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Jha KK, Gruza B, Sypko A, Kumar P, Chodkiewicz ML, Dominiak PM. Multipolar Atom Types from Theory and Statistical Clustering (MATTS) Data Bank: Restructurization and Extension of UBDB. J Chem Inf Model 2022; 62:3752-3765. [PMID: 35943747 PMCID: PMC9400107 DOI: 10.1021/acs.jcim.2c00144] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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A fast and accurate operational model of electron density
is crucial
in many scientific disciplines including crystallography, molecular
biology, pharmaceutical, and structural chemistry. In quantum crystallography,
the aspherical refinement of crystal structures is becoming increasingly
popular because of its accurate description in terms of physically
meaningful properties. The transferable aspherical atom model (TAAM)
is quick and precise, though it requires a robust algorithm for atom
typing and coverage of the most popular atom types present in small
organic molecules. Thus, the University at Buffalo Databank (UBDB)
has been renamed to the Multipolar Atom Types from Theory and Statistical
clustering (MATTS) data bank, broadened, restructured, and implemented
into the software DiSCaMB with 651 atom types obtained from 2316 small-molecule
crystal structures containing C, H, N, O, P, S, F, Cl, and Br atoms.
MATTS2021 data bank now covers most of the small molecules, peptides,
RNA, DNA, and some frequently occurring cations and anions in biological,
pharmaceutical, and organic materials, including the majority of known
crystal structures composed of the above elements. The multipole model
parameters (Pval, κ, κ′, Plm) obtained for different
atom types were greatly influenced by neighboring atom types, hybridization,
geometrical strain in the ring system, and charges on the molecule.
Contrary to previous findings, the atoms showing variable oxidation
states and ions deviate from the linear dependence of monopole-derived
charges on the expansion–contraction κ parameter.
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Affiliation(s)
- Kunal Kumar Jha
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, ul. Żwirki i Wigury 101, 02-089 Warszawa, Poland
| | - Barbara Gruza
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, ul. Żwirki i Wigury 101, 02-089 Warszawa, Poland
| | - Aleksandra Sypko
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, ul. Żwirki i Wigury 101, 02-089 Warszawa, Poland
| | - Prashant Kumar
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, ul. Żwirki i Wigury 101, 02-089 Warszawa, Poland
| | - Michał Leszek Chodkiewicz
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, ul. Żwirki i Wigury 101, 02-089 Warszawa, Poland
| | - Paulina Maria Dominiak
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, ul. Żwirki i Wigury 101, 02-089 Warszawa, Poland
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Dittrich B. Is there a future for topological analysis in experimental charge-density research? ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE CRYSTAL ENGINEERING AND MATERIALS 2017; 73:325-329. [DOI: 10.1107/s2052520617006680] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 05/03/2017] [Indexed: 11/11/2022]
Abstract
Topological analysis using Bader and co-worker'sAtoms in Moleculestheory has seen many applications in theoretical chemistry and experimental charge-density research. A brief overview of successful early developments, establishing topological analysis as a research tool for characterizing intramolecular chemical bonding, is provided. A lack of vision in many `descriptive but not predictive' subsequent studies is discussed. Limitations of topology for providing accurate energetic estimates of intermolecular interaction energies are put into perspective. It is recommended that topological analyses of well understood bonding situations are phased out and are only reported for unusual bonding. Descriptive studies of intermolecular interactions should have a clear research focus.
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Dittrich B, Matta CF. Contributions of charge-density research to medicinal chemistry. IUCRJ 2014; 1:457-69. [PMID: 25485126 PMCID: PMC4224464 DOI: 10.1107/s2052252514018867] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 08/20/2014] [Indexed: 06/04/2023]
Abstract
This article reviews efforts in accurate experimental charge-density studies with relevance to medicinal chemistry. Initially, classical charge-density studies that measure electron density distribution via least-squares refinement of aspherical-atom population parameters are summarized. Next, interaction density is discussed as an idealized situation resembling drug-receptor interactions. Scattering-factor databases play an increasing role in charge-density research, and they can be applied both to small-molecule and macromolecular structures in refinement and analysis; software development facilitates their use. Therefore combining both of these complementary branches of X-ray crystallography is recommended, and examples are given where such a combination already proved useful. On the side of the experiment, new pixel detectors are allowing rapid measurements, thereby enabling both high-throughput small-molecule studies and macromolecular structure determination to higher resolutions. Currently, the most ambitious studies compute intermolecular interaction energies of drug-receptor complexes, and it is recommended that future studies benefit from recent method developments. Selected new developments in theoretical charge-density studies are discussed with emphasis on its symbiotic relation to crystallography.
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Affiliation(s)
- Birger Dittrich
- Institut für Anorganische und Angewandte Chemie, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Chérif F. Matta
- Department of Chemistry and Physics, Mount Saint Vincent University, Halifax, Nova Scotia B3M 2J6, Canada
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4J3M, Canada
- Department of Chemistry, Saint Mary’s University, Halifax, Nova Scotia B3H 3C3, Canada
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4
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Domagała S, Fournier B, Liebschner D, Guillot B, Jelsch C. An improved experimental databank of transferable multipolar atom models--ELMAM2. Construction details and applications. Acta Crystallogr A 2012; 68:337-51. [PMID: 22514066 DOI: 10.1107/s0108767312008197] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 02/23/2012] [Indexed: 11/10/2022] Open
Abstract
ELMAM2 is a generalized and improved library of experimentally derived multipolar atom types. The previously published ELMAM database is restricted mostly to protein atoms. The current database is extended to common functional groups encountered in organic molecules and is based on optimized local axes systems taking into account the local pseudosymmetry of the molecular fragment. In this approach, the symmetry-restricted multipoles have zero populations, while others take generally significant values. The various applications of the database are described. The deformation electron densities, electrostatic potentials and interaction energies calculated for several tripeptides and aromatic molecules are calculated using ELMAM2 electron-density parameters and compared with the former ELMAM database and density functional theory calculations.
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Affiliation(s)
- Sławomir Domagała
- Laboratoire de Cristallographie, Résonance Magnétique et Modélisations (CRM2), CNRS, UMR 7036, Institut Jean Barriol, Faculté des Sciences et Technologies, Nancy Université, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex, France
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Domagała S, Munshi P, Ahmed M, Guillot B, Jelsch C. Structural analysis and multipole modelling of quercetin monohydrate – a quantitative and comparative study. ACTA CRYSTALLOGRAPHICA SECTION B: STRUCTURAL SCIENCE 2010; 67:63-78. [DOI: 10.1107/s0108768110041996] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 10/16/2010] [Indexed: 11/11/2022]
Abstract
The multipolar atom model, constructed by transferring the charge-density parameters from an experimental or theoretical database, is considered to be an easy replacement of the widely used independent atom model. The present study on a new crystal structure of quercetin monohydrate [2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-chromen-4-one monohydrate], a plant flavonoid, determined by X-ray diffraction, demonstrates that the transferred multipolar atom model approach greatly improves several factors: the accuracy of atomic positions and the magnitudes of atomic displacement parameters, the residual electron densities and the crystallographic figures of merit. The charge-density features, topological analysis and electrostatic interaction energies obtained from the multipole models based on experimental database transfer and periodic quantum mechanical calculations are found to compare well. This quantitative and comparative study shows that in the absence of high-resolution diffraction data, the database transfer approach can be applied to the multipolar electron density features very accurately.
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Meindl K, Henn J, Kocher N, Leusser D, Zachariasse KA, Sheldrick GM, Koritsanszky T, Stalke D. Experimental Charge Density Studies of Disordered N-Phenylpyrrole and N-(4-Fluorophenyl)pyrrole. J Phys Chem A 2009; 113:9684-91. [DOI: 10.1021/jp9026157] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Kathrin Meindl
- Institut für Anorganische Chemie, Georg-August-Universität
Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany,
Spektroskopie und Photochemische Kinetik, Max-Planck-Institut für
Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany,
and Department of Chemistry, Middle Tennessee State University, MTSU
Box 0395, 1301 East Main Street, Murfreesboro, Tennessee 37132
| | - Julian Henn
- Institut für Anorganische Chemie, Georg-August-Universität
Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany,
Spektroskopie und Photochemische Kinetik, Max-Planck-Institut für
Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany,
and Department of Chemistry, Middle Tennessee State University, MTSU
Box 0395, 1301 East Main Street, Murfreesboro, Tennessee 37132
| | - Nikolaus Kocher
- Institut für Anorganische Chemie, Georg-August-Universität
Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany,
Spektroskopie und Photochemische Kinetik, Max-Planck-Institut für
Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany,
and Department of Chemistry, Middle Tennessee State University, MTSU
Box 0395, 1301 East Main Street, Murfreesboro, Tennessee 37132
| | - Dirk Leusser
- Institut für Anorganische Chemie, Georg-August-Universität
Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany,
Spektroskopie und Photochemische Kinetik, Max-Planck-Institut für
Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany,
and Department of Chemistry, Middle Tennessee State University, MTSU
Box 0395, 1301 East Main Street, Murfreesboro, Tennessee 37132
| | - Klaas A. Zachariasse
- Institut für Anorganische Chemie, Georg-August-Universität
Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany,
Spektroskopie und Photochemische Kinetik, Max-Planck-Institut für
Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany,
and Department of Chemistry, Middle Tennessee State University, MTSU
Box 0395, 1301 East Main Street, Murfreesboro, Tennessee 37132
| | - George M. Sheldrick
- Institut für Anorganische Chemie, Georg-August-Universität
Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany,
Spektroskopie und Photochemische Kinetik, Max-Planck-Institut für
Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany,
and Department of Chemistry, Middle Tennessee State University, MTSU
Box 0395, 1301 East Main Street, Murfreesboro, Tennessee 37132
| | - Tibor Koritsanszky
- Institut für Anorganische Chemie, Georg-August-Universität
Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany,
Spektroskopie und Photochemische Kinetik, Max-Planck-Institut für
Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany,
and Department of Chemistry, Middle Tennessee State University, MTSU
Box 0395, 1301 East Main Street, Murfreesboro, Tennessee 37132
| | - Dietmar Stalke
- Institut für Anorganische Chemie, Georg-August-Universität
Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany,
Spektroskopie und Photochemische Kinetik, Max-Planck-Institut für
Biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany,
and Department of Chemistry, Middle Tennessee State University, MTSU
Box 0395, 1301 East Main Street, Murfreesboro, Tennessee 37132
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Soave R, Barzaghi M, Destro R. Progress in the understanding of drug-receptor interactions, part 2: experimental and theoretical electrostatic moments and interaction energies of an angiotensin II receptor antagonist (C30H30N6(O)3S). Chemistry 2007; 13:6942-56. [PMID: 17539033 DOI: 10.1002/chem.200601516] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A combined experimental and theoretical charge density study of an angiotensin II receptor antagonist (1) is presented focusing on electrostatic properties such as atomic charges, molecular electric moments up to the fourth rank and energies of the intermolecular interactions, to gain an insight into the physical nature of the drug-receptor interaction. Electrostatic properties were derived from both the experimental electron density (multipole refinement of X-ray data collected at T=17 K) and the ab initio wavefunction (single molecule and fully periodic calculations at the DFT level). The relevance of SO and SN intramolecular interactions on the activity of 1 is highlighted by using both the crystal and gas-phase geometries and their electrostatic nature is documented by means of QTAIM atomic charges. The derived electrostatic properties are consistent with a nearly spherical electron density distribution, characterised by an intermingling of electropositive and -negative zones rather than by a unique electrophilic region opposed to a nucleophilic area. This makes the first molecular moment scarcely significant and ill-determined, whereas the second moment is large, significant and highly reliable. A comparison between experimental and theoretical components of the third electric moment shows a few discrepancies, whereas the agreement for the fourth electric moment is excellent. The most favourable intermolecular bond is show to be an NHN hydrogen bond with an energy of about 50 kJ mol(-1). Key pharmacophoric features responsible for attractive electrostatic interactions include CHX hydrogen bonds. It is shown that methyl and methylene groups, known to be essential for the biological activity of the drug, provide a significant energetic contribution to the total binding energy. Dispersive interactions are important at the thiophene and at both the phenyl fragments. The experimental estimates of the electrostatic contribution to the intermolecular interaction energies of six molecular pairs, obtained by a new model proposed by Spackman, predict the correct relative electrostatic energies with no exceptions.
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Affiliation(s)
- Raffaella Soave
- CNR-ISTM, Istituto di Scienze e Tecnologie Molecolari, Via Golgi 19, 20133 Milano, Italy.
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Munshi P, Cameron E, Row TNG, Ferrara JD, Cameron TS. Investigation of Inter-Ion Interactions in N,N,N',N'-Tetramethylethylenediammonium Dithiocyanate via Experimental and Theoretical Charge Density Studies. J Phys Chem A 2007; 111:7888-97. [PMID: 17658769 DOI: 10.1021/jp068554x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The crystal structure of the N,N,N',N'-tetramethylethylenediammonium dithiocyanate salt has been examined by experimental charge density studies from high-resolution X-ray diffraction data. The corresponding results are compared with multipole refinements, using theoretical structure factors obtained from a periodic density functional theory calculation at the B3LYP level with a 6-31G(**) basis set. The salt crystallizes in space group P and contains only a single ion pair with an inversion center in the cation. The salt has thus one unique classical N+-H...(NCS)(-) hydrogen bond but also has six other weaker interactions: four C-H...S, one C-H...N, and one C-H...C(pi). The nature of all these interactions has been examined topologically using Bader's quantum theory of "atoms in molecules" and all eight of the Koch-Popelier criteria. The experimental and theoretical approaches agree well and both show that the inter-ion interactions, even in this simplest of systems, play an integrated and complex role in the packing of the ions in the crystal. Electrostatic potential maps are derived from experimental charge densities. This is the first time such a system has been examined in detail by these methods.
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Affiliation(s)
- Parthapratim Munshi
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
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9
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Munshi P, Guru Row TN. Evaluation of weak intermolecular interactions in molecular crystalsviaexperimental and theoretical charge densities. CRYSTALLOGR REV 2005. [DOI: 10.1080/08893110500245899] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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10
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Matta CF. Application of the quantum theory of atoms in molecules to selected physico-chemical and biophysical problems: focus on correlation with experiment. J Comput Chem 2003; 24:453-63. [PMID: 12594788 DOI: 10.1002/jcc.10208] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This article reviews how the quantum theory of atoms in molecules (QTAIM) can be used to predict experimental physico-chemical properties of molecules of biologic interest: the amino acids, the polycyclic aromatic hydrocarbons (PAH), and the opiates, for example, morphine and PEO. The predicted experimental properties are as diverse as the partial molar volumes, the free energies of hydration, the second code-letter in the genetic code, the resonance energies, and the proton spin-spin coupling constants. Recent examples of the utilization of QTAIM to construct excellent statistical models (with squared correlation coefficients (r(2)) > 0.9) correlating properties of the electron density and of the pair density to experiment are reviewed. Some new results on the solvent effects on electron delocalization are also presented.
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Affiliation(s)
- Chérif F Matta
- Lash Miller Chemical Laboratories, Chemistry Department, University of Toronto, 80 Saint George Street, Toronto, Ontario, Canada M5S 3H6.
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Matta CF, Bader RFW. Atoms-in-molecules study of the genetically encoded amino acids. II. Computational study of molecular geometries. Proteins 2002; 48:519-38. [PMID: 12112676 DOI: 10.1002/prot.10170] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The geometries of the 20 genetically encoded amino acids were optimized at the restricted Hartree-Fock level of theory using the 6-31+G* basis set. A detailed comparison showed the calculated geometries to be in excellent agreement with those determined by X-ray crystallography. The study demonstrated that the geometric parameters for the main-chain group and for the bonds and common functional groups of the side-chains exhibit a high degree of transferability among the members of this set of molecules. This geometric transferability is a necessary prerequisite for the corresponding transferability of their electron density distributions and hence of their bond and atomic properties. The transferability of the electron distributions will be demonstrated and exploited in the following paper of this series, which uses the topology of the electron density to define an atom within the quantum theory of atoms in molecules. Particular features of the geometries of the amino acids are discussed. It has been shown, for example, how the apparent anomaly of the Calpha-N bond length in a peptide being shorter than in the charged species Calpha-NH3+ is resolved when the charge separation is gauged by the differences in the charges of the Calpha and N atoms as opposed to the use of formal charges. A compilation of literature sources on experimental geometries covering each member of the 20 amino acids is presented. A set of rules for labeling the atoms and bonds, complementing the generally accepted IUPAC-IUB rules, is proposed to uniquely identify every atom and bond in the amino acids.
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Affiliation(s)
- Chérif F Matta
- Lash Miller Chemical Laboratories, Chemistry Department, University of Toronto, Toronto, Canada
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Knop O, Rankin KN, Boyd RJ. Coming to Grips with N−H···N Bonds. 1. Distance Relationships and Electron Density at the Bond Critical Point. J Phys Chem A 2001. [DOI: 10.1021/jp0106348] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Osvald Knop
- Department of Chemistry, Dalhousie University, Halifax NS, Canada B3H 4J3
| | - Kathryn N. Rankin
- Department of Chemistry, Dalhousie University, Halifax NS, Canada B3H 4J3
| | - Russell J. Boyd
- Department of Chemistry, Dalhousie University, Halifax NS, Canada B3H 4J3
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Affiliation(s)
- T S Koritsanszky
- Department of Chemistry, University of the Witwatersrand, WITS 2050, Johannesburg, South Africa
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Srinivasa Gopalan R, Kulkarni G, Rao C. An Experimental Charge Density Study of the Effect of the Noncentric Crystal Field on the Molecular Properties of Organic NLO Materials. Chemphyschem 2000; 1:127-35. [DOI: 10.1002/1439-7641(20001103)1:3<127::aid-cphc127>3.0.co;2-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2000] [Indexed: 11/11/2022]
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Matta CF, Bader RF. An atoms-in-molecules study of the genetically-encoded amino acids: I. Effects of conformation and of tautomerization on geometric, atomic, and bond properties. Proteins 2000; 40:310-29. [PMID: 10842344 DOI: 10.1002/(sici)1097-0134(20000801)40:2<310::aid-prot110>3.0.co;2-a] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The theory of Atoms-In-Molecules (AIM) is a partitioning of the real space of a molecule into disjoint atomic constituents as determined by the topology of the electron density, rho(r). This theory identifies an atom in a molecule with a quantum mechanical open system and, consequently, all of the atom's properties are unambiguously defined. AIM recovers the basic empirical cornerstone of chemistry: that atoms and functional groups possess characteristic and additive properties that in many cases exhibit a remarkable transferability between different molecules. As a result, the theory enables the theoretical synthesis of a large molecule and the prediction of its properties by joining fragments that are predetermined as open systems. The present article is the first of a series (in preparation) that explore this possibility for polypeptides by determining the transferability of the building blocks: the amino acid residues. Transferability of group properties requires transferability of the electron density rho(r), which in turn requires the transferability of the geometric parameters. This article demonstrates that these parameters are conformation-insensitive for a representative amino acid, leucine, and that the atomic and bond properties exhibit a corresponding transferability. The effects of hydrogen bonding are determined and a set of geometrical conditions for the occurrence of such bonding is identified. The effects of transforming neutral leucine into its zwitter-ionic form on its atomic and bond properties are shown to be localized primarily to the sites of ionization.
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Affiliation(s)
- C F Matta
- Chemistry Department, McMaster University, Hamilton, Ontario, Canada
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Wang SG, Schwarz W. Über die Bindung zwischen abgeschlossenen Schalen, über Löcher in d-Schalen, über polare Kovalenz und über die Abbildung von Orbitalen: der Fall Cuprit. Angew Chem Int Ed Engl 2000. [DOI: 10.1002/(sici)1521-3757(20000515)112:10<1827::aid-ange1827>3.0.co;2-k] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Destro R, Roversi P, Barzaghi M, Marsh RE. Experimental Charge Density of α-Glycine at 23 K. J Phys Chem A 2000. [DOI: 10.1021/jp993505o] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Riccardo Destro
- Contribution from the Beckman Institute, California Institute of Technology, Pasadena, California 91125, and Department of Physical Chemistry and CSRSRC Center of the CNR, University of Milan, 20133 Milano, Italy
| | - Pietro Roversi
- Contribution from the Beckman Institute, California Institute of Technology, Pasadena, California 91125, and Department of Physical Chemistry and CSRSRC Center of the CNR, University of Milan, 20133 Milano, Italy
| | - Mario Barzaghi
- Contribution from the Beckman Institute, California Institute of Technology, Pasadena, California 91125, and Department of Physical Chemistry and CSRSRC Center of the CNR, University of Milan, 20133 Milano, Italy
| | - Richard E. Marsh
- Contribution from the Beckman Institute, California Institute of Technology, Pasadena, California 91125, and Department of Physical Chemistry and CSRSRC Center of the CNR, University of Milan, 20133 Milano, Italy
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Bader RFW, Heard GL. The mapping of the conditional pair density onto the electron density. J Chem Phys 1999. [DOI: 10.1063/1.480226] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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