DOCSLIB.ORG

Charge-Density Analysis of a Protein Structure at Subatomic Resolution

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Charge-Density Analysis of a Protein Structure at Subatomic Resolution Charge-density analysis of a protein structure at subatomic resolution: the human aldose reductase case Benoit Guillot, Christian Jelsch, Alberto Podjarny, Claude Lecomte To cite this version: Benoit Guillot, Christian Jelsch, Alberto Podjarny, Claude Lecomte. Charge-density analysis of a protein structure at subatomic resolution: the human aldose reductase case. Acta Crystallographica Section D: Biological Crystallography, International Union of Crystallography, 2008, 64 (5), pp.567- 588. 10.1107/S0907444908006082. hal-02918883 HAL Id: hal-02918883 https://hal.archives-ouvertes.fr/hal-02918883 Submitted on 25 Aug 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. electronic reprint Acta Crystallographica Section D Biological Crystallography ISSN 0907-4449 Editors: E. N. Baker and Z. Dauter Charge-density analysis of a protein structure at subatomic resolution: the human aldose reductase case Benoˆıt Guillot, Christian Jelsch, Alberto Podjarny and Claude Lecomte Acta Cryst. (2008). D64, 567–588 Copyright c International Union of Crystallography Author(s) of this paper may load this reprint on their own web site or institutional repository provided that this cover page is retained. Republication of this article or its storage in electronic databases other than as specified above is not permitted without prior permission in writing from the IUCr. For further information see http://journals.iucr.org/services/authorrights.html Acta Crystallographica Section D: Biological Crystallography welcomes the submission of papers covering any aspect of structural biology, with a particular emphasis on the struc- tures of biological macromolecules and the methods used to determine them. Reports on new protein structures are particularly encouraged, as are structure–function papers that could include crystallographic binding studies, or structural analysis of mutants or other modified forms of a known protein structure. The key criterion is that such papers should present new insights into biology, chemistry or structure. Papers on crystallo- graphic methods should be oriented towards biological crystallography, and may include new approaches to any aspect of structure determination or analysis. Crystallography Journals Online is available from journals.iucr.org Acta Cryst. (2008). D64, 567–588 Guillot et al. · Charge-density analysis of human aldolase reductase research papers Acta Crystallographica Section D Biological Charge-density analysis of a protein structure at Crystallography subatomic resolution: the human aldose reductase ISSN 0907-4449 case Benoıˆt Guillot,a Christian The valence electron density of the protein human aldose Received 29 October 2007 Jelsch,a* Alberto Podjarnyb and reductase was analyzed at 0.66 A˚ resolution. The methodo- Accepted 5 March 2008 Claude Lecomtea logical developments in the software MoPro to adapt standard charge-density techniques from small molecules to macro- This article is dedicated to molecular structures are described. The deformation electron Professor Niels Kristian a Laboratoire de Cristallographie et Mode´lisation density visible in initial residual Fourier difference maps was Hansen, who developed the des Mate´riaux Mine´raux et Biologiques, LCM3B, significantly enhanced after high-order refinement. The multipolar model of the CNRS, UMR 7036, Nancy Universite´, Faculte´ atomic electron density during des Sciences et Techniques, BP 239, 54506 protein structure was refined after transfer of the experi- his PhD under the supervision Vandoeuvre-le`s-Nancy CEDEX, France, and mental library multipolar atom model (ELMAM). The effects of Professor P. Coppens. bDe´partement de Biologie et Ge´nomique Struc- on the crystallographic statistics, on the atomic thermal turales, IGBMC, CNRS INSERM ULP, Illkirch, displacement parameters and on the structure stereochemistry France are analyzed. Constrained refinements of the transferred valence populations Pval and multipoles Plm were performed Correspondence e-mail: against the X-ray diffraction data on a selected substructure of [email protected] the protein with low thermal motion. The resulting charge densities are of good quality, especially for chemical groups with many copies present in the polypeptide chain. To check the effect of the starting point on the result of the constrained multipolar refinement, the same charge-density refinement strategy was applied but using an initial neutral spherical atom model, i.e. without transfer from the ELMAM library. The best starting point for a protein multipolar refinement is the structure with the electron density transferred from the database. This can be assessed by the crystallographic statistical indices, including Rfree, and the quality of the static deformation electron-density maps, notably on the oxygen electron lone pairs. The analysis of the main-chain bond lengths suggests that stereochemical dictionaries would benefit from a revision based on recently determined unrestrained atomic resolution protein structures. 1. Introduction Biocrystallography has evolved significantly in recent years, with the introduction of new methods and techniques in each stage of protein structure resolution. Data-collection tech- niques and data quality have been significantly improved thanks to third-generation synchrotron sources, automated data reduction and methodological improvements (Petrova & Podjarny, 2004; Schmidt & Lamzin, 2002; Dauter et al., 1997; Dauter, 2003). Moreover, protein model building and refinement can now in many cases be performed almost automatically, allowing the scientist to spend more time on structure analysis and interpretation. Some of these improvements arise from so-called high-throughput crystallography, which is dedicated to almost automated and # 2008 International Union of Crystallography very rapid protein structure determination in the context of Printed in Singapore – all rights reserved genomic projects. All these improvements, but in particular Acta Cryst. (2008). D64, 567–588 doi:10.1107/S0907444908006082 567 electronic reprint research papers those in crystallogenesis and synchrotron-radiation sources, et al., 1991). This first successful application of the transfer- have another extremely important consequence: more and ability principle is based on the assumption that the defor- more protein or nucleic acid structures are being solved and mation electron-density features are similar for a given atom refined at atomic or subatomic resolution. The record reso- type in different molecules or crystal contexts. This principle lutions for proteins are currently crambin at 0.54 A˚ resolution was subsequently extended to the possibility of transferring (Jelsch et al., 2000), an antifreeze protein at 0.62 A˚ (Ko et al., average deformation electron-density parameters obtained 2003), triclinic lysozyme at 0.65 A˚ (Wang et al., 2007), human from subatomic resolution peptide and amino-acid charge- aldose reductase (hAR) at 0.66 A˚ (Podjarny et al., 2003; density studies to larger compounds or protein structures Howard et al., 2004), a rubredoxin at 0.69 A˚ (Bo¨nisch et al., solved at lower resolution (Pichon-Pesme et al., 1995; Jelsch et 2005), a domain of syntenin at 0.73 A˚ (Kang et al., 2004) and a al., 1998; Volkov et al., 2007). These results and the determi- hydrophobin at 0.75 A˚ (Hakanpa¨a¨ et al., 2006). Protein nation of several precise charge densities of peptides and structures at resolutions between 1 and 0.5 A˚ allow detailed amino acids prompted the creation of the experimental library analysis of the protein structure on the atomic scale. Most of multipolar atom model (ELMAM; Pichon-Pesme et al., 1995, the H atoms then become visible in difference Fourier 2004; Zarychta et al., 2007). The library contains all the Fobs À Fcalc maps. This is of extreme importance for under- multipolar parameters, in the Hansen & Coppens (1978) standing enzymatic catalysis and for protein-structure inter- formalism, needed to describe the electron density of each pretation. Many recent reviews have indeed described the chemical moiety that can be found in protein structures. At the importance of such resolution in protein-structure analysis same time, in order to apply the multipole formalism to (Dauter et al., 1997; Schmidt & Lamzin, 2002; Housset et al., protein structures, the MoPro software suite was developed by 2000). Moreover, subatomic resolution (0.7 A˚ or higher) has our group (Guillot et al., 2001; Jelsch et al., 2005), imple- another advantage: the level of detail that can be observed in menting the ELMAM database. This program suite includes experimental electron density goes far beyond the localization the techniques developed by the small-molecule charge- of atoms and the identification of their chemical species. density community, as well as the refinement methods such as Indeed, at subatomic resolution it becomes possible to observe stereochemical restraints and conjugate-gradient iterations the nonspherical character of atomic electron densities or, in used in protein crystallography.
Load more

Recommended publications
  • Quantum-Chemical Descriptors in QSAR/QSPR Studies
    1027 Quantum-Chemical Descriptors in QSAR/QSPR Studies Mati Karelson* and Victor S. Lobanov Department of Chemistry, University of Tartu, 2 Jakobi Str., Tartu, EE 2400, Estonia Alan R. Katritzky Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200 Received August 21, 1995 (Revised Manuscript Received February 26, 1996) Contents Recent progress in computational hardware and the development of efficient algorithms has assisted I. Introduction 1027 the routine development of molecular quantum- II. Quantum Chemical Methods 1027 mechanical calculations. New semiempirical meth- III. Quantum Chemical Descriptors 1029 ods supply realistic quantum-chemical molecular IV. QSAR/QSPR Results 1033 quantities in a relatively short computational time A. Biological Activities 1033 frame. Quantum chemical calculations are thus an B. Chemical Reactivities 1035 attractive source of new molecular descriptors, which C. Partition Coefficients 1036 can, in principle, express all of the electronic and D. Chromatographic Retention Indexes and 1036 geometric properties of molecules and their interac- Response Factors tions. Indeed, many recent QSAR/QSPR studies E. Other Physicochemical Properties 1037 have employed quantum chemical descriptors alone F. Substituent Constants 1038 or in combination with conventional descriptors. Quantum chemistry provides a more accurate and G. Solvational Characteristics 1038 detailed description of electronic effects than empiri- H. CoMFA 1040 cal methods.1
    [Show full text]
  • Electron Paramagnetic Resonance of Radicals and Metal Complexes. 2. International Conference of the Polish EPR Association. Wars
    ! U t S - PL — voZ, PL9700944 Warsaw, 9-13 September 1996 ELECTRON PARAMAGNETIC RESONANCE OF RADICALS AND METAL COMPLEXES 2nd International Conference of the Polish EPR Association INSTITUTE OF NUCLEAR CHEMISTRY AND TECHNOLOGY UNIVERSITY OF WARSAW VGL 2 8 Hi 1 2 ORGANIZING COMMITTEE Institute of Nuclear Chemistry and Technology Prof. Andrzej G. Chmielewski, Ph.D., D.Sc. Assoc. Prof. Hanna B. Ambroz, Ph.D., D.Sc. Assoc. Prof. Jacek Michalik, Ph.D., D.Sc. Dr Zbigniew Zimek University of Warsaw Prof. Zbigniew Kqcki, Ph.D., D.Sc. ADDRESS OF ORGANIZING COMMITTEE Institute of Nuclear Chemistry and Technology, Dorodna 16,03-195 Warsaw, Poland phone: (0-4822) 11 23 47; telex: 813027 ichtj pi; fax: (0-4822) 11 15 32; e-mail: [email protected] .waw.pl Abstracts are published in the form as received from the Authors SPONSORS The organizers would like to thank the following sponsors for their financial support: » State Committee of Scientific Research » Stiftung fur Deutsch-Polnische Zusammenarbeit » National Atomic Energy Agency, Warsaw, Poland » Committee of Chemistry, Polish Academy of Sciences, Warsaw, Poland » Committee of Physics, Polish Academy of Sciences, Poznan, Poland » The British Council, Warsaw, Poland » CIECH S.A. » ELEKTRIM S.A. » Broker Analytische Messtechnik, Div. ESR/MINISPEC, Germany 3 CONTENTS CONFERENCE PROGRAM 9 LECTURES 15 RADICALS IN DNA AS SEEN BY ESR SPECTROSCOPY M.C.R. Symons 17 ELECTRON AND HOLE TRANSFER WITHIN DNA AND ITS HYDRATION LAYER M.D. Sevilla, D. Becker, Y. Razskazovskii 18 MODELS FOR PHOTOSYNTHETIC REACTION CENTER: STEADY STATE AND TIME RESOLVED EPR SPECTROSCOPY H. Kurreck, G. Eiger, M. Fuhs, A Wiehe, J.
    [Show full text]
  • Arxiv:1711.08955V1 [Cond-Mat.Mes-Hall] 24 Nov 2017
    Theory of excitation transfer between two-dimensional semiconductor and molecular layers Judith Specht,1, ∗ Eike Verdenhalven,1 Bj¨ornBieniek,2 Patrick Rinke,2, 3 Andreas Knorr,1 and Marten Richter1, y 1Institut f¨urTheoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universit¨atBerlin, Hardenbergstr. 36, 10623 Berlin, Germany 2Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany 3COMP Department of Applied Physics, Aalto University, P.O. Box 11100, Aalto FI-00076, Finland (Dated: July 13, 2018) Abstract The geometry-dependent energy transfer rate from an electrically pumped inorganic semicon- ductor quantum well into an organic molecular layer is studied theoretically. We focus on F¨orster- type nonradiative excitation transfer between the organic and inorganic layer and include quasi- momentum conservation and intermolecular coupling between the molecules in the organic film. (Transition) partial charges calculated from density-functional theory are used to calculate the coupling elements. The partial charges describe the spatial charge distribution and go beyond the common dipole-dipole interaction. We find that the transfer rates are highly sensitive to variations in the geometry of the hybrid inorganic/organic system. For instance, the transfer effi- ciency is improved by orders of magnitude by tuning the relative orientation and positioning of the molecules. Also, the operating regime is identified where in-scattering dominates over unwanted back-scattering from the molecular layer into the substrate. arXiv:1711.08955v1 [cond-mat.mes-hall] 24 Nov 2017 ∗ [email protected] y [email protected] 1 I. INTRODUCTION A potential advantage of hybrid inorganic/organic systems over their individual con- stituents is that a synergistic combination can lead to novel optoelectronic properties and tunable functionality [1{9].
    [Show full text]
  • Modeling Organic Electronic Materials: Bridging Length and Time Scales
    UC Davis UC Davis Previously Published Works Title Modeling organic electronic materials: bridging length and time scales Permalink https://escholarship.org/uc/item/6jv1c5zk Journal Molecular Simulation, 43(10-11) ISSN 0892-7022 Authors Harrelson, TF Moulé, AJ Faller, R Publication Date 2017-07-03 DOI 10.1080/08927022.2016.1273526 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Molecular Simulation ISSN: 0892-7022 (Print) 1029-0435 (Online) Journal homepage: http://www.tandfonline.com/loi/gmos20 Modeling organic electronic materials: bridging length and time scales Thomas F. Harrelson, Adam J. Moulé & Roland Faller To cite this article: Thomas F. Harrelson, Adam J. Moulé & Roland Faller (2017): Modeling organic electronic materials: bridging length and time scales, Molecular Simulation To link to this article: http://dx.doi.org/10.1080/08927022.2016.1273526 Published online: 02 Mar 2017. Submit your article to this journal View related articles View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=gmos20 Download by: [The UC Davis Libraries] Date: 02 March 2017, At: 08:51 MOLECULAR SIMULATION, 2017 http://dx.doi.org/10.1080/08927022.2016.1273526 ENERGY APPLICATIONS Modeling organic electronic materials: bridging length and time scales Thomas F. Harrelson, Adam J. Moulé, Roland Faller Chemical Engineering, UC Davis, Davis, USA ABSTRACT ARTICLE HISTORY Organic electronics is a popular and rapidly growing field of research. The optical, electrical and mechanical Received 2 October 2016 properties of organic molecules and materials can be tailored using increasingly well controlled synthetic Accepted 10 December 2016 methods.
    [Show full text]
  • Effects of Partial Charge-Transfer Solute – Solvent Interactions in Absorption Spectra of Aromatic Hydrocarbons in Aqueous and Alcoholic Solutions
    Effects of partial charge-transfer solute – solvent interactions in absorption spectra of aromatic hydrocarbons in aqueous and alcoholic solutions I.A. Ar’ev*, N.I. Lebovka, E.A. Solovieva Institute of Biocolloid Chemistry, Ukraine, 03142, Kyiv, bulv. Vernadskogo, 42 A method for study of charge-transfer interactions between solute molecules and solvent based on the comparison of the ratios of spectral shifts of different electronic transitions in solute molecules in chemically inert solvent is proposed. The method is applicable to molecules that do not change their dipole moment on excitation. As an example, a presence of charge transfer interactions in higher electronic states of aromatic hydrocarbons (benzene, phenanthrene, and naphthalene) dissolved in water and alcohols was demonstrated. Keywords: partial electron transfer; spectral shifts; high energy states 1. Introduction Many of chemical reactions pass through an intermediate excited complex, or the exciplex stage [1-3]. In a solute-solvent system, the electronic interactions of various electronically excited states of the solute and solvent molecules may be also substantial. A very important question is to find out how strong is the interaction between the electronic systems of the solute and the solvent. In this work, a useful method for detection of such charge transfer interactions is proposed. The method lies in comparison of the ratios of spectral shifts of different electronic transitions of solute molecules in a chemically inert solvent and in the target solvent. As an example, a presence of charge transfer interactions in higher electronic states of aromatic hydrocarbons (benzene, phenanthrene, and naphthalene) dissolved in water and alcohols was demonstrated.
    [Show full text]
  • Optimized Atomic Partial Charges and Radii Defined by Radical Voronoi
    molecules Article Optimized Atomic Partial Charges and Radii Defined by Radical Voronoi Tessellation of Bulk Phase Simulations Martin Brehm * and Martin Thomas Institut für Chemie, Martin-Luther-Universität Halle–Wittenberg, von-Danckelmann-Platz 4, D-06120 Halle (Saale), Germany * Correspondence: [email protected] Abstract: We present a novel method for the computation of well-defined optimized atomic partial charges and radii from the total electron density. Our method is based on a two-step radical Voronoi tessellation of the (possibly periodic) system and subsequent integration of the total electron density within each Voronoi cell. First, the total electron density is partitioned into the contributions of each molecule, and subsequently the electron density within each molecule is assigned to the individual atoms using a second set of atomic radii for the radical Voronoi tessellation. The radii are optimized on-the-fly to minimize the fluctuation (variance) of molecular and atomic charges. Therefore, our method is completely free of empirical parameters. As a by-product, two sets of optimized atomic radii are produced in each run, which take into account many specific properties of the system investigated. The application of an on-the-fly interpolation scheme reduces discretization noise in the Voronoi integration. The approach is particularly well suited for the calculation of partial charges in periodic bulk phase systems. We apply the method to five exemplary liquid phase simulations and show how the optimized charges can help to understand the interactions in the systems. Well-known effects such as reduced ion charges below unity in ionic liquid systems are correctly predicted without Citation: Brehm, M.; Thomas, M.
    [Show full text]
  • Electron Paramagnetic Resonance of Radicals and Metal Complexes
    PL -- PL9700944 Warsaw, 9-13 September 1996 ELECTRON PARAMAGNETIC RESONANCE OF RADICALS AND METAL COMPLEXES 2nd International Conference of the Polish EPR Association INSTITUTE OF NUCLEAR CHEMISTRY AND TECHNOLOGY UNIVERSITY OF WARSAW 28*12 ORGANIZING COMMITTEE Institute of Nuclear Chemistry and Technology Prof. Andrzej G. Chmielewski, Ph.D., D.Sc. Assoc. Prof. Hanna B. Ambroz, Ph.D., D.Sc. Assoc. Prof. JacekMichalik, Ph.D., D.Sc. Dr Zbigniew Zimek University of Warsaw Prof. Zbigniew Kqcki, Ph.D., D.Sc. ADDRESS OF ORGANIZING COMMITTEE Institute of Nuclear Chemistry and Technology, Dorodna 16,03-195 Warsaw, Poland phone: (0-4822) 11 23 47; telex: 813027 ichtj pi; fax: (0-4822) 1115 32; e-mail: [email protected] Abstracts are published in the form as received from the Authors SPONSORS The organizers would like to thank the following sponsors for their financial support: » State Committee of Scientific Research » Stiftung fur Deutsch-Polnische Zusammenarbeit » National Atomic Energy Agency, Warsaw, Poland » Committee of Chemistry, Polish Academy of Sciences, Warsaw, Poland » Committee of Physics, Polish Academy of Sciences, Poznan, Poland » The British Council, Warsaw, Poland » CIECH S.A. » ELEKTRIM S.A. » Bruker Analytische Messtechnik, Div. ESR/MINISPEC, Germany - 3 - CONTENTS CONFERENCE PROGRAM 9 LECTURES 15 RADICALS IN DNA AS SEEN BY ESR SPECTROSCOPY M.C.R. Symons 17 ELECTRON AND HOLE TRANSFER WITHIN DNA AND ITS HYDRATION LAYER M.D. Sevilla, D. Becker, Y. Razskazovskii 18 MODELS FOR PHOTOSYNTHETIC REACTION CENTER: STEADY STATE AND TIME RESOLVED EPR SPECTROSCOPY H. Kurreck, G. Elger, M. Fuhs, A. Wiehe, J. von Gersdorff, P. Tian 19 FREE RADICAL FORMATION IN RED BLOOD CELL COMPONENTS UPON PARAQUAT TREATMENT K.
    [Show full text]
  • Thomas W. Shattuck Department of Chemistry Colby College Waterville, Maine 04901 2
    Thomas W. Shattuck Department of Chemistry Colby College Waterville, Maine 04901 2 Colby College Molecular Mechanics Tutorial Introduction September 2008 Thomas W. Shattuck Department of Chemistry Colby College Waterville, Maine 04901 Please, feel free to use this tutorial in any way you wish , provided that you acknowledge the source and you notify us of your usage. Please notify us by e-mail at [email protected] or at the above address. This material is supplied as is, with no guarantee of correctness. If you find any errors, please send us a note. 3 Table of Contents Introduction to Molecular Mechanics Section 1: Steric Energy Section 2: Enthalpy of Formation Section 3: Comparing Steric Energies Section 4: Energy Minimization Section 5: Molecular Dynamics Section 6: Distance Geometry and 2D to 3D Model Conversion Section 7: Free Energy Perturbation Theory, FEP Section 8: Continuum Solvation Electrostatics Section 9: Normal Mode Analysis Section 10: Partial Atomic Charges An accompanying manual with exercises specific to MOE is available at: http://www.colby.edu/chemistry/CompChem/MOEtutor.pdf 4 Introduction to Molecular Mechanics Section 1 Summary The goal of molecular mechanics is to predict the detailed structure and physical properties of molecules. Examples of physical properties that can be calculated include enthalpies of formation, entropies, dipole moments, and strain energies. Molecular mechanics calculates the energy of a molecule and then adjusts the energy through changes in bond lengths and angles to obtain the minimum energy structure. Steric Energy A molecule can possess different kinds of energy such as bond and thermal energy. Molecular mechanics calculates the steric energy of a molecule--the energy due to the geometry or conformation of a molecule.
    [Show full text]
  • Improved Partial Charge Models in Siliceous Zeolites for the Simulation of Adsorption and Identification of Catalytic Sites
    UNLV Theses, Dissertations, Professional Papers, and Capstones August 2017 Improved Partial Charge Models in Siliceous Zeolites for the Simulation of Adsorption and Identification of Catalytic Sites Jarod J. Wolffis University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/thesesdissertations Part of the Inorganic Chemistry Commons, and the Quantum Physics Commons Repository Citation Wolffis, Jarod J., "Improved Partial Charge Models in Siliceous Zeolites for the Simulation of Adsorption and Identification of Catalytic Sites" (2017). UNLV Theses, Dissertations, Professional Papers, and Capstones. 3107. http://dx.doi.org/10.34917/11156845 This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in UNLV Theses, Dissertations, Professional Papers, and Capstones by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. IMPROVED PARTIAL CHARGE MODELS IN SILICEOUS ZEOLITES FOR THE SIMULATION OF ADSORPTION AND IDENTIFICATION OF CATALYTIC SITES By Jarod J. Wolffis Bachelor of Science – Chemistry University of Nevada Las Vegas 2013 A thesis submitted in partial fulfillment of the requirements for the Master of Science – Chemistry Department of Chemistry and Biochemistry College of Sciences The Graduate College University of Nevada, Las Vegas August 2017 Thesis Approval The Graduate College The University of Nevada, Las Vegas July 27, 2017 This thesis prepared by Jarod J.
    [Show full text]
  • Ws 3- Dipole Moment.Docx Page 1 of 3 Alscher
    WS 3:Dipole Moment1 In a hydrogen molecule, each nucleus has a unit charge of +1. Electrons are attracted equally to both nuclei. The result is a symmetrical orbital in which electron density near one nucleus is the same as the electron density near the other nucleus. Although a more complicated atom, when fluorine bonds to itself, a similar situation occurs for the formation of the fluorine molecule. In the chemical bond between the two identical atoms, the bonding electrons are shared equally. In contrast to a symmetrical molecule, an unsymmetrical molecule has unsymmetrical attractive forces. The bonding electrons are attracted by different nuclear charges. On the hydrogen atom, we see a +1 nucleus, while on F, there is a +9 nucleus, screened by electrons in 1s, 2s, and 2p orbitals. We have already discussed the shielding abilities of s and p orbitals, so we know the bonding pair don’t feel a full +9 charge, but they feel a positive charge greater than the charge on the hydrogen atom. Unsymmetrical attractive forces lead to an unsymmetrical distribution of electrons. The electron density is concentrated closest to the nucleus with the larger Zeff. The bond is polarized because of this shift in density. The hydrogen is a little positive because it has lost some electron density and the fluorine is more negative because it has gained electron density. This is a polar-covalent bond. Polar covalent bonds are said to arise when there is an electronegativity difference between atoms. This difference is sufficient to cause partial charges on the bonding atoms, but not so large that it produces an ionic bond.
    [Show full text]
  • Electronic Structure and Partial Charge Distribution of Doxorubicin Under Different Molecular Environments
    ELECTRONIC STRUCTURE AND PARTIAL CHARGE DISTRIBUTION OF DOXORUBICIN UNDER DIFFERENT MOLECULAR ENVIRONMENTS A THESIS IN Physics Presented to the Faculty of the University of Missouri-Kansas City in partial fulfillment of the requirements for the degree MASTER IN SCIENCE by LOKENDRA POUDEL B.Sc., Tribhuvan University, Kathmandu, Nepal, 2003 M.Sc., Tribhuvan University, Kathmandu, Nepal, 2005 Kansas City, Missouri 2014 c 2014 LOKENDRA POUDEL ALL RIGHTS RESERVED ELECTRONIC STRUCTURE AND PARTIAL CHARGE DISTRIBUTION OF DOXORUBICIN UNDER DIFFERENT MOLECULAR ENVIRONMENTS Lokendra Poudel, Candidate for the Master in Science Degree University of Missouri-Kansas City, 2014 ABSTRACT Doxorubicin (trade name Adriamycin, abbreviated DOX) is a well-known an- thracyclic chemotherapeutic used in treating a variety of cancers including acute leukemia, lymphoma, multiple myeloma, and a range of stomach, lung, bladder, bone, breast, and ovarian cancers. The purpose of the present work is to study electronic structure, partial charge distribution and interaction energy of DOX under different environments. It provides a framework for better understanding of bioactivity of DOX with DNA. While in this work, we focus on DOX−DNA interactions; the obtained knowledge could be translated to other drug−target interactions or biomolecular in- teractions. The electronic structure and partial charge distribution of DOX in three different molecular environments: isolated, solvated, and intercalated into a DNA complex, were studied by first principles density functional methods. It is shown that the ad- dition of solvating water molecules to DOX and the proximity and interaction with DNA has a significant impact on the electronic structure as well as the partial charge distribution. The calculated total partial charges for DOX in the three models are 0.0, +0.123 and -0.06 electrons for the isolated, solvated, and intercalated state, re- spectively.
    [Show full text]
  • 003-Chapter from Chemistry 3 (ES)
    Chapter from Chemistry 3 Chemical bonds. Chemical reactions. Chemical equation Chemical Bonds. Chemical reactions. Chemical equations. Balanced Chemical Equations. Stoichiometry Nomenclature of inorganic compounds. Ionic bond The base of ionic bond is the transfer of electrons and the formation of ions, cations - positive charged and anions - negatively charged particles. The typical model is structure of NaCl. Positively charged Na (Na +) is attracted by negatively charged Cl (Cl -). Na + results from electroneutral atom (parent atom) of sodium by loss of 1 electron, Cl - by admission of 1 electron. Ionic bonds are the bonds of oppositely charged ions. They are very strong, and crystals of ionic compounds are rigid up to high temperatures, after which the crystals melt. The force of attraction that Na + has for a negative charge radiates equally in all directions, like light from a light bulb. Many common substances are ionic compounds (recall from your study at the Secondary school that chemical and physical properties of neutral atoms and ions of these atoms are different, for example Na and Na+). Every fluid in every living thing, whether plant or animal, contains dissolved ions. At the molecular level of life, the shapes and sizes of ions and molecules are as important as anything else about them. Sodium ions and chloride ions have quite different sizes. In general, when a cation forms from a metal atom, the remaining electron cloud shrinks because the positive nuclear charge now numerically exceeds the negative charge of the electron cloud. The excess positive charge in the cation pulls the electron cloud more tightly inward, so metal ions are always smaller than their parent atoms.
    [Show full text]