Enrico Chiavazza | Università degli Studi di Torino (original) (raw)

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Papers by Enrico Chiavazza

Research paper thumbnail of Charge-transfer complexes of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with amino molecules in polar solvents

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015

The charge-transfer complexes have scientific relevance because this type of molecular interactio... more The charge-transfer complexes have scientific relevance because this type of molecular interaction is at the basis of the activity of pharmacological compounds and because the absorption bands of the complexes can be used for the quantification of electron donor molecules. This work aims to assess the stability of the charge-transfer complexes between the electron acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and two drugs, procaine and atenolol, in acetonitrile and ethanol. The stability of DDQ in solution and the time required to obtain the maximum complex formation were evaluated. The stoichiometry and the stability of the complexes were determined, respectively, by Job's plot method and by the elaboration of UV-vis titrations data. The latter task was carried out by using the non-linear global analysis approach to determine the equilibrium constants. This approach to data elaboration allowed us to overcome the disadvantages of the classical linear-regression method, to obtain reliable values of the association constants and to calculate the entire spectra of the complexes. NMR spectra were recorded to identify the portion of the donor molecule that was involved in the interaction. The data support the participation of the aliphatic amino groups in complex formation and exclude the involvement of the aromatic amine present in the procaine molecule.

Research paper thumbnail of Voltammetric analysis of Acetaminophen: when complexity does not pay

Research paper thumbnail of Hyperpolarization quenching in 13C nuclei bound to fast relaxing quadrupolar 14N mediated by scalar coupling relaxation in amide groups exposed to Earth's magnetic field

Hyperpolarization quenching in 13 C nuclei bound to fast relaxing quadrupolar 14 N mediated by sc... more Hyperpolarization quenching in 13 C nuclei bound to fast relaxing quadrupolar 14 N mediated by scalar coupling relaxation in amide groups exposed to Earth's magnetic field

Research paper thumbnail of In Vivo Magnetic Resonance Imaging Detection of Paramagnetic Liposomes Loaded with Amphiphilic Gadolinium(III) Complexes: Impact of Molecular Structure on Relaxivity and Excretion Efficiency

Research paper thumbnail of CT complexes of DDQ with amino molecules in polar solvents

The charge--transfer (CT) complexes formed from the reac=on of electron acceptors with donors con... more The charge--transfer (CT) complexes formed from the reac=on of electron acceptors with donors containing heteroatoms, such as nitrogen, sulphur or oxygen, have seen a growing importance in recent years. In par=cular, they can play an important role in analy=cal chemistry because they can be used in the quan=ta=ve es=ma=ons of drugs [1--5]. In this work the interac=on of the acceptor DDQ with molecules containing nitrogen atoms in acetonitrile and ethanol was studied. We evaluated that the DDQ preferen=ally interacts with not aroma=c amines, therefore the aJen=on was focused on the study of the interac=on of DDQ with two molecules containing these func=onal groups: a ß--adrenergic blocking drug, the atenolol, and a synthe=c local anaesthe=c drug, the procaine .

Research paper thumbnail of Earth’s magnetic field enabled scalar coupling relaxation of 13C nuclei bound to fast-relaxing quadrupolar 14N in amide groups

Journal of Magnetic Resonance, 2013

Scalar coupling relaxation, which is usually only associated with closely resonant nuclei (e.g., ... more Scalar coupling relaxation, which is usually only associated with closely resonant nuclei (e.g., 79 Br-13 C), can be a very effective relaxation mechanism. While working on hyperpolarized [5-13 C]glutamine, fast liquid-state polarization decay during transfer to the MRI scanner was observed. This behavior could hypothetically be explained by substantial T 1 shortening due to a scalar coupling contribution (type II) to the relaxation caused by the fast-relaxing quadrupolar 14 N adjacent to the 13 C nucleus in the amide group. This contribution is only effective in low magnetic fields (i.e., less than 800 lT) and prevents the use of molecules bearing the 13 C-amide group as hyperpolarized MRS/MRI probes. In the present work, this hypothesis is explored both theoretically and experimentally. The results show that high hyperpolarization levels can be retained using either a 15 N-labeled amide or by applying a magnetic field during transfer of the sample from the polarizer to the MRI scanner.

Research paper thumbnail of 15 N- P ermethylated amino acids as efficient probes for MRI-DNP applications

Contrast Media & Molecular Imaging, 2013

The synthesis, NMR properties and preliminary polarization tests on protonated and perdeuterated ... more The synthesis, NMR properties and preliminary polarization tests on protonated and perdeuterated forms of a-trimethylglutamine (NMe 3 Gln), a-trimethylglutamate (NMe 3 Glu) and «-trimethyllysine (NMe 3 Lys) are reported. The 15 N-permethylated, perdeuterated amino acids display very long 15 N-T 1 values, ranging between 190 and 330 s, are well polarized by the dynamic nuclear polarization (DNP) procedure, yielding good polarization levels (10%), and appear to be well tolerated by cells and mice. The obtained results make perdeuterated amino acids excellent candidates for innovative DNP 15 N-MRI applications such as perfusion or targeting studies.

Research paper thumbnail of Charge-transfer complexes of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with amino molecules in polar solvents

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015

The charge-transfer complexes have scientific relevance because this type of molecular interactio... more The charge-transfer complexes have scientific relevance because this type of molecular interaction is at the basis of the activity of pharmacological compounds and because the absorption bands of the complexes can be used for the quantification of electron donor molecules. This work aims to assess the stability of the charge-transfer complexes between the electron acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and two drugs, procaine and atenolol, in acetonitrile and ethanol. The stability of DDQ in solution and the time required to obtain the maximum complex formation were evaluated. The stoichiometry and the stability of the complexes were determined, respectively, by Job's plot method and by the elaboration of UV-vis titrations data. The latter task was carried out by using the non-linear global analysis approach to determine the equilibrium constants. This approach to data elaboration allowed us to overcome the disadvantages of the classical linear-regression method, to obtain reliable values of the association constants and to calculate the entire spectra of the complexes. NMR spectra were recorded to identify the portion of the donor molecule that was involved in the interaction. The data support the participation of the aliphatic amino groups in complex formation and exclude the involvement of the aromatic amine present in the procaine molecule.

Research paper thumbnail of Voltammetric analysis of Acetaminophen: when complexity does not pay

Research paper thumbnail of Hyperpolarization quenching in 13C nuclei bound to fast relaxing quadrupolar 14N mediated by scalar coupling relaxation in amide groups exposed to Earth's magnetic field

Hyperpolarization quenching in 13 C nuclei bound to fast relaxing quadrupolar 14 N mediated by sc... more Hyperpolarization quenching in 13 C nuclei bound to fast relaxing quadrupolar 14 N mediated by scalar coupling relaxation in amide groups exposed to Earth's magnetic field

Research paper thumbnail of In Vivo Magnetic Resonance Imaging Detection of Paramagnetic Liposomes Loaded with Amphiphilic Gadolinium(III) Complexes: Impact of Molecular Structure on Relaxivity and Excretion Efficiency

Research paper thumbnail of CT complexes of DDQ with amino molecules in polar solvents

The charge--transfer (CT) complexes formed from the reac=on of electron acceptors with donors con... more The charge--transfer (CT) complexes formed from the reac=on of electron acceptors with donors containing heteroatoms, such as nitrogen, sulphur or oxygen, have seen a growing importance in recent years. In par=cular, they can play an important role in analy=cal chemistry because they can be used in the quan=ta=ve es=ma=ons of drugs [1--5]. In this work the interac=on of the acceptor DDQ with molecules containing nitrogen atoms in acetonitrile and ethanol was studied. We evaluated that the DDQ preferen=ally interacts with not aroma=c amines, therefore the aJen=on was focused on the study of the interac=on of DDQ with two molecules containing these func=onal groups: a ß--adrenergic blocking drug, the atenolol, and a synthe=c local anaesthe=c drug, the procaine .

Research paper thumbnail of Earth’s magnetic field enabled scalar coupling relaxation of 13C nuclei bound to fast-relaxing quadrupolar 14N in amide groups

Journal of Magnetic Resonance, 2013

Scalar coupling relaxation, which is usually only associated with closely resonant nuclei (e.g., ... more Scalar coupling relaxation, which is usually only associated with closely resonant nuclei (e.g., 79 Br-13 C), can be a very effective relaxation mechanism. While working on hyperpolarized [5-13 C]glutamine, fast liquid-state polarization decay during transfer to the MRI scanner was observed. This behavior could hypothetically be explained by substantial T 1 shortening due to a scalar coupling contribution (type II) to the relaxation caused by the fast-relaxing quadrupolar 14 N adjacent to the 13 C nucleus in the amide group. This contribution is only effective in low magnetic fields (i.e., less than 800 lT) and prevents the use of molecules bearing the 13 C-amide group as hyperpolarized MRS/MRI probes. In the present work, this hypothesis is explored both theoretically and experimentally. The results show that high hyperpolarization levels can be retained using either a 15 N-labeled amide or by applying a magnetic field during transfer of the sample from the polarizer to the MRI scanner.

Research paper thumbnail of 15 N- P ermethylated amino acids as efficient probes for MRI-DNP applications

Contrast Media & Molecular Imaging, 2013

The synthesis, NMR properties and preliminary polarization tests on protonated and perdeuterated ... more The synthesis, NMR properties and preliminary polarization tests on protonated and perdeuterated forms of a-trimethylglutamine (NMe 3 Gln), a-trimethylglutamate (NMe 3 Glu) and «-trimethyllysine (NMe 3 Lys) are reported. The 15 N-permethylated, perdeuterated amino acids display very long 15 N-T 1 values, ranging between 190 and 330 s, are well polarized by the dynamic nuclear polarization (DNP) procedure, yielding good polarization levels (10%), and appear to be well tolerated by cells and mice. The obtained results make perdeuterated amino acids excellent candidates for innovative DNP 15 N-MRI applications such as perfusion or targeting studies.