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  • 1
    Electronic Resource
    Electronic Resource
    Formation Constants of Ternary Complexes of Some Heavy Metal Ions with N-(2-Acetamido)iminodiacetic Acid and Aliphatic or Aromatic Acids (1994)
    s.l. : American Chemical Society
    Journal of chemical & engineering data 39 (1994), S. 565-567 
    Details
    ISSN: 1520-5134
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/je00015a037
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  • 2
    Electronic Resource
    Electronic Resource
    A study on the electronic spectra of vinylpyridines and 1,2-(dipyridyl)ethylenes. Molecular orbital calculations (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 39 (1991), S. 211-226 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic absorption spectra of 2-, 3-, and 4-vinylpyridines and 1,2-(2,3-dipyridyl), 1,2-(2,4-dipyridyl), 1,2-(3,4-dipyridyl), and 1,2-(4,4-dipyridyl) ethylenes have been investigated in polar and nonpolar solvents. A correlation has been made between the geometry of the molecule and the observed spectrum. Molecular orbital calculations have been carried out using the INDO/S—CI procedure and a limited geometry optimization. The solvent effect at the MO level has been calculated. MO calculations predicted the existence of nπ* transitions that were not observed experimentally. The wave functions of the different CI states were calculated. The experimental transition energy as well as oscillator strength corresponded satisfactorily with the calculated ones. The observed transitions were assigned according to the results of MO calculations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560390210
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular orbital treatment of phenylfurans and bifurans (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 383-399 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecule-in-molecule method of computation has been applied in a SCF study of the electronic absorption spectra of 2- and 3-phenylfurans and 2,2′- and 3,3′-bifurans. The computed values for the transition energies and band intensities differ for the different isomers and help one to assign the preferred conformer of the studied molecules. Computations were performed on planar as well as nonplanar conformers. The calculated parameters as well as the interaction energy suggest all-planar configuration for the studied molecules. A model potential for the sigma framework for the ortho-hydrogens is considered. The calculated steric repulsion energy is negligible compared to the π delocalization. The height of the rotational barrier was larger for 2-phenylfuran than for 3-phenylfuran, and larger for 2,2′-bifuran than for 3,3′-bifuran. This result is in accord with predictions based on the extent of “π” conjugation in these molecules.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190303
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular-orbital treatment of some heterocycles with three hetero-atoms and their benzo-derivatives (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 731-740 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular-orbital calculations, using the INDO procedures, were carried out on the tautomers of 1, 2, 4-triazole and its benzo-derivative as well as on 1, 2, 5-oxadiazole and its benzo-derivative. Calculations of the transition energy as well as the dipole moment helped to predict the predominant tautomer in an equilibrium mixture. The correspondence between the calculated and observed data is satisfactory. The results of calculations indicated some differences in the electronic structures of the tautomers of a compound.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280608
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  • 5
    Electronic Resource
    Electronic Resource
    Equilibrium geometry and electronic structure of benzylidene, arylethylidene, and heterocyclic arylidene malononitriles (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 805-816 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The equilibrium geometry of some benzylidene, arylethylidene, and heterocyclic arylidene malononitriles has been calculated within the framework of the MNDO-MO formalism. Various structural factors are analyzed and discussed in terms of localized and delocalized MOS and π-interaction between methylene malononitrile (MMN) and aryl moieties. The possibility of charge transfer (CT) from aryl to MMN moieties has been examined. The presence of a heterocyclic ring introduces a small perturbation into the MMN nuclear frame. p-Substituents have a pronounced effect on the magnitude and direction of the dipole moment. The variation of ionization potentials and bond order with the Hammet σ p are examined and a straight-line relationship is obtained. The correlation between physiological activity and quantum mechanical properties is analyzed in terms of heat of formation, ionization potential, dipole moment, and charge density on the aryl ring. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560490605
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  • 6
    Electronic Resource
    Electronic Resource
    A molecular orbital treatment of the electronic spectra of some tryptamines (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 379-392 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic absorption spectra of tryptamine, 5-methoxytryptamine, 6-fluorotryptamine, N-acetyl-5-hydroxytryptamine, gramine, and melatonin were investigated. The observed transitions were π-π*, and the values of band maxima and intensity reflected an extent of interaction between the indole ring and the alkylamine side chain. Molecular orbital calculations at the level of INDO/S-CI were performed on all the studied molecules. State functions and transition energies were calculated. The correspondence between the experimental and theoretical results was satisfactory. © 1992 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560440306
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic spectra of phenyl-, 3-pyridyl-, furfuryl-, and 2-theinyl-imino derivatives of thiazole: Molecular orbital treatment (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 66 (1998), S. 415-423 
    Details
    ISSN: 0020-7608
    Keywords: Spectra ; MO calculations ; INDO/S-CI ; thiazoles ; geometry optimization ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic spectra of phenylmethylene, 3-pyridylmethylene, furfurylmethylene, and theinylmethylene derivatives of 2-aminothiazole have been investigated. Gaussian analysis for the spectra indicates the existence of four electronic transitions in the 350-220 nm region. Geometry optimization using AM1 method followed by INDO/S-CI calculations was carried out. The results confirmed the absence of n-π* transitions. The coefficients of configuration interaction (CI) wave functions defined the type of electronic transitions, which are of major charge transfer (CT) character. The anticonformer is the predominant one. The gap energies of the studied compounds are of the same order, which indicates that their reactivities are expected to be the same.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66: 415-423, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Mean-square hydrophobic moment for partially helical polypeptides (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 201-212 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mean-square helical hydrophobic moment, 〈h2〉, is defined for polypeptides in analogy to the mean-square dipole moment, 〈μ2〉, for polymer chains. For a freely jointed polymer chain, 〈μ2〉 is given by Σmi2, where mi denotes the dipole moment associated with bond i. In the absence of any correlations in the hydrophobic moments of individual amino acid residues in the helix, 〈h2〉 is specified by ΣHi2, where Hi denotes the hydrophobicity of residue i. The tendency for correlations in orientations of residue hydrophobic moments in helices therefore dictates the size of 〈h2〉/〈H2〉, where 〈H2〉 denotes the average value of ΣHi2 for all helices. The value of 〈h2〉/〈H2〉 will be greater than one in amphiphilic helices. A necessary prerequisite for this diagnostic usage of 〈h2〉/〈H2〉 is that the residue hydrophobic moment be oriented prependicular to the principal axis of the helix. Matrix-generation schemes are formulated that permit rapid evaluation of 〈h2〉 and 〈H2〉. The behavior of 〈h2〉/〈H2〉 is illustrated by calculations performed for model sequential copolypeptides.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230204
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  • 9
    Electronic Resource
    Electronic Resource
    Behavior of amphipathic helices on analysis via matrix methods, with application to glucagon, secretin, and vasoactive intestinal peptide (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1003-1021 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A configuration partition function, which incorporates concepts embodied in the amphipathic helix hypothesis, has been formulated for a polypeptide in the presence of zwitterionic phospholipid. An enhanced probability is assigned to helix formation in any region of the polypeptide chain where side chains bearing charges of opposite sign will be situated on the same side of the α-helix but displaced from one another by one turn. This situation will arise when residues i - 4 (or i - 3) and i bear charges of opposite sign and residue i - 4 (or i - 3) through i are in a helical state. Illustrative calculations are performed for polypeptide chains in which the generalized nonionic amino acid residue serving as host has Zimm-Bragg parameters of σ = 10-4, s = 1. These calculations define conditions under which two interacting charged pairs can cooperate in a synergistic helix augmentation even when the two pairs are separated by significantly more than four generalized nonionic amino acid residues. Furthermore, the two interacting charged pairs, as well as the intervening amino acid residues, may become helical as one unit. Significant augmentation in helicity is observed with plausible values for the enhanced probablity assigned to helix formation for an interacting pair. This model predicts correctly that glucagon and secretin, but not vasoactive intestinal peptide, undergo a coil-to-helix trnsition in the presence of zwitterionic phospholipid. This prediction is made with plausible values for the parameter used to express the helicity enhancement. The experimental observation with zwitterionic phospholipids is the direct opposite of that seen for these three peptides in the presence of anionic lipids and detergents. In anionic lipids the amount of induced helicity is in the following order: glucagon 〈 secretin 〈 vasoactive intestinal peptide. Results obtained with these three peptides demonstrate that the nature of the head group of the lipid is important for lipid-protein interaction and that the resulting conformational changes can be rationalized by matrix methods.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220317
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  • 10
    Electronic Resource
    Electronic Resource
    Mean-square helical hydrophobic moments in partially ordered proteins (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1057-1066 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Helical hydrophobic moment ratios, 〈h2〉/〈H2〉, have been evaluated for 34 polypeptides under conditions where the helix content is dictated solely by the short-range interactions operative in aqueous media. The mean-square helical hydrophobic moment is denoted by 〈h2〉, and 〈H2〉 is the averaged of the squared hydrophobicites. This ratio would be one in absence of any correlation in the hydrophobicities of amino acid residues in helices. The 〈h2〉/〈H2〉 tend to be substantially larger than values of the analogous ratio formulated for the mean-square dipole moments of typical synthetic polymers. For 24 of the 34 polypeptide chains considered, 〈h2〉/〈H2〉 is found to be greater than one, indicating a tendency to form helices with amphiphilic character. The ratio is exceptionally large in the case of the δ-hemolysins. It is also large for two other surface-active peptides, for two of the four apolipoproteins examined, and for myohemerythrin. A much smaller 〈h2〉/〈H2〉 is found for melittins. If melittins is to form helices with large 〈h2〉/〈H2〉, the configurational statistics must be governed by effects in addition to those short-range interactions that occur when water is the solvent.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230607
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