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Papers by Graziella Ranghino
Nature Structural & Molecular Biology, 2003
Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Protein and Peptide Letters, 1996
Crystallography in Molecular Biology, 1987
The 18-crown-6 ether, a simple model for macrocyclic ion receptors and carriers is flexible, and ... more The 18-crown-6 ether, a simple model for macrocyclic ion receptors and carriers is flexible, and displays several conformations in crystals, depending on the nature of its environment, and on the presence and nature of the complexed cation (1,2): e.g., the uncomplexed crown has Ci symmetry, the sodium and potassium complexes are Cl and D3d, respectively. Molecular mechanics calculations on the isolated macrocycle (3) indicate that Ci is the most stable form compared to D3d and Cl (ΔE =0, 1,9 kcal/ mole).
Protides of the Biological Fluids, 1987
ABSTRACT Some new computer programs, especially formulated to investigate the low-energy regions ... more ABSTRACT Some new computer programs, especially formulated to investigate the low-energy regions of molecular conformational energy surfaces, were applied to the analgesic heptapeptide dermorphin. It was found that, in the absence of intermolecular interactions, the most stable conformations are bent, due to various kinds of internal hydrogen bonds, while extended structures have somewhat higher energy.
Medicinal Chemistry Advances, 1981
ABSTRACT Quantum chemical investigations of the base-catalysed breaking of the endocyclic amide b... more ABSTRACT Quantum chemical investigations of the base-catalysed breaking of the endocyclic amide bond of some β-lactams are presented and discussed through ab initio Hartree-Fock calculations of the potential energy surfaces of the β-lactam + OH–, CH3O-β-lactam+OH–, and 3-cephem+OH– reactions. The initial attack of the nucleophile is similar for each reaction and gives a tetrahedral intermediate. The breaking of the amide bond occurs with a reaction barrier which is remarkably lower in 3-cephem than in the monocyclic β-lactams owing to the electron-withdrawing effect of the enamine group. The product is stabilized by an intramolecular hydrogen bond and its energy depends on intramolecular steric interactions. The theoretical results are correlated with some experimental data on the antibiotic activity of β-lactams.
International Journal of Quantum Chemistry, 1980
Potential-energy curves for CH4·CH4 have been calculated using the SCF LCAO MO method. Six differ... more Potential-energy curves for CH4·CH4 have been calculated using the SCF LCAO MO method. Six different mutual orientations of the molecules have been considered and several basis sets have been employed. An analytical potential has been fitted to the computed energy values and used in a Monte Carlo calculation to yield a spherically averaged CH4·CH4 potential. The potential, if corrected for dispersion interaction, agrees fairly well with that derived from thermophysical data. At short distances it disagrees with the potentials derived from scattering experiments which, however, are also incompatible with the experimental potential for large distances.
Computers & Chemistry, 1982
Trends in QSAR and Molecular Modelling 92, 1993
Journal of Molecular Structure, 1983
Journal of Inorganic Biochemistry, 2002
Nature Structural & Molecular Biology, 2003
Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Protein and Peptide Letters, 1996
Crystallography in Molecular Biology, 1987
The 18-crown-6 ether, a simple model for macrocyclic ion receptors and carriers is flexible, and ... more The 18-crown-6 ether, a simple model for macrocyclic ion receptors and carriers is flexible, and displays several conformations in crystals, depending on the nature of its environment, and on the presence and nature of the complexed cation (1,2): e.g., the uncomplexed crown has Ci symmetry, the sodium and potassium complexes are Cl and D3d, respectively. Molecular mechanics calculations on the isolated macrocycle (3) indicate that Ci is the most stable form compared to D3d and Cl (ΔE =0, 1,9 kcal/ mole).
Protides of the Biological Fluids, 1987
ABSTRACT Some new computer programs, especially formulated to investigate the low-energy regions ... more ABSTRACT Some new computer programs, especially formulated to investigate the low-energy regions of molecular conformational energy surfaces, were applied to the analgesic heptapeptide dermorphin. It was found that, in the absence of intermolecular interactions, the most stable conformations are bent, due to various kinds of internal hydrogen bonds, while extended structures have somewhat higher energy.
Medicinal Chemistry Advances, 1981
ABSTRACT Quantum chemical investigations of the base-catalysed breaking of the endocyclic amide b... more ABSTRACT Quantum chemical investigations of the base-catalysed breaking of the endocyclic amide bond of some β-lactams are presented and discussed through ab initio Hartree-Fock calculations of the potential energy surfaces of the β-lactam + OH–, CH3O-β-lactam+OH–, and 3-cephem+OH– reactions. The initial attack of the nucleophile is similar for each reaction and gives a tetrahedral intermediate. The breaking of the amide bond occurs with a reaction barrier which is remarkably lower in 3-cephem than in the monocyclic β-lactams owing to the electron-withdrawing effect of the enamine group. The product is stabilized by an intramolecular hydrogen bond and its energy depends on intramolecular steric interactions. The theoretical results are correlated with some experimental data on the antibiotic activity of β-lactams.
International Journal of Quantum Chemistry, 1980
Potential-energy curves for CH4·CH4 have been calculated using the SCF LCAO MO method. Six differ... more Potential-energy curves for CH4·CH4 have been calculated using the SCF LCAO MO method. Six different mutual orientations of the molecules have been considered and several basis sets have been employed. An analytical potential has been fitted to the computed energy values and used in a Monte Carlo calculation to yield a spherically averaged CH4·CH4 potential. The potential, if corrected for dispersion interaction, agrees fairly well with that derived from thermophysical data. At short distances it disagrees with the potentials derived from scattering experiments which, however, are also incompatible with the experimental potential for large distances.
Computers & Chemistry, 1982
Trends in QSAR and Molecular Modelling 92, 1993
Journal of Molecular Structure, 1983
Journal of Inorganic Biochemistry, 2002