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Baumann V, Achleitner S, Tulli S, Schuschnig M, Klune L, Martens S. Faa1 membrane binding drives positive feedback in autophagosome biogenesis via fatty acid activation. J Cell Biol 2024; 223:e202309057. [PMID: 38573225 PMCID: PMC10993510 DOI: 10.1083/jcb.202309057] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Revised: 02/14/2024] [Accepted: 03/22/2024] [Indexed: 04/05/2024] Open
Abstract
Autophagy serves as a stress response pathway by mediating the degradation of cellular material within lysosomes. In autophagy, this material is encapsulated in double-membrane vesicles termed autophagosomes, which form from precursors referred to as phagophores. Phagophores grow by lipid influx from the endoplasmic reticulum into Atg9-positive compartments and local lipid synthesis provides lipids for their expansion. How phagophore nucleation and expansion are coordinated with lipid synthesis is unclear. Here, we show that Faa1, an enzyme activating fatty acids, is recruited to Atg9 vesicles by directly binding to negatively charged membranes with a preference for phosphoinositides such as PI3P and PI4P. We define the membrane-binding surface of Faa1 and show that its direct interaction with the membrane is required for its recruitment to phagophores. Furthermore, the physiological localization of Faa1 is key for its efficient catalysis and promotes phagophore expansion. Our results suggest a positive feedback loop coupling phagophore nucleation and expansion to lipid synthesis.
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Affiliation(s)
- Verena Baumann
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - Sonja Achleitner
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
- Vienna BioCenter PhD Program, A Doctoral School of the University of Vienna, Medical University of Vienna, Vienna, Austria
| | - Susanna Tulli
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - Martina Schuschnig
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - Lara Klune
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - Sascha Martens
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
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Coudevylle N, Banaś B, Baumann V, Schuschnig M, Zawadzka-Kazimierczuk A, Koźmiński W, Martens S. Mechanism of Atg9 recruitment by Atg11 in the cytoplasm-to-vacuole targeting pathway. J Biol Chem 2022; 298:101573. [PMID: 35007534 PMCID: PMC8814668 DOI: 10.1016/j.jbc.2022.101573] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 12/23/2021] [Indexed: 11/22/2022] Open
Abstract
Autophagy is a lysosomal degradation pathway for the removal of damaged and superfluous cytoplasmic material. This is achieved by the sequestration of this cargo material within double-membrane vesicles termed autophagosomes. Autophagosome formation is mediated by the conserved autophagy machinery. In selective autophagy, this machinery including the transmembrane protein Atg9 is recruited to specific cargo material via cargo receptors and the Atg11/FIP200 scaffold protein. The molecular details of the interaction between Atg11 and Atg9 are unclear, and it is still unknown how the recruitment of Atg9 is regulated. Here we employ NMR spectroscopy of the N-terminal disordered domain of Atg9 (Atg9-NTD) to map its interaction with Atg11 revealing that it involves two short peptides both containing a PLF motif. We show that the Atg9-NTD binds to Atg11 with an affinity of about 1 μM and that both PLF motifs contribute to the interaction. Mutation of the PLF motifs abolishes the interaction of the Atg9-NTD with Atg11, reduces the recruitment of Atg9 to the precursor aminopeptidase 1 (prApe1) cargo, and blocks prApe1 transport into the vacuole by the selective autophagy-like cytoplasm-to-vacuole (Cvt) targeting pathway while not affecting bulk autophagy. Our results provide mechanistic insights into the interaction of the Atg11 scaffold with the Atg9 transmembrane protein in selective autophagy and suggest a model where only clustered Atg11 when bound to the prApe1 cargo is able to efficiently recruit Atg9 vesicles.
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Affiliation(s)
| | - Bartłomiej Banaś
- Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| | - Verena Baumann
- Max Perutz Laboratories, University of Vienna, Vienna, Austria; Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | | | | | - Wiktor Koźmiński
- Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| | - Sascha Martens
- Max Perutz Laboratories, University of Vienna, Vienna, Austria.
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Sawa-Makarska J, Baumann V, Coudevylle N, von Bülow S, Nogellova V, Abert C, Schuschnig M, Graef M, Hummer G, Martens S. Reconstitution of autophagosome nucleation defines Atg9 vesicles as seeds for membrane formation. Science 2020; 369:369/6508/eaaz7714. [PMID: 32883836 DOI: 10.1126/science.aaz7714] [Citation(s) in RCA: 136] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 05/16/2020] [Accepted: 07/06/2020] [Indexed: 12/15/2022]
Abstract
Autophagosomes form de novo in a manner that is incompletely understood. Particularly enigmatic are autophagy-related protein 9 (Atg9)-containing vesicles that are required for autophagy machinery assembly but do not supply the bulk of the autophagosomal membrane. In this study, we reconstituted autophagosome nucleation using recombinant components from yeast. We found that Atg9 proteoliposomes first recruited the phosphatidylinositol 3-phosphate kinase complex, followed by Atg21, the Atg2-Atg18 lipid transfer complex, and the E3-like Atg12-Atg5-Atg16 complex, which promoted Atg8 lipidation. Furthermore, we found that Atg2 could transfer lipids for Atg8 lipidation. In selective autophagy, these reactions could potentially be coupled to the cargo via the Atg19-Atg11-Atg9 interactions. We thus propose that Atg9 vesicles form seeds that establish membrane contact sites to initiate lipid transfer from compartments such as the endoplasmic reticulum.
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Affiliation(s)
- Justyna Sawa-Makarska
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, 1030 Vienna, Austria.
| | - Verena Baumann
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, 1030 Vienna, Austria
| | - Nicolas Coudevylle
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, 1030 Vienna, Austria
| | - Sören von Bülow
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Veronika Nogellova
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, 1030 Vienna, Austria
| | - Christine Abert
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, 1030 Vienna, Austria
| | - Martina Schuschnig
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, 1030 Vienna, Austria
| | - Martin Graef
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany.,Institute for Biophysics, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
| | - Sascha Martens
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, 1030 Vienna, Austria.
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Schmidt O, Weyer Y, Sprenger S, Widerin MA, Eising S, Baumann V, Angelova M, Loewith R, Stefan CJ, Hess MW, Fröhlich F, Teis D. TOR complex 2 (TORC2) signaling and the ESCRT machinery cooperate in the protection of plasma membrane integrity in yeast. J Biol Chem 2020; 295:12028-12044. [PMID: 32611771 PMCID: PMC7443507 DOI: 10.1074/jbc.ra120.013222] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 06/24/2020] [Indexed: 12/26/2022] Open
Abstract
The endosomal sorting complexes required for transport (ESCRT) mediate evolutionarily conserved membrane remodeling processes. Here, we used budding yeast (Saccharomyces cerevisiae) to explore how the ESCRT machinery contributes to plasma membrane (PM) homeostasis. We found that in response to reduced membrane tension and inhibition of TOR complex 2 (TORC2), ESCRT-III/Vps4 assemblies form at the PM and help maintain membrane integrity. In turn, the growth of ESCRT mutants strongly depended on TORC2-mediated homeostatic regulation of sphingolipid (SL) metabolism. This was caused by calcineurin-dependent dephosphorylation of Orm2, a repressor of SL biosynthesis. Calcineurin activity impaired Orm2 export from the endoplasmic reticulum (ER) and thereby hampered its subsequent endosome and Golgi-associated degradation (EGAD). The ensuing accumulation of Orm2 at the ER in ESCRT mutants necessitated TORC2 signaling through its downstream kinase Ypk1, which repressed Orm2 and prevented a detrimental imbalance of SL metabolism. Our findings reveal compensatory cross-talk between the ESCRT machinery, calcineurin/TORC2 signaling, and the EGAD pathway important for the regulation of SL biosynthesis and the maintenance of PM homeostasis.
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Affiliation(s)
- Oliver Schmidt
- Institute for Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.
| | - Yannick Weyer
- Institute for Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Simon Sprenger
- Institute for Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Michael A Widerin
- Institute for Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Sebastian Eising
- Department of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany
| | - Verena Baumann
- Institute for Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Mihaela Angelova
- Cancer Evolution and Genome Instability Laboratory, Francis Crick Institute, London, United Kingdom
| | - Robbie Loewith
- Department of Molecular Biology, University of Geneva, Geneva, Switzerland
| | - Christopher J Stefan
- MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Michael W Hess
- Institute for Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria
| | - Florian Fröhlich
- Department of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany
| | - David Teis
- Institute for Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
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Dey P, Baumann V, Rodríguez-Fernández J. Gold Nanorod Assemblies: The Roles of Hot-Spot Positioning and Anisotropy in Plasmon Coupling and SERS. Nanomaterials (Basel) 2020; 10:E942. [PMID: 32423172 PMCID: PMC7279447 DOI: 10.3390/nano10050942] [Citation(s) in RCA: 20] [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] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 05/08/2020] [Accepted: 05/09/2020] [Indexed: 12/13/2022]
Abstract
Plasmon-coupled colloidal nanoassemblies with carefully sculpted "hot-spots" and intense surface-enhanced Raman scattering (SERS) are in high demand as photostable and sensitive plasmonic nano-, bio-, and chemosensors. When maximizing SERS signals, it is particularly challenging to control the hot-spot density, precisely position the hot-spots to intensify the plasmon coupling, and introduce the SERS molecule in those intense hot-spots. Here, we investigated the importance of these factors in nanoassemblies made of a gold nanorod (AuNR) core and spherical nanoparticle (AuNP) satellites with ssDNA oligomer linkers. Hot-spot positioning at the NR tips was made possible by selectively burying the ssDNA in the lateral facets via controlled Ag overgrowth while retaining their hybridization and assembly potential at the tips. This strategy, with slight alterations, allowed us to form nanoassemblies that only contained satellites at the NR tips, i.e., directional anisotropic nanoassemblies; or satellites randomly positioned around the NR, i.e., nondirectional nanoassemblies. Directional nanoassemblies featured strong plasmon coupling as compared to nondirectional ones, as a result of strategically placing the hot-spots at the most intense electric field position of the AuNR, i.e., retaining the inherent plasmon anisotropy. Furthermore, as the dsDNA was located in these anisotropic hot-spots, this allowed for the tag-free detection down to 10 dsDNA and a dramatic SERS enhancement of 1.6 × 108 for the SERS tag SYBR gold, which specifically intercalates into the dsDNA. This dramatic SERS performance was made possible by manipulating the anisotropy of the nanoassemblies, which allowed us to emphasize the critical role of hot-spot positioning and SERS molecule positioning in nanoassemblies.
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Affiliation(s)
- Priyanka Dey
- Department of Physics and CeNS, Ludwig-Maximilians-Universität München, 80539 Munich, Germany; (V.B.); (J.R.-F.)
- Nanosystems Initiative Munich (NIM), 80799 Munich, Germany
| | - Verena Baumann
- Department of Physics and CeNS, Ludwig-Maximilians-Universität München, 80539 Munich, Germany; (V.B.); (J.R.-F.)
- Nanosystems Initiative Munich (NIM), 80799 Munich, Germany
| | - Jessica Rodríguez-Fernández
- Department of Physics and CeNS, Ludwig-Maximilians-Universität München, 80539 Munich, Germany; (V.B.); (J.R.-F.)
- Nanosystems Initiative Munich (NIM), 80799 Munich, Germany
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Schmidt O, Weyer Y, Baumann V, Widerin MA, Eising S, Angelova M, Schleiffer A, Kremser L, Lindner H, Peter M, Fröhlich F, Teis D. Endosome and Golgi-associated degradation (EGAD) of membrane proteins regulates sphingolipid metabolism. EMBO J 2019; 38:e101433. [PMID: 31368600 PMCID: PMC6669922 DOI: 10.15252/embj.2018101433] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 05/08/2019] [Accepted: 05/08/2019] [Indexed: 12/13/2022] Open
Abstract
Cellular homeostasis requires the ubiquitin-dependent degradation of membrane proteins. This was assumed to be mediated exclusively either by endoplasmic reticulum-associated degradation (ERAD) or by endosomal sorting complexes required for transport (ESCRT)-dependent lysosomal degradation. We identified in Saccharomyces cerevisiae an additional pathway that selectively extracts membrane proteins at Golgi and endosomes for degradation by cytosolic proteasomes. One endogenous substrate of this endosome and Golgi-associated degradation pathway (EGAD) is the ER-resident membrane protein Orm2, a negative regulator of sphingolipid biosynthesis. Orm2 degradation is initiated by phosphorylation, which triggers its ER export. Once on Golgi and endosomes, Orm2 is poly-ubiquitinated by the membrane-embedded "Defective in SREBP cleavage" (Dsc) ubiquitin ligase complex. Cdc48/VCP then extracts ubiquitinated Orm2 from membranes, which is tightly coupled to the proteasomal degradation of Orm2. Thereby, EGAD prevents the accumulation of Orm2 at the ER and in post-ER compartments and promotes the controlled de-repression of sphingolipid biosynthesis. Thus, the selective degradation of membrane proteins by EGAD contributes to proteostasis and lipid homeostasis in eukaryotic cells.
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Affiliation(s)
- Oliver Schmidt
- Division of Cell BiologyBiocenterMedical University of InnsbruckInnsbruckAustria
| | - Yannick Weyer
- Division of Cell BiologyBiocenterMedical University of InnsbruckInnsbruckAustria
| | - Verena Baumann
- Division of Cell BiologyBiocenterMedical University of InnsbruckInnsbruckAustria
- Present address:
MFPLUniversity of ViennaViennaAustria
| | - Michael A Widerin
- Division of Cell BiologyBiocenterMedical University of InnsbruckInnsbruckAustria
| | - Sebastian Eising
- Department of Biology/ChemistryUniversity of OsnabrückOsnabrückGermany
| | - Mihaela Angelova
- INSERMLaboratory of Integrative Cancer ImmunologySorbonne UniversitéSorbonne Paris CitéUniversité Paris DescartesCentre de Recherche des CordeliersUniversité Paris DiderotParisFrance
| | - Alexander Schleiffer
- Research Institute of Molecular Pathology (IMP)Vienna Biocenter (VBC)ViennaAustria
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA)Vienna Biocenter (VBC)ViennaAustria
| | - Leopold Kremser
- Division of Clinical Biochemistry, Protein Micro‐Analysis FacilityBiocenterMedical University of InnsbruckInnsbruckAustria
| | - Herbert Lindner
- Division of Clinical Biochemistry, Protein Micro‐Analysis FacilityBiocenterMedical University of InnsbruckInnsbruckAustria
| | | | - Florian Fröhlich
- Department of Biology/ChemistryUniversity of OsnabrückOsnabrückGermany
| | - David Teis
- Division of Cell BiologyBiocenterMedical University of InnsbruckInnsbruckAustria
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Baxmann A, Krummenauer F, Baumann V, Reinhard J, Noè G, Schiermeier S. Personalisierte CTG-Analyse. Geburtshilfe Frauenheilkd 2016. [DOI: 10.1055/s-0036-1592933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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8
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Baumann V, Friedrich Röttgermann PJ, Haase F, Szendrei K, Dey P, Lyons K, Wyrwich R, Gräßel M, Stehr J, Ullerich L, Bürsgens F, Rodríguez-Fernández J. Highly stable and biocompatible gold nanorod–DNA conjugates as NIR probes for ultrafast sequence-selective DNA melting. RSC Adv 2016. [DOI: 10.1039/c6ra17156g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Colloidally stable and biocompatible DNA-functionalized Au nanorods are proved as NIR-addressable probes and mediators for ultrafast and sequence-selective DNA melting.
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Affiliation(s)
- Verena Baumann
- Photonics and Optoelectronics Group
- Department of Physics and Center for NanoScience (CeNS)
- Ludwig-Maximilians-Universität München
- 80799 Munich
- Germany
| | - Peter Johan Friedrich Röttgermann
- Soft Condensed Matter Group
- Department of Physics and Center for NanoScience (CeNS)
- Ludwig-Maximilians-Universität München
- 80539 Munich
- Germany
| | - Frederik Haase
- Photonics and Optoelectronics Group
- Department of Physics and Center for NanoScience (CeNS)
- Ludwig-Maximilians-Universität München
- 80799 Munich
- Germany
| | - Katalin Szendrei
- Photonics and Optoelectronics Group
- Department of Physics and Center for NanoScience (CeNS)
- Ludwig-Maximilians-Universität München
- 80799 Munich
- Germany
| | - Priyanka Dey
- Photonics and Optoelectronics Group
- Department of Physics and Center for NanoScience (CeNS)
- Ludwig-Maximilians-Universität München
- 80799 Munich
- Germany
| | - Katja Lyons
- Photonics and Optoelectronics Group
- Department of Physics and Center for NanoScience (CeNS)
- Ludwig-Maximilians-Universität München
- 80799 Munich
- Germany
| | - Regina Wyrwich
- Department of Chemistry
- Ludwig-Maximilians-Universität München
- 81377 Munich
- Germany
| | - Matthias Gräßel
- Photonics and Optoelectronics Group
- Department of Physics and Center for NanoScience (CeNS)
- Ludwig-Maximilians-Universität München
- 80799 Munich
- Germany
| | | | | | | | - Jessica Rodríguez-Fernández
- Photonics and Optoelectronics Group
- Department of Physics and Center for NanoScience (CeNS)
- Ludwig-Maximilians-Universität München
- 80799 Munich
- Germany
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Baumann V, Habeeb Muhammed MA, Blanch AJ, Dey P, Rodríguez-Fernández J. Biomolecules in Metal and Semiconductor Nanoparticle Growth. Isr J Chem 2015. [DOI: 10.1002/ijch.201500031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Baumann V, Stumpf F, Steinl T, Forchel A, Schneider C, Höfling S, Kamp M. Site-controlled growth of InP/GaInP quantum dots on GaAs substrates. Nanotechnology 2012; 23:375301. [PMID: 22922443 DOI: 10.1088/0957-4484/23/37/375301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A technology platform for the epitaxial growth of site-controlled InP quantum dots (QDs) on GaAs substrates is presented. Nanoholes are patterned in a GaInP layer on a GaAs substrate by electron beam lithography and dry chemical etching, serving as QD nucleation centers. The effects of a thermal treatment on the structured surfaces for deoxidation are investigated in detail. By regrowth on these surfaces, accurate QD positioning is obtained for square array arrangements with lattice periods of 1.25 μm along with a high suppression of interstitial island formation. The optical properties of these red-emitting QDs (λ ~ 670 nm) are investigated by means of ensemble- and micro-photoluminescence spectroscopy at cryogenic temperatures.
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Affiliation(s)
- V Baumann
- Technische Physik, Physikalisches Institut and Wilhelm Conrad Röntgen Research Center for Complex Material Systems, Universität Würzburg, Würzburg, Germany.
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11
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Henderson EJ, Shuhendler AJ, Prasad P, Baumann V, Maier-Flaig F, Faulkner DO, Lemmer U, Wu XY, Ozin GA. Colloidally stable silicon nanocrystals with near-infrared photoluminescence for biological fluorescence imaging. Small 2011; 7:2507-16. [PMID: 21739601 DOI: 10.1002/smll.201100845] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2011] [Indexed: 05/14/2023]
Abstract
Luminescent silicon nanocrystals (ncSi) are showing great promise as photoluminescent tags for biological fluorescence imaging, with size-dependent emission that can be tuned into the near-infrared biological window and reported lack of toxicity. Here, colloidally stable ncSi with NIR photoluminescence are synthesized from (HSiO1.5)n sol-gel glasses and are used in biological fluorescence imaging. Modifications to the thermal processing conditions of (HSiO1.5)n sol-gel glasses, the development of new ncSi oxide liberation chemistry, and an appropriate alkyl surface passivation scheme lead to the formation of colloidally stable ncSi with photoluminescence centered at 955 nm. Water solubility and biocompatibility are achieved through encapsulation of the hydrophobic alkyl-capped ncSi within PEG-terminated solid lipid nanoparticles. Their applicability to biological imaging is demonstrated with the in-vitro fluorescence labelling of human breast tumor cells.
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Affiliation(s)
- Eric J Henderson
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, Canada M5S 3H6
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12
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Gerhard S, Baumann V, Höfling S, Forchel A. The structural and optical characterization of high areal density Ga(x)In(1-x)P quantum dots on GaP. Nanotechnology 2009; 20:434016. [PMID: 19801768 DOI: 10.1088/0957-4484/20/43/434016] [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] [Indexed: 05/28/2023]
Abstract
We present a study of the growth, morphology and optical properties of Ga(x)In(1-x)P quantum dots (QDs) grown by molecular beam epitaxy (MBE) for various Ga concentrations x. QD areal densities up to 10(11) cm(-2) have been achieved showing strong dependence on the amount of gallium supplied. Structural properties are evaluated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) and are related to photoluminescence properties of the QDs. Both structural and optical properties are promising for future applications of the herein reported QDs in visible wavelength optoelectronic devices.
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Affiliation(s)
- S Gerhard
- Wilhelm Conrad Röntgen Research Center for Complex Material Systems, Technische Physik, Universität Würzburg, Würzburg, Germany.
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13
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Schönauer T, Baumann V. [Group infection caused by Salmonella enteritidis]. Offentl Gesundheitswes 1990; 52:158-9. [PMID: 2139508] [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: 12/30/2022]
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14
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Rosental R, Babarykin D, Fomina O, Smelters G, Valiniece M, Baumann V. [Hypophosphatemia after successful transplantation of the kidney. Clinico-experimental study]. Z Urol Nephrol 1982; 75:393-9. [PMID: 6750972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The dynamic of indices changes of phosphorus treatment with nefrons in 16 patients after kidney transplantation was studied. The transitory hypophosphatemia accompanied with urine was typical in the majority of patients. The decrease of reabsorption and elevation of phosphorus clearance were noted. In a number of cases the phosphatemia level was increased due to reduction of prednisolone doses. It was experimentally revealed that prednisolone reduces the phosphorus absorption in intestine at 25% and the treatment by 1,25-dihydroxy-vitamin D3 and 1 alpha-hydroxyvitamin D3 promotes the normalization of this process.
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15
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Hüttenrauch R, Fricke S, Baumann V. [State of order, properties and dynamics of structure in shear-crystallized ointments (author's transl)]. Pharmazie 1982; 37:25-8. [PMID: 7071108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Using polyethylene-ointments the influence of different stirring rates upon the course of melt-congealing and upon the forming of rheological properties was investigated. Shearing disturbs the process of ordering in the solid phase and causes a higher strength of the ointment. During storage the viscosity increases in the nonsheared ointments and it decreases in the sheared ones. Both systems tend to form a dynamic equilibrium of order characterized by relative intensive lattive defects in the solid phase of the gel matrix.
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Gheorghiu T, Oette K, Baumann V. [Calculation of hydrolysis correction factors for the analysis of bound sugars and its application to gastric juice]. Z Naturforsch B 1970; 25:829-34. [PMID: 4394216 DOI: 10.1515/znb-1970-0811] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Different conditions for the acid hydrolysis of carbohydrate-containing substances, e. g. glycoproteins or mucopolysaccharides of body fluids were tested. The errors arising during quantitative analysis of hydrolysate components are discussed. Hydrolysis correction factors can be used in order to obtain the original sugar composition of the specimen. The authors tried to develop a procedure generally appliable to the calculation of such factors as a function of release and decomposition of sugars under standard acid hydrolysis conditions (3 ɴ HCl for 3 h at 100 °C, sealed tubes, N2). The experiments were performed with lyophilisates of non-dialyzable substances of gastric juice and with the respective free sugars.
Decomposition rates of sugars in the presence of a corresponding hydrolysate of juice proteins were studied under various conditions; the rate curves showed a nearly logarithmical evolution, their slope expressing the acid resistance of the sugar in the given case. Basing on these rates and on the concentration curves of sugars in the native juice hydrolysed under the same conditions, an empirical formula was developed whose different mathematical aspects are subsequently analyzed.
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