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Sim E, Larkin J, Burke K, Bock CW. Testing the kinetic energy functional: Kinetic energy density as a density functional. J Chem Phys 2003. [DOI: 10.1063/1.1565316] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Bock CW, Markham GD, Katz AK, Glusker JP. The arrangement of first- and second-shell water molecules in trivalent aluminum complexes: results from density functional theory and structural crystallography. Inorg Chem 2003; 42:1538-48. [PMID: 12611521 DOI: 10.1021/ic020602e] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structural and energetic features of a variety of gas-phase aluminum ion hydrates containing up to 18 water molecules have been studied computationally using density functional theory. Comparisons are made with experimental data from neutron diffraction studies of aluminum-containing crystal structures listed in the Cambridge Structural Database. Computational studies indicate that the hexahydrated structure Al[H(2)O](6)(3+) (with symmetry T(h)()), in which all six water molecules are located in the innermost coordination shell, is lower in energy than that of Al[H(2)O](5)(3+).[H(2)O], where only five water molecules are in the inner shell and one water molecule is in the second shell. The analogous complex with four water molecules in the inner shell and two in the outer shell undergoes spontaneous proton transfer during the optimization to give [Al[H(2)O](2)[OH](2)](+).[H(3)O(+)](2), which is lower in energy than Al[H(2)O](6)(3+); this finding of H(3)O(+) is consistent with the acidity of concentrated Al(3+) solutions. Since, however, Al[H(2)O](6)(3+) is detected in solutions of Al(3+), additional water molecules are presumed to stabilize the hexa-aquo Al(3+) cation. Three models of a trivalent aluminum ion complex surrounded by a total of 18 water molecules arranged in a first shell containing 6 water molecules and a second shell of 12 water molecules are discussed. We find that a model with S(6) symmetry for which the Al[H(2)O](6)(3+) unit remains essentially octahedral and participates in an integrated hydrogen bonded network with the 12 outer-shell water molecules is lowest in energy. Interactions between the 12 second-shell water molecules and the trivalent aluminum ion in Al[H(2)O](6)(3+) do not appear to be sufficiently strong to orient the dipole moments of these second-shell water molecules toward the Al(3+) ion.
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Bock CW, Brendley WH, Hamann H, Bhat KL. Formation of bis (chloromethyl) ether in the vapor phase: a computational investigation. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s0166-1280(02)00577-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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30
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Bock CW, Trachtman M. Binding of the two-valence-electron metal ions Sc(+), Ti(2+), and V(3+) to the second-row hydrides BeH(2), BH(3), NH(3), OH(2), and FH: a computational study. Inorg Chem 2002; 41:4680-8. [PMID: 12206691 DOI: 10.1021/ic020216x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report results from a computational study of the binding in complexes formed from one of the transition-metal ions Sc(+), Ti(2+), or V(3+), each of which has two valence electrons outside an argon core, and one of the second-row hydrides FH, OH(2), NH(3), BH(3), or BeH(2). The complexes that involve the electron-rich ligands FH, OH(2), and NH(3) have strong ion-dipole components to their binding. There are large stabilization energies for sigma-interactions that transfer charge from occupied lone-pair natural bond orbitals on the F, O, or N atom of the (idealized) Lewis structure into empty non-Lewis orbitals on the metal ions; these interactions effectively increase electron density in the bonding region between the metal ion and liganded atom, and the metal ions in these complexes act in the capacity of Lewis acids. The complexes formed from the electron-poor hydrides BH(3) and BeH(2) consistently incorporate bridging hydrogen atoms to support binding, and there are large stabilization energies for interactions that transfer charge from the Be-H or B-H bonds into the region between the metal ion and liganded atom. The metal ions in Sc(+)-BeH(2), Ti(2+)-BeH(2), Ti(2+)-BH(3), and V(3+)-BH(3) act in the capacity of Lewis acids, whereas the scandium ion in Sc(+)-BH(3) acts as a Lewis base.
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Markham GD, Norrby PO, Bock CW. S-adenosylmethionine conformations in solution and in protein complexes: conformational influences of the sulfonium group. Biochemistry 2002; 41:7636-46. [PMID: 12056895 DOI: 10.1021/bi025682c] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
S-Adenosylmethionine (AdoMet) and other sulfonium ions play central roles in the metabolism of all organisms. The conformational preferences of AdoMet and two other biologically important sulfonium ions, S-methylmethionine and dimethylsulfonioproprionic acid, have been investigated by NMR and computational studies. Molecular mechanics parameters for the sulfonium center have been developed for the AMBER force field to permit analysis of NMR results and to enable comparison of the relative energies of the different conformations of AdoMet that have been found in crystal structures of complexes with proteins. S-Methylmethionine and S-dimethylsulfonioproprionate adopt a variety of conformations in aqueous solution; a conformation with an electrostatic interaction between the sulfonium sulfur and the carboxylate group is not noticeably favored, in contrast to the preferred conformation found by in vacuo calculations. Nuclear Overhauser effect measurements and computational results for AdoMet indicate a predominantly anti conformation about the glycosidic bond with a variety of conformations about the methionyl C(alpha)-C(beta) and C(beta)-C(gamma) bonds. An AdoMet conformation in which the positively charged sulfonium sulfur is near an electronegative oxygen in the ribose ring is common. Comparisons of NMR results for AdoMet with those for the uncharged S-adenosylhomocysteine and 5'-methylthioadenosine, and the anionic ATP, indicate that the solution conformations are not dictated mainly by molecular charge. In 20 reported structures of AdoMet.protein complexes, both anti and syn glycosidic torsional angles are found. The methionyl group typically adopts an extended conformation in complexes with enzymes that transfer the methyl group from the sulfonium center, but is more folded in complexes with proteins that do not catalyze reactions involving the sulfur and which can use the sulfonium sulfur solely as a binding site. The conformational energies of AdoMet in these crystal structures are comparable to those found for AdoMet in solution. The sulfonium sulfur is in van der Waals contact with a protein heteroatom in the structures of four proteins, which reflects an energetically favorable contact. Interactions of the sulfonium with aromatic rings are rarely observed.
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Bock CW, Trachtman M, Murphy C, Muschert B, Mains GJ. Ab initio molecular orbital study of boron, aluminum, gallium .mu.-hydrido-bridged hexahydrides. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100159a041] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Cremer D, Kraka E, Gauss J, Bock CW. Theoretical determination of molecular structure and conformation. 19. Configurational changes of bridged annulenes: inversion at an ether oxygen atom. J Am Chem Soc 2002. [DOI: 10.1021/ja00276a014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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34
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Dobbs KD, Trachtman M, Bock CW, Cowley AH. Gallane-arsine, H3Ga.cntdot.AsH3: prediction of a stable Ga-As bonded species. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100376a006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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35
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George P, Glusker JP, Bock CW. Ab initio study of protonated radical species that may be involved in the enzyme-coenzyme B12 catalyzed dehydration of 1,2-dihydroxyethane. J Am Chem Soc 2002. [DOI: 10.1021/ja00145a032] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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36
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George P, Bock CW, Glusker JP. Semiempirical and ab initio molecular orbital studies on the mechanism of the acid-catalyzed isomerization benzene oxide .fwdarw. phenol. 1. Structure of protonated benzene oxide. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100384a034] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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George P, Bock CW, Trachtman M. An ab initio study of the planar hydrogen maleate ion with full geometry optimization. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100234a002] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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38
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Markham GD, Bock CW. Interaction of the Sulfides CH3SCH3 and CH3SCH2CO2- with Water Molecules. An ab Initio Molecular Orbital Study. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100025a012] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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39
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Bock CW, Roberts C, O'Malley K, Trachtman M, Mains GJ. An ab initio molecular orbital study of the structures, stabilities, and spectra of tris[tetrahydroborato(1-)]boron, tris[tetrahydroborato(1-)]aluminum, and tris[tetrahydroaluminato(1-)]aluminum. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100191a026] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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40
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Bock CW, George P, Glusker JP. Ab initio molecular orbital studies on C2H5O+ and C2H4FO+: oxonium ion, carbocation, protonated aldehyde, and related transition-state structures. J Org Chem 2002. [DOI: 10.1021/jo00073a049] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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41
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Bock CW, Trachtman M. An ab initio molecular orbital study of the thermal decomposition mechanisms of ethylarsine and ethylgallane. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100199a040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Redington RL, Bock CW. MO study of singlets, triplets, and tunneling in tropolone. 1. Geometries, tunneling, and vibrations in the ground electronic state. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100178a011] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Cremer D, Schmidt T, Bock CW. Theoretical determination of molecular structure and conformation. 14. Is bicyclo[6.2.0]decapentaene aromatic or antiaromatic? J Org Chem 2002. [DOI: 10.1021/jo00215a018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Bock CW, Trachtman M. Ab initio molecular orbital study of the thermal decomposition of (CH3)HGa-AsH(CH3). ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100115a021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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De Mare GR, Panchenko YN, Bock CW. An MP2/6-31G*//MP2/6-31G* vibrational analysis of s-trans- and s-cis-acryloyl fluoride, CH2=CH-CF=O. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100056a008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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47
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48
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Bock CW, George P, Trachtman M. Comparative molecular orbital study of the singlet state of o-benzyne and molecules with similar structural elements. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j150652a005] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Borisenko KB, Bock CW, Hargittai I. Intramolecular Hydrogen Bonding and Molecular Geometry of 2-Nitrophenol from a Joint Gas-Phase Electron Diffraction and ab Initio Molecular Orbital Investigation. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100056a012] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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50
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Bock CW, Trachtman M, Mains GJ. Stability of substituted Lewis adducts of substituted gallanes and arsines. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100186a043] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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