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Ehrman J, Shumilov K, Jenkins AJ, Kasper JM, Vitova T, Batista ER, Yang P, Li X. Unveiling Hidden Shake-Up Features in the Uranyl M 4-Edge Spectrum. JACS Au 2024; 4:1134-1141. [PMID: 38559711 PMCID: PMC10976573 DOI: 10.1021/jacsau.3c00838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 02/14/2024] [Accepted: 02/15/2024] [Indexed: 04/04/2024]
Abstract
The M4,5-edge high energy resolution X-ray absorption near-edge structure (HR-XANES) spectra of actinyls offer valuable insights into the electronic structure and bonding properties of heavy-element complexes. To conduct a comprehensive spectral analysis, it is essential to employ computational methods that accurately account for relativistic effects and electron correlation. In this work, we utilize variational relativistic multireference configurational interaction methods to compute and analyze the X-ray M4-edge absorption spectrum of uranyl. By employing these advanced computational techniques, we achieve excellent agreement between the calculated spectral features and experimental observations. Moreover, the calculations unveil significant shake-up features, which arise from the intricate interplay between strongly correlated 3d core-electron and ligand excitations. This research provides important theoretical insights into the spectral characteristics of heavy-element complexes. Furthermore, it establishes the foundation for utilizing M4,5-edge spectroscopy as a means to investigate the chemical activities of such complexes. By leveraging this technique, we can gain a deeper understanding of the bonding behavior and reactivity of heavy-element compounds.
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Affiliation(s)
- Jordan
N. Ehrman
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Kirill Shumilov
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Andrew J. Jenkins
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Joseph M. Kasper
- Theoretical
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Tonya Vitova
- Institute
for Nuclear Waste Disposal (INE), Karlsruhe
Institute of Technology, P.O. Box 3640, Karlsruhe D-76021, Germany
| | - Enrique R. Batista
- Theoretical
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Ping Yang
- Theoretical
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Xiaosong Li
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
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2
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Hao G, Dale AS, N'Diaye AT, Chopdekar RV, Koch RJ, Jiang X, Mellinger C, Zhang J, Cheng R, Xu X, Dowben PA. Intermolecular interaction and cooperativity in an Fe(II) spin crossover molecular thin film system. J Phys Condens Matter 2022; 34:295201. [PMID: 35508146 DOI: 10.1088/1361-648x/ac6cbc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 05/04/2022] [Indexed: 06/14/2023]
Abstract
Compact domain features have been observed in spin crossover [Fe{H2B(pz)2}2(bipy)] molecular thin film systems via soft x-ray absorption spectroscopy and photoemission electron microscopy. The domains are in a mixed spin state that on average corresponds to roughly 2/3 the high spin occupation of the pure high spin state. Monte Carlo simulations support the presence of intermolecular interactions that can be described in terms of an Ising model in which interactions beyond nearest-neighbors cannot be neglected. This suggests the presence of short-range order to permit interactions between molecules beyond nearest neighbor that contribute to the formation of largely high spin state domains structure. The formation of a spin state domain structure appears to be the result of extensive cooperative effects.
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Affiliation(s)
- Guanhua Hao
- Department of Physics and Astronomy, Jorgensen Hall, University of Nebraska, Lincoln, NE 68588, United States of America
- Advanced Light Source, Lawrence Berkeley National Lab, One Cyclotron Rd, Berkeley, CA 94720, United States of America
| | - Ashley S Dale
- Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202, United States of America
| | - Alpha T N'Diaye
- Advanced Light Source, Lawrence Berkeley National Lab, One Cyclotron Rd, Berkeley, CA 94720, United States of America
| | - Rajesh V Chopdekar
- Advanced Light Source, Lawrence Berkeley National Lab, One Cyclotron Rd, Berkeley, CA 94720, United States of America
| | - Roland J Koch
- Advanced Light Source, Lawrence Berkeley National Lab, One Cyclotron Rd, Berkeley, CA 94720, United States of America
| | - Xuanyuan Jiang
- Department of Physics and Astronomy, Jorgensen Hall, University of Nebraska, Lincoln, NE 68588, United States of America
| | - Corbyn Mellinger
- Department of Physics and Astronomy, Jorgensen Hall, University of Nebraska, Lincoln, NE 68588, United States of America
| | - Jian Zhang
- The Molecular Foundry, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, United States of America
| | - Ruihua Cheng
- Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202, United States of America
| | - Xiaoshan Xu
- Department of Physics and Astronomy, Jorgensen Hall, University of Nebraska, Lincoln, NE 68588, United States of America
| | - Peter A Dowben
- Department of Physics and Astronomy, Jorgensen Hall, University of Nebraska, Lincoln, NE 68588, United States of America
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3
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Probst J, Borca CN, Newton MA, van Bokhoven J, Huthwelker T, Stavrakis S, deMello A. In Situ X-ray Absorption Spectroscopy and Droplet-Based Microfluidics: An Analysis of Calcium Carbonate Precipitation. ACS Meas Sci Au 2021; 1:27-34. [PMID: 36785734 PMCID: PMC9836070 DOI: 10.1021/acsmeasuresciau.1c00005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Droplet-based microfluidic systems are ideally suited for the investigation of nucleation and crystallization processes. To best leverage the features of such platforms (including exquisite time resolution and high-throughput operation), sensitive and in situ detection schemes are needed to extract real-time chemical information about all species of interest. In this regard, the extension of conventional (UV, visible, and infrared) optical detection schemes to the X-ray region of the electromagnetic spectrum is of high current interest, as techniques such as X-ray absorption spectroscopy (XAS) provide for the element-specific investigation of the local chemical environment. Accordingly, herein, we report for the first time the integration of millisecond droplet-based microfluidics with XAS. Such a platform allows for the sensitive acquisition of X-ray absorption data from picoliter-volume droplets moving at high linear velocities. Significantly, the high-temporal resolution of the droplet-based microfluidic platform enables unprecedented access to the early stages of the reaction. Using such an approach, we demonstrate in situ monitoring of calcium carbonate precipitation by extracting XAS spectra at the early time points of the reaction with a dead time as low as 10 ms. We obtain insights into the kinetics of the formation of amorphous calcium carbonate (ACC) as a first species during the crystallization process by monitoring the proportion of calcium ions converted into ACC. Within the confined and homogeneous environment of picoliter-volume droplets, the ACC content reaches 60% over the first 130 ms. More generally, the presented method offers new opportunities for the real-time monitoring of fast chemical and biological processes.
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Affiliation(s)
- Julie Probst
- Institute
for Chemical and Bioengineering, Department of Chemistry and Applied
Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland
| | | | - Mark A. Newton
- Institute
for Chemical and Bioengineering, Department of Chemistry and Applied
Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland
| | - Jeroen van Bokhoven
- Institute
for Chemical and Bioengineering, Department of Chemistry and Applied
Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland
- Paul
Scherrer Institute, 5232 Villigen, Switzerland
| | | | - Stavros Stavrakis
- Institute
for Chemical and Bioengineering, Department of Chemistry and Applied
Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland
| | - Andrew deMello
- Institute
for Chemical and Bioengineering, Department of Chemistry and Applied
Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland
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4
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Klein BP, Hall SJ, Maurer RJ. The nuts and bolts of core-hole constrained ab initiosimulation for K-shell x-ray photoemission and absorption spectra. J Phys Condens Matter 2021; 33. [PMID: 33682682 DOI: 10.1088/1361-648x/abdf00] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 01/22/2021] [Indexed: 05/13/2023]
Abstract
X-ray photoemission (XPS) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy play an important role in investigating the structure and electronic structure of materials and surfaces.Ab initiosimulations provide crucial support for the interpretation of complex spectra containing overlapping signatures. Approximate core-hole simulation methods based on density functional theory (DFT) such as the delta-self-consistent-field (ΔSCF) method or the transition potential (TP) method are widely used to predictK-shell XPS and NEXAFS signatures of organic molecules, inorganic materials and metal-organic interfaces at reliable accuracy and affordable computational cost. We present the numerical and technical details of our variants of the ΔSCF and TP method (coined ΔIP-TP) to simulate XPS and NEXAFS transitions. Using exemplary molecules in gas-phase, in bulk crystals, and at metal-organic interfaces, we systematically assess how practical simulation choices affect the stability and accuracy of simulations. These include the choice of exchange-correlation functional, basis set, the method of core-hole localization, and the use of periodic boundary conditions (PBC). We particularly focus on the choice of aperiodic or periodic description of systems and how spurious charge effects in periodic calculations affect the simulation outcomes. For the benefit of practitioners in the field, we discuss sensible default choices, limitations of the methods, and future prospects.
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Affiliation(s)
- Benedikt P Klein
- Department of Chemistry, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, United Kingdom
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
| | - Samuel J Hall
- Department of Chemistry, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, United Kingdom
- MAS CDT, Senate House, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, United Kingdom
| | - Reinhard J Maurer
- Department of Chemistry, University of Warwick, Gibbet Hill Rd, Coventry, CV4 7AL, United Kingdom
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5
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Li Y, Samant P, Wang S, Behrooz A, Li D, Xiang L. 3-D X-Ray-Induced Acoustic Computed Tomography With a Spherical Array: A Simulation Study on Bone Imaging. IEEE Trans Ultrason Ferroelectr Freq Control 2020; 67:1613-1619. [PMID: 32286967 PMCID: PMC7394001 DOI: 10.1109/tuffc.2020.2983732] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
X-ray-induced acoustic computed tomography (XACT) is a promising imaging modality combining high X-ray absorption contrast with the 3-D propagation advantages provided by high-resolution ultrasound waves. The purpose of this study was to optimize the configuration of a 3-D XACT imaging system for bone imaging. A 280 ultrasonic sensors with peak frequency of 10 MHz was designed to distribute on a spherical surface to optimize the 3-D volumetric imaging capability. We performed both theoretical calculations and simulations of this optimized XACT imaging configuration on a mouse-sized digital phantom containing various X-ray absorption coefficients. Iteration algorithm based on total variation has been used for 3-D XACT image reconstruction. The spatial resolution of imaging was estimated to about [Formula: see text] along both axial and lateral directions. We simulate XACT imaging of bone microstructures using digital phantoms generated from micro-CT images of real biological samples, showing that XACT imaging can provide high-resolution imaging of the mouse paw. Results of this study will greatly enhance the potential of XACT imaging in the evaluation of bone diseases for future clinical use.
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Affiliation(s)
- Y. Li
- Shandong Key Laboratory of Medical Physics and Image Processing, Shandong Institute of Industrial Technology for Health Sciences and Precision Medicine, School of Physics and Electronics, Shandong Normal University, Jinan, Shandong 250358, China
| | - P. Samant
- The School of Biomedical Engineering at the University of Oklahoma, Norman, US
| | - S. Wang
- The School of Electrical and Computer Engineering at the University of Oklahoma, Norman, US
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6
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Khan M, Xiao J, Zhou F, Yablonskikh M, MacFarlane DR, Spiccia L, Aziz EF. On the Origin of the Improvement of Electrodeposited MnOx Films in Water Oxidation Catalysis Induced by Heat Treatment. ChemSusChem 2015; 8:1980-1985. [PMID: 25940315 DOI: 10.1002/cssc.201500330] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [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: 03/04/2015] [Indexed: 06/04/2023]
Abstract
Manganese oxides (MnOx ) are considered to be promising catalysts for water oxidation. Building on our previous studies showing that the catalytic activity of MnOx films electrodeposited from aqueous electrolytes is improved by a simple heat treatment, we have explored the origin of the catalytic enhancement at an electronic level by X-ray absorption spectroscopy (XAS). The Mn L-edge XA spectra measured at various heating stages were fitted by linear combinations of the spectra of the well-defined manganese oxides-MnO, Mn3 O4 , Mn2 O3 , MnO2 and birnessite. This analysis identified two major manganese oxides, Mn3 O4 and birnessite, that constitute 97 % of the MnOx films. Moreover, the catalytic improvement on heat treatment at 90 °C is related to the conversion of a small amount of birnessite to the Mn3 O4 phase, accompanied by an irreversible dehydration process. Further dehydration at higher temperature (120 °C), however, leads to a poorer catalytic performance.
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Affiliation(s)
- Munirah Khan
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin (Germany)
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany)
| | - Jie Xiao
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin (Germany).
| | - Fengling Zhou
- School of Chemistry and ARC Centre of Excellence for Electromaterials Science, Monash University, Clayton, VIC, 3800 (Australia)
| | - Mikhail Yablonskikh
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin (Germany)
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany)
| | - Douglas R MacFarlane
- School of Chemistry and ARC Centre of Excellence for Electromaterials Science, Monash University, Clayton, VIC, 3800 (Australia)
| | - Leone Spiccia
- School of Chemistry and ARC Centre of Excellence for Electromaterials Science, Monash University, Clayton, VIC, 3800 (Australia).
| | - Emad F Aziz
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin (Germany).
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany).
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7
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Ruiz-Soria G, Pérez Paz A, Sauer M, Mowbray DJ, Lacovig P, Dalmiglio M, Lizzit S, Yanagi K, Rubio A, Goldoni A, Ayala P, Pichler T. Revealing the adsorption mechanisms of nitroxides on ultrapure, metallicity-sorted carbon nanotubes. ACS Nano 2014; 8:1375-83. [PMID: 24404865 PMCID: PMC3936481 DOI: 10.1021/nn405114z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Carbon nanotubes are a natural choice as gas sensor components given their high surface to volume ratio, electronic properties, and capability to mediate chemical reactions. However, a realistic assessment of the interaction of the tube wall and the adsorption processes during gas phase reactions has always been elusive. Making use of ultraclean single-walled carbon nanotubes, we have followed the adsorption kinetics of NO2 and found a physisorption mechanism. Additionally, the adsorption reaction directly depends on the metallic character of the samples. Franck-Condon satellites, hitherto undetected in nanotube-NOx systems, were resolved in the N 1s X-ray absorption signal, revealing a weak chemisorption, which is intrinsically related to NO dimer molecules. This has allowed us to identify that an additional signal observed in the higher binding energy region of the core level C 1s photoemission signal is due to the C ═ O species of ketene groups formed as reaction byproducts . This has been supported by density functional theory calculations. These results pave the way toward the optimization of nanotube-based sensors with tailored sensitivity and selectivity to different species at room temperature.
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Affiliation(s)
- Georgina Ruiz-Soria
- Faculty of Physics, University of Vienna, Strudlhofgasse 4, A-1090 Vienna, Austria
| | - Alejandro Pérez Paz
- Nano-Bio Spectroscopy Group and ETSF Scientific Development Centre, Departamento de Física de Materiales, Centro de Física de Materiales CSIC-UPV/EHU-MPC and DIPC, Universidad del País Vasco UPV/EHU, E-20018 San Sebastián, Spain
| | - Markus Sauer
- Faculty of Physics, University of Vienna, Strudlhofgasse 4, A-1090 Vienna, Austria
| | - Duncan John Mowbray
- Nano-Bio Spectroscopy Group and ETSF Scientific Development Centre, Departamento de Física de Materiales, Centro de Física de Materiales CSIC-UPV/EHU-MPC and DIPC, Universidad del País Vasco UPV/EHU, E-20018 San Sebastián, Spain
| | - Paolo Lacovig
- Sincrotrone Trieste, s.s. 14 km 163.5, 34149 Trieste, Italy
| | | | - Silvano Lizzit
- Sincrotrone Trieste, s.s. 14 km 163.5, 34149 Trieste, Italy
| | - Kazuhiro Yanagi
- Department of Physics, Tokyo Metropolitan University, Hachioji, 192-0397 Tokyo, Japan
| | - Angel Rubio
- Nano-Bio Spectroscopy Group and ETSF Scientific Development Centre, Departamento de Física de Materiales, Centro de Física de Materiales CSIC-UPV/EHU-MPC and DIPC, Universidad del País Vasco UPV/EHU, E-20018 San Sebastián, Spain
| | - Andrea Goldoni
- Sincrotrone Trieste, s.s. 14 km 163.5, 34149 Trieste, Italy
| | - Paola Ayala
- Faculty of Physics, University of Vienna, Strudlhofgasse 4, A-1090 Vienna, Austria
- Address correspondence to ,
| | - Thomas Pichler
- Faculty of Physics, University of Vienna, Strudlhofgasse 4, A-1090 Vienna, Austria
- Address correspondence to ,
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8
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Wojcik GS. Determining the Uncertainty of X-Ray Absorption Measurements. J Res Natl Inst Stand Technol 2004; 109:479-496. [PMID: 27366627 PMCID: PMC4849570 DOI: 10.6028/jres.109.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 09/28/2004] [Indexed: 06/06/2023]
Abstract
X-ray absorption (or more properly, x-ray attenuation) techniques have been applied to study the moisture movement in and moisture content of materials like cement paste, mortar, and wood. An increase in the number of x-ray counts with time at a location in a specimen may indicate a decrease in moisture content. The uncertainty of measurements from an x-ray absorption system, which must be known to properly interpret the data, is often assumed to be the square root of the number of counts, as in a Poisson process. No detailed studies have heretofore been conducted to determine the uncertainty of x-ray absorption measurements or the effect of averaging data on the uncertainty. In this study, the Poisson estimate was found to adequately approximate normalized root mean square errors (a measure of uncertainty) of counts for point measurements and profile measurements of water specimens. The Poisson estimate, however, was not reliable in approximating the magnitude of the uncertainty when averaging data from paste and mortar specimens. Changes in uncertainty from differing averaging procedures were well-approximated by a Poisson process. The normalized root mean square errors decreased when the x-ray source intensity, integration time, collimator size, and number of scanning repetitions increased. Uncertainties in mean paste and mortar count profiles were kept below 2 % by averaging vertical profiles at horizontal spacings of 1 mm or larger with counts per point above 4000. Maximum normalized root mean square errors did not exceed 10 % in any of the tests conducted.
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Affiliation(s)
- Gary S Wojcik
- National Institute of Standards and Technology, Gaithersburg, MD 20899-8615
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9
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Kleifeld O, Shi SP, Zarivach R, Eisenstein M, Sagi I. The conserved Glu-60 residue in Thermoanaerobacter brockii alcohol dehydrogenase is not essential for catalysis. Protein Sci 2003; 12:468-79. [PMID: 12592017 PMCID: PMC2312447 DOI: 10.1110/ps.0221603] [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] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Glu-60 of the zinc-dependent Thermoanaerobacter brockii alcohol dehydrogenase (TbADH) is a strictly conserved residue in all members of the alcohol dehydrogenase (ADH) family. Unlike most other ADHs, the crystal structures of TbADH and its analogs, ADH from Clostridium beijerinckii (CbADH), exhibit a unique zinc coordination environment in which this conserved residue is directly coordinated to the catalytic zinc ion in the native form of the enzymes. To explore the role of Glu-60 in TbADH catalysis, we have replaced it by alanine (E60A-TbADH) and aspartate (E60D-TbADH). Steady-state kinetic measurements show that the catalytic efficiency of these mutants is only four- and eightfold, respectively, lower than that of wild-type TbADH. We applied X-ray absorption fine-structure (EXAFS) and near-UV circular dichroism to characterize the local environment around the catalytic zinc ion in the variant enzymes in their native, cofactor-bound, and inhibited forms. We show that the catalytic zinc site in the studied complexes of the variant enzymes exhibits minor changes relative to the analogous complexes of wild-type TbADH. These moderate changes in the kinetic parameters and in the zinc ion environment imply that the Glu-60 in TbADH does not remain bound to the catalytic zinc ion during catalysis. Furthermore, our results suggest that a water molecule replaces this residue during substrate turnover.
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Affiliation(s)
- Oded Kleifeld
- Department of Structural Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
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10
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Abstract
Quantitative electron probe analysis is based on models based on the physics or x-ray generation, empirically adjusted to the analyses of specimens of known composition. Their accuracy can be estimated by applying them to a set of specimens of presumably well-known composition.
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Affiliation(s)
- Kurt F J Heinrich
- National Institute of Standards and Technology, Gaithersburg, MD 10899-0001
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11
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Liu Y, Ogata CM, Hendrickson WA. Multiwavelength anomalous diffraction analysis at the M absorption edges of uranium. Proc Natl Acad Sci U S A 2001; 98:10648-53. [PMID: 11526210 PMCID: PMC58520 DOI: 10.1073/pnas.191003998] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/03/2001] [Indexed: 11/18/2022] Open
Abstract
The multiwavelength anomalous diffraction (MAD) method for phase evaluation is now widely used in macromolecular crystallography. Successful MAD structure determinations have been carried out at the K or L absorption edges of a variety of elements. In this study, we investigate the anomalous scattering properties of uranium at its M(IV) (3.326 A) and M(V) (3.490 A) edge. Fluorescence spectra showed remarkably strong anomalous scattering at these edges (f' = -70e, f" = 80e at the M(IV) edge and f' = -90e, f" = 105e at the M(V) edge), many times higher than from any anomalous scatterers used previously for MAD phasing. However, the large scattering angles and high absorption at the low energies of these edges present some difficulties not found in typical crystallographic studies. We conducted test experiments at the M(IV) edge with crystals of porcine elastase derivatized with uranyl nitrate. A four-wavelength MAD data set complete to 3.2-A Bragg spacings was collected from a single small frozen crystal. Analysis of the data yielded satisfactory phase information (average difference of (0)phi(T) - (0)phi(A) for replicated determinations is 32 degrees ) and produced an interpretable electron-density map. Our results demonstrate that it is practical to measure macromolecular diffraction data at these edges with current instrumentation and that phase information of good accuracy can be extracted from such experiments. We show that such experiments have potential for the phasing of very large macromolecular assemblages.
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Affiliation(s)
- Y Liu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
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