Simona Lai - Academia.edu (original) (raw)
Papers by Simona Lai
Polyhedron, 2002
Due to the increasing interest in the use of biomasses from agriculture as removing agents for he... more Due to the increasing interest in the use of biomasses from agriculture as removing agents for heavy metals in waste effluents, we present here a joint potentiometric and 13 C MAS and cross polarization-magic angle spinning NMR (CP-MAS NMR) study on cork interaction with Cu(II) and Ni(II). Through potentiometry we were able to distinguish two kind of interactions, a stronger one which involves protonated sites on cork and a second that allows hydroxide precipitation of the bound metal ion into the cork structure. NMR signal analysis suggests a specific metal complexation on the carbohydrate moieties of polymeric cork matrix. The 13 C MAS NMR suggests that the dynamics in the MHz range and the overall arrangement of polymeric matrix is not affected by metal binding; and the spin relaxation times T 1r ( 1 H) and T 1r ( 13 C) show that no significant difference of relaxation processes in the KHz range is introduced by metal coordination. #
Journal of Polymer Science Part A-polymer Chemistry, 2003
Dry and hydrated poly(vinyl alcohol) (PVA) gels with 55% (a-PVA) and 61% (s-PVA) syndiotacticity ... more Dry and hydrated poly(vinyl alcohol) (PVA) gels with 55% (a-PVA) and 61% (s-PVA) syndiotacticity and related PVA/lactyl chitosan (LC) blends have been investigated with 129Xe and cross-polarization/magic-angle-spinning 13C NMR techniques. Although the dry gels exhibit two broad 129Xe resonances in the slow-to-intermediate exchange limit, both hydrated gels show three resonances. The corresponding dry blends exhibit two signals, the chemical shifts and line widths of which change with respect to those of pure PVA, whereas one (a-PVA/LC) or two (s-PVA/LC) signals appear in the spectra of the hydrated blends. A comparative analysis of the data demonstrates that LC rearranges the domains of the polymeric matrix in both the dry and hydrated blends according to the syndiotacticity of the PVA chains. Information on the molecular motions of the amorphous and swollen polymeric domains in the kilohertz range has been obtained from an analysis of the spin-lattice relaxation times. These data indicate that the dynamics and arrangement of the PVA chains in the gels are strongly affected by their tacticity and the addition of the copolymer LC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3123–3131, 2003
Solid State Nuclear Magnetic Resonance, 2002
Poly(vinyl alcohol) (PVA) with 55% and 61% syndiotacticity, and their related dry and hydrated ge... more Poly(vinyl alcohol) (PVA) with 55% and 61% syndiotacticity, and their related dry and hydrated gels obtained by two different freeze-thawing cycles have been investigated using the solid-state 13 C CP-MAS NMR technique. From a comparative analysis of the spectra, evidence was obtained that the gelation process largely disrupts the intramolecular hydrogen-bonded network of the PVA. The addition of water to the dry gels favours their swelling, destroying intra-chain hydrogen bonds between hydroxyl groups as a function of the degree of tacticity and the gelation procedure, and promotes the formation of new networks of interchain hydrogen bonds. Information on the dynamics of the polymeric domains in the kilohertz range has been obtained from the analysis of the spin relaxation times T 1r ð 1 HÞ and T 1r ð 13 CÞ, indicating that homogeneous arrangements of the amorphous or swollen polymeric chains exist, independent of the preparation method or the tacticity of the PVA chains. # 2002 Elsevier Science (USA)
Carbohydrate Research, 2003
An inclusion complex between imazalil (IMZ), a selected fungicide, and cyclomaltoheptaose (β-cycl... more An inclusion complex between imazalil (IMZ), a selected fungicide, and cyclomaltoheptaose (β-cyclodextrin, βCD) was obtained using supercritical fluid carbon dioxide. The best preparation conditions were determined, and the inclusion complex was investigated by means of 1H NMR spectroscopy in aqueous solution and 13C CPMAS NMR spectroscopy in the solid state. Information on the geometry of the βCD/IMZ complex was obtained from ROESY spectroscopy, while the dynamics of the inclusion complex in the kilohertz range was obtained from the proton spin-lattice relaxation times in the rotating frame, T1ρ (1H).
Phytochemistry, 2003
Grapefruit, Citrus paradisi, were injured, inoculated with Penicillium digitatum and incubated un... more Grapefruit, Citrus paradisi, were injured, inoculated with Penicillium digitatum and incubated under conditions favourable for the accumulation of defence related material. Histochemical examination revealed that tissues adjacent to inoculated injuries contained phloroglucinol-HCl (PG-HCl) reactive material. Solvent washed cell wall preparations of intact and injured-inoculated peel were further purified using a mixture of cell wall degrading enzymes. Samples from injured inoculated tissue contained PG-HCl reactive globular material in addition to the fragments of xylem and cuticle found in controls. The principal chemical moieties of the material that accumulates in grapefruit injuries during wound-healing were studied by solid state 13 C cross-polarization magic angle spinning NMR. A complete assignment of the NMR signals was made. From the analysis evidence was found that cellulose and hemicellulose are the biopolymers present in the intact peel samples, in addition, relevant quantities of cutin were found in the residues of enzyme digest. The NMR difference spectrum intact-wounded peels showed resonances which were attributed to all major functional groups of the aromatic-aliphatic suberin polyester of new material produced by the wounds. Information on the latter polyester was obtained by analyzing the T 1 r ( 1 H) relaxation. #
Chemistry & Biodiversity, 2004
β-Cyclodextrin (β-CD) inclusion complexes with carvacrol (1), thymol (2), and eugenol (3) (compon... more β-Cyclodextrin (β-CD) inclusion complexes with carvacrol (1), thymol (2), and eugenol (3) (components of essential oils of vegetable origin) were prepared by the supercritical CO2 technique, and their structural characterization was achieved by means of 1H-NMR in aqueous solution and 13C-CPMAS NMR in the solid state. Evidence of the formation of the inclusion complexes for all the examined systems was obtained by 1H-NMR in solution, while 2D-ROESY-NMR experiments were used to investigate the geometry of inclusion. In addition, the dynamics of these inclusion complexes in the kHz timescale was investigated by analysis of the 1H and 13C spin-lattice relaxation times in the rotating frame.
Polyhedron, 2002
Due to the increasing interest in the use of biomasses from agriculture as removing agents for he... more Due to the increasing interest in the use of biomasses from agriculture as removing agents for heavy metals in waste effluents, we present here a joint potentiometric and 13 C MAS and cross polarization-magic angle spinning NMR (CP-MAS NMR) study on cork interaction with Cu(II) and Ni(II). Through potentiometry we were able to distinguish two kind of interactions, a stronger one which involves protonated sites on cork and a second that allows hydroxide precipitation of the bound metal ion into the cork structure. NMR signal analysis suggests a specific metal complexation on the carbohydrate moieties of polymeric cork matrix. The 13 C MAS NMR suggests that the dynamics in the MHz range and the overall arrangement of polymeric matrix is not affected by metal binding; and the spin relaxation times T 1r ( 1 H) and T 1r ( 13 C) show that no significant difference of relaxation processes in the KHz range is introduced by metal coordination. #
Journal of Polymer Science Part A-polymer Chemistry, 2003
Dry and hydrated poly(vinyl alcohol) (PVA) gels with 55% (a-PVA) and 61% (s-PVA) syndiotacticity ... more Dry and hydrated poly(vinyl alcohol) (PVA) gels with 55% (a-PVA) and 61% (s-PVA) syndiotacticity and related PVA/lactyl chitosan (LC) blends have been investigated with 129Xe and cross-polarization/magic-angle-spinning 13C NMR techniques. Although the dry gels exhibit two broad 129Xe resonances in the slow-to-intermediate exchange limit, both hydrated gels show three resonances. The corresponding dry blends exhibit two signals, the chemical shifts and line widths of which change with respect to those of pure PVA, whereas one (a-PVA/LC) or two (s-PVA/LC) signals appear in the spectra of the hydrated blends. A comparative analysis of the data demonstrates that LC rearranges the domains of the polymeric matrix in both the dry and hydrated blends according to the syndiotacticity of the PVA chains. Information on the molecular motions of the amorphous and swollen polymeric domains in the kilohertz range has been obtained from an analysis of the spin-lattice relaxation times. These data indicate that the dynamics and arrangement of the PVA chains in the gels are strongly affected by their tacticity and the addition of the copolymer LC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3123–3131, 2003
Solid State Nuclear Magnetic Resonance, 2002
Poly(vinyl alcohol) (PVA) with 55% and 61% syndiotacticity, and their related dry and hydrated ge... more Poly(vinyl alcohol) (PVA) with 55% and 61% syndiotacticity, and their related dry and hydrated gels obtained by two different freeze-thawing cycles have been investigated using the solid-state 13 C CP-MAS NMR technique. From a comparative analysis of the spectra, evidence was obtained that the gelation process largely disrupts the intramolecular hydrogen-bonded network of the PVA. The addition of water to the dry gels favours their swelling, destroying intra-chain hydrogen bonds between hydroxyl groups as a function of the degree of tacticity and the gelation procedure, and promotes the formation of new networks of interchain hydrogen bonds. Information on the dynamics of the polymeric domains in the kilohertz range has been obtained from the analysis of the spin relaxation times T 1r ð 1 HÞ and T 1r ð 13 CÞ, indicating that homogeneous arrangements of the amorphous or swollen polymeric chains exist, independent of the preparation method or the tacticity of the PVA chains. # 2002 Elsevier Science (USA)
Carbohydrate Research, 2003
An inclusion complex between imazalil (IMZ), a selected fungicide, and cyclomaltoheptaose (β-cycl... more An inclusion complex between imazalil (IMZ), a selected fungicide, and cyclomaltoheptaose (β-cyclodextrin, βCD) was obtained using supercritical fluid carbon dioxide. The best preparation conditions were determined, and the inclusion complex was investigated by means of 1H NMR spectroscopy in aqueous solution and 13C CPMAS NMR spectroscopy in the solid state. Information on the geometry of the βCD/IMZ complex was obtained from ROESY spectroscopy, while the dynamics of the inclusion complex in the kilohertz range was obtained from the proton spin-lattice relaxation times in the rotating frame, T1ρ (1H).
Phytochemistry, 2003
Grapefruit, Citrus paradisi, were injured, inoculated with Penicillium digitatum and incubated un... more Grapefruit, Citrus paradisi, were injured, inoculated with Penicillium digitatum and incubated under conditions favourable for the accumulation of defence related material. Histochemical examination revealed that tissues adjacent to inoculated injuries contained phloroglucinol-HCl (PG-HCl) reactive material. Solvent washed cell wall preparations of intact and injured-inoculated peel were further purified using a mixture of cell wall degrading enzymes. Samples from injured inoculated tissue contained PG-HCl reactive globular material in addition to the fragments of xylem and cuticle found in controls. The principal chemical moieties of the material that accumulates in grapefruit injuries during wound-healing were studied by solid state 13 C cross-polarization magic angle spinning NMR. A complete assignment of the NMR signals was made. From the analysis evidence was found that cellulose and hemicellulose are the biopolymers present in the intact peel samples, in addition, relevant quantities of cutin were found in the residues of enzyme digest. The NMR difference spectrum intact-wounded peels showed resonances which were attributed to all major functional groups of the aromatic-aliphatic suberin polyester of new material produced by the wounds. Information on the latter polyester was obtained by analyzing the T 1 r ( 1 H) relaxation. #
Chemistry & Biodiversity, 2004
β-Cyclodextrin (β-CD) inclusion complexes with carvacrol (1), thymol (2), and eugenol (3) (compon... more β-Cyclodextrin (β-CD) inclusion complexes with carvacrol (1), thymol (2), and eugenol (3) (components of essential oils of vegetable origin) were prepared by the supercritical CO2 technique, and their structural characterization was achieved by means of 1H-NMR in aqueous solution and 13C-CPMAS NMR in the solid state. Evidence of the formation of the inclusion complexes for all the examined systems was obtained by 1H-NMR in solution, while 2D-ROESY-NMR experiments were used to investigate the geometry of inclusion. In addition, the dynamics of these inclusion complexes in the kHz timescale was investigated by analysis of the 1H and 13C spin-lattice relaxation times in the rotating frame.