The Experts below are selected from a list of 177 Experts worldwide ranked by ideXlab platform
Bruce M. Foxman - One of the best experts on this subject based on the ideXlab platform.
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The Structure and Solid State Reactivity of a Cocrystal of Propynoic Acid and 4-(1 -pyrrolidino)-pyridine. A Study of γ-Ray-Induced vs. Thermal Reactivity
Molecular Crystals and Liquid Crystals, 2006Co-Authors: Kraig A. Wheeler, Bruce M. FoxmanAbstract:Abstract Mixing Propynoic Acid and 4-(l-pyrrolidino)-pyridine in ethanol produces the salt 4-(l-pyrrolidino)-pyridinium propynoate (1) in high yield. An X-ray structure determination of 1 (Space Group P2I , Z=4) shows it to contain two independent cation-anion sets. Each set is interconnected by N-H-0 and C-H-O hydrogen bonds; there are no hydrogen bonds formed between the two sets. Each set contains an infinite array of short acetylene-acetylene contacts (3.57 and 3.74 A, respectively); despite this characteristic, the material does not polymerize upon exposure to 60Co γ-rays. Heating 1 at 125 °C for 23 hours converts it, in high yield, to a 19:1 mixture of (E and Z)-4-(l-pyrrolidino)-pyridinium-l-acrylate. To the best of our knowledge, this is the first example of the addition of a pyridine moiety to an acetylene in the solid state.
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Crystal and Molecular Structure of Ammonium trans-2-Butenoate, and a Preliminary Investigation of its Solid-State Reactivity
Molecular Crystals and Liquid Crystals, 2006Co-Authors: Lin Yang, Bruce M. FoxmanAbstract:Ammonium trans-2-butenoate, NH4(O2CCH=CHCH3) 5 crystallizes in a similar fashion to metal two-dimensional coordination polymers, and thus is a candidate for facile radiation-induced solid-state reactions. The tetrahedral coordination of the ammonium is an obvious consequence of hydrogen bonding, but the relatively long N…O distance (compared to a Group IA metal) leads to repeat distances along the bilayer of ca. 4.7 A˚ . Interlayer contacts appear to be suitable for a radiation-induced Michael addition to occur. However, as observed for other nonmetal salts (e.g., those of Propynoic Acid), the material is stable to γ-ray doses up to 336 kGy.
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Structure and γ-ray-induced solid-state polymerization of sodium propynoate : Influence of bilayer formation on solid-state reactivity
IEEE Journal of Solid-state Circuits, 2000Co-Authors: J. D. Jaufmann, C.b. Case, Robert B. Sandor, Bruce M. FoxmanAbstract:Abstract Sodium propynoate, Na(O2CC≡CH) 1, was synthesized from Propynoic Acid and sodium hydroxide in methanol solution. Irradiation of solid 1 with 60Co γ-rays (654 kGy dose) leads to an amorphous dark-colored acetylenic polymer in high yield. An X-ray structure determination of compound 1 shows that the sodium ion is five-coordinate, with a square-pyramidal geometry. The five-coordinate local moiety is part of an unusual two-dimensional polymer in the crystal bc plane. Crystal packing of the two-dimensional, solid-state polymers leads to a bilayer motif, and the relatively short metal–metal distance of 3.575 A promotes close packing of the organic tails with parallel acetylene moieties and a very short –C≡C–···–C≡C– contact of 3.29 A along the crystallographic b direction. Crystal data for 1: orthorhombic, space group Pna21, a=19.837(6), b=3.575(1), and c=5.232(1) A; V=371.0 A3; Z=4; R=0.0262; Rw=0.0327 for 427 data for which I>1.96σ(I).
Richard L. Redington - One of the best experts on this subject based on the ideXlab platform.
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Theoretical study of the ground‐state gas‐phase unimolecular decomposition channels of Propynoic Acid
International Journal of Quantum Chemistry, 2004Co-Authors: Edmund Moses N. Ndip, Manoj K. Shukla, Jerzy Leszczynski, Richard L. RedingtonAbstract:Theoretical studies have been carried out to elucidate the ground-state unimolecular decomposition channels for Propynoic Acid (PA) in the gas phase. In this paper we present details of mechanisms for the decarboxylation and decarbonylation channels of PA. The transformations of PA result in the formation of carbon dioxide and acetylene from the decarboxylation channel while carbon monoxide and hydroxyacetylene, ultimately the ketene, are formed from the decarbonylation pathway. Equilibrium structures and the principal transition states (TSs) for each pathway have been identified and characterized. The Gaussian 98 suite of programs and MOLDEN were used for computation and visualization. All computations of equilibrium and TS structures relevant to the two competing unimolecular decomposition channels (decarboxylation and decarbonylation) were performed with second-order Moller–Plesset (MP2) and Becke's three-parameter exchange functional and the gradient-corrected functional of Lee, Yang, and Paar (B3LYP) levels using the 6-31G(d,p), 6-311++G (d, p) and Dunning's correlation-consistent polarized valence basis set (aug-cc-pVDZ). The geometries were fully optimized and characterized as minima (0 imaginary frequencies) or first-order saddle points (1 imaginary frequency) by harmonic vibrational analysis at the MP2/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. All the calculations indicate that the lowest energy decomposition pathway for PA is decarboxylation. Decarboxylation of PA occurs most easily through a three-step mechanism: conversion of s-cis-HCCCO2H to s-trans-HCCCO2H, followed by a 1, 3-hydrogen migration of hydroxyl hydrogen, resulting in a four-center TS that decays easily to acetylene and carbon dioxide, with an activation barrier of 61.3–79.9 kcal/mol (average 65.67 kcal/mol). Decarbonylation, leading to hydroxyacetylene (and subsequently the ketene) and carbon monoxide, occurs easily via a direct (one-step) three-center TS. The direct (one-step) elimination of carbon monoxide from Propynoic Acid has a calculated average activation barrier of 67.9–81.7 kcal/mol (average, 74.1 kcal/mol). The decarboxylation pathway is shown to occur with a maximum exothermicity of 28 kcal/mol. On the contrary, the decarbonylation of PA is predicted to occur with an overall endothermicity of ≈29.2 kcal/mol for formation of hydroxyacetylene and carbon monoxide and an average exothermicity of −7.69 kcal/mol for formation of the ketene and carbon monoxide. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
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theoretical study of the ground state gas phase unimolecular decomposition channels of Propynoic Acid
International Journal of Quantum Chemistry, 2004Co-Authors: Edmund Moses N. Ndip, Manoj K. Shukla, Jerzy Leszczynski, Richard L. RedingtonAbstract:Theoretical studies have been carried out to elucidate the ground-state unimolecular decomposition channels for Propynoic Acid (PA) in the gas phase. In this paper we present details of mechanisms for the decarboxylation and decarbonylation channels of PA. The transformations of PA result in the formation of carbon dioxide and acetylene from the decarboxylation channel while carbon monoxide and hydroxyacetylene, ultimately the ketene, are formed from the decarbonylation pathway. Equilibrium structures and the principal transition states (TSs) for each pathway have been identified and characterized. The Gaussian 98 suite of programs and MOLDEN were used for computation and visualization. All computations of equilibrium and TS structures relevant to the two competing unimolecular decomposition channels (decarboxylation and decarbonylation) were performed with second-order Moller–Plesset (MP2) and Becke's three-parameter exchange functional and the gradient-corrected functional of Lee, Yang, and Paar (B3LYP) levels using the 6-31G(d,p), 6-311++G (d, p) and Dunning's correlation-consistent polarized valence basis set (aug-cc-pVDZ). The geometries were fully optimized and characterized as minima (0 imaginary frequencies) or first-order saddle points (1 imaginary frequency) by harmonic vibrational analysis at the MP2/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. All the calculations indicate that the lowest energy decomposition pathway for PA is decarboxylation. Decarboxylation of PA occurs most easily through a three-step mechanism: conversion of s-cis-HCCCO2H to s-trans-HCCCO2H, followed by a 1, 3-hydrogen migration of hydroxyl hydrogen, resulting in a four-center TS that decays easily to acetylene and carbon dioxide, with an activation barrier of 61.3–79.9 kcal/mol (average 65.67 kcal/mol). Decarbonylation, leading to hydroxyacetylene (and subsequently the ketene) and carbon monoxide, occurs easily via a direct (one-step) three-center TS. The direct (one-step) elimination of carbon monoxide from Propynoic Acid has a calculated average activation barrier of 67.9–81.7 kcal/mol (average, 74.1 kcal/mol). The decarboxylation pathway is shown to occur with a maximum exothermicity of 28 kcal/mol. On the contrary, the decarbonylation of PA is predicted to occur with an overall endothermicity of ≈29.2 kcal/mol for formation of hydroxyacetylene and carbon monoxide and an average exothermicity of −7.69 kcal/mol for formation of the ketene and carbon monoxide. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Edmund Moses N. Ndip - One of the best experts on this subject based on the ideXlab platform.
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Theoretical study of the ground‐state gas‐phase unimolecular decomposition channels of Propynoic Acid
International Journal of Quantum Chemistry, 2004Co-Authors: Edmund Moses N. Ndip, Manoj K. Shukla, Jerzy Leszczynski, Richard L. RedingtonAbstract:Theoretical studies have been carried out to elucidate the ground-state unimolecular decomposition channels for Propynoic Acid (PA) in the gas phase. In this paper we present details of mechanisms for the decarboxylation and decarbonylation channels of PA. The transformations of PA result in the formation of carbon dioxide and acetylene from the decarboxylation channel while carbon monoxide and hydroxyacetylene, ultimately the ketene, are formed from the decarbonylation pathway. Equilibrium structures and the principal transition states (TSs) for each pathway have been identified and characterized. The Gaussian 98 suite of programs and MOLDEN were used for computation and visualization. All computations of equilibrium and TS structures relevant to the two competing unimolecular decomposition channels (decarboxylation and decarbonylation) were performed with second-order Moller–Plesset (MP2) and Becke's three-parameter exchange functional and the gradient-corrected functional of Lee, Yang, and Paar (B3LYP) levels using the 6-31G(d,p), 6-311++G (d, p) and Dunning's correlation-consistent polarized valence basis set (aug-cc-pVDZ). The geometries were fully optimized and characterized as minima (0 imaginary frequencies) or first-order saddle points (1 imaginary frequency) by harmonic vibrational analysis at the MP2/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. All the calculations indicate that the lowest energy decomposition pathway for PA is decarboxylation. Decarboxylation of PA occurs most easily through a three-step mechanism: conversion of s-cis-HCCCO2H to s-trans-HCCCO2H, followed by a 1, 3-hydrogen migration of hydroxyl hydrogen, resulting in a four-center TS that decays easily to acetylene and carbon dioxide, with an activation barrier of 61.3–79.9 kcal/mol (average 65.67 kcal/mol). Decarbonylation, leading to hydroxyacetylene (and subsequently the ketene) and carbon monoxide, occurs easily via a direct (one-step) three-center TS. The direct (one-step) elimination of carbon monoxide from Propynoic Acid has a calculated average activation barrier of 67.9–81.7 kcal/mol (average, 74.1 kcal/mol). The decarboxylation pathway is shown to occur with a maximum exothermicity of 28 kcal/mol. On the contrary, the decarbonylation of PA is predicted to occur with an overall endothermicity of ≈29.2 kcal/mol for formation of hydroxyacetylene and carbon monoxide and an average exothermicity of −7.69 kcal/mol for formation of the ketene and carbon monoxide. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
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theoretical study of the ground state gas phase unimolecular decomposition channels of Propynoic Acid
International Journal of Quantum Chemistry, 2004Co-Authors: Edmund Moses N. Ndip, Manoj K. Shukla, Jerzy Leszczynski, Richard L. RedingtonAbstract:Theoretical studies have been carried out to elucidate the ground-state unimolecular decomposition channels for Propynoic Acid (PA) in the gas phase. In this paper we present details of mechanisms for the decarboxylation and decarbonylation channels of PA. The transformations of PA result in the formation of carbon dioxide and acetylene from the decarboxylation channel while carbon monoxide and hydroxyacetylene, ultimately the ketene, are formed from the decarbonylation pathway. Equilibrium structures and the principal transition states (TSs) for each pathway have been identified and characterized. The Gaussian 98 suite of programs and MOLDEN were used for computation and visualization. All computations of equilibrium and TS structures relevant to the two competing unimolecular decomposition channels (decarboxylation and decarbonylation) were performed with second-order Moller–Plesset (MP2) and Becke's three-parameter exchange functional and the gradient-corrected functional of Lee, Yang, and Paar (B3LYP) levels using the 6-31G(d,p), 6-311++G (d, p) and Dunning's correlation-consistent polarized valence basis set (aug-cc-pVDZ). The geometries were fully optimized and characterized as minima (0 imaginary frequencies) or first-order saddle points (1 imaginary frequency) by harmonic vibrational analysis at the MP2/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. All the calculations indicate that the lowest energy decomposition pathway for PA is decarboxylation. Decarboxylation of PA occurs most easily through a three-step mechanism: conversion of s-cis-HCCCO2H to s-trans-HCCCO2H, followed by a 1, 3-hydrogen migration of hydroxyl hydrogen, resulting in a four-center TS that decays easily to acetylene and carbon dioxide, with an activation barrier of 61.3–79.9 kcal/mol (average 65.67 kcal/mol). Decarbonylation, leading to hydroxyacetylene (and subsequently the ketene) and carbon monoxide, occurs easily via a direct (one-step) three-center TS. The direct (one-step) elimination of carbon monoxide from Propynoic Acid has a calculated average activation barrier of 67.9–81.7 kcal/mol (average, 74.1 kcal/mol). The decarboxylation pathway is shown to occur with a maximum exothermicity of 28 kcal/mol. On the contrary, the decarbonylation of PA is predicted to occur with an overall endothermicity of ≈29.2 kcal/mol for formation of hydroxyacetylene and carbon monoxide and an average exothermicity of −7.69 kcal/mol for formation of the ketene and carbon monoxide. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Michal Dobkowski - One of the best experts on this subject based on the ideXlab platform.
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click chemistry synthesis and capillary electrophoresis study of 1 4 linked 1 2 3 triazole azt systemin conjugate
Journal of Peptide Science, 2014Co-Authors: Aleksandra Szychowska, Malgorzata Pieszko, Anna Miszka, Magdalena Alenowicz, Monika Wojciechowska, Michal Dobkowski, Piotr Rekowski, Jaroslaw Ruczynski, Lech CelewiczAbstract:The Cu(I) catalyzed Huisgen 1,3-dipolar azide-alkyne cycloaddition (CuAAC) was applied for a nucleoside-peptide bioconjugation. Systemin (Sys), an 18-aa plant signaling peptide naturally produced in response to wounding or pathogen attack, was chemically synthesized as its N-Propynoic Acid functionalized analog (Prp-Sys) using the SPPS. Next, CuAAC was applied to conjugate Prp-Sys with 3′-azido-2′,3′-dideoxythymidine (AZT), a model cargo molecule. 1,4-Linked 1,2,3-triazole AZT-Sys conjugate was designed to characterize the spreading properties and ability to translocate of cargo molecules of systemin. CuAAC allowed the synthesis of the conjugate in a chemoselective and regioselective manner, with high purity and yield. The presence of Cu(I) ions generated in situ drove the CuAAC reaction to completion within a few minutes without any by-products. Under typical separation conditions of phosphate ‘buffer’ at low pH and uncoated fused bare-silica capillary, an increasing peak intensity assigned to triazole-linked AZT-Sys conjugate was observed using capillary electrophoresis (CE) during CuAAC. CE analysis showed that systemin peptides are stable in tomato leaf extract for up to a few hours. CE-ESI-MS revealed that the native Sys and its conjugate with AZT are translocated through the tomato stem and can be directly detected in stem exudates. The results show potential application of systemin as a transporter of low molecular weight cargo molecules in tomato plant and of CE method to characterize a behavior of plant peptides and its analogs. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.
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‘Click’ chemistry synthesis and capillary electrophoresis study of 1,4‐linked 1,2,3‐triazole AZT‐systemin conjugate
Journal of Peptide Science, 2014Co-Authors: Michal Dobkowski, Aleksandra Szychowska, Malgorzata Pieszko, Anna Miszka, Magdalena Alenowicz, Lech Celewicz, Monika Wojciechowska, Jarosław Ruczyński, Piotr Rekowski, Jan BarciszewskiAbstract:The Cu(I) catalyzed Huisgen 1,3-dipolar azide-alkyne cycloaddition (CuAAC) was applied for a nucleoside-peptide bioconjugation. Systemin (Sys), an 18-aa plant signaling peptide naturally produced in response to wounding or pathogen attack, was chemically synthesized as its N-Propynoic Acid functionalized analog (Prp-Sys) using the SPPS. Next, CuAAC was applied to conjugate Prp-Sys with 3′-azido-2′,3′-dideoxythymidine (AZT), a model cargo molecule. 1,4-Linked 1,2,3-triazole AZT-Sys conjugate was designed to characterize the spreading properties and ability to translocate of cargo molecules of systemin. CuAAC allowed the synthesis of the conjugate in a chemoselective and regioselective manner, with high purity and yield. The presence of Cu(I) ions generated in situ drove the CuAAC reaction to completion within a few minutes without any by-products. Under typical separation conditions of phosphate ‘buffer’ at low pH and uncoated fused bare-silica capillary, an increasing peak intensity assigned to triazole-linked AZT-Sys conjugate was observed using capillary electrophoresis (CE) during CuAAC. CE analysis showed that systemin peptides are stable in tomato leaf extract for up to a few hours. CE-ESI-MS revealed that the native Sys and its conjugate with AZT are translocated through the tomato stem and can be directly detected in stem exudates. The results show potential application of systemin as a transporter of low molecular weight cargo molecules in tomato plant and of CE method to characterize a behavior of plant peptides and its analogs. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.
Manoj K. Shukla - One of the best experts on this subject based on the ideXlab platform.
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Theoretical study of the ground‐state gas‐phase unimolecular decomposition channels of Propynoic Acid
International Journal of Quantum Chemistry, 2004Co-Authors: Edmund Moses N. Ndip, Manoj K. Shukla, Jerzy Leszczynski, Richard L. RedingtonAbstract:Theoretical studies have been carried out to elucidate the ground-state unimolecular decomposition channels for Propynoic Acid (PA) in the gas phase. In this paper we present details of mechanisms for the decarboxylation and decarbonylation channels of PA. The transformations of PA result in the formation of carbon dioxide and acetylene from the decarboxylation channel while carbon monoxide and hydroxyacetylene, ultimately the ketene, are formed from the decarbonylation pathway. Equilibrium structures and the principal transition states (TSs) for each pathway have been identified and characterized. The Gaussian 98 suite of programs and MOLDEN were used for computation and visualization. All computations of equilibrium and TS structures relevant to the two competing unimolecular decomposition channels (decarboxylation and decarbonylation) were performed with second-order Moller–Plesset (MP2) and Becke's three-parameter exchange functional and the gradient-corrected functional of Lee, Yang, and Paar (B3LYP) levels using the 6-31G(d,p), 6-311++G (d, p) and Dunning's correlation-consistent polarized valence basis set (aug-cc-pVDZ). The geometries were fully optimized and characterized as minima (0 imaginary frequencies) or first-order saddle points (1 imaginary frequency) by harmonic vibrational analysis at the MP2/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. All the calculations indicate that the lowest energy decomposition pathway for PA is decarboxylation. Decarboxylation of PA occurs most easily through a three-step mechanism: conversion of s-cis-HCCCO2H to s-trans-HCCCO2H, followed by a 1, 3-hydrogen migration of hydroxyl hydrogen, resulting in a four-center TS that decays easily to acetylene and carbon dioxide, with an activation barrier of 61.3–79.9 kcal/mol (average 65.67 kcal/mol). Decarbonylation, leading to hydroxyacetylene (and subsequently the ketene) and carbon monoxide, occurs easily via a direct (one-step) three-center TS. The direct (one-step) elimination of carbon monoxide from Propynoic Acid has a calculated average activation barrier of 67.9–81.7 kcal/mol (average, 74.1 kcal/mol). The decarboxylation pathway is shown to occur with a maximum exothermicity of 28 kcal/mol. On the contrary, the decarbonylation of PA is predicted to occur with an overall endothermicity of ≈29.2 kcal/mol for formation of hydroxyacetylene and carbon monoxide and an average exothermicity of −7.69 kcal/mol for formation of the ketene and carbon monoxide. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
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theoretical study of the ground state gas phase unimolecular decomposition channels of Propynoic Acid
International Journal of Quantum Chemistry, 2004Co-Authors: Edmund Moses N. Ndip, Manoj K. Shukla, Jerzy Leszczynski, Richard L. RedingtonAbstract:Theoretical studies have been carried out to elucidate the ground-state unimolecular decomposition channels for Propynoic Acid (PA) in the gas phase. In this paper we present details of mechanisms for the decarboxylation and decarbonylation channels of PA. The transformations of PA result in the formation of carbon dioxide and acetylene from the decarboxylation channel while carbon monoxide and hydroxyacetylene, ultimately the ketene, are formed from the decarbonylation pathway. Equilibrium structures and the principal transition states (TSs) for each pathway have been identified and characterized. The Gaussian 98 suite of programs and MOLDEN were used for computation and visualization. All computations of equilibrium and TS structures relevant to the two competing unimolecular decomposition channels (decarboxylation and decarbonylation) were performed with second-order Moller–Plesset (MP2) and Becke's three-parameter exchange functional and the gradient-corrected functional of Lee, Yang, and Paar (B3LYP) levels using the 6-31G(d,p), 6-311++G (d, p) and Dunning's correlation-consistent polarized valence basis set (aug-cc-pVDZ). The geometries were fully optimized and characterized as minima (0 imaginary frequencies) or first-order saddle points (1 imaginary frequency) by harmonic vibrational analysis at the MP2/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. All the calculations indicate that the lowest energy decomposition pathway for PA is decarboxylation. Decarboxylation of PA occurs most easily through a three-step mechanism: conversion of s-cis-HCCCO2H to s-trans-HCCCO2H, followed by a 1, 3-hydrogen migration of hydroxyl hydrogen, resulting in a four-center TS that decays easily to acetylene and carbon dioxide, with an activation barrier of 61.3–79.9 kcal/mol (average 65.67 kcal/mol). Decarbonylation, leading to hydroxyacetylene (and subsequently the ketene) and carbon monoxide, occurs easily via a direct (one-step) three-center TS. The direct (one-step) elimination of carbon monoxide from Propynoic Acid has a calculated average activation barrier of 67.9–81.7 kcal/mol (average, 74.1 kcal/mol). The decarboxylation pathway is shown to occur with a maximum exothermicity of 28 kcal/mol. On the contrary, the decarbonylation of PA is predicted to occur with an overall endothermicity of ≈29.2 kcal/mol for formation of hydroxyacetylene and carbon monoxide and an average exothermicity of −7.69 kcal/mol for formation of the ketene and carbon monoxide. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
