1
|
Lai R, Li G, Cui Q. Flexibility of Binding Site is Essential to the Ca 2+ Selectivity in EF-Hand Calcium-Binding Proteins. J Am Chem Soc 2024; 146:7628-7639. [PMID: 38456823 PMCID: PMC11102802 DOI: 10.1021/jacs.3c13981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2024]
Abstract
High binding affinity and selectivity of metal ions are essential to the function of metalloproteins. Thus, understanding the factors that determine these binding characteristics is of major interest for both fundamental mechanistic investigations and guiding of the design of novel metalloproteins. In this work, we perform QM cluster model calculations and quantum mechanics/molecular mechanics (QM/MM) free energy simulations to understand the binding selectivity of Ca2+ and Mg2+ in the wild-type carp parvalbumin and its mutant. While a nonpolarizable MM model (CHARMM36) does not lead to the correct experimental trend, treatment of the metal binding site with the DFTB3 model in a QM/MM framework leads to relative binding free energies (ΔΔGbind) comparable with experimental data. For the wild-type (WT) protein, the calculated ΔΔGbind is ∼6.6 kcal/mol in comparison with the experimental value of 5.6 kcal/mol. The good agreement highlights the value of a QM description of the metal binding site and supports the role of electronic polarization and charge transfer to metal binding selectivity. For the D51A/E101D/F102W mutant, different binding site models lead to considerable variations in computed binding affinities. With a coordination number of seven for Ca2+, which is shown by QM/MM metadynamics simulations to be the dominant coordination number for the mutant, the calculated relative binding affinity is ∼4.8 kcal/mol, in fair agreement with the experimental value of 1.6 kcal/mol. The WT protein is observed to feature a flexible binding site that accommodates a range of coordination numbers for Ca2+, which is essential to the high binding selectivity for Ca2+ over Mg2+. In the mutant, the E101D mutation reduces the flexibility of the binding site and limits the dominant coordination number of Ca2+ to be seven, thereby leading to reduced binding selectivity against Mg2+. Our results highlight that the binding selectivity of metal ions depends on both the structural and dynamical properties of the protein binding site.
Collapse
Affiliation(s)
- Rui Lai
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Guohui Li
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Qiang Cui
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
- Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, Massachusetts 02215, United States
| |
Collapse
|
2
|
Rossi E, Ferrarini A, Sulpizi M. Modeling of minimal systems based on ATP-Zn coordination for chemically fueled self-assembly. Phys Chem Chem Phys 2023; 25:6102-6111. [PMID: 36752043 DOI: 10.1039/d2cp05516c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Following nature's example, there is currently strong interest in using adenosine 5'-triphosphate (ATP) as a fuel for the self-assembly of functional materials with transient/non-equilibrium behaviours. These hold great promise for applications, e.g. in catalysis and drug delivery. In a recent seminal work [Maiti et al., Nat. Chem., 2016, 8, 725], binding of ATP to the metallosurfactant zinc hexadecyl-1,4,7-triazacyclononane ([ZnC16 TACN]2+) was exploited to produce ATP-fueled transient vesicles. Crucial to the complex formation is the ability of ATP to bind to the metal ion. As a first step to unveil the key elements underlying this process, we investigate the interaction of ATP with Zn2+ and with methyl-1,4,7-triazacyclononane ([ZnCH3 TACN]2+), using all-atom molecular dynamics simulations. The free energy landscape of the complex formation is sampled using well-tempered metadynamics with three collective variables, corresponding to the coordination numbers of Zn2+ with the oxygen atoms of the three phosphate groups. We find that the structure of the ternary complex is controlled by direct triphosphate coordination to zinc, with a minor role played by the interactions between ATP and CH3 TACN which, however, may be important for the build-up of supramolecular assemblies.
Collapse
Affiliation(s)
- Emma Rossi
- Department of Chemical Sciences, University of Padova, Via Francesco Marzolo, 1, 35131, Padova, Italy.
| | - Alberta Ferrarini
- Department of Chemical Sciences, University of Padova, Via Francesco Marzolo, 1, 35131, Padova, Italy.
| | - Marialore Sulpizi
- Department of Physics, Ruhr Universität Bochum, NB6, 65, 44780, Bochum, Germany.
| |
Collapse
|
3
|
Paoletti F, Covaceuszach S, Cassetta A, Calabrese AN, Novak U, Konarev P, Grdadolnik J, Lamba D, Golič Grdadolnik S. Distinct conformational changes occur within the intrinsically unstructured pro-domain of pro-Nerve Growth Factor in the presence of ATP and Mg 2. Protein Sci 2023; 32:e4563. [PMID: 36605018 PMCID: PMC9878617 DOI: 10.1002/pro.4563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 11/24/2022] [Accepted: 01/03/2023] [Indexed: 01/07/2023]
Abstract
Nerve growth factor (NGF), the prototypical neurotrophic factor, is involved in the maintenance and growth of specific neuronal populations, whereas its precursor, proNGF, is involved in neuronal apoptosis. Binding of NGF or proNGF to TrkA, p75NTR , and VP10p receptors triggers complex intracellular signaling pathways that can be modulated by endogenous small-molecule ligands. Here, we show by isothermal titration calorimetry and NMR that ATP binds to the intrinsically disordered pro-peptide of proNGF with a micromolar dissociation constant. We demonstrate that Mg2+ , known to play a physiological role in neurons, modulates the ATP/proNGF interaction. An integrative structural biophysics analysis by small angle X-ray scattering and hydrogen-deuterium exchange mass spectrometry unveils that ATP binding induces a conformational rearrangement of the flexible pro-peptide domain of proNGF. This suggests that ATP may act as an allosteric modulator of the overall proNGF conformation, whose likely distinct biological activity may ultimately affect its physiological homeostasis.
Collapse
Affiliation(s)
- Francesca Paoletti
- Laboratory for Molecular Structural Dynamics, Theory DepartmentNational Institute of ChemistryLjubljanaSlovenia
| | | | - Alberto Cassetta
- Institute of Crystallography—C.N.R.—Trieste OutstationTriesteItaly
| | - Antonio N. Calabrese
- School of Molecular and Cellular Biology, Astbury Centre for Structural Molecular BiologyUniversity of LeedsLeedsUK
| | - Urban Novak
- Laboratory for Molecular Structural Dynamics, Theory DepartmentNational Institute of ChemistryLjubljanaSlovenia
| | - Petr Konarev
- A.V. Shubnikov Institute of Crystallography of Federal Scientific Research Centre “Crystallography and Photonics”Russian Academy of SciencesMoscowRussia
| | - Jože Grdadolnik
- Laboratory for Molecular Structural Dynamics, Theory DepartmentNational Institute of ChemistryLjubljanaSlovenia
| | - Doriano Lamba
- Institute of Crystallography—C.N.R.—Trieste OutstationTriesteItaly
- Interuniversity Consortium “Biostructures and Biosystems National Institute”RomeItaly
| | - Simona Golič Grdadolnik
- Laboratory for Molecular Structural Dynamics, Theory DepartmentNational Institute of ChemistryLjubljanaSlovenia
| |
Collapse
|
4
|
Kaur R, Aboelnga MM, Nikkel DJ, Wetmore SD. The metal dependence of single-metal mediated phosphodiester bond cleavage: a QM/MM study of a multifaceted human enzyme. Phys Chem Chem Phys 2022; 24:29130-29140. [PMID: 36444615 DOI: 10.1039/d2cp04338f] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nucleases catalyze the cleavage of phosphodiester bonds in nucleic acids using a range of metal cofactors. Although it is well accepted that many nucleases rely on two metal ions, the one-metal mediated pathway is debated. Furthermore, one-metal mediated nucleases maintain activity in the presence of many different metals, but the underlying reasons for this broad metal specificity are unknown. The human apurinic/apyrimidinic endonuclease (APE1), which plays a key role in DNA repair, transcription regulation, and gene expression, is a prototypical example of a one-metal dependent nuclease. Although Mg2+ is the native metal cofactor, APE1 remains catalytically active in the presence of several metals, with the rate decreasing as Mg2+ > Mn2+ > Ni2+ > Zn2+, while Ca2+ completely abolished the activity. The present work uses quantum mechanics-molecular mechanics techniques to map APE1-facilitated phosphodiester bond hydrolysis in the presence of these metals. The structural differences in stationary points along the reaction pathway shed light on the interplay between several factors that allow APE1 to remain catalytically active for various metals, with the trend in the barrier heights correlating with the experimentally reported APE1 catalytic activity. In contrast, Ca2+ significantly changes the metal coordination and active site geometry, and thus completely inhibits catalysis. Our work thereby provides support for the controversial single-metal mediated phosphodiester bond cleavage and clarifies uncertainties regarding the role of the metal and metal identity in this important reaction. This information is key for future medicinal and biotechnological applications including disease diagnosis and treatment, and protein engineering.
Collapse
Affiliation(s)
- Rajwinder Kaur
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta, T1K 3M4, Canada.
| | - Mohamed M Aboelnga
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta, T1K 3M4, Canada.
| | - Dylan J Nikkel
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta, T1K 3M4, Canada.
| | - Stacey D Wetmore
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta, T1K 3M4, Canada.
| |
Collapse
|
5
|
Grauffel C, Weng WH, Lim C. Factors allowing small monovalent Li + to displace Ca 2+ in proteins. Phys Chem Chem Phys 2022; 24:17759-17769. [PMID: 35848546 DOI: 10.1039/d2cp02072f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Because Li+ and Ca2+ differ in both charge and size, the possibility that monovalent Li+ could dislodge the bulkier, divalent Ca2+ in Ca2+ proteins had not been considered. However, our recent density functional theory/continuum dielectric calculations predicted that Li+ could displace the native Ca2+ from the C2 domain of cytosolic PKCα/γ. This would reduce electrostatic interactions between the Li+-bound C2 domain and the membrane, consistent with experimental studies showing that Li+ can inhibit the translocation of cytoplasmic PKC to membranes. Besides the trinuclear Ca2+-site in the PKCα/γ C2 domain, it is not known whether other Ca2+-sites in human proteins may be susceptible to Li+ substitution. Furthermore, it is unclear what factors determine the outcome of the competition between divalent Ca2+ and monovalent Li+. Here we show that the net charge of residues in the first and second coordination shell is a key determinant of the selectivity for divalent Ca2+ over monovalent Li+ in proteins: neutral/anionic Ca2+-carboxylate sites are protected against Li+ attack. They are further protected by outer-shell Asp-/Glu- and the protein matrix rigidifying the Ca2+-site or limiting water entry. In contrast, buried, cationic Ca2+-sites surrounded by Arg+/Lys+, which are found in the C2 domains of PKCα/γ, as well as certain synaptotagmins, are prone to Li+ attack.
Collapse
Affiliation(s)
- Cédric Grauffel
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
| | - Wei-Hsiang Weng
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
| | - Carmay Lim
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan. .,Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan
| |
Collapse
|
6
|
Hu X, Lenz-Himmer MO, Baldauf C. Better force fields start with better data: A data set of cation dipeptide interactions. Sci Data 2022; 9:327. [PMID: 35715420 PMCID: PMC9205945 DOI: 10.1038/s41597-022-01297-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Accepted: 03/18/2022] [Indexed: 11/08/2022] Open
Abstract
We present a data set from a first-principles study of amino-methylated and acetylated (capped) dipeptides of the 20 proteinogenic amino acids - including alternative possible side chain protonation states and their interactions with selected divalent cations (Ca2+, Mg2+ and Ba2+). The data covers 21,909 stationary points on the respective potential-energy surfaces in a wide relative energy range of up to 4 eV (390 kJ/mol). Relevant properties of interest, like partial charges, were derived for the conformers. The motivation was to provide a solid data basis for force field parameterization and further applications like machine learning or benchmarking. In particular the process of creating all this data on the same first-principles footing, i.e. density-functional theory calculations employing the generalized gradient approximation with a van der Waals correction, makes this data suitable for first principles data-driven force field development. To make the data accessible across domain borders and to machines, we formalized the metadata in an ontology.
Collapse
Affiliation(s)
- Xiaojuan Hu
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany.
| | | | - Carsten Baldauf
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany.
| |
Collapse
|
7
|
Grotz KK, Schwierz N. Optimized Magnesium Force Field Parameters for Biomolecular Simulations with Accurate Solvation, Ion-Binding, and Water-Exchange Properties in SPC/E, TIP3P-fb, TIP4P/2005, TIP4P-Ew, and TIP4P-D. J Chem Theory Comput 2022; 18:526-537. [PMID: 34881568 PMCID: PMC8757469 DOI: 10.1021/acs.jctc.1c00791] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Indexed: 12/14/2022]
Abstract
Magnesium is essential in many vital processes. To correctly describe Mg2+ in physiological processes by molecular dynamics simulations, accurate force fields are fundamental. Despite the importance, force fields based on the commonly used 12-6 Lennard-Jones potential showed significant shortcomings. Recently progress was made by an optimization procedure that implicitly accounts for polarizability. The resulting microMg and nanoMg force fields (J. Chem. Theory Comput. 2021, 17, 2530-2540) accurately reproduce a broad range of experimental solution properties and the binding affinity to nucleic acids in TIP3P water. Since countless simulation studies rely on available water models and ion force fields, we here extend the optimization and provide Mg2+ parameters in combination with the SPC/E, TIP3P-fb, TIP4P/2005, TIP4P-Ew, and TIP4P-D water models. For each water model, the Mg2+ force fields reproduce the solvation free energy, the distance to oxygens in the first hydration shell, the hydration number, the activity coefficient derivative in MgCl2 solutions, and the binding affinity and distance to the phosphate oxygens on nucleic acids. We present two parameter sets: MicroMg yields water exchange on the microsecond time scale and matches the experimental exchange rate. Depending on the water model, nanoMg yields accelerated water exchange in the range of 106 to 108 exchanges per second. The nanoMg parameters can be used to enhance the sampling of binding events, to obtain converged distributions of Mg2+, or to predict ion binding sites in biomolecular simulations. The parameter files are freely available at https://github.com/bio-phys/optimizedMgFFs.
Collapse
Affiliation(s)
- Kara K. Grotz
- Department of Theoretical
Biophysics, Max-Planck-Institute of Biophysics, Frankfurt am Main 60438, Germany
| | - Nadine Schwierz
- Department of Theoretical
Biophysics, Max-Planck-Institute of Biophysics, Frankfurt am Main 60438, Germany
| |
Collapse
|
8
|
Dudev T, Grauffel C, Lim C. Calcium in Signaling: Its Specificity and Vulnerabilities toward Biogenic and Abiogenic Metal Ions. J Phys Chem B 2021; 125:10419-10431. [PMID: 34515482 DOI: 10.1021/acs.jpcb.1c05154] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Divalent calcium ion (Ca2+) plays an indispensable role as a second messenger in a myriad of signal transduction processes. Of utmost importance for the faultless functioning of calcium-modulated signaling proteins is their binding selectivity of the native metal cation over rival biogenic/abiogenic metal ion contenders in the intra/extracellular fluids. In this Perspective, we summarize recent findings on the competition between the cognate Ca2+ and other biogenic or abiogenic divalent cations for binding to Ca2+-signaling proteins or organic cofactors. We describe the competition between the two most abundant intracellular biogenic metal ions (Mg2+ and Ca2+) for Ca2+-binding sites in signaling proteins, followed by the rivalry between native Ca2+ and "therapeutic" Li+ as well as "toxic" Pb2+. We delineate the key factors governing the rivalry between the native and non-native cations in proteins and highlight key implications for the biological performance of the respective proteins/organic cofactors.
Collapse
Affiliation(s)
- Todor Dudev
- Faculty of Chemistry and Pharmacy, Sofia University, Sofia 1164, Bulgaria
| | - Cédric Grauffel
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Carmay Lim
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.,Department of Chemistry, National Tsing Hua University, Hsinchu 300 Taiwan
| |
Collapse
|
9
|
Grauffel C, Weng WH, Dudev T, Lim C. Trinuclear Calcium Site in the C2 Domain of PKCα/γ Is Prone to Lithium Attack. ACS OMEGA 2021; 6:20657-20666. [PMID: 34396011 PMCID: PMC8359144 DOI: 10.1021/acsomega.1c02882] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 07/13/2021] [Indexed: 05/10/2023]
Abstract
Lithium (Li+) is the first-line therapy for bipolar disorder and a candidate drug for various diseases such as amyotrophic lateral sclerosis, multiple sclerosis, and stroke. Despite being the captivating subject of many studies, the mechanism of lithium's therapeutic action remains unclear. To date, it has been shown that Li+ competes with Mg2+ and Na+ to normalize the activity of inositol and neurotransmitter-related signaling proteins, respectively. Furthermore, Li+ may co-bind with Mg2+-loaded adenosine or guanosine triphosphate to alter the complex's susceptibility to hydrolysis and mediate cellular signaling. Bipolar disorder patients exhibit abnormally high cytosolic Ca2+ levels and protein kinase C (PKC) hyperactivity that can be downregulated by long-term Li+ treatment. However, the possibility that monovalent Li+ could displace the bulkier divalent Ca2+ and inhibit PKC activity has not been considered. Here, using density functional theory calculations combined with continuum dielectric methods, we show that Li+ may displace the native dication from the positively charged trinuclear site in the C2 domain of cytosolic PKCα/γ. This would affect the membrane-docking ability of cytosolic PKCα/γ and reduce the abnormally high membrane-associated active PKCα/γ levels, thus downregulating the PKC hyperactivity found in bipolar patients.
Collapse
Affiliation(s)
- Cédric Grauffel
- Institute of Biomedical
Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Wei-Hsiang Weng
- Institute of Biomedical
Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Todor Dudev
- Faculty of Chemistry and Pharmacy, Sofia University, Sofia 1164, Bulgaria
| | - Carmay Lim
- Institute of Biomedical
Sciences, Academia Sinica, Taipei 115, Taiwan
- Department of Chemistry, National Tsing
Hua University, Hsinchu 300, Taiwan
| |
Collapse
|
10
|
Grauffel C, Dudev T, Lim C. Metal Affinity/Selectivity of Monophosphate-Containing Signaling/Lipid Molecules. J Chem Theory Comput 2021; 17:2444-2456. [PMID: 33818070 DOI: 10.1021/acs.jctc.0c01007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Monophosphate, an essential component of nucleic acids, as well as cell membranes and signaling molecules, is often bound to metal cations. Despite the biological importance of monophosphate-containing cell-signaling or lipid molecules, their propensity to bind the two most abundant cellular dications, Mg2+ and Ca2+, in a particular mode (inner/outer shell, mono/bidentate) is not well understood. Whether they prefer binding to Mg2+ than to Ca2+ and if they can outcompete the carboxylates of excitatory Asp/Glu and inhibitory gamma-aminobutyric acid (GABA) neurotransmitters in binding to Mg2+/Ca2+ remain unclear. To address these questions, we modeled cyclic adenosine/guanosine monophosphate (cAMP/cGMP), nucleoside 2',3'-cyclic phosphate, phosphatidylinositol (PI), phosphatidylserine (PS), and phosphatidylethanolamine (PEA) and determined their most stable metal-binding modes, including those of Asp/Glu and GABA, as well as their selectivity for Mg2+/Ca2+ using density functional theory combined with the polarizable continuum model. The results obtained, which are consistent with the available experimental findings, reveal that the structurally and functionally diverse monophosphate-containing ligands studied prefer monodentate coordination of Mg2+ because of the greater strain encountered upon bidentate coordination, whereas the larger Ca2+ imposes less strain upon bidentate binding and has reduced/no preference for monodentate coordination. We further show that in a low-dielectric environment, negatively charged monophosphate-containing ligands favor the better charge-accepting dication, that is, Mg2+ rather than Ca2+. By promoting Mg2+ over Ca2+ binding, signaling monophosphates (cAMP/cGMP) do not entrap cellular Ca2+ and interfere with signal transduction processes employing Ca2+ as a second messenger. In regions with high glutamate cytoplasmic concentration, glutamate may sequester Mg2+ bound to isolated five-/six-membered ring phosphates, PI, or neutral PEA, but not anionic phospholipids constituting the inner leaflet of the cell membrane.
Collapse
Affiliation(s)
- Cédric Grauffel
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Todor Dudev
- Faculty of Chemistry and Pharmacy, Sofia University, Sofia 1164, Bulgaria
| | - Carmay Lim
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan.,Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan
| |
Collapse
|