse sequence (T. Karlsson, M. Edén, H. Luthman, and M. H. Levitt, J. Magn. Reson. 145, 95-107, 2000) suffers losses in double-quantum-filtration efficiencies. The double-quantum-filtration efficiency of another pulse sequence (N. C. Nielsen, F. Creuzet, R. G. Griffin, and M. H. Levitt, J. Chem. Phys. 96, 5668-5677, 1992) is less afflicted by the presence of large chemical shielding anisotropies. Both sequences deliver double-quantum-filtered lineshapes that sensitively reflect chemical shielding tensor orientations. It is further shown that double-quantum-filtered rotational-resonance lineshapes of spin systems composed of more than two spins offer a suitable experimental approach for determining chemical shielding tensor orientations for cases where conventional rotational-resonance experiments are not applicable due to the presence of additional background resonances.
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Affiliation(s)
- M Bechmann
- Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
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Abstract
PURPOSE To report an eye with a full-thickness macular hole and an associated optic pit and the noteworthy intraoperative findings. METHODS Case report. A 56-year-old woman presented with visual acuity LE: 20/100, a full thickness macular hole, and an optic pit. Optical coherence tomography and ophthalmic examination were performed preoperatively and postoperatively. RESULTS Although usually a macular hole associated with an optic pit tends to be a lamellar and characterized by outer layer defects within preexisting macular detachments or schisis-like cavities, this type of macular hole was not presented in this case. Although the macular hole resembled the idiopathic type on clinical examination as well as on optical coherence tomography, it could only be closed in the third surgical attempt after using silicone oil as a long-standing tamponade. Peeling of an epiretinal membrane or the internal limiting membrane was not possible during any of the three surgeries. CONCLUSION Our observations suggest that in cases of macular hole in association with optic pit, instillation of silicone oil should be considered in the first surgical procedure, especially if no epiretinal membrane or internal limiting membrane peeling is possible intraoperatively.
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Affiliation(s)
- M Bechmann
- Department of Ophthalmology, Ludwig-Maximilians-University, Munich, Germany.
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Rudolph G, Meindl A, Bechmann M, Schworm HD, Achatz H, Boergen KP, Kampik A, Berninger T, Meitinger T. X-linked ocular albinism (Nettleship-Falls): a novel 29-bp deletion in exon 1. Carrier detection by ophthalmic examination and DNA analysis. Graefes Arch Clin Exp Ophthalmol 2001; 239:167-72. [PMID: 11405065 DOI: 10.1007/s004170000234] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
BACKGROUND Mutations in the OA1 gene on the short arm of the X chromosome are known to cause X-linked ocular albinism (x1OA) in males. A four-generation family with this disorder, including asymptomatic carrier females, was investigated by molecular analysis of the OA1 gene. METHODS DNA samples were available from 22 individuals of this family, including 6 affected males and 6 obligate carriers. The nine exons of the OA1 gene were amplified and further analyzed by SSCP and sequencing. RESULTS A detailed clinical examination of the index patient and two female carriers showed the typical signs of ocular albinism. Visual evoked potential responses showed markedly asymmetrical responses from the two hemispheres in the affected person as well as in the carriers, as a result of misrouting and decussation of optic nerve fibers. Molecular genetic analysis demonstrated a previously undescribed 29-bp deletion at position 225-253 in exon 1 of the OA1 gene, which segregated in the family. CONCLUSION Clinical examination combined with molecular genetic analysis enhances the potential for a precise diagnosis for persons at risk of x1OA and provide an accurate basis for genetic counseling.
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Affiliation(s)
- G Rudolph
- Augenklinik der Universität München, Mathildenstrasse 8, 80336 Munich, Germany.
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Rudolph G, Bechmann M, Berninger T, Kutschbach E, Held U, Tornow RP, Kalpadakis P, Zol'nikova IV, Shamshinova AM. [Topographic mapping of retinal function with a scanning laser ophthalmoscope and multifocal electroretinography using short M-sequences]. Vestn Oftalmol 2001; 117:32-5. [PMID: 11510163] [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: 02/21/2023]
Abstract
A new method of multifocal electroretinography making use of scanning laser ophthalmoscope with a wavelength of 630 nm (SLO-m-ERG), evoking short spatial visual stimuli on the retina, is proposed. Algorithm of presenting the visual stimuli and analysis of distribution of local electroretinograms on the surface of the retina is based on short m-sequences. Mathematical cross correlation analysis shows a three-dimensional distribution of bioelectrical activity of the retina in the central visual field. In normal subjects the cone bioelectrical activity is the maximum in the macular area (corresponding to the density of cone distribution) and absent in the blind spot. The method detects the slightest pathological changes in the retina under control of the site of stimulation and ophthalmoscopic picture of the fundus oculi. The site of the pathological process correlates with the topography of changes in bioelectrical activity of the examined retinal area in diseases of the macular area and pigmented retinitis detectable by ophthalmoscopy.
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Bechmann M, Thiel MJ, Neubauer AS, Ullrich S, Ludwig K, Kenyon KR, Ulbig MW. Central corneal thickness measurement with a retinal optical coherence tomography device versus standard ultrasonic pachymetry. Cornea 2001; 20:50-4. [PMID: 11189004 DOI: 10.1097/00003226-200101000-00010] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
PURPOSE To demonstrate the capability of a standard, commercially available optical coherence tomography device (originally designed to measure retinal thickness) to image the human cornea in vivo and to measure central corneal thickness (CCT) in normal and edematous corneas. The intrapatient precision and interpatient variability of this novel application was compared to standard ultrasonic pachymetry. Also, the correlation of both methods was investigated. METHODS CCT measurements using optical coherence tomography (OCT) and ultrasonic pachymetry (PACH) were obtained in 36 normal eyes and 16 eyes with corneal edema. RESULTS Direct in vivo imaging of the cornea and measurements of CCT by OCT could be performed in all eyes. In normal subjects, CCT(OCT) was 530+/-32 microm and CCT(PACH) was 581+/-34 microm. The two methods showed a highly significant correlation with a standardized regression coefficient of 0.988. The difference between both methods was constant over the range of CCT (mean difference, 49.4+/-5.9 microm). The mean intrapatient SD of CCT measurements was 4.90 microm and 4.96 microm for OCT and PACH, respectively. In patients with corneal edema, mean CCT(OCT) was 601+/-59 microm, and mean CCT(PACH) was 667+/-68 microm. The difference between the two techniques increased slightly with increasing corneal edema (mean difference, 66.9+/-10.9 microm). CONCLUSION Imaging of the human cornea can be performed by a standard retinal OCT device, and OCT measurement of CCT shows excellent correlation to values obtained by PACH, giving similar readings separated by a constant difference. In corneal edema, the difference between the two methods is additionally increased, but continues to demonstrate excellent consistency.
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Affiliation(s)
- M Bechmann
- Department of Ophthalmology, Ludwig-Maximilians-University, Munich, Germany.
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Thiel MJ, Bechmann M, Ullrich S, Gass C, Haritoglou C, Binder C, Kristin N, Lackerbauer CA, Gandorfer A, Ulbig MW. [Imaging of vitreoretinal adhesions in the partner eye of patients with penetrating macular foramina in optical coherence tomography]. Ophthalmologe 2000; 97:821-6. [PMID: 11227151 DOI: 10.1007/s003470070001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND Vitreoretinal adhesions play a crucial role in the development of a macular hole. To visualize vitreoretinal adhesion we used optical coherence tomography to investigate fellow eyes of patients with macular holes. METHODS In a prospective study we scanned the retina in 188 patients with a macular hole stage III or IV (Gass classification). The foveal shape and vitreous were classified into grades. RESULTS Of the 188 patients 45% showed no vitreous reflex, 45% a partial vitreous detachment with foveolar adhesions, and 10% a vitreous detachment with complete separation from the fovea. While eyes with normal foveolar shape displayed partial vitreous detachment in 33%, this figure rose to 66% in eyes with a macular hole stage I. CONCLUSION Diffuse thickening of the fovea is followed by an intraretinal split and formation of a cyst. The shape of the foveolar adhesion suggests that continuing anteroposterior vitreal traction leads to a retinal break and formation of a full-thickness macular hole.
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Affiliation(s)
- M J Thiel
- Augenklinik, Ludwig-Maximilians Universität München, Klinikum Innenstadt, Mathildenstrasse 8, 80336 München.
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Bechmann M, Thiel MJ, Roesen B, Ullrich S, Ulbig MW, Ludwig K. Central corneal thickness determined with optical coherence tomography in various types of glaucoma. Br J Ophthalmol 2000; 84:1233-7. [PMID: 11049946 PMCID: PMC1723313 DOI: 10.1136/bjo.84.11.1233] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIMS To evaluate central corneal thickness determined by optical coherence tomography (OCT) in various types of glaucoma, and its influence on intraocular pressure (IOP) measurement. METHODS Central corneal thickness (CCT) was determined by using OCT in 167 subjects (167 eyes). 20 had primary open angle glaucoma (POAG), 42 had low tension glaucoma (LTG), 22 had ocular hypertension (OHT), 10 had primary angle closure glaucoma (AC), 24 had pseudoexfoliation glaucoma (PEX), 13 had pigmentary glaucoma (PIG), and 36 were normal. RESULTS CCT was significantly higher in ocular hypertensive subjects (593 (SD 35) microm, p <0.0001) than in the controls (530 (32) microm), whereas patients with LTG (482 (28) microm, p < 0. 0001), PEX (493 (33) microm, p <0.0001), and POAG (512 (30) microm, p <0.05) showed significantly lower readings. There was no statistically significant difference between the controls and patients with PIG (510 (39) microm) and AC (539 (37) microm). CONCLUSIONS Because of thinner CCT in patients with LTG, PEX, and POAG this may result in underestimation of IOP, whereas thicker corneas may lead to an overestimation of IOP in subjects with OH. By determining CCT with OCT, a new and precise technique to measure CCT, this study emphasises the need for a combined measurement of IOP and CCT in order to obtain exact IOP readings.
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Affiliation(s)
- M Bechmann
- Department of Ophthalmology, Ludwig-Maximilians- University, Munich, Germany.
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Schmitz F, Bechmann M, Drenckhahn D. Purification of synaptic ribbons, structural components of the photoreceptor active zone complex. J Neurosci 1996; 16:7109-16. [PMID: 8929420 PMCID: PMC6578940] [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] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Synaptic ribbons are plasma membrane-associated structural elements in photoreceptor synaptic terminals. They seem to act as high capacity "docking sites" of synaptic vesicles that provide the fusion sites of the photoreceptor synapse ("active zones"), with a large supply of immobilized synaptic vesicles rapidly available for exocytosis. Synaptic ribbons are regarded as a specialized type of presynaptic densities found in virtually all synapses. The molecular composition of presynaptic densities and synaptic ribbons is unknown. The aim of this study was the isolation of synaptic ribbons from photoreceptor synapses. For this purpose, we first isolated a membrane fraction from the bovine retina that was strongly enriched in photoreceptor synapses. From this fraction, a Triton X-100-resistant subfraction was purified that consisted mainly of synaptic ribbons and their disassembly products. The high enrichment of synaptic ribbons was verified by electron microscopy and immunolabeling using an antibody that specifically binds to synaptic ribbons. SDS-PAGE analysis of this synaptic ribbon fraction displayed several major polypeptide bands migrating at approximately 240, 60, 55, 43, and 30 kDa. The purification procedure described here is a first promising step toward the identification of the yet unknown constituents of synaptic ribbons from photoreceptor synapses and possibly also of presynaptic densities from other synapses.
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Affiliation(s)
- F Schmitz
- Institute of Anatomy, University of Würzburg, Germany
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Nowack K, Bechmann M. [Management of problem children in a school for behavior disordered children--model pedagogic and therapeutic center]. Offentl Gesundheitswes 1986; 48:618-22. [PMID: 2949181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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