1
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Liebschner D, Afonine PV, Poon BK, Moriarty NW, Adams PD. Improved joint X-ray and neutron refinement procedure in Phenix. Acta Crystallogr D Struct Biol 2023; 79:1079-1093. [PMID: 37942718 PMCID: PMC10833352 DOI: 10.1107/s2059798323008914] [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: 07/14/2023] [Accepted: 10/11/2023] [Indexed: 11/10/2023] Open
Abstract
Neutron diffraction is one of the three crystallographic techniques (X-ray, neutron and electron diffraction) used to determine the atomic structures of molecules. Its particular strengths derive from the fact that H (and D) atoms are strong neutron scatterers, meaning that their positions, and thus protonation states, can be derived from crystallographic maps. However, because of technical limitations and experimental obstacles, the quality of neutron diffraction data is typically much poorer (completeness, resolution and signal to noise) than that of X-ray diffraction data for the same sample. Further, refinement is more complex as it usually requires additional parameters to describe the H (and D) atoms. The increase in the number of parameters may be mitigated by using the `riding hydrogen' refinement strategy, in which the positions of H atoms without a rotational degree of freedom are inferred from their neighboring heavy atoms. However, this does not address the issues related to poor data quality. Therefore, neutron structure determination often relies on the presence of an X-ray data set for joint X-ray and neutron (XN) refinement. In this approach, the X-ray data serve to compensate for the deficiencies of the neutron diffraction data by refining one model simultaneously against the X-ray and neutron data sets. To be applicable, it is assumed that both data sets are highly isomorphous, and preferably collected from the same crystals and at the same temperature. However, the approach has a number of limitations that are discussed in this work by comparing four separately re-refined neutron models. To address the limitations, a new method for joint XN refinement is introduced that optimizes two different models against the different data sets. This approach is tested using neutron models and data deposited in the Protein Data Bank. The efficacy of refining models with H atoms as riding or as individual atoms is also investigated.
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Affiliation(s)
- Dorothee Liebschner
- Molecular Biosciences and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Pavel V. Afonine
- Molecular Biosciences and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Billy K. Poon
- Molecular Biosciences and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Nigel W. Moriarty
- Molecular Biosciences and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Paul D. Adams
- Molecular Biosciences and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720, USA
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2
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Karton A, Greatrex BW, O'Reilly RJ. Intramolecular Proton-Coupled Hydride Transfers with Relatively Low Activation Barriers. J Phys Chem A 2023. [PMID: 37368352 DOI: 10.1021/acs.jpca.3c03166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
We report that bifunctional molecules containing hydroxyl and carbonyl functional groups can undergo an effective transfer hydrogenation via an intramolecular proton-coupled hydride transfer (PCHT) mechanism. In this reaction mechanism, a hydride transfer between two carbon atoms is coupled with a proton transfer between two oxygen atoms via a cyclic bond rearrangement transition structure. The coupled transfer of the two hydrogens as Hδ+ and Hδ- is supported by atomic polar tensor charges. The activation energy for the PCHT reaction is strongly dependent on the length of the alkyl chain between the hydroxyl and carbonyl functional groups but relatively weakly dependent on the functional groups attached to the hydroxyl and carbonyl carbons. We investigate the PCHT reaction mechanism using the Gaussian-4 thermochemical protocol and obtain high activation energy barriers (ΔH‡298) of 210.5-228.3 kJ mol-1 for chain lengths of one carbon atom and 160.2-163.9 kJ mol-1 for chain lengths of two carbon atoms. However, for longer chain lengths containing 3-4 carbon atoms, we obtain ΔH‡298 values as low as 101.9 kJ mol-1. Importantly, the hydride transfer between two carbon atoms proceeds without the need for a catalyst or hydride transfer activating agent. These results indicate that the intramolecular PCHT reaction provides an effective avenue for uncatalyzed, metal-free hydride transfers at ambient temperatures.
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Affiliation(s)
- Amir Karton
- School of Science and Technology, University of New England, Armidale, NSW 2351, Australia
| | - Ben W Greatrex
- School of Rural Medicine, University of New England, Armidale, NSW 2351, Australia
| | - Robert J O'Reilly
- School of Science and Technology, University of New England, Armidale, NSW 2351, Australia
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3
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Moreno-Chicano T, Carey LM, Axford D, Beale JH, Doak RB, Duyvesteyn HME, Ebrahim A, Henning RW, Monteiro DCF, Myles DA, Owada S, Sherrell DA, Straw ML, Šrajer V, Sugimoto H, Tono K, Tosha T, Tews I, Trebbin M, Strange RW, Weiss KL, Worrall JAR, Meilleur F, Owen RL, Ghiladi RA, Hough MA. Complementarity of neutron, XFEL and synchrotron crystallography for defining the structures of metalloenzymes at room temperature. IUCRJ 2022; 9:610-624. [PMID: 36071813 PMCID: PMC9438502 DOI: 10.1107/s2052252522006418] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 06/21/2022] [Indexed: 06/15/2023]
Abstract
Room-temperature macromolecular crystallography allows protein structures to be determined under close-to-physiological conditions, permits dynamic freedom in protein motions and enables time-resolved studies. In the case of metalloenzymes that are highly sensitive to radiation damage, such room-temperature experiments can present challenges, including increased rates of X-ray reduction of metal centres and site-specific radiation-damage artefacts, as well as in devising appropriate sample-delivery and data-collection methods. It can also be problematic to compare structures measured using different crystal sizes and light sources. In this study, structures of a multifunctional globin, dehaloperoxidase B (DHP-B), obtained using several methods of room-temperature crystallographic structure determination are described and compared. Here, data were measured from large single crystals and multiple microcrystals using neutrons, X-ray free-electron laser pulses, monochromatic synchrotron radiation and polychromatic (Laue) radiation light sources. These approaches span a range of 18 orders of magnitude in measurement time per diffraction pattern and four orders of magnitude in crystal volume. The first room-temperature neutron structures of DHP-B are also presented, allowing the explicit identification of the hydrogen positions. The neutron data proved to be complementary to the serial femtosecond crystallography data, with both methods providing structures free of the effects of X-ray radiation damage when compared with standard cryo-crystallography. Comparison of these room-temperature methods demonstrated the large differences in sample requirements, data-collection time and the potential for radiation damage between them. With regard to the structure and function of DHP-B, despite the results being partly limited by differences in the underlying structures, new information was gained on the protonation states of active-site residues which may guide future studies of DHP-B.
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Affiliation(s)
- Tadeo Moreno-Chicano
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom
| | - Leiah M. Carey
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA
| | - Danny Axford
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - John H. Beale
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - R. Bruce Doak
- Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Helen M. E. Duyvesteyn
- Division of Structural Biology (STRUBI), University of Oxford, The Henry Wellcome Building for Genomic Medicine, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
| | - Ali Ebrahim
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - Robert W. Henning
- BioCARS, University of Chicago, Building 434B, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Diana C. F. Monteiro
- Hauptman–Woodward Medical Research Institute, 700 Ellicott Street, Buffalo, NY 14203-1102, USA
| | - Dean A. Myles
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Shigeki Owada
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Darren A. Sherrell
- Structural Biology Center, X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Megan L. Straw
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom
| | - Vukica Šrajer
- BioCARS, University of Chicago, Building 434B, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | | | - Kensuke Tono
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Takehiko Tosha
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Ivo Tews
- Biological Sciences, University of Southampton, University Road, Southampton SO17 1BJ, United Kingdom
| | - Martin Trebbin
- Hauptman–Woodward Medical Research Institute, 700 Ellicott Street, Buffalo, NY 14203-1102, USA
- Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260, USA
| | - Richard W. Strange
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom
| | - Kevin L. Weiss
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Jonathan A. R. Worrall
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom
| | - Flora Meilleur
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Robin L. Owen
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - Reza A. Ghiladi
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA
| | - Michael A. Hough
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
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4
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Drago VN, Dajnowicz S, Parks JM, Blakeley MP, Keen DA, Coquelle N, Weiss KL, Gerlits O, Kovalevsky A, Mueser TC. An N⋯H⋯N low-barrier hydrogen bond preorganizes the catalytic site of aspartate aminotransferase to facilitate the second half-reaction. Chem Sci 2022; 13:10057-10065. [PMID: 36128223 PMCID: PMC9430417 DOI: 10.1039/d2sc02285k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 07/20/2022] [Indexed: 11/21/2022] Open
Abstract
Pyridoxal 5'-phosphate (PLP)-dependent enzymes have been extensively studied for their ability to fine-tune PLP cofactor electronics to promote a wide array of chemistries. Neutron crystallography offers a straightforward approach to studying the electronic states of PLP and the electrostatics of enzyme active sites, responsible for the reaction specificities, by enabling direct visualization of hydrogen atom positions. Here we report a room-temperature joint X-ray/neutron structure of aspartate aminotransferase (AAT) with pyridoxamine 5'-phosphate (PMP), the cofactor product of the first half reaction catalyzed by the enzyme. Between PMP NSB and catalytic Lys258 Nζ amino groups an equally shared deuterium is observed in an apparent low-barrier hydrogen bond (LBHB). Density functional theory calculations were performed to provide further evidence of this LBHB interaction. The structural arrangement and the juxtaposition of PMP and Lys258, facilitated by the LBHB, suggests active site preorganization for the incoming ketoacid substrate that initiates the second half-reaction.
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Affiliation(s)
- Victoria N Drago
- Department of Chemistry and Biochemistry, University of Toledo Toledo OH 43606 USA
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Steven Dajnowicz
- Department of Chemistry and Biochemistry, University of Toledo Toledo OH 43606 USA
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Jerry M Parks
- Biosciences Division, Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Matthew P Blakeley
- Large Scale Structures Group, Institut Laue-Langevin 71 Avenue des Martyrs 38000 Grenoble France
| | - David A Keen
- ISIS Facility, Rutherford Appleton Laboratory, Harwell Campus Didcot OX11 0QX UK
| | - Nicolas Coquelle
- Large Scale Structures Group, Institut Laue-Langevin 71 Avenue des Martyrs 38000 Grenoble France
| | - Kevin L Weiss
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Oksana Gerlits
- Department of Natural Sciences, Tennessee Wesleyan University Athens TN 37303 USA
| | - Andrey Kovalevsky
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Timothy C Mueser
- Department of Chemistry and Biochemistry, University of Toledo Toledo OH 43606 USA
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5
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Truong DP, Rousseau S, Machala BW, Huddleston JP, Zhu M, Hull KG, Romo D, Raushel FM, Sacchettini JC, Glasner ME. Second-Shell Amino Acid R266 Helps Determine N-Succinylamino Acid Racemase Reaction Specificity in Promiscuous N-Succinylamino Acid Racemase/ o-Succinylbenzoate Synthase Enzymes. Biochemistry 2021; 60:3829-3840. [PMID: 34845903 DOI: 10.1021/acs.biochem.1c00627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Catalytic promiscuity is the coincidental ability to catalyze nonbiological reactions in the same active site as the native biological reaction. Several lines of evidence show that catalytic promiscuity plays a role in the evolution of new enzyme functions. Thus, studying catalytic promiscuity can help identify structural features that predispose an enzyme to evolve new functions. This study identifies a potentially preadaptive residue in a promiscuous N-succinylamino acid racemase/o-succinylbenzoate synthase (NSAR/OSBS) enzyme from Amycolatopsis sp. T-1-60. This enzyme belongs to a branch of the OSBS family which includes many catalytically promiscuous NSAR/OSBS enzymes. R266 is conserved in all members of the NSAR/OSBS subfamily. However, the homologous position is usually hydrophobic in other OSBS subfamilies, whose enzymes lack NSAR activity. The second-shell amino acid R266 is close to the catalytic acid/base K263, but it does not contact the substrate, suggesting that R266 could affect the catalytic mechanism. Mutating R266 to glutamine in Amycolatopsis NSAR/OSBS profoundly reduces NSAR activity but moderately reduces OSBS activity. This is due to a 1000-fold decrease in the rate of proton exchange between the substrate and the general acid/base catalyst K263. This mutation is less deleterious for the OSBS reaction because K263 forms a cation-π interaction with the OSBS substrate and/or the intermediate, rather than acting as a general acid/base catalyst. Together, the data explain how R266 contributes to NSAR reaction specificity and was likely an essential preadaptation for the evolution of NSAR activity.
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Affiliation(s)
- Dat P Truong
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, Texas 77843-2128, United States
| | - Simon Rousseau
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, Texas 77843-2128, United States
| | - Benjamin W Machala
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, Texas 77843-2128, United States
| | - Jamison P Huddleston
- Department of Chemistry, Texas A&M University, 3255 TAMU, College Station, Texas 77843-3255, United States
| | - Mingzhao Zhu
- Baylor Synthesis and Drug-Lead Discovery Laboratory, Department of Chemistry and Biochemistry, Baylor University, One Bear Place, Waco, Texas 76798-7348, United States
| | - Kenneth G Hull
- Baylor Synthesis and Drug-Lead Discovery Laboratory, Department of Chemistry and Biochemistry, Baylor University, One Bear Place, Waco, Texas 76798-7348, United States
| | - Daniel Romo
- Baylor Synthesis and Drug-Lead Discovery Laboratory, Department of Chemistry and Biochemistry, Baylor University, One Bear Place, Waco, Texas 76798-7348, United States
| | - Frank M Raushel
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, Texas 77843-2128, United States.,Department of Chemistry, Texas A&M University, 3255 TAMU, College Station, Texas 77843-3255, United States
| | - James C Sacchettini
- Department of Chemistry, Texas A&M University, 3255 TAMU, College Station, Texas 77843-3255, United States
| | - Margaret E Glasner
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, Texas 77843-2128, United States
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6
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Duoc PND, Binh NH, Hau TV, Thanh CT, Trinh PV, Tuyen NV, Quynh NV, Tu NV, Duc Chinh V, Thi Thu V, Thang PD, Minh PN, Chuc NV. A novel electrochemical sensor based on double-walled carbon nanotubes and graphene hybrid thin film for arsenic(V) detection. JOURNAL OF HAZARDOUS MATERIALS 2020; 400:123185. [PMID: 32563905 DOI: 10.1016/j.jhazmat.2020.123185] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 06/08/2020] [Accepted: 06/08/2020] [Indexed: 06/11/2023]
Abstract
In this work, we demonstrate the preparation of hybrid thin films based on double-walled carbon nanotubes and graphene for electrochemical sensing applications. The hybrid films were synthesized on polycrystalline copper foil by thermal chemical vapor deposition under low pressure. This carbonaceous hybrid film has exhibited high transparency with a transmittance of 94.3 %. The occurrence of this hybrid material on the electrode surface of screen-printed electrodes was found to increase electroactive surface area by 1.4 times, whereas electrochemical current was enhanced by 2.4 times. Such a highly transparent and conductive hybrid film was utilized as a transducing platform of enzymatic electrochemical arsenic(V) sensor. The as-prepared sensor shows the linear detection of arsenic(V) in the range from 1 to 10 ppb, with a limit of detection as low as 0.287 ppb. These findings provide a promising approach to develop new multifunctional electrochemical sensing systems for environmental monitoring and biomedical diagnostics.
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Affiliation(s)
- Phan Nguyen Duc Duoc
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam; VNU-University of Engineering and Technology, 144 Xuan Thuy, Cau Giay, Hanoi, Vietnam; Department of Physics, Nha Trang University, 02 Nguyen Dinh Chieu, Nha Trang, Vietnam
| | - Nguyen Hai Binh
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - Tran Van Hau
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam; VNU-University of Engineering and Technology, 144 Xuan Thuy, Cau Giay, Hanoi, Vietnam
| | - Cao Thi Thanh
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - Pham Van Trinh
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - Nguyen Viet Tuyen
- Faculty of Physics, VNU University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam
| | - Nguyen Van Quynh
- University of Science and Technology of Hanoi, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - Nguyen Van Tu
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - Vu Duc Chinh
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - Vu Thi Thu
- University of Science and Technology of Hanoi, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - Pham Duc Thang
- VNU-University of Engineering and Technology, 144 Xuan Thuy, Cau Giay, Hanoi, Vietnam
| | - Phan Ngoc Minh
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam; Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam; Center for High Technology Development, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
| | - Nguyen Van Chuc
- Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam; Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam.
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7
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G Jayanthi K, S K S. Cholesterol oxidase immobilized inulin based nanocomposite as the sensing material for cholesterol in biological and food samples. Enzyme Microb Technol 2020; 140:109631. [PMID: 32912691 DOI: 10.1016/j.enzmictec.2020.109631] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 07/07/2020] [Accepted: 07/07/2020] [Indexed: 01/16/2023]
Abstract
In the present study, inulin based nanocomposite viz., TiO2-MWCNT@Inulin was prepared by embedding Inulin (a biopolymer extracted from Allium sativum L.) with TiO2 and MWCNTs. The morphology of the prepared nanocomposite was characterized by High Resolution transmission electron microscopy (HRTEM). Cholesterol oxidase (ChOx) enzyme was then immobilized into the nanocomposite and the immobilization was examined by UV-vis and FT-IR spectral studies. The ChOx immobilized nanocomposite was integrated into carbon paste (CP) matrix to prepare the working electrode for the sensing of cholesterol. Electrochemical characterization of the modified CP/TiO2-MWCNT@Inulin/ChOx electrode was done by cyclic voltammetric (CV) and electrochemical impedance spectroscopic (EIS) studies. Differential pulse voltammetric (DPV) studies were carried out to determine the concentration of cholesterol at the interface of the newly fabricated electrode. The fabricated electrode demonstrated a linear range from 83 μM to 14.28 mM, low limit of detection (35 μM), good sensitivity (21.26 μA mM-1 cm-2), low Km (0.49 mM), high stability (120 days) and good selectivity. The presence of Inulin biopolymer played a vital role in attaching ChOx enzyme firmly to the nanocomposite thereby enhancing the stability and electron transfer efficiency of the electrode. The analysis of product that was formed within the electrochemical cell during the electrochemical oxidation of cholesterol was performed by using sodium nitroprusside. This resulted in a deep purple coloured solution which suggested the electrochemical conversion of cholesterol to cholestenone. The practical applicability of the fabricated electrode was also assessed by the determination of cholesterol in spiked blood serum and milk samples.
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Affiliation(s)
| | - Suja S K
- Department of Chemistry, Lady Doak College, Madurai, India.
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8
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Kerber T, Vrielink A. The role of hydrogen atoms in redox catalysis by the flavoenzyme cholesterol oxidase. Methods Enzymol 2020; 634:361-377. [PMID: 32093840 DOI: 10.1016/bs.mie.2019.12.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
Abstract
Flavoenzymes comprise a large class of proteins that carry out a diverse range of important redox chemistry. Although X-ray crystal structures of many flavoenzymes have been determined, there are still unresolved questions regarding the actual oxidation state of the flavin cofactors in these structures due to photoreduction by the ionizing radiation of the X-ray beam during the diffraction experiment. Additionally, the ability to visualize hydrogen atoms in X-ray structures is difficult due to the weak scattering capability of these atoms. Since hydrogen atoms affect the electrostatic nature of enzyme active sites and play important roles in the chemistry of key amino acid residues, visualizing the precise positions of these atoms provides a more detailed understanding of their role in enzyme catalysis. Single crystal neutron diffraction is an alternative method to structure determination, circumventing problems associated with photoreduction of the sample thus providing a clearer view of the structural features of a flavoenzyme in different redox states. Additionally, the larger neutron scattering factors for hydrogen and deuterium atoms enables one to visualize these atoms much more easily than from X-ray scattering measurements. In this chapter we give an overview of neutron and X-ray crystallography studies on the flavoenzyme, cholesterol oxidase and how the observations of unusual hydrogen atom positions provide insight into the redox chemistry of the flavin cofactor.
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Affiliation(s)
- Tatiana Kerber
- School of Molecular Sciences, University of Western Australia, Perth, WA, Australia
| | - Alice Vrielink
- School of Molecular Sciences, University of Western Australia, Perth, WA, Australia.
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9
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Tai Y, Takaba K, Hanazono Y, Dao HA, Miki K, Takeda K. X-ray crystallographic studies on the hydrogen isotope effects of green fluorescent protein at sub-ångström resolutions. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2019; 75:1096-1106. [PMID: 31793903 DOI: 10.1107/s2059798319014608] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 10/28/2019] [Indexed: 11/10/2022]
Abstract
Hydrogen atoms are critical to the nature and properties of proteins, and thus deuteration has the potential to influence protein function. In fact, it has been reported that some deuterated proteins show different physical and chemical properties to their protiated counterparts. Consequently, it is important to investigate protonation states around the active site when using deuterated proteins. Here, hydrogen isotope effects on the S65T/F99S/M153T/V163A variant of green fluorescent protein (GFP), in which the deprotonated B form is dominant at pH 8.5, were investigated. The pH/pD dependence of the absorption and fluorescence spectra indicates that the protonation state of the chromophore is the same in protiated GFP in H2O and protiated GFP in D2O at pH/pD 8.5, while the pKa of the chromophore became higher in D2O. Indeed, X-ray crystallographic analyses at sub-ångström resolution revealed no apparent changes in the protonation state of the chromophore between the two samples. However, detailed comparisons of the hydrogen OMIT maps revealed that the protonation state of His148 in the vicinity of the chromophore differed between the two samples. This indicates that protonation states around the active site should be carefully adjusted to be the same as those of the protiated protein when neutron crystallographic analyses of proteins are performed.
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Affiliation(s)
- Yang Tai
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Kiyofumi Takaba
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yuya Hanazono
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Hoang Anh Dao
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Kunio Miki
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Kazuki Takeda
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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10
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Ashkar R, Bilheux HZ, Bordallo H, Briber R, Callaway DJE, Cheng X, Chu XQ, Curtis JE, Dadmun M, Fenimore P, Fushman D, Gabel F, Gupta K, Herberle F, Heinrich F, Hong L, Katsaras J, Kelman Z, Kharlampieva E, Kneller GR, Kovalevsky A, Krueger S, Langan P, Lieberman R, Liu Y, Losche M, Lyman E, Mao Y, Marino J, Mattos C, Meilleur F, Moody P, Nickels JD, O'Dell WB, O'Neill H, Perez-Salas U, Peters J, Petridis L, Sokolov AP, Stanley C, Wagner N, Weinrich M, Weiss K, Wymore T, Zhang Y, Smith JC. Neutron scattering in the biological sciences: progress and prospects. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2018; 74:1129-1168. [PMID: 30605130 DOI: 10.1107/s2059798318017503] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 12/12/2018] [Indexed: 12/11/2022]
Abstract
The scattering of neutrons can be used to provide information on the structure and dynamics of biological systems on multiple length and time scales. Pursuant to a National Science Foundation-funded workshop in February 2018, recent developments in this field are reviewed here, as well as future prospects that can be expected given recent advances in sources, instrumentation and computational power and methods. Crystallography, solution scattering, dynamics, membranes, labeling and imaging are examined. For the extraction of maximum information, the incorporation of judicious specific deuterium labeling, the integration of several types of experiment, and interpretation using high-performance computer simulation models are often found to be particularly powerful.
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Affiliation(s)
- Rana Ashkar
- Department of Physics, Virginia Polytechnic Institute and State University, 850 West Campus Drive, Blacksburg, VA 24061, USA
| | - Hassina Z Bilheux
- Neutron Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, USA
| | | | - Robert Briber
- Materials Science and Engineeering, University of Maryland, 1109 Chemical and Nuclear Engineering Building, College Park, MD 20742, USA
| | - David J E Callaway
- Department of Chemistry and Biochemistry, The City College of New York, 160 Convent Avenue, New York, NY 10031, USA
| | - Xiaolin Cheng
- Department of Medicinal Chemistry and Pharmacognosy, Ohio State University College of Pharmacy, 642 Riffe Building, Columbus, OH 43210, USA
| | - Xiang Qiang Chu
- Graduate School of China Academy of Engineering Physics, Beijing, 100193, People's Republic of China
| | - Joseph E Curtis
- NIST Center for Neutron Research, National Institutes of Standard and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, MD 20899, USA
| | - Mark Dadmun
- Department of Chemistry, University of Tennessee Knoxville, Knoxville, TN 37996, USA
| | - Paul Fenimore
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - David Fushman
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Organization, University of Maryland, College Park, MD 20742, USA
| | - Frank Gabel
- Institut Laue-Langevin, Université Grenoble Alpes, CEA, CNRS, IBS, 38042 Grenoble, France
| | - Kushol Gupta
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Frederick Herberle
- Neutron Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, USA
| | - Frank Heinrich
- NIST Center for Neutron Research, National Institutes of Standard and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, MD 20899, USA
| | - Liang Hong
- Department of Physics and Astronomy, Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - John Katsaras
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Zvi Kelman
- Institute for Bioscience and Biotechnology Research, National Institute of Standards and Technology and the University of Maryland, Rockville, MD 20850, USA
| | - Eugenia Kharlampieva
- Department of Chemistry, University of Alabama at Birmingham, 901 14th Street South, Birmingham, AL 35294, USA
| | - Gerald R Kneller
- Centre de Biophysique Moléculaire, CNRS, Université d'Orléans, Chateau de la Source, Avenue du Parc Floral, Orléans, France
| | - Andrey Kovalevsky
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Susan Krueger
- NIST Center for Neutron Research, National Institutes of Standard and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, MD 20899, USA
| | - Paul Langan
- Neutron Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, USA
| | - Raquel Lieberman
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Yun Liu
- NIST Center for Neutron Research, National Institutes of Standard and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, MD 20899, USA
| | - Mathias Losche
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Edward Lyman
- Department of Physics and Astrophysics, University of Delaware, Newark, DE 19716, USA
| | - Yimin Mao
- NIST Center for Neutron Research, National Institutes of Standard and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, MD 20899, USA
| | - John Marino
- Institute for Bioscience and Biotechnology Research, National Institute of Standards and Technology and the University of Maryland, Rockville, MD 20850, USA
| | - Carla Mattos
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, USA
| | - Flora Meilleur
- Neutron Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, USA
| | - Peter Moody
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 9HN, England
| | - Jonathan D Nickels
- Department of Physics, Virginia Polytechnic Institute and State University, 850 West Campus Drive, Blacksburg, VA 24061, USA
| | - William B O'Dell
- Institute for Bioscience and Biotechnology Research, National Institute of Standards and Technology and the University of Maryland, Rockville, MD 20850, USA
| | - Hugh O'Neill
- Neutron Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, USA
| | - Ursula Perez-Salas
- Neutron Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, USA
| | | | - Loukas Petridis
- Materials Science and Engineeering, University of Maryland, 1109 Chemical and Nuclear Engineering Building, College Park, MD 20742, USA
| | - Alexei P Sokolov
- Department of Chemistry, University of Tennessee Knoxville, Knoxville, TN 37996, USA
| | - Christopher Stanley
- Neutron Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, USA
| | - Norman Wagner
- Department of Chemistry and Biochemistry, The City College of New York, 160 Convent Avenue, New York, NY 10031, USA
| | - Michael Weinrich
- NIST Center for Neutron Research, National Institutes of Standard and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, MD 20899, USA
| | - Kevin Weiss
- Neutron Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, USA
| | - Troy Wymore
- Graduate School of China Academy of Engineering Physics, Beijing, 100193, People's Republic of China
| | - Yang Zhang
- NIST Center for Neutron Research, National Institutes of Standard and Technology, 100 Bureau Drive, Mail Stop 6102, Gaithersburg, MD 20899, USA
| | - Jeremy C Smith
- Department of Medicinal Chemistry and Pharmacognosy, Ohio State University College of Pharmacy, 642 Riffe Building, Columbus, OH 43210, USA
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11
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The Neutron Macromolecular Crystallography Instruments at Oak Ridge National Laboratory: Advances, Challenges, and Opportunities. CRYSTALS 2018. [DOI: 10.3390/cryst8100388] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The IMAGINE and MaNDi instruments, located at Oak Ridge National Laboratory High Flux Isotope Reactor and Spallation Neutron Source, respectively, are powerful tools for determining the positions of hydrogen atoms in biological macromolecules and their ligands, orienting water molecules, and for differentiating chemical states in macromolecular structures. The possibility to model hydrogen and deuterium atoms in neutron structures arises from the strong interaction of neutrons with the nuclei of these isotopes. Positions can be unambiguously assigned from diffraction studies at the 1.5–2.5 Å resolutions, which are typical for protein crystals. Neutrons have the additional benefit for structural biology of not inducing radiation damage to protein crystals, which can be critical in the study of metalloproteins. Here we review the specifications of the IMAGINE and MaNDi beamlines and illustrate their complementarity. IMAGINE is suitable for crystals with unit cell edges up to 150 Å using a quasi-Laue technique, whereas MaNDi provides neutron crystallography resources for large unit cell samples with unit cell edges up to 300 Å using the time of flight (TOF) Laue technique. The microbial culture and crystal growth facilities which support the IMAGINE and MaNDi user programs are also described.
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12
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Schröder GC, O'Dell WB, Myles DAA, Kovalevsky A, Meilleur F. IMAGINE: neutrons reveal enzyme chemistry. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2018; 74:778-786. [DOI: 10.1107/s2059798318001626] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 01/26/2018] [Indexed: 11/10/2022]
Abstract
Neutron diffraction is exquisitely sensitive to the positions of H atoms in protein crystal structures. IMAGINE is a high-intensity, quasi-Laue neutron crystallography beamline developed at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. This state-of-the-art facility for neutron diffraction has enabled detailed structural analysis of macromolecules. IMAGINE is especially suited to resolve individual H atoms in protein structures, enabling neutron protein structures to be determined at or near atomic resolutions from crystals with volumes of less than 1 mm3 and unit-cell edges of less than 150 Å. Beamline features include elliptical focusing mirrors that deliver neutrons into a 2.0 × 3.2 mm focal spot at the sample position, and variable short- and long-wavelength cutoff optics that provide automated exchange between multiple wavelength configurations. This review gives an overview of the IMAGINE beamline at the HFIR, presents examples of the scientific questions being addressed at this beamline, and highlights important findings in enzyme chemistry that have been made using the neutron diffraction capabilities offered by IMAGINE.
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13
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Neutron macromolecular crystallography. Emerg Top Life Sci 2018; 2:39-55. [DOI: 10.1042/etls20170083] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 12/12/2017] [Accepted: 12/19/2017] [Indexed: 01/02/2023]
Abstract
Neutron diffraction techniques permit direct determination of the hydrogen (H) and deuterium (D) positions in crystal structures of biological macromolecules at resolutions of ∼1.5 and 2.5 Å, respectively. In addition, neutron diffraction data can be collected from a single crystal at room temperature without radiation damage issues. By locating the positions of H/D-atoms, protonation states and water molecule orientations can be determined, leading to a more complete understanding of many biological processes and drug-binding. In the last ca. 5 years, new beamlines have come online at reactor neutron sources, such as BIODIFF at Heinz Maier-Leibnitz Zentrum and IMAGINE at Oak Ridge National Laboratory (ORNL), and at spallation neutron sources, such as MaNDi at ORNL and iBIX at the Japan Proton Accelerator Research Complex. In addition, significant improvements have been made to existing beamlines, such as LADI-III at the Institut Laue-Langevin. The new and improved instrumentations are allowing sub-mm3 crystals to be regularly used for data collection and permitting the study of larger systems (unit-cell edges >100 Å). Owing to this increase in capacity and capability, many more studies have been performed and for a wider range of macromolecules, including enzymes, signalling proteins, transport proteins, sugar-binding proteins, fluorescent proteins, hormones and oligonucleotides; of the 126 structures deposited in the Protein Data Bank, more than half have been released since 2013 (65/126, 52%). Although the overall number is still relatively small, there are a growing number of examples for which neutron macromolecular crystallography has provided the answers to questions that otherwise remained elusive.
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14
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Yu LJ, Golden E, Chen N, Zhao Y, Vrielink A, Karton A. Computational insights for the hydride transfer and distinctive roles of key residues in cholesterol oxidase. Sci Rep 2017; 7:17265. [PMID: 29222497 PMCID: PMC5722936 DOI: 10.1038/s41598-017-17503-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 11/27/2017] [Indexed: 11/10/2022] Open
Abstract
Cholesterol oxidase (ChOx), a member of the glucose-methanol-choline (GMC) family, catalyzes the oxidation of the substrate via a hydride transfer mechanism and concomitant reduction of the FAD cofactor. Unlike other GMC enzymes, the conserved His447 is not the catalytic base that deprotonates the substrate in ChOx. Our QM/MM MD simulations indicate that the Glu361 residue acts as a catalytic base facilitating the hydride transfer from the substrate to the cofactor. We find that two rationally chosen point mutations (His447Gln and His447Asn) cause notable decreases in the catalytic activity. The binding free energy calculations show that the Glu361 and His447 residues are important in substrate binding. We also performed high-level double-hybrid density functional theory simulations using small model systems, which support the QM/MM MD results. Our work provides a basis for unraveling the substrate oxidation mechanism in GMC enzymes in which the conserved histidine does not act as a base.
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Affiliation(s)
- Li-Juan Yu
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
| | - Emily Golden
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
| | - Nanhao Chen
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, 510006, China.,Department of Chemistry, University of California, Davis, California, 95616, United States
| | - Yuan Zhao
- The Key Laboratory of Natural Medicine and Immuno-Engineering, Henan University, Kaifeng, 475004, China.
| | - Alice Vrielink
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia
| | - Amir Karton
- School of Molecular Sciences, The University of Western Australia, Perth, WA, 6009, Australia.
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