Sonia Melandri | Università di Bologna (original) (raw)
Papers by Sonia Melandri
European Journal of Biochemistry, 1994
Calcitonin (CT) inhibits osteoclastic bone resorption and induces calcium uptake from body fluids... more Calcitonin (CT) inhibits osteoclastic bone resorption and induces calcium uptake from body fluids. A comparative study of the conformational behaviours of therapeutic calcitonins [salmon (s), eel (e), a synthetic eel calcitonin analogue (Elcatonin), porcine (p) and human (h) calcitonins] as a function of solvent polarity and temperature have been performed by circular dichroism spectroscopy. Elements of secondary structure were lacking in H,O but could be observed in 2,2,2-trifluoroethanol and sodium dodecyl sulphate. In particular, similar amounts of a-helical content (four ahelical turns) were estimated in trifluoroethanol despite the considerable differences in amino acid sequences. The relative ability to form an a helix, assessed by trifluoroethanol/H,O titration, was found to be Elcatonin > sCT > pCT > eCT > hCT. In Elcatonin, sCT, pCT and eCT the four ahelical turns were promoted almost completely in a single step, between 0 and 35 % trifluoroethanol, unlike hCT where helical structure formation has been reported to involve two steps over the whole trifluoroethanol/H,O range [Arvinte, T. & Drake, A. F. (1993) J. Biol. Chem. 268, 6408-64141. In SDS, which mimics the membrane environment, conformational differences (3 -4 helical turns in Elcatonin, sCT, eCT versus one helical turn in pCT, hCT) were observed and correlate well with biological activity (Elcatonin = sCT = eCT > pCT = hCT).
Angewandte Chemie-international Edition, 1999
Discussion: More Realism in the Matter of Predicting Molecules? ... A shortening of the C−H bond ... more Discussion: More Realism in the Matter of Predicting Molecules? ... A shortening of the C−H bond lengths and a blue shift of the C−H stretching frequencies for the CF⋅⋅⋅HC groups indicates that anti-hydrogen bonds are present the difluoromethane dimer. The most stable ...
Chemical Physics Letters, 1997
The assignment of the free jet millimeter wave spectrum of the normal and N-D isotopomers of puri... more The assignment of the free jet millimeter wave spectrum of the normal and N-D isotopomers of purine reported in the above paper has shown that the N(9)H tautomer is the more stable. Unfortunately the labels N(7)H and N(9)H have been inverted in .
Chemical Physics Letters, 2006
Internal rotation or inversion motions of light groups, such as methyl, amino and OH groups, gene... more Internal rotation or inversion motions of light groups, such as methyl, amino and OH groups, generate splittings of rotational transitions, which are useful data for the experimental determination of the corresponding potential energy surfaces. A very high number of molecules with ...
Journal of The American Chemical Society, 1998
The free jet millimeter wave spectra of the 1:1 complex between 1,4-dioxane and four isotopomers ... more The free jet millimeter wave spectra of the 1:1 complex between 1,4-dioxane and four isotopomers of water (H 2 O, D 2 O, HDO, and H 2 18 O) have been assigned. The water molecule lies in the plane of symmetry of 1,4-dioxane; the water hydrogen involved in the hydrogen bond is axial with respect to the ring, while the "free" hydrogen is entgegen to the ring. The three atoms involved in the hydrogen bond adopt a bent arrangement with a distance O ring ‚‚‚H of about 1.90 Å and ∠(O ring ‚‚‚H-O) = 163°.
Angewandte Chemie, 1998
ABSTRACT
Journal of Physical Chemistry A, 2009
We report a free jet microwave absorption study of 2-amino-1-phenylethanol and 2-methylamino-1phe... more We report a free jet microwave absorption study of 2-amino-1-phenylethanol and 2-methylamino-1phenylethanol, which are analogues of noradrenaline and adrenaline, respectively. The spectra, recorded under different expansion conditions and with different carrier gases, show the presence of several conformational species: two conformers for 2-amino-1-phenylethanol and three for 2-methylamino-1-phenylethanol. The assignment is based on the comparison of the experimental rotational constants and the orientation of the molecular dipole moment with the ones predicted by theoretical methods and allows the univocal identification of all observed conformers while intensity measurements give information on their relative stability. All of the observed conformational species are stabilized by an intramolecular hydrogen bond between the hydroxyl hydrogen atom and the amino nitrogen atom, whereas the alkylamino side chain can be in the extended anti or folded gauche conformation. The presence of the bulky methyl group substituent on the alkylamino side chain of 2-methylamino-1-phenylethanol influences the relative stability of the conformers. * Corresponding author. Figure 1. Sketch of the relevant biomolecules and their analogues.
Angewandte Chemie, 1999
... Zuschrift. Die CF⋅⋅⋅HC-Anti-Wasserstoffbrückenbindung in der Gasphase: mikrowellenspektrosk... more ... Zuschrift. Die CF⋅⋅⋅HC-Anti-Wasserstoffbrückenbindung in der Gasphase: mikrowellenspektroskopisch ermittelte Struktur des Difluormethan-Dimers. Walther Caminati,;Sonia Melandri,; Paolo Moreschini,; Paolo G. Favero. Article first published online: 24 SEP 1999. ...
Journal of Molecular Structure, 2005
The free jet millimeter wave spectrum of difluoromethanewater (since now on DFM-H 2 O) has been ... more The free jet millimeter wave spectrum of difluoromethanewater (since now on DFM-H 2 O) has been reported recently [1]. Information on the configuration and on the structural and energetic details of the OH FC hydrogen bond have been obtained, leading to the shape of the ...
Journal of The American Chemical Society, 1999
... Walther Caminati,* Sonia Melandri, Ivan Rossi, and ... H···O, O−H···N, O−H···S, O−H···π, N−... more ... Walther Caminati,* Sonia Melandri, Ivan Rossi, and ... H···O, O−H···N, O−H···S, O−H···π, N−H···N, N−H···O, X−H···N, and X−H···O (X = F, Cl, CN) hydrogen bonds has generally been obtained from molecular beam Fourier transform microwave spectroscopy, as reported by Novick. ...
Chemical Physics Letters, 1996
A free jet millimeter wave spectrometer has been modified in order to observe the rotational spec... more A free jet millimeter wave spectrometer has been modified in order to observe the rotational spectra of van der Waals molecular complexes. Here the free jet millimeter wave spectrum of the pyridine-argon molecular complex, as investigated in the 60-78 GHz frequency range, is reported.
The nucleobases cytosine, thymine and uracil are pyrimidine derivatives. They pair with their com... more The nucleobases cytosine, thymine and uracil are pyrimidine derivatives. They pair with their complementary purines, guanine and adenine, through hydrogen bonding to form DNA and RNA chains. The tautomeric forms of DNA bases are capable of unusual base pairing like thymine-guanine and cytosine-adenine and create mutations, which are the precursors of some molecular-based diseases. Low energy spectroscopies such as microwave, laser and infrared techniques are commonly used as methods to investigate the conformatonal and tautomeric equilibria of biomolecules, while the high energy technique of x-ray photoemission spectroscopy (XPS) has yielded a smaller amount of significant structural information about biomolecules in the gas phase. In the present studies we successfully apply XPS to the study of five nucleic acid base tautomers, as well as the prototypical system 2-hydroxypyridimine and the related molecules S-methyl-2-thiouracil and 2-thiouracil in the vapor phase. XPS is a quantitative technique, allowing the experimental determination of the populations of keto and enol tautomers at known equilibrium temperatures: it is difficult to obtain this information otherwise. The effect of different substituents on stability of tautomers has been revealed. Quantum chemistry calculations have been carried out in order to obtain information about the structure, relative stability and difference in populations of the tautomers and conformers under study.
Angewandte Chemie-international Edition, 1999
Discussion: More Realism in the Matter of Predicting Molecules? ... A shortening of the C−H bond ... more Discussion: More Realism in the Matter of Predicting Molecules? ... A shortening of the C−H bond lengths and a blue shift of the C−H stretching frequencies for the CF⋅⋅⋅HC groups indicates that anti-hydrogen bonds are present the difluoromethane dimer. The most stable ...
Chemical Physics Letters, 1997
The assignment of the free jet millimeter wave spectrum of the normal and N-D isotopomers of puri... more The assignment of the free jet millimeter wave spectrum of the normal and N-D isotopomers of purine reported in the above paper has shown that the N(9)H tautomer is the more stable. Unfortunately the labels N(7)H and N(9)H have been inverted in .
Journal of Molecular Spectroscopy, 1995
224 Fig. I. Equatorial and axial conformations of l-fluorosilacyclobutane, indicating the angles ... more 224 Fig. I. Equatorial and axial conformations of l-fluorosilacyclobutane, indicating the angles a and В subject to structural relaxation. ionicity, ie, the formation of ionic structures such as Y3Si+X~ and subsequently to a shortening of both the SiF and SiY bonds. In this ...
Chemical Physics Letters, 2006
Internal rotation or inversion motions of light groups, such as methyl, amino and OH groups, gene... more Internal rotation or inversion motions of light groups, such as methyl, amino and OH groups, generate splittings of rotational transitions, which are useful data for the experimental determination of the corresponding potential energy surfaces. A very high number of molecules with ...
Angewandte Chemie-international Edition, 2006
Unlike H 2 O⋅⋅⋅F 2 , the adduct H 2 O⋅⋅⋅F 2 CH 2 displayed an O H⋅⋅⋅F hydrogen bond; for this rea... more Unlike H 2 O⋅⋅⋅F 2 , the adduct H 2 O⋅⋅⋅F 2 CH 2 displayed an O H⋅⋅⋅F hydrogen bond; for this reason, we thought that the study of the rotational spectrum of an adduct of water with an aliphatic molecule containing both Cl and F atoms would give direct evidence ...
Journal of The American Chemical Society, 1998
The free jet millimeter wave spectra of the 1:1 complex between 1,4-dioxane and four isotopomers ... more The free jet millimeter wave spectra of the 1:1 complex between 1,4-dioxane and four isotopomers of water (H 2 O, D 2 O, HDO, and H 2 18 O) have been assigned. The water molecule lies in the plane of symmetry of 1,4-dioxane; the water hydrogen involved in the hydrogen bond is axial with respect to the ring, while the "free" hydrogen is entgegen to the ring. The three atoms involved in the hydrogen bond adopt a bent arrangement with a distance O ring ‚‚‚H of about 1.90 Å and ∠(O ring ‚‚‚H-O) = 163°.
Angewandte Chemie-international Edition, 1998
Completely planar is the hydrogen-bonded complex of pyrazine and water (see sketch), which was ob... more Completely planar is the hydrogen-bonded complex of pyrazine and water (see sketch), which was obtained by supersonic expansion and investigated by rotational spectroscopy. The water molecule lies in the plane of the aromatic ring, and the lone pair of electrons on the ...
Angewandte Chemie, 1998
ABSTRACT
European Journal of Biochemistry, 1994
Calcitonin (CT) inhibits osteoclastic bone resorption and induces calcium uptake from body fluids... more Calcitonin (CT) inhibits osteoclastic bone resorption and induces calcium uptake from body fluids. A comparative study of the conformational behaviours of therapeutic calcitonins [salmon (s), eel (e), a synthetic eel calcitonin analogue (Elcatonin), porcine (p) and human (h) calcitonins] as a function of solvent polarity and temperature have been performed by circular dichroism spectroscopy. Elements of secondary structure were lacking in H,O but could be observed in 2,2,2-trifluoroethanol and sodium dodecyl sulphate. In particular, similar amounts of a-helical content (four ahelical turns) were estimated in trifluoroethanol despite the considerable differences in amino acid sequences. The relative ability to form an a helix, assessed by trifluoroethanol/H,O titration, was found to be Elcatonin > sCT > pCT > eCT > hCT. In Elcatonin, sCT, pCT and eCT the four ahelical turns were promoted almost completely in a single step, between 0 and 35 % trifluoroethanol, unlike hCT where helical structure formation has been reported to involve two steps over the whole trifluoroethanol/H,O range [Arvinte, T. & Drake, A. F. (1993) J. Biol. Chem. 268, 6408-64141. In SDS, which mimics the membrane environment, conformational differences (3 -4 helical turns in Elcatonin, sCT, eCT versus one helical turn in pCT, hCT) were observed and correlate well with biological activity (Elcatonin = sCT = eCT > pCT = hCT).
Angewandte Chemie-international Edition, 1999
Discussion: More Realism in the Matter of Predicting Molecules? ... A shortening of the C−H bond ... more Discussion: More Realism in the Matter of Predicting Molecules? ... A shortening of the C−H bond lengths and a blue shift of the C−H stretching frequencies for the CF⋅⋅⋅HC groups indicates that anti-hydrogen bonds are present the difluoromethane dimer. The most stable ...
Chemical Physics Letters, 1997
The assignment of the free jet millimeter wave spectrum of the normal and N-D isotopomers of puri... more The assignment of the free jet millimeter wave spectrum of the normal and N-D isotopomers of purine reported in the above paper has shown that the N(9)H tautomer is the more stable. Unfortunately the labels N(7)H and N(9)H have been inverted in .
Chemical Physics Letters, 2006
Internal rotation or inversion motions of light groups, such as methyl, amino and OH groups, gene... more Internal rotation or inversion motions of light groups, such as methyl, amino and OH groups, generate splittings of rotational transitions, which are useful data for the experimental determination of the corresponding potential energy surfaces. A very high number of molecules with ...
Journal of The American Chemical Society, 1998
The free jet millimeter wave spectra of the 1:1 complex between 1,4-dioxane and four isotopomers ... more The free jet millimeter wave spectra of the 1:1 complex between 1,4-dioxane and four isotopomers of water (H 2 O, D 2 O, HDO, and H 2 18 O) have been assigned. The water molecule lies in the plane of symmetry of 1,4-dioxane; the water hydrogen involved in the hydrogen bond is axial with respect to the ring, while the "free" hydrogen is entgegen to the ring. The three atoms involved in the hydrogen bond adopt a bent arrangement with a distance O ring ‚‚‚H of about 1.90 Å and ∠(O ring ‚‚‚H-O) = 163°.
Angewandte Chemie, 1998
ABSTRACT
Journal of Physical Chemistry A, 2009
We report a free jet microwave absorption study of 2-amino-1-phenylethanol and 2-methylamino-1phe... more We report a free jet microwave absorption study of 2-amino-1-phenylethanol and 2-methylamino-1phenylethanol, which are analogues of noradrenaline and adrenaline, respectively. The spectra, recorded under different expansion conditions and with different carrier gases, show the presence of several conformational species: two conformers for 2-amino-1-phenylethanol and three for 2-methylamino-1-phenylethanol. The assignment is based on the comparison of the experimental rotational constants and the orientation of the molecular dipole moment with the ones predicted by theoretical methods and allows the univocal identification of all observed conformers while intensity measurements give information on their relative stability. All of the observed conformational species are stabilized by an intramolecular hydrogen bond between the hydroxyl hydrogen atom and the amino nitrogen atom, whereas the alkylamino side chain can be in the extended anti or folded gauche conformation. The presence of the bulky methyl group substituent on the alkylamino side chain of 2-methylamino-1-phenylethanol influences the relative stability of the conformers. * Corresponding author. Figure 1. Sketch of the relevant biomolecules and their analogues.
Angewandte Chemie, 1999
... Zuschrift. Die CF⋅⋅⋅HC-Anti-Wasserstoffbrückenbindung in der Gasphase: mikrowellenspektrosk... more ... Zuschrift. Die CF⋅⋅⋅HC-Anti-Wasserstoffbrückenbindung in der Gasphase: mikrowellenspektroskopisch ermittelte Struktur des Difluormethan-Dimers. Walther Caminati,;Sonia Melandri,; Paolo Moreschini,; Paolo G. Favero. Article first published online: 24 SEP 1999. ...
Journal of Molecular Structure, 2005
The free jet millimeter wave spectrum of difluoromethanewater (since now on DFM-H 2 O) has been ... more The free jet millimeter wave spectrum of difluoromethanewater (since now on DFM-H 2 O) has been reported recently [1]. Information on the configuration and on the structural and energetic details of the OH FC hydrogen bond have been obtained, leading to the shape of the ...
Journal of The American Chemical Society, 1999
... Walther Caminati,* Sonia Melandri, Ivan Rossi, and ... H···O, O−H···N, O−H···S, O−H···π, N−... more ... Walther Caminati,* Sonia Melandri, Ivan Rossi, and ... H···O, O−H···N, O−H···S, O−H···π, N−H···N, N−H···O, X−H···N, and X−H···O (X = F, Cl, CN) hydrogen bonds has generally been obtained from molecular beam Fourier transform microwave spectroscopy, as reported by Novick. ...
Chemical Physics Letters, 1996
A free jet millimeter wave spectrometer has been modified in order to observe the rotational spec... more A free jet millimeter wave spectrometer has been modified in order to observe the rotational spectra of van der Waals molecular complexes. Here the free jet millimeter wave spectrum of the pyridine-argon molecular complex, as investigated in the 60-78 GHz frequency range, is reported.
The nucleobases cytosine, thymine and uracil are pyrimidine derivatives. They pair with their com... more The nucleobases cytosine, thymine and uracil are pyrimidine derivatives. They pair with their complementary purines, guanine and adenine, through hydrogen bonding to form DNA and RNA chains. The tautomeric forms of DNA bases are capable of unusual base pairing like thymine-guanine and cytosine-adenine and create mutations, which are the precursors of some molecular-based diseases. Low energy spectroscopies such as microwave, laser and infrared techniques are commonly used as methods to investigate the conformatonal and tautomeric equilibria of biomolecules, while the high energy technique of x-ray photoemission spectroscopy (XPS) has yielded a smaller amount of significant structural information about biomolecules in the gas phase. In the present studies we successfully apply XPS to the study of five nucleic acid base tautomers, as well as the prototypical system 2-hydroxypyridimine and the related molecules S-methyl-2-thiouracil and 2-thiouracil in the vapor phase. XPS is a quantitative technique, allowing the experimental determination of the populations of keto and enol tautomers at known equilibrium temperatures: it is difficult to obtain this information otherwise. The effect of different substituents on stability of tautomers has been revealed. Quantum chemistry calculations have been carried out in order to obtain information about the structure, relative stability and difference in populations of the tautomers and conformers under study.
Angewandte Chemie-international Edition, 1999
Discussion: More Realism in the Matter of Predicting Molecules? ... A shortening of the C−H bond ... more Discussion: More Realism in the Matter of Predicting Molecules? ... A shortening of the C−H bond lengths and a blue shift of the C−H stretching frequencies for the CF⋅⋅⋅HC groups indicates that anti-hydrogen bonds are present the difluoromethane dimer. The most stable ...
Chemical Physics Letters, 1997
The assignment of the free jet millimeter wave spectrum of the normal and N-D isotopomers of puri... more The assignment of the free jet millimeter wave spectrum of the normal and N-D isotopomers of purine reported in the above paper has shown that the N(9)H tautomer is the more stable. Unfortunately the labels N(7)H and N(9)H have been inverted in .
Journal of Molecular Spectroscopy, 1995
224 Fig. I. Equatorial and axial conformations of l-fluorosilacyclobutane, indicating the angles ... more 224 Fig. I. Equatorial and axial conformations of l-fluorosilacyclobutane, indicating the angles a and В subject to structural relaxation. ionicity, ie, the formation of ionic structures such as Y3Si+X~ and subsequently to a shortening of both the SiF and SiY bonds. In this ...
Chemical Physics Letters, 2006
Internal rotation or inversion motions of light groups, such as methyl, amino and OH groups, gene... more Internal rotation or inversion motions of light groups, such as methyl, amino and OH groups, generate splittings of rotational transitions, which are useful data for the experimental determination of the corresponding potential energy surfaces. A very high number of molecules with ...
Angewandte Chemie-international Edition, 2006
Unlike H 2 O⋅⋅⋅F 2 , the adduct H 2 O⋅⋅⋅F 2 CH 2 displayed an O H⋅⋅⋅F hydrogen bond; for this rea... more Unlike H 2 O⋅⋅⋅F 2 , the adduct H 2 O⋅⋅⋅F 2 CH 2 displayed an O H⋅⋅⋅F hydrogen bond; for this reason, we thought that the study of the rotational spectrum of an adduct of water with an aliphatic molecule containing both Cl and F atoms would give direct evidence ...
Journal of The American Chemical Society, 1998
The free jet millimeter wave spectra of the 1:1 complex between 1,4-dioxane and four isotopomers ... more The free jet millimeter wave spectra of the 1:1 complex between 1,4-dioxane and four isotopomers of water (H 2 O, D 2 O, HDO, and H 2 18 O) have been assigned. The water molecule lies in the plane of symmetry of 1,4-dioxane; the water hydrogen involved in the hydrogen bond is axial with respect to the ring, while the "free" hydrogen is entgegen to the ring. The three atoms involved in the hydrogen bond adopt a bent arrangement with a distance O ring ‚‚‚H of about 1.90 Å and ∠(O ring ‚‚‚H-O) = 163°.
Angewandte Chemie-international Edition, 1998
Completely planar is the hydrogen-bonded complex of pyrazine and water (see sketch), which was ob... more Completely planar is the hydrogen-bonded complex of pyrazine and water (see sketch), which was obtained by supersonic expansion and investigated by rotational spectroscopy. The water molecule lies in the plane of the aromatic ring, and the lone pair of electrons on the ...
Angewandte Chemie, 1998
ABSTRACT