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Zech T, Schmutzler T, Noll DM, Appavou MS, Unruh T. Effect of Bromide on the Surfactant Stabilization Layer Density of Gold Nanorods. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:2227-2237. [PMID: 35113578 DOI: 10.1021/acs.langmuir.1c02733] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Some studies have speculated that the concentration of bromide ions plays a crucial role in the surfactant density surrounding gold nanorods (AuNR). Small-angle X-ray and neutron scattering (SAXS and SANS) experiments were conducted to analyze any influence the bromide ions might have on the stabilization layer and the aggregation behavior of the ligand CTAB molecules in general. The AuNR were immersed in solutions containing a fixed CTA+ concentration of 2 mM and varying bromide ion concentrations from 0 to 22 mM. A patchy AuNR stabilization shell at low bromide ion concentrations was found, contrary to previously published SANS studies on the AuNR stabilization shell. However, with increasing bromide ion concentration, the density of the stabilization shell increases asymptotically toward a closed/collapsed bilayer configuration. AuNR grown under similar conditions show higher anisotropy with larger bromide ion concentrations. Both results indicate that anisotropic growth strongly depends on a sufficiently dense stabilization layer established by high bromide ion concentrations.
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Affiliation(s)
- Tobias Zech
- Insitute for Crystallography and Structural Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 3, 91058 Erlangen, Germany
- Center for Nanoanalysis and Electron Microscopy (CENEM) and Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 3, 91058 Erlangen, Germany
| | - Tilo Schmutzler
- Insitute for Crystallography and Structural Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 3, 91058 Erlangen, Germany
- Center for Nanoanalysis and Electron Microscopy (CENEM) and Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 3, 91058 Erlangen, Germany
| | - Dennis M Noll
- Insitute for Crystallography and Structural Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 3, 91058 Erlangen, Germany
| | - Marie-Sousai Appavou
- Forschungszentrum Jülich, JCNS at MLZ, Lichtenbergstr. 1, 85748 Garching, Germany
| | - Tobias Unruh
- Insitute for Crystallography and Structural Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 3, 91058 Erlangen, Germany
- Center for Nanoanalysis and Electron Microscopy (CENEM) and Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 3, 91058 Erlangen, Germany
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Light Scattering and Absorption Complementarities to Neutron Scattering: In Situ FTIR and DLS Techniques at the High-Intensity and Extended Q-Range SANS Diffractometer KWS-2. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11115135] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Understanding soft and biological materials requires global knowledge of their microstructural features from elementary units at the nm scale up to larger complex aggregates in the micrometer range. Such a wide range of scale can be explored using the KWS-2 small-angle neutron (SANS) diffractometer. Additional information obtained by in situ complementary techniques sometimes supports the SANS analysis of systems undergoing structural modifications under external stimuli or which are stable only for short times. Observations at the local molecular level structure and conformation assists with an unambiguous interpretation of the SANS data using appropriate structural models, while monitoring of the sample condition during the SANS investigation ensures the sample stability and desired composition and chemical conditions. Thus, we equipped the KWS-2 with complementary light absorption and scattering capabilities: Fourier transform infrared (FTIR) spectroscopy can now be performed simultaneously with standard and time-resolved SANS, while in situ dynamic light scattering (DLS) became available for routine experiments, which enables the observation of either changes in the sample composition, due to sedimentation effects, or in size of morphologies, due to aggregation processes. The performance of each setup is demonstrated here using systems representative of those typically investigated on this beamline and benchmarked to studies performed offline.
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Ramos L, Banc A, Louhichi A, Pincemaille J, Jestin J, Fu Z, Appavou MS, Menut P, Morel MH. Impact of the protein composition on the structure and viscoelasticity of polymer-like gluten gels. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:144001. [PMID: 33494081 DOI: 10.1088/1361-648x/abdf91] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 01/25/2021] [Indexed: 06/12/2023]
Abstract
We investigate the structure of gluten polymer-like gels in a binary mixture of water/ethanol, 50/50 v/v, a good solvent for gluten proteins. Gluten comprises two main families of proteins, monomeric gliadins and polymer glutenins. In the semi-dilute regime, scattering experiments highlight two classes of behavior, akin to standard polymer solution and polymer gel, depending on the protein composition. We demonstrate that these two classes are encoded in the structural features of the proteins in very dilute solution, and are correlated with the presence of proteins assemblies of typical size tens of nanometers. The assemblies only exist when the protein mixture is sufficiently enriched in glutenins. They are found directly associated to the presence in the gel of domains enriched in non-exchangeable H-bonds and of size comparable to that of the protein assemblies. The domains are probed in neutron scattering experiments thanks to their unique contrast. We show that the sample visco-elasticity is also directly correlated to the quantity of domains enriched in H-bonds, showing the key role of H-bonds in ruling the visco-elasticity of polymer gluten gels.
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Affiliation(s)
- Laurence Ramos
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Amélie Banc
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Ameur Louhichi
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Justine Pincemaille
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
- Ingénierie des Agro-polymères et Technologies Emergentes (IATE), Univ. Montpellier, CIRAD, INRAE, Montpellier SupAgro, Montpellier, France
| | - Jacques Jestin
- Laboratoire Léon Brillouin, UMR 12, Université Paris-Saclay, IRAMIS/CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - Zhendong Fu
- Forschungszentrum Jülich GmbH, JCNS am MLZ Lichtenbergstr. 1, 85748 Garching, Germany
| | - Marie-Sousai Appavou
- Forschungszentrum Jülich GmbH, JCNS am MLZ Lichtenbergstr. 1, 85748 Garching, Germany
| | - Paul Menut
- Ingénierie des Agro-polymères et Technologies Emergentes (IATE), Univ. Montpellier, CIRAD, INRAE, Montpellier SupAgro, Montpellier, France
- Université Paris-Saclay, INRAE, AgroParisTech, UMR SayFood, 91300 Massy, France
| | - Marie-Hélène Morel
- Ingénierie des Agro-polymères et Technologies Emergentes (IATE), Univ. Montpellier, CIRAD, INRAE, Montpellier SupAgro, Montpellier, France
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Costanzo S, Banc A, Louhichi A, Chauveau E, Wu B, Morel MH, Ramos L. Tailoring the Viscoelasticity of Polymer Gels of Gluten Proteins through Solvent Quality. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c01466] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Salvatore Costanzo
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Amélie Banc
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Ameur Louhichi
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Edouard Chauveau
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
| | - Baohu Wu
- Forschungszentrum Jülich GmbH JCNS am MLZ,Lichtenbergstr. 1, Garching 85748, Germany
| | - Marie-Hélène Morel
- Ingénierie des Agro-Polymères et Technologies Emergentes (IATE), Univ. Montpellier, CIRAD, INRAE, Montpellier SupAgro, Montpellier, France
| | - Laurence Ramos
- Laboratoire Charles Coulomb (L2C), Univ. Montpellier, CNRS, Montpellier, France
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Ünnep R, Paul S, Zsiros O, Kovács L, Székely NK, Steinbach G, Appavou MS, Porcar L, Holzwarth AR, Garab G, Nagy G. Thylakoid membrane reorganizations revealed by small-angle neutron scattering of Monstera deliciosa leaves associated with non-photochemical quenching. Open Biol 2020; 10:200144. [PMID: 32931722 PMCID: PMC7536078 DOI: 10.1098/rsob.200144] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 08/14/2020] [Indexed: 12/14/2022] Open
Abstract
Non-photochemical quenching (NPQ) is an important photoprotective mechanism in plants and algae. Although the process is extensively studied, little is known about its relationship with ultrastructural changes of the thylakoid membranes. In order to better understand this relationship, we studied the effects of illumination on the organization of thylakoid membranes in Monstera deliciosa leaves. This evergreen species is known to exhibit very large NPQ and to possess giant grana with dozens of stacked thylakoids. It is thus ideally suited for small-angle neutron scattering measurements (SANS)-a non-invasive technique, which is capable of providing spatially and statistically averaged information on the periodicity of the thylakoid membranes and their rapid reorganizations in vivo. We show that NPQ-inducing illumination causes a strong decrease in the periodic order of granum thylakoid membranes. Development of NPQ and light-induced ultrastructural changes, as well as the relaxation processes, follow similar kinetic patterns. Surprisingly, whereas NPQ is suppressed by diuron, it impedes only the relaxation of the structural changes and not its formation, suggesting that structural changes do not cause but enable NPQ. We also demonstrate that the diminishment of SANS peak does not originate from light-induced redistribution and reorientation of chloroplasts inside the cells.
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Affiliation(s)
- Renáta Ünnep
- Neutron Spectroscopy Department, Centre for Energy Research, H-1121 Budapest, Konkoly-Thege Miklós út 29-33, Hungary
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Suman Paul
- Max-Planck-Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim a.d. Ruhr, Germany
| | - Ottó Zsiros
- Biological Research Centre, Institute of Plant Biology, 6726 Szeged, Hungary
| | - László Kovács
- Biological Research Centre, Institute of Plant Biology, 6726 Szeged, Hungary
| | - Noémi K. Székely
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at MLZ, 85748 Garching, Germany
| | - Gábor Steinbach
- Biological Research Centre, Institute of Biophysics, Temesvári körút 62, 6726 Szeged, Hungary
| | - Marie-Sousai Appavou
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at MLZ, 85748 Garching, Germany
| | - Lionel Porcar
- Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France
| | - Alfred R. Holzwarth
- Max-Planck-Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim a.d. Ruhr, Germany
| | - Győző Garab
- Biological Research Centre, Institute of Plant Biology, 6726 Szeged, Hungary
- Department of Physics, Faculty of Science, Ostrava University, Chittussiho 10, 710 00 Ostrava, Czech Republic
| | - Gergely Nagy
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- European Spallation Source ESS ERIC, PO Box 176, 221 00 Lund, Sweden
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, 1121 Budapest, Hungary
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Schiavone MM, Lamparelli DH, Zhao Y, Zhu F, Revay Z, Radulescu A. The Effects of Temperature and Humidity on the Microstructure of Sulfonated Syndiotactic-polystyrene Ionic Membranes. MEMBRANES 2020; 10:E187. [PMID: 32824025 PMCID: PMC7466101 DOI: 10.3390/membranes10080187] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 08/09/2020] [Accepted: 08/12/2020] [Indexed: 11/16/2022]
Abstract
Polymeric membranes based on the semi-crystalline syndiotactic-polystyrene (sPS) become hydrophilic, and therefore conductive, following the functionalization of the amorphous phase by the solid-state sulfonation procedure. Because the crystallinity of the material, and thus the mechanical strength of the membranes, is maintained and the resistance to oxidation decomposition can be improved by doping the membranes with fullerenes, the sPS becomes attractive for proton-exchange membranes fuel cells (PEMFC) and energy storage applications. In the current work we report the micro-structural characterization by small-angle neutron scattering (SANS) method of sulfonated sPS films and sPS-fullerene composite membranes at different temperatures between 20 °C and 80 °C, under the relative humidity (RH) level from 10% to 70%. Complementary characterization of membranes was carried out by FTIR, UV-Vis spectroscopy and prompt-γ neutron activation analysis in terms of composition, following the specific preparation and functionalization procedure, and by XRD with respect to crystallinity. The hydrated ionic clusters are formed in the hydrated membrane and shrink slightly with the increasing temperature, which leads to a slight desorption of water at high temperatures. However, it seems that the conductive properties of the membranes do not deteriorate with the increasing temperature and that all membranes equilibrated in liquid water show an increased conductivity at 80 °C compared to the room temperature. The presence of fullerenes in the composite membrane induces a tremendous increase in the conductivity at high temperatures compared to fullerenes-free membranes. Apparently, the observed effects may be related to the formation of additional hydrated pathways in the composite membrane in conjunction with changes in the dynamics of water and polymer.
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Affiliation(s)
- Maria-Maddalena Schiavone
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), 85747 Garching, Germany; (M.-M.S.); (F.Z.)
| | - David Hermann Lamparelli
- Dipartimento di Chimica e Biologia “Adolfo Zambelli”, Università di Salerno, I-84084 Fisciano, Italy;
| | - Yue Zhao
- Department of Advanced Functional Materials Research, Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology (QST), Watanuki-machi 1233, Takasaki 370-1292, Japan;
| | - Fengfeng Zhu
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), 85747 Garching, Germany; (M.-M.S.); (F.Z.)
| | - Zsolt Revay
- Technische Universität Müchen, Forschungsneutronenquelle Heinz Maier-Leibnitz FRM II, Heinz Maier-Leibnitz Zentrum (MLZ), 85747 Garching, Germany;
| | - Aurel Radulescu
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), 85747 Garching, Germany; (M.-M.S.); (F.Z.)
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The Multilevel Structure of Sulfonated Syndiotactic-Polystyrene Model Polyelectrolyte Membranes Resolved by Extended Q-Range Contrast Variation SANS. MEMBRANES 2019; 9:membranes9110136. [PMID: 31652905 PMCID: PMC6918273 DOI: 10.3390/membranes9110136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/21/2019] [Accepted: 10/22/2019] [Indexed: 11/17/2022]
Abstract
Membranes based on sulfonated synditoactic polystyrene (s-sPS) were thoroughly characterized by contrast variation small-angle neutron scattering (SANS) over a wide Q-range in dry and hydrated states. Following special sulfonation and treatment procedures, s-sPS is an attractive material for fuel cells and energy storage applications. The film samples were prepared by solid-state sulfonation, resulting in uniform sulfonation of only the amorphous phase while preserving the crystallinity of the membrane. Fullerenes, which improve the resistance to oxidation decomposition, were incorporated in the membranes. The fullerenes seem to be chiefly located in the amorphous regions of the samples, and do not influence the formation and evolution of the morphologies in the polymer films, as no significant differences were observed in the SANS patterns compared to the fullerenes-free s-sPS membranes, which were investigated in a previous study. The use of uniaxially deformed film samples, and neutron contrast variation allowed for the identification and characterization of different structural levels with sizes between nm and μm, which form and evolve in both the dry and hydrated states. The scattering length density of the crystalline regions was varied using the guest exchange procedure between different toluene isotopologues incorporated into the sPS lattice, while the variation of the scattering properties of the hydrated amorphous regions was achieved using different H2O/D2O mixtures. Due to the deformation of the films, the scattering characteristics of different structures can be distinguished on specific detection sectors and at different detection distances after the sample, depending on their size and orientation.
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Synthetic calcium carbonate improves the effectiveness of treatments with nanolime to contrast decay in highly porous limestone. Sci Rep 2019; 9:15278. [PMID: 31649279 PMCID: PMC6813344 DOI: 10.1038/s41598-019-51836-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 10/09/2019] [Indexed: 11/08/2022] Open
Abstract
Three synthetized polymorphs of calcium carbonate have been tested in combination with the suspension of nanolime particles as potential consolidating agents for contrasting stone decay and overcome some of the limitations of nanolime agents when applied to substrates with large porosity. The modifications induced in the pore network of the Maastricht limestone were analyzed with microscopy and in a non-invasive fashion with small angle neutron scattering and synchrotron radiation micro-computed tomography. A reduction in porosity and pore accessibility at the micrometric scale was detected with the latter technique, and ascribed to the improved pore-filling capacity of the consolidation agent containing CaCO3 particles. These were found to be effectively bound to the carbonated nanolime, strengthening the pore-matrix microstructure. Penetration depth and positive effect on porosity were found to depend on the particle size and shape. Absence of significant changes in the fractal nature of the pore surface at the nanoscale, was interpreted as indication of the negligible contribution of nanolime-based materials in the consolidation of stones with large porosity. However, the results indicate that in such cases, their effectiveness may be enhanced when used in combination with CaCO3 particles, owing to the synergic effect of chemical/structural compatibility and particle size distribution.
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Talley SJ, Vivod SL, Nguyen BA, Meador MAB, Radulescu A, Moore RB. Hierarchical Morphology of Poly(ether ether ketone) Aerogels. ACS APPLIED MATERIALS & INTERFACES 2019; 11:31508-31519. [PMID: 31379150 DOI: 10.1021/acsami.9b09699] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The phase diagram for the thermoreversible gelation of poly(ether ether ketone) (PEEK) in 4-chlorophenol (4CP) was constructed over broad temperature and concentration ranges, revealing that PEEK is capable of dissolving and forming gels in both 4CP and dichloroacetic acid (DCA) up to a concentration of 25 wt %. Highly porous aerogels of PEEK were prepared through simple solvent exchange followed by one of two drying methods of solvent removal from the wet gel: freeze-drying or supercritical CO2 fluid extraction (SC-drying). The field-emission scanning electron microscopy analysis showed that gelation of PEEK in 4CP, followed by SC-drying, produced aerogels with well-defined lamellar aggregates as compared to less ordered aggregates formed from DCA. Mechanical properties (in compression) were shown to improve with increasing density, resulting in equivalent compressive moduli at comparable density, regardless of the preparation method (gelation solvent selection, concentration variation, or drying method). Nitrogen adsorption-desorption isotherms indicate that PEEK aerogels are comprised of mesopores (2-50 nm diameter pores) formed from stacked crystalline lamella. PEEK aerogels prepared using SC-drying exhibit higher Brunauer-Emmett-Teller surface areas than freeze-dried aerogels of comparable density. The ultra-small-angle X-ray scattering/small-angle X-ray scattering (SAXS)/wide-angle X-ray scattering analysis revealed a hierarchical morphology of the PEEK aerogels with structural features from PEEK crystallites to agglomerates of stacked lamella that spanned a wide range of length scales. SANS contrast-matching confirmed that the morphological origin of the principle scattering feature in PEEK aerogels is stacked crystalline lamella. Nitrogen sorption measurements of porosity and the specific surface area of the PEEK aerogels were correlated with the SAXS analysis to reveal a remarkably high surface area attributed to the platelet-like, lamellar morphology. Contact angle and contact angle hysteresis (CAH) revealed that low-density PEEK aerogels (ρ < 0.15 g/cm3) have water contact angles above the superhydrophobicity cutoff angle (>150°) and a very low CAH near 1°.
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Affiliation(s)
- Samantha J Talley
- Department of Chemistry, Macromolecules Innovation Institute (MII) , Virginia Tech , Blacksburg , Virginia 24061 , United States
| | - Stephanie L Vivod
- NASA Glenn Research Center , 21000 Brookpark Road , Cleveland , Ohio 44135 , United States
| | - Baochau A Nguyen
- Ohio Aerospace Institute , 22800 Cedar Point Road , Cleveland , Ohio 44142 , United States
| | - Mary Ann B Meador
- NASA Glenn Research Center , 21000 Brookpark Road , Cleveland , Ohio 44135 , United States
| | - Aurel Radulescu
- Jülich Center for Neutron Science, JCNS Outstation at MLZ , Forschungszentrum Jülich GmbH , Lichtenbergstrasse 1 , Garching 85747 , Germany
| | - Robert B Moore
- Department of Chemistry, Macromolecules Innovation Institute (MII) , Virginia Tech , Blacksburg , Virginia 24061 , United States
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Schmutzler T, Schindler T, Goetz K, Appavou MS, Lindner P, Prevost S, Unruh T. Concentration dependent morphology and composition of n-alcohol modified cetyltrimethylammonium bromide micelles. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:495001. [PMID: 30426969 DOI: 10.1088/1361-648x/aae9c3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Cetyltrimethylammonium bromide (CTAB) is one of the most commonly used surfactants in nanoparticle synthesis and stabilization. Usually, CTAB is used in high concentrations besides co-surfactants leading to well defined products but the complex mesoscopic CTAB structures stay mostly unknown. N-alcohols for instance are widely used co-surfactants which modify the properties of native CTAB dispersions. In this paper we report about a detailed structure analysis of n-alcohol modified CTAB micelles. In particular, n-pentanol and n-hexanol exhibit a significantly different influence on the size, shape and composition of CTAB micelles. Using a combination of small-angle x-ray spectroscopy (SAXS) and neutron scattering spectroscopy (SANS), we applied a method for a complete structural characterization of such micelles. The incorporation of n-pentanol into CTAB micelles generally does not influence the morphology but enhances the number of micelles due to the volume of the added alcohol. N-hexanol, however, leads to an elongation of the micelles as a function of its concentration. It was found by extended contrast variation measurements that this difference is caused by a different distribution of the alcohols between the micellar core and shell. N-pentanol molecules are generally located at the core-shell interface of the CTAB micelles with not only the head group but also two additional methylene bridging groups located in the micellar shell. This leads to an increase of its effective head group volume. In comparison, in n-hexanol modified micelles the whole alkyl chain is located within the micellar core. The detailed structure for n-alcohol modified CTAB micelles is described herein for the first time. The knowledge of the structural details found is indispensable for an in-depth understanding of CTAB-n-alcohol-water interfaces in general which is relevant for the synthesis of many functional nanostructures like mesoporous silica and gold or silver nanoparticles.
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Affiliation(s)
- Tilo Schmutzler
- Institute for Crystallography and Structural Physics (ICSP), Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstrasse 3, 91058 Erlangen, Germany
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Anghel L, Radulescu A, Erhan RV. Structural aspects of human lactoferrin in the iron-binding process studied by molecular dynamics and small-angle neutron scattering. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2018; 41:109. [PMID: 30229350 DOI: 10.1140/epje/i2018-11720-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 08/28/2018] [Indexed: 06/08/2023]
Abstract
Lactoferrin is a non-heme protein known for its ability to bind tightly Fe(III) ions in various physiological environments. Due to this feature lactoferrin plays an important role in the processes of iron regulation at the cellular level preventing the body from damages produced by high levels of free iron ions. The X-ray crystal structure of human lactoferrin shows that the iron-binding process leads to conformational changes within the protein structure. The present study was addressed to conformation stability of human lactoferrin in solution. Using molecular dynamics simulations, it was shown that Arg121 is the key amino acid in the stabilization of the Fe(III) ion in the N-lobe of human lactoferrin. The small-angle neutron scattering method allowed us to detect the structural differences between the open and closed conformation of human lactoferrin in solution. Our results indicate that the radius of gyration of apolactoferrin appears to be smaller than that of the hololactoferrin, [Formula: see text] Å and [Formula: see text] Å, respectively. The low-resolution three-dimensional models computed for both forms of human lactoferrin in solution also show visible differences, both having a more compact conformation compared to the high-resolution structure.
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Affiliation(s)
- Lilia Anghel
- Institute of Chemistry (ICh), Academiei 3, MD-2028, Chisinau, Republic of Moldova
| | - Aurel Radulescu
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstraße 1, 85748, Garching, Germany
| | - Raul Victor Erhan
- Neutron materials characterization (NØYTRON), Institute for Energy Technology (IFE), Instituttveien 18, P.O. Box 40, 2027, Kjeller, Norway.
- Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH), Reactorului 30, P.O. Box MG-6, Bucharest - Magurele, Romania.
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Phase behaviour, micellar structure and linear rheology of tetrablock copolymer Tetronic 908. J Colloid Interface Sci 2018; 524:42-51. [DOI: 10.1016/j.jcis.2018.03.096] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 03/21/2018] [Accepted: 03/27/2018] [Indexed: 11/23/2022]
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Bar Eyal L, Ranjbar Choubeh R, Cohen E, Eisenberg I, Tamburu C, Dorogi M, Ünnep R, Appavou MS, Nevo R, Raviv U, Reich Z, Garab G, van Amerongen H, Paltiel Y, Keren N. Changes in aggregation states of light-harvesting complexes as a mechanism for modulating energy transfer in desert crust cyanobacteria. Proc Natl Acad Sci U S A 2017; 114:9481-9486. [PMID: 28808031 PMCID: PMC5584450 DOI: 10.1073/pnas.1708206114] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
In this paper we propose an energy dissipation mechanism that is completely reliant on changes in the aggregation state of the phycobilisome light-harvesting antenna components. All photosynthetic organisms regulate the efficiency of excitation energy transfer (EET) to fit light energy supply to biochemical demands. Not many do this to the extent required of desert crust cyanobacteria. Following predawn dew deposition, they harvest light energy with maximum efficiency until desiccating in the early morning hours. In the desiccated state, absorbed energy is completely quenched. Time and spectrally resolved fluorescence emission measurements of the desiccated desert crust Leptolyngbya ohadii strain identified (i) reduced EET between phycobilisome components, (ii) shorter fluorescence lifetimes, and (iii) red shift in the emission spectra, compared with the hydrated state. These changes coincide with a loss of the ordered phycobilisome structure, evident from small-angle neutron and X-ray scattering and cryo-transmission electron microscopy data. Based on these observations we propose a model where in the hydrated state the organized rod structure of the phycobilisome supports directional EET to reaction centers with minimal losses due to thermal dissipation. In the desiccated state this structure is lost, giving way to more random aggregates. The resulting EET path will exhibit increased coupling to the environment and enhanced quenching.
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Affiliation(s)
- Leeat Bar Eyal
- Department of Plant & Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Reza Ranjbar Choubeh
- Laboratory of Biophysics, Wageningen University, 6700 ET Wageningen, The Netherlands
| | - Eyal Cohen
- Applied Physics Department, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
- The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Ido Eisenberg
- Applied Physics Department, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
- The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Carmen Tamburu
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Márta Dorogi
- Biological Research Centre, Hungarian Academy of Sciences, Szeged 6726, Hungary
| | - Renata Ünnep
- Wigner Research Centre for Physics, Hungarian Academy of Sciences, H-1525 Budapest 114, Hungary
| | - Marie-Sousai Appavou
- Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum, Forschungszentrum Jülich GmbH, 85748 Garching, Germany
| | - Reinat Nevo
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 7600, Israel
| | - Uri Raviv
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Ziv Reich
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 7600, Israel
| | - Győző Garab
- Biological Research Centre, Hungarian Academy of Sciences, Szeged 6726, Hungary
| | - Herbert van Amerongen
- Laboratory of Biophysics, Wageningen University, 6700 ET Wageningen, The Netherlands
| | - Yossi Paltiel
- Applied Physics Department, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
- The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Nir Keren
- Department of Plant & Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel;
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