Antonio Raudino | Università di Catania (original) (raw)
Papers by Antonio Raudino
Il Nuovo Cimento D, 1991
ABSTRACT Summary In the present study of fusion between lipid vesicles performed by thermomechani... more ABSTRACT Summary In the present study of fusion between lipid vesicles performed by thermomechanical analysis, isothermal volume variation has been shown to be a reliable tool to follow these kinetics without introducing perturbing probes. In fact, the fusion process is accompanied by bilayer strain release which causes an overall volume decrease of the fused vesicles. Volumetric variations induced by side processes, such as adhesion or ion binding onto the vesicle surface, were accounted for in our measurements. Moreover, by the same technique we followed segregation effects of the membrane lipid components in mixed vesicles. The systems examined were neutral and anionic phospholipids containing vesicles. The role of temperature, vesicle size, lipid composition as well as the influence of different cations were also investigated.
Liquid Crystals, 1989
Lyotropic ternary mixtures of K-palmitate/K-laurate/water with different compositions have been i... more Lyotropic ternary mixtures of K-palmitate/K-laurate/water with different compositions have been investigated by H N.M.R., differential scanning calorimetry and thermo-volumetric analysis. The transitions between rectangular ribbon-like aggregates and lamellar structures have been characterized and explained on the basis of a theoretical model. Our results suggest that for ternary systems containing a small amount of short chain lipids the ribbon structure is
Liquid Crystals, 1988
... by DOMENICO GRASSO, CARMELO LA ROSA, ANTONIO RAUDINO and FELICE ZUCCARELLO Dipartimento di Sc... more ... by DOMENICO GRASSO, CARMELO LA ROSA, ANTONIO RAUDINO and FELICE ZUCCARELLO Dipartimento di Scienze Chimiche, Universita di Catania, Viale ... analysis, for DPPC vesicles in the absence of calcium ions is in excellent agreement with the Wilkinson and Nagle ...
International Journal of Biological Macromolecules, 2001
The interaction between monomeric insulin and monosaccharides has been investigated through circu... more The interaction between monomeric insulin and monosaccharides has been investigated through circular dichroism, fluorescence spectroscopy and two dimensional nuclear magnetic resonance. CD spectra indicate that d-glucose interacts with monomeric insulin whereas d-galactose, d-mannose and 2-deoxy-d-glucose have a lower effect. Fluorescence emission was quenched at sugar concentrations of 5–10 mM. Titration with the different sugars produces a quenching of the tyrosine spectrum from which a binding free energy value for the insulin–sugar complexes has been evaluated. Transfer nuclear Overhauser enhancement NMR experiments indicate the existence of dipolar interactions at short interatomic distances between C-1 proton of d-glucose in the β form and the monomeric insulin. Further, NMR total correlation spectra experiments revealed that the hormone is in the monomeric form and that upon addition of glucose no aggregation occurs. The interaction does not involve relevant changes in the secondary structure of insulin suggesting that the interaction occur at the side chain level. Molecular dynamics simulations and modeling studies, based on the dynamic fluctuations of potential binding moiety sidechains, argued from results of NMR spectroscopy, provide additional informations to locate the putative binding sites of d-glucose to insulin.
International Journal of Biological Macromolecules, 2001
The interaction between monomeric insulin and monosaccharides has been investigated through circu... more The interaction between monomeric insulin and monosaccharides has been investigated through circular dichroism, fluorescence spectroscopy and two dimensional nuclear magnetic resonance. CD spectra indicate that d-glucose interacts with monomeric insulin whereas d-galactose, d-mannose and 2-deoxy-d-glucose have a lower effect. Fluorescence emission was quenched at sugar concentrations of 5–10 mM. Titration with the different sugars produces a quenching of the tyrosine spectrum from which a binding free energy value for the insulin–sugar complexes has been evaluated. Transfer nuclear Overhauser enhancement NMR experiments indicate the existence of dipolar interactions at short interatomic distances between C-1 proton of d-glucose in the β form and the monomeric insulin. Further, NMR total correlation spectra experiments revealed that the hormone is in the monomeric form and that upon addition of glucose no aggregation occurs. The interaction does not involve relevant changes in the secondary structure of insulin suggesting that the interaction occur at the side chain level. Molecular dynamics simulations and modeling studies, based on the dynamic fluctuations of potential binding moiety sidechains, argued from results of NMR spectroscopy, provide additional informations to locate the putative binding sites of d-glucose to insulin.
Http Dx Doi Org 10 1080 02678298808086562, Sep 25, 2007
ABSTRACT
Langmuir, 2007
We present an extensive set of radio wave dielectric relaxation spectroscopy measurements of aque... more We present an extensive set of radio wave dielectric relaxation spectroscopy measurements of aqueous suspensions of different size unilamellar L-alpha-dipalmitoylphosphatidylcholine (DPPC) vesicles, in a temperature range between 15 and 55 C, where the lipidic bilayer experiences structural transitions from the gel to the rippled phase (at the pretransition temperature) and from the rippled to the liquid phase (at the main transition temperature). The dielectric spectra have been analyzed in the light of the Cole-Cole relaxation function, and the main dielectric parameters-the dielectric increment Deltaepsilon and the mean relaxation frequency omega(0)--have been evaluated as a function of temperature. These parameters display a very complex phenomenology, depending on the structural arrangement of the lipid-water interface. The structural parameters that govern the dielectric behavior of these systems associated with the lipid bilayer have been recognized within a recent dynamic mean-field model we have proposed, aimed to predict the dipolar relaxation of an array of strongly interacting dipoles anchored to a flat or corrugated surface. They are the prefactor A(T) of the distance-dependent part of the effective dipolar interaction energy, the term Gamma(vis), that takes into account the damping of the dipolar motion, the average dipolar distance related to the area a(0) per polar head, and the bilayer thickness. The present analysis furnishes, from a phenomenological point of view, the dependence of these parameters on the temperature and on the vesicle size.
Journal of Theoretical Biology, 1994
Macromolecules, Sep 1, 1992
ABSTRACT The interaction between charged lipid vesicles suspended in an electrolyte solution cont... more ABSTRACT The interaction between charged lipid vesicles suspended in an electrolyte solution containing uncharged polymers has been described by a theoretical model and some of the main predictions have been tested by differential scanning calorimetry (DSC) measurements. The model takes into account neutralization of the lipid head groups through the adsorption of specific ions. The distribution of the ions and polymer and the charge density on the vesicle's surface have been considered as variational parameters which can be calculated by minimizing the total free energy of the system. The model has been used to calculate the effect of the polymer on the lateral peak separation of lipids in the vesicle, and the inhomogeneous lipid distribution has been detected as a splitting of the calorimetric peak associated with the gel to liquid-crystal phase transition.
Journal of Molecular Structure Theochem, 1994
By combining statistical and quantum mechanical calculations, we have developed an approximate bu... more By combining statistical and quantum mechanical calculations, we have developed an approximate but simple method to investigate the effect of H-bonding on the mean height of a system formed by interacting polymer chains anchored to a flat surface (polymer brushes). In particular, we have investigated polymers lying in two dichotomic conformational states, one forming internal H-bonds and the other showing preferential interactions with solvent or adjacent chains. The model has been applied to polysaccharide chains attached to a flat surface selected as a model of a cell membrane surface.
Theochem Journal of Molecular Structure, 1988
Il Nuovo Cimento D, 1991
ABSTRACT Summary In the present study of fusion between lipid vesicles performed by thermomechani... more ABSTRACT Summary In the present study of fusion between lipid vesicles performed by thermomechanical analysis, isothermal volume variation has been shown to be a reliable tool to follow these kinetics without introducing perturbing probes. In fact, the fusion process is accompanied by bilayer strain release which causes an overall volume decrease of the fused vesicles. Volumetric variations induced by side processes, such as adhesion or ion binding onto the vesicle surface, were accounted for in our measurements. Moreover, by the same technique we followed segregation effects of the membrane lipid components in mixed vesicles. The systems examined were neutral and anionic phospholipids containing vesicles. The role of temperature, vesicle size, lipid composition as well as the influence of different cations were also investigated.
Journal of the Chemical Society, Faraday Transactions 2, 1989
ABSTRACT
Journal of the Chemical Society, Faraday Transactions 2, 1981
Journal of Molecular Structure: THEOCHEM, 1994
By combining statistical and quantum mechanical calculations, we have developed an approximate bu... more By combining statistical and quantum mechanical calculations, we have developed an approximate but simple method to investigate the effect of H-bonding on the mean height of a system formed by interacting polymer chains anchored to a flat surface (polymer brushes). In particular, we have investigated polymers lying in two dichotomic conformational states, one forming internal H-bonds and the other showing preferential interactions with solvent or adjacent chains. The model has been applied to polysaccharide chains attached to a flat surface selected as a model of a cell membrane surface.
Journal of the Chemical Society, Faraday Transactions 2, 1985
ABSTRACT
The Journal of Physical Chemistry, 1995
ABSTRACT The role of nonlinear dynamics in determining the shape of an isolated fluctuating lipid... more ABSTRACT The role of nonlinear dynamics in determining the shape of an isolated fluctuating lipid bilayer has been investigated. The bilayer has been modeled as consisting of two identical back-to-back coupled monolayers interacting with elastic forces. The anharmonic term in the bending energy of each isolated monolayer has been considered and the resulting equations of motion have been solved. The inclusion of the nonharmonic term in the bending elasticity leads to new phenomena, the most striking of which is the temperature-dependent shrinkage of the bilayer edge, which could stabilize the formation of finite size disks by reducing the unfavorable edge energy due to water exposure to the bilayer hydrophobic core. Theory predicts that dynamic disk stabilization could be allowed for very flexible bilayers bearing bulky hydrophilic head groups.
The Journal of Physical Chemistry, 1990
... Antonio Raudino,* Francesco Castelli, and Salvatore Gurrieri Dipartimenfo di Scienze Chimiche... more ... Antonio Raudino,* Francesco Castelli, and Salvatore Gurrieri Dipartimenfo di Scienze Chimiche, Universitci di Catania, Male Andrea Doria, 8-951 25 Catania, Italy (Received: April 25, 1989: In Final Form: August 4, 1989) ... Acta 1978,512,84. (b) Sackmann, E.; Ruppel, D.; Gebbart ...
The Journal of Physical Chemistry, 1996
... Antonio Grassi and Antonio Raudino*. Dipartimento di Scienze Chimiche, Universitá di Catania,... more ... Antonio Grassi and Antonio Raudino*. Dipartimento di Scienze Chimiche, Universitá di Catania, Viale A. Doria 6-95125, Catania, Italy. J. Phys. Chem. ... 5) Cruzeiro-Hansson, L.; Mouritsen, OG Biochim. Biophys. Acta 1988, 944, 63. ...
Il Nuovo Cimento D, 1991
ABSTRACT Summary In the present study of fusion between lipid vesicles performed by thermomechani... more ABSTRACT Summary In the present study of fusion between lipid vesicles performed by thermomechanical analysis, isothermal volume variation has been shown to be a reliable tool to follow these kinetics without introducing perturbing probes. In fact, the fusion process is accompanied by bilayer strain release which causes an overall volume decrease of the fused vesicles. Volumetric variations induced by side processes, such as adhesion or ion binding onto the vesicle surface, were accounted for in our measurements. Moreover, by the same technique we followed segregation effects of the membrane lipid components in mixed vesicles. The systems examined were neutral and anionic phospholipids containing vesicles. The role of temperature, vesicle size, lipid composition as well as the influence of different cations were also investigated.
Liquid Crystals, 1989
Lyotropic ternary mixtures of K-palmitate/K-laurate/water with different compositions have been i... more Lyotropic ternary mixtures of K-palmitate/K-laurate/water with different compositions have been investigated by H N.M.R., differential scanning calorimetry and thermo-volumetric analysis. The transitions between rectangular ribbon-like aggregates and lamellar structures have been characterized and explained on the basis of a theoretical model. Our results suggest that for ternary systems containing a small amount of short chain lipids the ribbon structure is
Liquid Crystals, 1988
... by DOMENICO GRASSO, CARMELO LA ROSA, ANTONIO RAUDINO and FELICE ZUCCARELLO Dipartimento di Sc... more ... by DOMENICO GRASSO, CARMELO LA ROSA, ANTONIO RAUDINO and FELICE ZUCCARELLO Dipartimento di Scienze Chimiche, Universita di Catania, Viale ... analysis, for DPPC vesicles in the absence of calcium ions is in excellent agreement with the Wilkinson and Nagle ...
International Journal of Biological Macromolecules, 2001
The interaction between monomeric insulin and monosaccharides has been investigated through circu... more The interaction between monomeric insulin and monosaccharides has been investigated through circular dichroism, fluorescence spectroscopy and two dimensional nuclear magnetic resonance. CD spectra indicate that d-glucose interacts with monomeric insulin whereas d-galactose, d-mannose and 2-deoxy-d-glucose have a lower effect. Fluorescence emission was quenched at sugar concentrations of 5–10 mM. Titration with the different sugars produces a quenching of the tyrosine spectrum from which a binding free energy value for the insulin–sugar complexes has been evaluated. Transfer nuclear Overhauser enhancement NMR experiments indicate the existence of dipolar interactions at short interatomic distances between C-1 proton of d-glucose in the β form and the monomeric insulin. Further, NMR total correlation spectra experiments revealed that the hormone is in the monomeric form and that upon addition of glucose no aggregation occurs. The interaction does not involve relevant changes in the secondary structure of insulin suggesting that the interaction occur at the side chain level. Molecular dynamics simulations and modeling studies, based on the dynamic fluctuations of potential binding moiety sidechains, argued from results of NMR spectroscopy, provide additional informations to locate the putative binding sites of d-glucose to insulin.
International Journal of Biological Macromolecules, 2001
The interaction between monomeric insulin and monosaccharides has been investigated through circu... more The interaction between monomeric insulin and monosaccharides has been investigated through circular dichroism, fluorescence spectroscopy and two dimensional nuclear magnetic resonance. CD spectra indicate that d-glucose interacts with monomeric insulin whereas d-galactose, d-mannose and 2-deoxy-d-glucose have a lower effect. Fluorescence emission was quenched at sugar concentrations of 5–10 mM. Titration with the different sugars produces a quenching of the tyrosine spectrum from which a binding free energy value for the insulin–sugar complexes has been evaluated. Transfer nuclear Overhauser enhancement NMR experiments indicate the existence of dipolar interactions at short interatomic distances between C-1 proton of d-glucose in the β form and the monomeric insulin. Further, NMR total correlation spectra experiments revealed that the hormone is in the monomeric form and that upon addition of glucose no aggregation occurs. The interaction does not involve relevant changes in the secondary structure of insulin suggesting that the interaction occur at the side chain level. Molecular dynamics simulations and modeling studies, based on the dynamic fluctuations of potential binding moiety sidechains, argued from results of NMR spectroscopy, provide additional informations to locate the putative binding sites of d-glucose to insulin.
Http Dx Doi Org 10 1080 02678298808086562, Sep 25, 2007
ABSTRACT
Langmuir, 2007
We present an extensive set of radio wave dielectric relaxation spectroscopy measurements of aque... more We present an extensive set of radio wave dielectric relaxation spectroscopy measurements of aqueous suspensions of different size unilamellar L-alpha-dipalmitoylphosphatidylcholine (DPPC) vesicles, in a temperature range between 15 and 55 C, where the lipidic bilayer experiences structural transitions from the gel to the rippled phase (at the pretransition temperature) and from the rippled to the liquid phase (at the main transition temperature). The dielectric spectra have been analyzed in the light of the Cole-Cole relaxation function, and the main dielectric parameters-the dielectric increment Deltaepsilon and the mean relaxation frequency omega(0)--have been evaluated as a function of temperature. These parameters display a very complex phenomenology, depending on the structural arrangement of the lipid-water interface. The structural parameters that govern the dielectric behavior of these systems associated with the lipid bilayer have been recognized within a recent dynamic mean-field model we have proposed, aimed to predict the dipolar relaxation of an array of strongly interacting dipoles anchored to a flat or corrugated surface. They are the prefactor A(T) of the distance-dependent part of the effective dipolar interaction energy, the term Gamma(vis), that takes into account the damping of the dipolar motion, the average dipolar distance related to the area a(0) per polar head, and the bilayer thickness. The present analysis furnishes, from a phenomenological point of view, the dependence of these parameters on the temperature and on the vesicle size.
Journal of Theoretical Biology, 1994
Macromolecules, Sep 1, 1992
ABSTRACT The interaction between charged lipid vesicles suspended in an electrolyte solution cont... more ABSTRACT The interaction between charged lipid vesicles suspended in an electrolyte solution containing uncharged polymers has been described by a theoretical model and some of the main predictions have been tested by differential scanning calorimetry (DSC) measurements. The model takes into account neutralization of the lipid head groups through the adsorption of specific ions. The distribution of the ions and polymer and the charge density on the vesicle's surface have been considered as variational parameters which can be calculated by minimizing the total free energy of the system. The model has been used to calculate the effect of the polymer on the lateral peak separation of lipids in the vesicle, and the inhomogeneous lipid distribution has been detected as a splitting of the calorimetric peak associated with the gel to liquid-crystal phase transition.
Journal of Molecular Structure Theochem, 1994
By combining statistical and quantum mechanical calculations, we have developed an approximate bu... more By combining statistical and quantum mechanical calculations, we have developed an approximate but simple method to investigate the effect of H-bonding on the mean height of a system formed by interacting polymer chains anchored to a flat surface (polymer brushes). In particular, we have investigated polymers lying in two dichotomic conformational states, one forming internal H-bonds and the other showing preferential interactions with solvent or adjacent chains. The model has been applied to polysaccharide chains attached to a flat surface selected as a model of a cell membrane surface.
Theochem Journal of Molecular Structure, 1988
Il Nuovo Cimento D, 1991
ABSTRACT Summary In the present study of fusion between lipid vesicles performed by thermomechani... more ABSTRACT Summary In the present study of fusion between lipid vesicles performed by thermomechanical analysis, isothermal volume variation has been shown to be a reliable tool to follow these kinetics without introducing perturbing probes. In fact, the fusion process is accompanied by bilayer strain release which causes an overall volume decrease of the fused vesicles. Volumetric variations induced by side processes, such as adhesion or ion binding onto the vesicle surface, were accounted for in our measurements. Moreover, by the same technique we followed segregation effects of the membrane lipid components in mixed vesicles. The systems examined were neutral and anionic phospholipids containing vesicles. The role of temperature, vesicle size, lipid composition as well as the influence of different cations were also investigated.
Journal of the Chemical Society, Faraday Transactions 2, 1989
ABSTRACT
Journal of the Chemical Society, Faraday Transactions 2, 1981
Journal of Molecular Structure: THEOCHEM, 1994
By combining statistical and quantum mechanical calculations, we have developed an approximate bu... more By combining statistical and quantum mechanical calculations, we have developed an approximate but simple method to investigate the effect of H-bonding on the mean height of a system formed by interacting polymer chains anchored to a flat surface (polymer brushes). In particular, we have investigated polymers lying in two dichotomic conformational states, one forming internal H-bonds and the other showing preferential interactions with solvent or adjacent chains. The model has been applied to polysaccharide chains attached to a flat surface selected as a model of a cell membrane surface.
Journal of the Chemical Society, Faraday Transactions 2, 1985
ABSTRACT
The Journal of Physical Chemistry, 1995
ABSTRACT The role of nonlinear dynamics in determining the shape of an isolated fluctuating lipid... more ABSTRACT The role of nonlinear dynamics in determining the shape of an isolated fluctuating lipid bilayer has been investigated. The bilayer has been modeled as consisting of two identical back-to-back coupled monolayers interacting with elastic forces. The anharmonic term in the bending energy of each isolated monolayer has been considered and the resulting equations of motion have been solved. The inclusion of the nonharmonic term in the bending elasticity leads to new phenomena, the most striking of which is the temperature-dependent shrinkage of the bilayer edge, which could stabilize the formation of finite size disks by reducing the unfavorable edge energy due to water exposure to the bilayer hydrophobic core. Theory predicts that dynamic disk stabilization could be allowed for very flexible bilayers bearing bulky hydrophilic head groups.
The Journal of Physical Chemistry, 1990
... Antonio Raudino,* Francesco Castelli, and Salvatore Gurrieri Dipartimenfo di Scienze Chimiche... more ... Antonio Raudino,* Francesco Castelli, and Salvatore Gurrieri Dipartimenfo di Scienze Chimiche, Universitci di Catania, Male Andrea Doria, 8-951 25 Catania, Italy (Received: April 25, 1989: In Final Form: August 4, 1989) ... Acta 1978,512,84. (b) Sackmann, E.; Ruppel, D.; Gebbart ...
The Journal of Physical Chemistry, 1996
... Antonio Grassi and Antonio Raudino*. Dipartimento di Scienze Chimiche, Universitá di Catania,... more ... Antonio Grassi and Antonio Raudino*. Dipartimento di Scienze Chimiche, Universitá di Catania, Viale A. Doria 6-95125, Catania, Italy. J. Phys. Chem. ... 5) Cruzeiro-Hansson, L.; Mouritsen, OG Biochim. Biophys. Acta 1988, 944, 63. ...