Mattei E.,Largo dellUniversita |
Lauro S.E.,Third University of Rome |
Pettinelli E.,Third University of Rome |
Vannaroni G.,Third University of Rome
IEEE Transactions on Instrumentation and Measurement | Year: 2013
We present the measurements performed with a custom coaxial-cage line designed to determine the complex dielectric permittivity of large samples, made of granular and/or liquid materials. The open structure of the cage facilitates the filling of the line, and allows the uniform compactness of the granular materials having large grain size. The electromagnetic parameters of the samples are retrieved using the line scattering coefficients ($S$- parameters), measured with a vector network analyzer in the frequency range 1 MHz to 3 GHz. The measurements are carried out on water, ethanol, and glass beads using the Boughriet method, which, for non magnetic materials, optimizes the Nicolson-Ross-Weir algorithm. The results confirm that such a device accurately estimates the material complex permittivity in a wide frequency band. However, at very low frequencies and at frequencies multiple of the line half-wavelength resonances, the accuracy significantly reduces. In particular, the accuracy gets worse for materials with high permittivity and low losses. Nevertheless, for natural geo-materials, usually characterized by appreciable losses, the coaxial-cage line can effectively be used to accurately estimate the material electromagnetic properties in a wide frequency band. © 2013 IEEE.
Torresi S.,SNC - Lavalin |
Frangipane M.T.,SNC - Lavalin |
Garzillo A.M.V.,Largo dellUniversita |
Massantini R.,SNC - Lavalin |
Contini M.,SNC - Lavalin
Food Research International | Year: 2014
Scientific researches on characterization of the commercial enological preparation of Lallzyme MMX® containing β-glucanase and its influence on autolysis of different yeast strains typically employed in the production of sparkling wine are lacking. The aim of the present work was to plug a gap in this field, studying the β-glucanase activity of Lallzyme MMX® and its interactions with BCS103® and EC1118® yeast strains. The results showed that β-glucanase was slightly inhibited by ethanol, but its residual activity at wine pH was sufficient for the purposes. Kinetic parameters showed a better enzyme-substrate complex formation for the EC1118® strain. The influence on yeast lysis during 12. months of bottle-aging was monitored, demonstrating that enzyme addition did not substantially influence either the content and progression of total proteins, or foam characteristics. However, scanning and transmission electron microscopy images and free amino acid analysis indicated β-glucanase improved cell wall degradation of both selected yeasts, evidencing a lower autolytic capacity of the BCS103® strain. Our study demonstrated that addition of β-glucanase catalyzed cell disorganization and promoted release of yeast components into sparkling wine, with strain-dependent effects. Therefore, employment of β-glucanase rich Lallzyme MMX® might effectively accelerate some aging characteristics of traditional sparkling wines. © 2013 Elsevier Ltd.
Baldacchini C.,Largo dellUniversita |
Baldacchini C.,CNR Institute of Neuroscience |
Cannistraro S.,Largo dellUniversita
Journal of Nanoscience and Nanotechnology | Year: 2010
Metalloproteins recently emerged as good candidates for signal transduction in bionanodevices, but the feasibility of such novel devices is strongly connected to the achievement of an efficient charge transport between single metalloproteins and metal electrodes. In this work, we propose the use of metallic single-walled carbon nanotubes as efficient linkers between metalloproteins and metal surfaces. By means of a conductive atomic force microscopy investigation, we compare the conduction across single yeast cytochrome c molecules covalently bound both to bare gold and to functionalized metallic single-walled carbon nanotubes lying on gold. At comparable forces applied by the microscope tip (i.e., comparable physical contact), the measured current is higher when a metallic single-walled carbon nanotubes is in between the metalloprotein and the gold surface. The analysis of the single molecule current responses by means of a non-resonant tunneling transport model suggests that the increasing in the conduction is due both to the strong electronic conjugation existing at the nanotubes/gold interface and to the participation of the nanotube electronic bands to the charge transport. Copyright © 2010 American Scientific Publishers All rights reserved.
Baldacchini C.,Largo dellUniversita |
Baldacchini C.,CNR Institute of Agro-environmental and Forest Biology |
Herrero Chamorro M.A.,University of Trieste |
Herrero Chamorro M.A.,University of Castilla - La Mancha |
And 2 more authors.
Advanced Functional Materials | Year: 2011
The integration of redox proteins with nanomaterials has attracted much interest in the past years, and metallic single-walled carbon nanotubes (SWNTs) have been introduced as efficient electrical wires to connect biomolecules to metal electrodes in advanced nano-biodevices. Besides preserving biofunctionality, the protein-nanotube connection should ensure appropriate molecular orientation, flexibility, and efficient, reproducible electrical conduction. In this respect, yeast cytochrome c redox proteins are connected to gold electrodes through lying-down functionalized metallic SWNTs. Immobilization of cytochromes to nanotubes is obtained via covalent bonding between the exposed protein thiols and maleimide-terminated functional chains attached to the carbon nanotubes. A single-molecule study performed by combining scanning probe nanoscopies ascertains that the protein topological properties are preserved upon binding and provides unprecedented current images of single proteins bound to carbon nanotubes that allow a detailed I-V characterization. Collectively, the results point out that the use as linkers of suitably functionalized metallic SWNTs results in an electrical communication between redox proteins and gold electrodes more efficient and reproducible than for proteins directly connected with metal surfaces. Metallic single-walled carbon nanotubes (SWNTs) functionalized with maleimide-terminated chains covalently target biomolecules with exposed thiols, controlling their orientation and preserving their functionality, which are crucial aspects for biosensing applications. Combining single-molecule scanning-probe nanoscopies, it is demonstrated that metallic SWNTs, used as linking spacers, render the electrical communication between redox proteins and gold electrodes more efficiently and reproducibly than for proteins directly connected with metal surfaces. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Bizzarri A.R.,Largo dellUniversita |
Cannistraro S.,Largo dellUniversita
Nanotechnology | Year: 2014
Atomic force spectroscopy is able to extract kinetic and thermodynamic parameters of biomolecular complexes provided that the registered unbinding force curves could be reliably attributed to the rupture of the specific complex interactions. To this aim, a commonly used strategy is based on the analysis of the stretching features of polymeric linkers which are suitably introduced in the biomolecule-substrate immobilization procedure. Alternatively, we present a method to select force curves corresponding to specific biorecognition events, which relies on a careful analysis of the force fluctuations of the biomolecule-functionalized cantilever tip during its approach to the partner molecules immobilized on a substrate. In the low frequency region, a characteristic 1/fα noise with α equal to one (flickering noise) is found to replace white noise in the cantilever fluctuation power spectrum when, and only when, a specific biorecognition process between the partners occurs. The method, which has been validated on a well-characterized antigen-antibody complex, represents a fast, yet reliable alternative to the use of linkers which may involve additional surface chemistry and reproducibility concerns. © 2014 IOP Publishing Ltd.