Center for Colloid and Surface Science

Firenze, Italy

Center for Colloid and Surface Science

Firenze, Italy

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Palazzo G.,University of Bari | Palazzo G.,Center for Colloid and Surface Science | Magliulo M.,University of Bari | Mallardi A.,CNR Institute for Chemical and Physical Processes | And 11 more authors.
ACS Nano | Year: 2014

An organic field-effect transistor (OFET) integrating bacteriorhodopsin (bR) nanoassembled lamellae is proposed for an in-depth study of the proton translocation processes occurring as the bioelectronic device is exposed either to light or to low concentrations of general anesthetic vapors. The study involves the morphological, structural, electrical, and spectroscopic characterizations necessary to assess the functional properties of the device as well as the bR biological activity once integrated into the functional biointerlayer (FBI)-OFET structure. The electronic transduction of the protons phototranslocation is shown as a current increase in the p-type channel only when the device is irradiated with photons known to trigger the bR photocycle, while Raman spectroscopy reveals an associated C=C isomer switch. Notably, higher energy photons bring the cis isomer back to its trans form, switching the proton pumping process off. The investigation is extended also to the study of a PM FBI-OFET exposed to volatile general anesthetics such as halothane. In this case an electronic current increase is seen upon exposure to low, clinically relevant, concentrations of anesthetics, while no evidence of isomer-switching is observed. The study of the direct electronic detection of the two different externally triggered proton translocation effects allows gathering insights into the underpinning of different bR molecular switching processes. © 2014 American Chemical Society.

Giustini M.,University of Rome La Sapienza | Giustini M.,Center for Colloid and Surface Science | Parente M.,Institute for Energy and Transport of the Netherlands | Mallardi A.,CNR Institute for Chemical and Physical Processes | And 2 more authors.
Biochimica et Biophysica Acta - Bioenergetics | Year: 2016

It is a common believe that intra-protein electron transfer (ET) involving reactants and products that are overall electroneutral are not influenced by the ions of the surrounding solution. The results presented here show an electrostatic coupling between the ionic atmosphere surrounding a membrane protein (the reaction center (RC) from the photosynthetic bacterium Rhodobacter sphaeroides) and two very different intra-protein ET processes taking place within it. Specifically we have studied the effect of salt concentration on: i) the kinetics of the charge recombination between the reduced primary quinone acceptor QA - and the primary photoxidized donor P+; ii) the thermodynamic equilibrium (QA - ↔ QB -) for the ET between QA - and the secondary quinone acceptor QB. A distinctive point of this investigation is that reactants and products are overall electroneutral. The protein electrostatics has been described adopting the lowest level of complexity sufficient to grasp the experimental phenomenology and the impact of salt on the relative free energy level of reactants and products has been evaluated according to suitable thermodynamic cycles. The ionic strength effect was found to be independent on the ion nature for P+ QA - charge recombination where the leading electrostatic term was the dipole moment. In the case of the QA - ↔ QB - equilibrium, the relative stability of QA - and QB - was found to depend on the salt concentration in a fashion that is different for chaotropic and kosmotropic ions. In such a case both dipole moment and quadrupole moments of the RC must be considered. © 2016 Elsevier B.V.

Marini S.,Center for Colloid and Surface Science | Marini S.,University of Bergamo | Strada C.,Center for Colloid and Surface Science | Strada C.,University of Bergamo | And 4 more authors.
Energy Conversion and Management | Year: 2014

The policies of curbing CO2 emissions have worked poorly on a global scale and an economically sound proposal of bringing electric power to Europe from an Algerian solar hub has just been dismissed. With reference to the Algerian - European relationships, we analyze the broad context where an environmental policy benefitting both developing and developed countries can be put in place. We then discuss the connection between anthropogenic CO2 emissions and acidification of Oceans along with a geo-engineering proposal aimed at solving these pressing problems with large-scale solar-powered chloralkali plants. While the cost of sequestering a ton of CO2 with dedicated chloralkali plants is unacceptably high, it is economically and environmentally sound to replace an existing European Cl2 plant (consuming fossils) with a solar-powered plant in Algeria. If the Algerian plant uses a new, more efficient chloralkali process, it will be competitive with existing European plants even at the current low market value of the carbon emission credits. We finally explore the possibility of coupling Cl2 production with CO2 reuse and syngas production through a novel electrochemical process. © 2014 Elsevier Ltd.

Bonechi C.,University of Siena | Bonechi C.,Center for Colloid and Surface Science | Martini S.,University of Siena | Martini S.,Center for Colloid and Surface Science | And 2 more authors.
Journal of Materials Science | Year: 2011

In this study, the interaction processes between a dye (indigo carmine) and two different macromolecular models were studied with the aim to obtain physical-chemistry information about the dyeing of textiles. Two macromolecules, albumin and dextran (DX), were chosen to simulate wool and cotton fibers during the coloration procedure in water. Proton NMR selective and non-selective spin-lattice relaxation rate measurements were used to monitor the strength of the overall complexation behavior of indigo carmine toward albumin or DX. The affinity index, a quantitative parameter related to the strength of the ligand-macromolecule interaction, was determined from selective spin-lattice relaxation rate enhancements due to the bound ligand molar fraction. Moreover, this approach allowed the calculation of the equilibrium constant of the complex formation (K) between the dye and macromolecular models. NMR data suggested a higher indigo carmine-albumin complex thermodynamic stability with respect to the indigo carmine-DX adduct. These results indicate a stronger persistence of the dyeing process in wool with respect to cotton fibers, in agreement with literature data. © 2010 Springer Science+Business Media, LLC.

Ricci M.,University of Siena | Ricci M.,Center for Colloid and Surface Science | Aggravi M.,University of Siena | Aggravi M.,Center for Colloid and Surface Science | And 8 more authors.
Journal of Biosciences | Year: 2012

In vivo NMR spectroscopy, together with selectively 13C-labelled substrates and 'statistical total correlation spec-troscopy' analysis (STOCSY), are valuable tools to collect and interpret the metabolic responses of a living organism to external stimuli. In this study, we applied this approach to evaluate the effects of increasing concentration of exogenous ethanol on the Saccharomyces cerevisiae fermentative metabolism. We show that the STOCSY analysis correctly identifies the different types of correlations among the enriched metabolites involved in the fermentation, and that these correlations are quite stable even in presence of a stressing factor such as the exogenous ethanol. © Indian Academy of Sciences.

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