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Graf J, Stuerzer T, Durst R, Atak K, Radcliffe P, Michaelsen C. Pushing the limits of microfocus X-ray sealed-tube sources for crystallography. Acta Cryst Sect A 2022. [DOI: 10.1107/s2053273322089847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
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2
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Wiesmann J, Graf J, Radcliffe P. Coordinated development of tubes and optics for microfocus sources: new possibilities for X-ray analytics of cultural heritage materials. Acta Cryst Sect A 2022. [DOI: 10.1107/s2053273322094438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
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3
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Wiesmann J, Graf J, Stuerzer T, Ott H, Benning M, Noll B, Durst R, Radcliffe P, Michaelsen C. Microfocus X-ray sealed tube sources with diamond hybrid anode technology for Cu, Mo and Ag radiation. Acta Crystallogr A Found Adv 2019. [DOI: 10.1107/s0108767319097952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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4
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Wernet P, Leitner T, Josefsson I, Mazza T, Miedema PS, Schröder H, Beye M, Kunnus K, Schreck S, Radcliffe P, Düsterer S, Meyer M, Odelius M, Föhlisch A. Communication: Direct evidence for sequential dissociation of gas-phase Fe(CO) 5 via a singlet pathway upon excitation at 266 nm. J Chem Phys 2018; 146:211103. [PMID: 28595420 DOI: 10.1063/1.4984774] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We prove the hitherto hypothesized sequential dissociation of Fe(CO)5 in the gas phase upon photoexcitation at 266 nm via a singlet pathway with time-resolved valence and core-level photoelectron spectroscopy with an x-ray free-electron laser. Valence photoelectron spectra are used to identify free CO molecules and to determine the time constants of stepwise dissociation to Fe(CO)4 within the temporal resolution of the experiment and further to Fe(CO)3 within 3 ps. Fe 3p core-level photoelectron spectra directly reflect the singlet spin state of the Fe center in Fe(CO)5, Fe(CO)4, and Fe(CO)3 showing that the dissociation exclusively occurs along a singlet pathway without triplet-state contribution. Our results are important for assessing intra- and intermolecular relaxation processes in the photodissociation dynamics of the prototypical Fe(CO)5 complex in the gas phase and in solution, and they establish time-resolved core-level photoelectron spectroscopy as a powerful tool for determining the multiplicity of transition metals in photochemical reactions of coordination complexes.
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Affiliation(s)
- Ph Wernet
- Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - T Leitner
- Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - I Josefsson
- Department of Physics, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden
| | - T Mazza
- European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany
| | - P S Miedema
- Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - H Schröder
- Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - M Beye
- Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - K Kunnus
- Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - S Schreck
- Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - P Radcliffe
- European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany
| | - S Düsterer
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
| | - M Meyer
- European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany
| | - M Odelius
- Department of Physics, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden
| | - A Föhlisch
- Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
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5
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Wernet P, Beye M, de Groot F, Düsterer S, Gaffney K, Grübel S, Hartsock R, Hennies F, Josefsson I, Kennedy B, Kunnus K, Leitner T, Mazza T, Meyer M, Nordlund D, Odelius M, Quevedo W, Radcliffe P, Rajkovic I, Schlotter B, Scholz M, Schreck S, Suljoti E, Techert S, Turner J, Weniger C, Zhang W, Föhlisch A. Mapping chemical bonding of reaction intermediates with femtosecond X-ray laser spectroscopy. EPJ Web of Conferences 2013. [DOI: 10.1051/epjconf/20134105025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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6
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Meyer M, Radcliffe P, Tschentscher T, Costello JT, Cavalieri AL, Grguras I, Maier AR, Kienberger R, Bozek J, Bostedt C, Schorb S, Coffee R, Messerschmidt M, Roedig C, Sistrunk E, Di Mauro LF, Doumy G, Ueda K, Wada S, Düsterer S, Kazansky AK, Kabachnik NM. Angle-resolved electron spectroscopy of laser-assisted Auger decay induced by a few-femtosecond x-ray pulse. Phys Rev Lett 2012; 108:063007. [PMID: 22401068 DOI: 10.1103/physrevlett.108.063007] [Citation(s) in RCA: 3] [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: 10/04/2011] [Indexed: 05/31/2023]
Abstract
Two-color (x-ray+infrared) electron spectroscopy is used for investigating laser-assisted KLL Auger decay following 1s photoionization of atomic Ne with few-femtosecond x-ray pulses from the Linac Coherent Light Source. In an angle-resolved experiment, the overall width of the laser-modified Auger-electron spectrum and its structure change significantly as a function of the emission angle. The spectra are characterized by a strong intensity variation of the sidebands revealing a gross structure. This variation is caused, as predicted by theory, by the interference of electrons emitted at different times within the duration of one optical cycle of the infrared dressing laser, which almost coincides with the lifetime of the Ne 1s vacancy.
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Affiliation(s)
- M Meyer
- European XFEL GmbH, Hamburg, Germany
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7
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Christen W, Radcliffe P, Przystawik A, Diederich T, Tiggesbäumker J. Argon Solvent Effects on Optical Properties of Silver Metal Clusters. J Phys Chem A 2011; 115:8779-82. [DOI: 10.1021/jp200487s] [Citation(s) in RCA: 4] [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: 11/28/2022]
Affiliation(s)
- W. Christen
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany, and
| | - P. Radcliffe
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| | - A. Przystawik
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| | - Th. Diederich
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
| | - J. Tiggesbäumker
- Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
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8
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Meyer M, Cubaynes D, Richardson V, Costello JT, Radcliffe P, Li WB, Düsterer S, Fritzsche S, Mihelic A, Papamihail KG, Lambropoulos P. Two-photon excitation and relaxation of the 3d-4d resonance in atomic Kr. Phys Rev Lett 2010; 104:213001. [PMID: 20867092 DOI: 10.1103/physrevlett.104.213001] [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: 02/07/2010] [Indexed: 05/29/2023]
Abstract
Two-photon excitation of a single-photon forbidden Auger resonance has been observed and investigated using the intense extreme ultraviolet radiation from the free electron laser in Hamburg. At the wavelength 26.9 nm (46 eV) two photons promoted a 3d core electron to the outer 4d shell. The subsequent Auger decay, as well as several nonlinear above threshold ionization processes, were studied by electron spectroscopy. The experimental data are in excellent agreement with theoretical predictions and analysis of the underlying multiphoton processes.
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Affiliation(s)
- M Meyer
- LIXAM, UMR 8624, CNRS-Université Paris Sud, Bâtiment 350, F-91405 Orsay Cedex, France
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9
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Senz V, Fischer T, Oelssner P, Tiggesbäumker J, Stanzel J, Bostedt C, Thomas H, Schöffler M, Foucar L, Martins M, Neville J, Neeb M, Möller T, Wurth W, Rühl E, Dörner R, Schmidt-Böcking H, Eberhardt W, Ganteför G, Treusch R, Radcliffe P, Meiwes-Broer KH. Core-hole screening as a probe for a metal-to-nonmetal transition in lead clusters. Phys Rev Lett 2009; 102:138303. [PMID: 19392409 DOI: 10.1103/physrevlett.102.138303] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Indexed: 05/27/2023]
Abstract
Metal clusters serve as model systems to study basic problems of electronic correlation. Vacuum ultraviolet light from the free-electron laser FLASH ionizes 5d electrons from mass-separated negatively charged clusters, thus transiently leading to core-ionized neutral systems. Shielding of the core hole affects the electron binding energy. From the strong deviation from expectations of the metallic droplet and jellium models we conclude on reduced electronic shielding once the cluster size falls below about 20 atoms. This suggests a metal-to-nonmetal transition, in agreement with previous local density approximation calculations.
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Affiliation(s)
- V Senz
- Institut für Physik, Universität Rostock, 18051 Rostock, Germany.
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10
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Zastrau U, Fortmann C, Fäustlin RR, Cao LF, Döppner T, Düsterer S, Glenzer SH, Gregori G, Laarmann T, Lee HJ, Przystawik A, Radcliffe P, Reinholz H, Röpke G, Thiele R, Tiggesbäumker J, Truong NX, Toleikis S, Uschmann I, Wierling A, Tschentscher T, Förster E, Redmer R. Bremsstrahlung and line spectroscopy of warm dense aluminum plasma heated by xuv free-electron-laser radiation. Phys Rev E Stat Nonlin Soft Matter Phys 2008; 78:066406. [PMID: 19256961 DOI: 10.1103/physreve.78.066406] [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] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Revised: 10/20/2008] [Indexed: 05/27/2023]
Abstract
We report the creation of solid-density aluminum plasma using free-electron laser (FEL) radiation at 13.5nm wavelength. Ultrashort pulses were focused on a bulk Al target, yielding an intensity of 2x10;{14}Wcm;{2} . The radiation emitted from the plasma was measured using an xuv spectrometer. Bremsstrahlung and line intensity ratios yield consistent electron temperatures of about 38eV , supported by radiation hydrodynamics simulations. This shows that xuv FELs heat up plasmas volumetrically and homogeneously at warm-dense-matter conditions, which are accurately characterized by xuv spectroscopy.
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Affiliation(s)
- U Zastrau
- Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität, Max-Wien Platz 1, 07743 Jena, Germany.
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11
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Meyer M, Cubaynes D, Glijer D, Dardis J, Hayden P, Hough P, Richardson V, Kennedy ET, Costello JT, Radcliffe P, Düsterer S, Azima A, Li WB, Redlin H, Feldhaus J, Taïeb R, Maquet A, Grum-Grzhimailo AN, Gryzlova EV, Strakhova SI. Polarization control in two-color above-threshold ionization of atomic helium. Phys Rev Lett 2008; 101:193002. [PMID: 19113264 DOI: 10.1103/physrevlett.101.193002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2008] [Indexed: 05/27/2023]
Abstract
Two-color multiphoton ionization of atomic helium was investigated by combining extreme ultraviolet (XUV) radiation from the Free Electron Laser in Hamburg with an intense synchronized optical laser. In the photoelectron spectrum, lines associated with direct ionization and above-threshold ionization show strong variations of their amplitudes as a function of both the intensity of the optical dressing field and the relative orientation of the linear polarization vectors of the two fields. The polarization dependence provides direct insight into the symmetry of the outgoing electrons in above-threshold ionization. In the high field regime, the monochromaticity of the XUV radiation enables the unperturbed observation of nonlinear processes in the optical field.
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Affiliation(s)
- M Meyer
- LIXAM, UMR 8624, CNRS-Université Paris Sud, Bâtiment 350, 91405 Orsay Cedex, France
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12
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Moshammer R, Jiang YH, Foucar L, Rudenko A, Ergler T, Schröter CD, Lüdemann S, Zrost K, Fischer D, Titze J, Jahnke T, Schöffler M, Weber T, Dörner R, Zouros TJM, Dorn A, Ferger T, Kühnel KU, Düsterer S, Treusch R, Radcliffe P, Plönjes E, Ullrich J. Few-photon multiple ionization of ne and ar by strong free-electron-laser pulses. Phys Rev Lett 2007; 98:203001. [PMID: 17677687 DOI: 10.1103/physrevlett.98.203001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2007] [Indexed: 05/16/2023]
Abstract
Few-photon multiple ionization of Ne and Ar atoms by strong vacuum ultraviolet laser pulses from the free-electron laser at Hamburg was investigated differentially with the Heidelberg reaction microscope. The light-intensity dependence of Ne2+ production reveals the dominance of nonsequential two-photon double ionization at intensities of I<6x10(12) W/cm2 and significant contributions of three-photon ionization as I increases. Ne2+ recoil-ion-momentum distributions suggest that two electrons absorbing "instantaneously" two photons are ejected most likely into opposite hemispheres with similar energies.
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Affiliation(s)
- R Moshammer
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
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13
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Düsterer S, Radcliffe P, Geloni G, Jastrow U, Kuhlmann M, Plönjes E, Tiedtke K, Treusch R, Feldhaus J, Nicolosi P, Poletto L, Yeates P, Luna H, Costello JT, Orr P, Cubaynes D, Meyer M. Spectroscopic characterization of vacuum ultraviolet free electron laser pulses. Opt Lett 2006; 31:1750-2. [PMID: 16688283 DOI: 10.1364/ol.31.001750] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Because of the stochastic nature of self-amplified spontaneous emission (SASE), it is crucial to measure for single pulses the spectral characteristics of ultrashort pulses from the vacuum ultraviolet free electron laser (FLASH) at DESY, Germany. To meet this particular challenge, we have employed both photon and photoelectron spectroscopy. Each FEL pulse is composed of an intense and spectrally complex fundamental, centered at a photon energy of about 38.5 eV, with a bandwidth of 0.5% accompanied by higher harmonics, each carrying an intensity of typically 0.3 to 0.6% of that of the fundamental. The correlation between the harmonics and the fundamental is in remarkable agreement with a simple statistical model of SASE FEL radiation.
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Affiliation(s)
- S Düsterer
- Hamburger Synchrotronstrahlungslabor(HASYLAB) at Deutsches Elektronen-Synchrotron, Germany
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14
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Schofield AB, Pusey PN, Radcliffe P. Stability of the binary colloidal crystals AB2 and AB13. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 72:031407. [PMID: 16241435 DOI: 10.1103/physreve.72.031407] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Indexed: 05/05/2023]
Abstract
Suspensions of binary mixtures of hard-sphere poly-methylmethacrylate colloidal particles were studied at six different size ratios alpha. The main aim was to determine the range of size ratios over which the binary colloidal crystals AB2 and AB13 are stable. Combining these results with those of earlier work, we found stability of AB2 for 0.60 approximately > alpha approximately > 0.425, in good agreement with theoretical predictions by computer simulation and cell model methods. AB13 was observed for 0.62 approximately > alpha approximately > 0.485, the lower limit being significantly smaller than the theoretical prediction of about 0.525. Rough measurements of crystallization rates showed that AB2 tended to crystallize fastest at small size ratios, whereas the opposite was true for AB13. These findings should provide a guide to the optimum conditions for materials applications of these binary colloidal crystals.
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Affiliation(s)
- A B Schofield
- Scottish Universities Physics Alliance, School of Physics, The University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JZ, United Kingdom
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15
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Care A, Vousden KA, Binley KM, Radcliffe P, Trevethick J, Mannazzu I, Sudbery PE. A synthetic lethal screen identifies a role for the cortical actin patch/endocytosis complex in the response to nutrient deprivation in Saccharomyces cerevisiae. Genetics 2004; 166:707-19. [PMID: 15020461 PMCID: PMC1470737 DOI: 10.1534/genetics.166.2.707] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [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: 11/18/2022] Open
Abstract
Saccharomyces cerevisiae whi2Delta cells are unable to halt cell division in response to nutrient limitation and are sensitive to a wide variety of stresses. A synthetic lethal screen resulted in the isolation of siw mutants that had a phenotype similar to that of whi2Delta. Among these were mutations affecting SIW14, FEN2, SLT2, and THR4. Fluid-phase endocytosis is severely reduced or abolished in whi2Delta, siw14Delta, fen2Delta, and thr4Delta mutants. Furthermore, whi2Delta and siw14Delta mutants produce large actin clumps in stationary phase similar to those seen in prk1Delta ark1Delta mutants defective in protein kinases that regulate the actin cytoskeleton. Overexpression of SIW14 in a prk1Delta strain resulted in a loss of cortical actin patches and cables and was lethal. Overexpression of SIW14 also rescued the caffeine sensitivity of the slt2 mutant isolated in the screen, but this was not due to alteration of the phosphorylation state of Slt2. These observations suggest that endocytosis and the organization of the actin cytoskeleton are required for the proper response to nutrient limitation. This hypothesis is supported by the observation that rvs161Delta, sla1Delta, sla2Delta, vrp1Delta, ypt51Delta, ypt52Delta, and end3Delta mutations, which disrupt the organization of the actin cytoskeleton and/or reduce endocytosis, have a phenotype similar to that of whi2Delta mutants.
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Affiliation(s)
- Alison Care
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
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16
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Waddington SN, Nivsarkar MS, Mistry AR, Buckley SMK, Kemball-Cook G, Mosley KL, Mitrophanous K, Radcliffe P, Holder MV, Brittan M, Georgiadis A, Al-Allaf F, Bigger BW, Gregory LG, Cook HT, Ali RR, Thrasher A, Tuddenham EGD, Themis M, Coutelle C. Permanent phenotypic correction of hemophilia B in immunocompetent mice by prenatal gene therapy. Blood 2004; 104:2714-21. [PMID: 15231566 DOI: 10.1182/blood-2004-02-0627] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.5] [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: 11/20/2022] Open
Abstract
Hemophilia B, also known as Christmas disease, arises from mutations in the factor IX (F9) gene. Its treatment in humans, by recombinant protein substitution, is expensive, thus limiting its application to intermittent treatment in bleeding episodes and prophylaxis during surgery; development of inhibitory antibodies is an associated hazard. This study demonstrates permanent therapeutic correction of his disease without development of immune reactions by introduction of an HIV-based lentiviral vector encoding the human factor IX protein into the fetal circulation of immunocompetent hemophiliac and normal outbred mice. Plasma factor IX antigen remained at around 9%, 13%, and 16% of normal in the 3 hemophilia B mice, respectively, until the last measurement at 14 months. Substantial improvement in blood coagulability as measured by coagulation assay was seen in all 3 mice and they rapidly stopped bleeding after venipuncture. No humoral or cellular immunity against the protein, elevation of serum liver enzymes, or vector spread to the germline or maternal circulation were detected.
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Affiliation(s)
- Simon N Waddington
- Imperial College London, Gene Therapy Research Group, Section of Cell and Molecular Biology, Sir Alexander Fleming Bldg, Imperial College Road, London, SW7 2AZ, United Kingdom.
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17
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Care A, Vousden KA, Binley KM, Radcliffe P, Trevethick J, Mannazzu I, Sudbery PE. A Synthetic Lethal Screen Identifies a Role for the Cortical Actin Patch/Endocytosis Complex in the Response to Nutrient Deprivation in Saccharomyces cerevisiae. Genetics 2004. [DOI: 10.1093/genetics/166.2.707] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Saccharomyces cerevisiae whi2Δ cells are unable to halt cell division in response to nutrient limitation and are sensitive to a wide variety of stresses. A synthetic lethal screen resulted in the isolation of siw mutants that had a phenotype similar to that of whi2Δ. Among these were mutations affecting SIW14, FEN2, SLT2, and THR4. Fluid-phase endocytosis is severely reduced or abolished in whi2Δ, siw14Δ, fen2Δ, and thr4Δ mutants. Furthermore, whi2Δ and siw14Δ mutants produce large actin clumps in stationary phase similar to those seen in prk1Δ ark1Δ mutants defective in protein kinases that regulate the actin cytoskeleton. Overexpression of SIW14 in a prk1Δ strain resulted in a loss of cortical actin patches and cables and was lethal. Overexpression of SIW14 also rescued the caffeine sensitivity of the slt2 mutant isolated in the screen, but this was not due to alteration of the phosphorylation state of Slt2. These observations suggest that endocytosis and the organization of the actin cytoskeleton are required for the proper response to nutrient limitation. This hypothesis is supported by the observation that rvs161Δ, sla1Δ, sla2Δ, vrp1Δ, ypt51Δ, ypt52Δ, and end3Δ mutations, which disrupt the organization of the actin cytoskeleton and/or reduce endocytosis, have a phenotype similar to that of whi2Δ mutants.
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Affiliation(s)
| | | | | | | | - Janet Trevethick
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | | | - Peter E Sudbery
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
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18
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Radcliffe P. Public relations is a serious business. Br J Theatre Nurs 1999; 9:35-40. [PMID: 10214148 DOI: 10.1177/175045899900900104] [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] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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19
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Radcliffe P, Hirata D, Childs D, Vardy L, Toda T. Identification of novel temperature-sensitive lethal alleles in essential beta-tubulin and nonessential alpha 2-tubulin genes as fission yeast polarity mutants. Mol Biol Cell 1998; 9:1757-71. [PMID: 9658169 PMCID: PMC25415 DOI: 10.1091/mbc.9.7.1757] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.2] [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: 11/11/2022] Open
Abstract
We have screened for temperature-sensitive (ts) fission yeast mutants with altered polarity (alp1-15). Genetic analysis indicates that alp2 is allelic to atb2 (one of two alpha-tubulin genes) and alp12 to nda3 (the single beta-tubulin gene). atb2(+) is nonessential, and the ts atb2 mutations we have isolated are dominant as expected. We sequenced two alleles of ts atb2 and one allele of ts nda3. In the ts atb2 mutants, the mutated residues (G246D and C356Y) are found at the longitudinal interface between alpha/beta-heterodimers, whereas in ts nda3 the mutated residue (Y422H) is situated in the domain located on the outer surface of the microtubule. The ts nda3 mutant is highly sensitive to altered gene dosage of atb2(+); overexpression of atb2(+) lowers the restrictive temperature, and, conversely, deletion rescues ts. Phenotypic analysis shows that contrary to undergoing mitotic arrest with high viability via the spindle assembly checkpoint as expected, ts nda3 mutants execute cytokinesis and septation and lose viability. Therefore, it appears that the ts nda3 mutant becomes temperature lethal because of irreversible progression through the cell cycle in the absence of activating the spindle assembly checkpoint pathway.
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Affiliation(s)
- P Radcliffe
- Laboratory of Cell Regulation, Imperial Cancer Research Fund, London WC2A 3PX, United Kingdom
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Mytilineou C, Leonardi EK, Radcliffe P, Heinonen EH, Han SK, Werner P, Cohen G, Olanow CW. Deprenyl and desmethylselegiline protect mesencephalic neurons from toxicity induced by glutathione depletion. J Pharmacol Exp Ther 1998; 284:700-6. [PMID: 9454817] [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: 02/06/2023] Open
Abstract
Oxidative stress is thought to play an important role in the pathogenesis of Parkinson's disease (PD). Glutathione (GSH), a major cellular antioxidant, is decreased in the substantia nigra pars compacta of PD patients. The aim of the present study was to investigate whether deprenyl and its desmethyl metabolite, putative neuroprotective agents in the treatment of PD, could protect cultured rat mesencephalic neurons from cell death caused by GSH depletion due to treatment with L-buthionine-(S,R)-sulfoximine (BSO). BSO (10 microM) caused extensive cell death after 48 hr, as demonstrated by disruption of cellular integrity and release of lactate dehydrogenase into the culture medium. Both deprenyl and desmethylselegiline, at concentrations of 5 and 50 microM, significantly protected dopaminergic neurons from toxicity without preventing the BSO-induced loss in GSH. Protection was not associated with monoamine oxidase type B inhibition in that pargyline, a potent MAO inhibitor, was ineffective and pretreatment with pargyline did not prevent the protective effects of deprenyl. Protection was not associated with inhibition of dopamine uptake by deprenyl because the dopamine uptake inhibitor mazindol did not diminish BSO toxicity. The antioxidant ascorbic acid (200 microM) also protected against BSO-induced cell death, suggesting that oxidative events were involved. This study demonstrates that deprenyl and its desmethyl metabolite can diminish cell death associated with GSH depletion.
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Affiliation(s)
- C Mytilineou
- Department of Neurology, Mount Sinai School of Medicine, New York, New York 10029, USA
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Abstract
Wild-type cells of the budding yeast Saccharbmyces cerevisiae arrest in G1 upon nutrient exhaustion. Cell cycle arrest requires the WHI2 gene since whi2 mutants continue to divide and become abnormally small as nutrients are depleted. Here we show that CLN1 and CLN2 transcript levels in a whi2 strain are higher during exponential growth, and persist longer upon starvation, than in an isogenic wild-type strain. In contrast to CLN1 and CLN2, CLN3 levels declined only at very high cell density and were unaffected by the whi2 mutation. Elevated CLN expression is sufficient to explain the whi2 phenotype since ectopic expression of CLN1 in a nutrient-depleted culture caused cells to continue dividing and interfered with the acquisition of heat resistance. These observations show that, either directly or indirectly, Whi2 negatively regulates G1 cyclin expression. Interestingly extremely high levels of Cln1 induced filamentous growth upon nutrient deprivation, suggesting a direct connection between G1 cyclin activity and morphological responses to poor nutrient conditions.
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Affiliation(s)
- P Radcliffe
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, U.K
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Abstract
L-Deprenyl is a relatively selective inhibitor of monoamine oxidase (MAO)-B that delays the emergence of disability and the progression of signs and symptoms of Parkinson's disease. Experimentally, deprenyl has also been shown to prevent neuronal cell death in various models through a mechanism that is independent of MAO-B inhibition. We examined the effect of deprenyl on cultured mesencephalic dopamine neurons subjected to daily changes of feeding medium, an experimental paradigm that causes neuronal death associated with activation of the NMDA subtype of glutamate receptors. Both deprenyl (0.5-50 microM) and the NMDA receptor blocker MK-801 (10 microM) protected dopamine neurons from damage caused by medium changes. The nonselective MAO inhibitor pargyline (0.5-50 microM) was not protective, indicating that protection by deprenyl was not due to MAO inhibition. Deprenyl (50 microM) also protected dopamine neurons from delayed neurotoxicity caused by exposure to NMDA. Because deprenyl had no inhibitory effect on NMDA receptor binding, it is likely that deprenyl protects from events occurring downstream from activation of glutamate receptors. As excitotoxic injury has been implicated in neurodegeneration, it is possible that deprenyl exerts its beneficial effects in Parkinson's disease by suppressing excitotoxic damage.
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Affiliation(s)
- C Mytilineou
- Department of Neurology, Mount Sinai School of Medicine, New York, New York 10029, USA
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