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Mufundirwa A, Sakurai Y, Arao M, Matsumoto M, Imai H, Iwamoto H. Contrast variation method applied to structural evaluation of catalysts by X-ray small-angle scattering. Sci Rep 2024; 14:2263. [PMID: 38278843 PMCID: PMC10817912 DOI: 10.1038/s41598-024-52671-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 01/22/2024] [Indexed: 01/28/2024] Open
Abstract
In the process of developing carbon-supported metal catalysts, determining the catalyst particle-size distribution is an essential step, because this parameter is directly related to the catalytic activities. The particle-size distribution is most effectively determined by small-angle X-ray scattering (SAXS). When metal catalysts are supported by high-performance mesoporous carbon materials, however, their mesopores may lead to erroneous particle-size estimation if the sizes of the catalysts and mesopores are comparable. Here we propose a novel approach to particle-size determination by introducing contrast variation-SAXS (CV-SAXS). In CV-SAXS, a multi-component sample is immersed in an inert solvent with a density equal to that of one of the components, thereby rendering that particular component invisible to X-rays. We used a mixture of tetrabromoethane and dimethyl sulfoxide as a contrast-matching solvent for carbon. As a test sample, we prepared a mixture of a small amount of platinum (Pt) catalyst and a bulk of mesoporous carbon, and subjected it to SAXS measurement in the absence and presence of the solvent. In the absence of the solvent, the estimated Pt particle size was affected by the mesopores, but in the presence of the solvent, the Pt particle size was correctly estimated in spite of the low Pt content. The results demonstrate that the CV-SAXS technique is useful for correctly determining the particle-size distribution for low-Pt-content catalysts, for which demands are increasing to reduce the use of expensive Pt.
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Affiliation(s)
- Albert Mufundirwa
- Research Project Division, Japan Synchrotron Radiation Research Institute, SPring-8, Sayo-Cho, Sayo-Gun, Hyogo, 679-5198, Japan
| | - Yoshiharu Sakurai
- Research Project Division, Japan Synchrotron Radiation Research Institute, SPring-8, Sayo-Cho, Sayo-Gun, Hyogo, 679-5198, Japan
| | - Masazumi Arao
- Fuel Cell Cutting-Edge Research Center Technology Research Association, 3147, Shimomukouyama-Cho, Kofu, Yamanashi, 400-1507, Japan
| | - Masashi Matsumoto
- Fuel Cell Cutting-Edge Research Center Technology Research Association, 3147, Shimomukouyama-Cho, Kofu, Yamanashi, 400-1507, Japan
| | - Hideto Imai
- Fuel Cell Cutting-Edge Research Center Technology Research Association, 3147, Shimomukouyama-Cho, Kofu, Yamanashi, 400-1507, Japan
| | - Hiroyuki Iwamoto
- Research Project Division, Japan Synchrotron Radiation Research Institute, SPring-8, Sayo-Cho, Sayo-Gun, Hyogo, 679-5198, Japan.
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Chen SH, Weiss KL, Stanley C, Bhowmik D. Structural characterization of an intrinsically disordered protein complex using integrated small-angle neutron scattering and computing. Protein Sci 2023; 32:e4772. [PMID: 37646172 PMCID: PMC10503416 DOI: 10.1002/pro.4772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 08/22/2023] [Accepted: 08/27/2023] [Indexed: 09/01/2023]
Abstract
Characterizing structural ensembles of intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) of proteins is essential for studying structure-function relationships. Due to the different neutron scattering lengths of hydrogen and deuterium, selective labeling and contrast matching in small-angle neutron scattering (SANS) becomes an effective tool to study dynamic structures of disordered systems. However, experimental timescales typically capture measurements averaged over multiple conformations, leaving complex SANS data for disentanglement. We hereby demonstrate an integrated method to elucidate the structural ensemble of a complex formed by two IDRs. We use data from both full contrast and contrast matching with residue-specific deuterium labeling SANS experiments, microsecond all-atom molecular dynamics (MD) simulations with four molecular mechanics force fields, and an autoencoder-based deep learning (DL) algorithm. From our combined approach, we show that selective deuteration provides additional information that helps characterize structural ensembles. We find that among the four force fields, a99SB-disp and CHARMM36m show the strongest agreement with SANS and NMR experiments. In addition, our DL algorithm not only complements conventional structural analysis methods but also successfully differentiates NMR and MD structures which are indistinguishable on the free energy surface. Lastly, we present an ensemble that describes experimental SANS and NMR data better than MD ensembles generated by one single force field and reveal three clusters of distinct conformations. Our results demonstrate a new integrated approach for characterizing structural ensembles of IDPs.
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Affiliation(s)
- Serena H. Chen
- Computational Sciences and Engineering DivisionOak Ridge National LaboratoryOak RidgeTennesseeUSA
| | - Kevin L. Weiss
- Neutron Scattering DivisionOak Ridge National LaboratoryOak RidgeTennesseeUSA
| | - Christopher Stanley
- Computational Sciences and Engineering DivisionOak Ridge National LaboratoryOak RidgeTennesseeUSA
| | - Debsindhu Bhowmik
- Computational Sciences and Engineering DivisionOak Ridge National LaboratoryOak RidgeTennesseeUSA
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Hjelm RP, Taylor MA, Frash LP, Hawley ME, Ding M, Xu H, Barker J, Olds D, Heath J, Dewers T. Flow-through compression cell for small-angle and ultra-small-angle neutron scattering measurements. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:055115. [PMID: 29864818 DOI: 10.1063/1.5022678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In situ measurements of geological materials under compression and with hydrostatic fluid pressure are important in understanding their behavior under field conditions, which in turn provides critical information for application-driven research. In particular, understanding the role of nano- to micro-scale porosity in the subsurface liquid and gas flow is critical for the high-fidelity characterization of the transport and more efficient extraction of the associated energy resources. In other applications, where parts are produced by the consolidation of powders by compression, the resulting porosity and crystallite orientation (texture) may affect its in-use characteristics. Small-angle neutron scattering (SANS) and ultra SANS are ideal probes for characterization of these porous structures over the nano to micro length scales. Here we show the design, realization, and performance of a novel neutron scattering sample environment, a specially designed compression cell, which provides compressive stress and hydrostatic pressures with effective stress up to 60 MPa, using the neutron beam to probe the effects of stress vectors parallel to the neutron beam. We demonstrate that the neutron optics is suitable for the experimental objectives and that the system is highly stable to the stress and pressure conditions of the measurements.
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Affiliation(s)
- Rex P Hjelm
- Materials Science in Radiation and Dynamics Extremes, Materials Science and Technology Division and the Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Mark A Taylor
- Engineering Services, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Luke P Frash
- Earth Systems Observations, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Marilyn E Hawley
- Engineered Materials, Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Mei Ding
- Earth Systems Observations, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Hongwu Xu
- Earth Systems Observations, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - John Barker
- National Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Daniel Olds
- The Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Jason Heath
- Geomechanics, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Thomas Dewers
- Geomechanics, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
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