Giulia Tomba

Publications of Giulia Tomba

• Adsorption and reduction of glutathione disulfide on α-Al2O3 nanoparticles: experiments and modeling.

  Authors: Ralf Dringen, Yvonne Koehler, Ludmilla Derr, Giulia Tomba, Maike M Schmidt, Laura Treccani, Lucio Colombi Ciacchi, Kurosch Rezwan

  Langmuir : the ACS journal of surfaces and colloids. 06/2011; 27(15):9449-57.

  Glutathione disulfide (GSSG; γ-GluCysGly disulfide) was used as a physiologically relevant model molecule to investigate the fundamental adsorption mechanisms of polypeptides onto α-aluminaGlutathione disulfide (GSSG; γ-GluCysGly disulfide) was used as a physiologically relevant model molecule to investigate the fundamental adsorption mechanisms of polypeptides onto α-alumina nanoparticles. Its adsorption/desorption behavior was studied by enzymatic quantification of the bound GSSG combined with zeta potential measurements of the particles. The adsorption of GSSG to alumina nanoparticles was rapid, was prevented by alkaline pH, was reversed by increasing ionic strength, and followed a nearly ideal Langmuir isotherm with a standard Gibbs adsorption energy of -34.7 kJ/mol. Molecular dynamics simulations suggest that only one of the two glutathionyl moieties contained in GSSG binds stably to the nanoparticle surface. This was confirmed experimentally by the release of GSH from the bound GSSG upon reducing its disulfide bond with dithiothreitol. Our data indicate that electrostatic interactions via the carboxylate groups of one of the two glutathionyl moieties of GSSG are predominantly responsible for the binding of GSSG to the alumina surface. The results and conclusions presented here can provide a base for further experimental and modeling studies on the interactions of biomolecules with ceramic materials.

• Supramolecular self-assembly driven by electrostatic repulsion: The 1D aggregation of rubrene pentagons on Au111.

  Authors: Giulia Tomba, Massimiliano Stengel, Wolf-Dieter Schneider, Alfonso Baldereschi, Alessandro De Vita

  ACS nano. 11/2010; 4(12):7545-51.

  At present, organic molecules are among the best candidate "building blocks" for the construction of self-assembling nanoscale devices based on metal substrates. Control of the formation of specificAt present, organic molecules are among the best candidate "building blocks" for the construction of self-assembling nanoscale devices based on metal substrates. Control of the formation of specific patterns in the submonolayer regime is usually achieved by appropriate choice and/or functionalization of the adsorbates. The effect of this intervention, though, is limited by the typically short-range character of the bonding. We present here a theoretical study on the system rubrene/gold to show that substrate-induced molecular charging can instead determine the assembly on larger scales. DFT calculations and electrostatic considerations are used to discuss the charge transfer at the metal/organic interface. This allows rationalization of previous puzzling experimental results and, in particular, of the unusual molecular gap broadening upon adsorption observed in STS spectra. The self-assembly process is further studied by means of classical molecular dynamics simulations. The charged adsorbates are modeled as mutually repulsive standing dipoles, with van der Waals interactions intervening at short distances. The striking resemblance between the experimental STM images and the results of our MD simulations shows that this simple model is able to capture the key effects driving the assembly in this system. The competition between long-range repulsive interactions and short-range attractive forces leads to characteristic and easily recognizable 1D patterns. We suggest that experimental evidence of the presence of similar patterns in other metal/organic systems can provide crucial information on the electronic level alignment at the interface, that is, on the occurrence of charge-transfer processes between metal and organic adsorbates.

• Structure and energetics of diphenylalanine self-assembling on Cu(110).

  Authors: Giulia Tomba, Magalí Lingenfelder, Giovanni Costantini, Klaus Kern, Florian Klappenberger, Johannes V Barth, Lucio Colombi Ciacchi, Alessandro De Vita

  The journal of physical chemistry. A. 01/2008; 111(49):12740-8.

  We investigate the dynamical features of the adsorption of diphenylalanine molecules on the Cu(110) surface and of their assembling into supramolecular structures by a combination of quantum andWe investigate the dynamical features of the adsorption of diphenylalanine molecules on the Cu(110) surface and of their assembling into supramolecular structures by a combination of quantum and classical atomistic modeling with dynamic scanning tunneling microscopy and spectroscopic experiments. Our results reveal a self-assembling mechanism in which isolated adsorbed molecules change their conformation and adsorption mode as a consequence of their mutual interactions. In particular, the formation of zwitterions after proton transfer between initially neutral molecules is found to be the key event of the assembling process, which stabilizes the supramolecular structures. Because of the constraints on the intermolecular bonds exerted by the surface-molecule interactions, the assembly process is strictly stereoselective, and may suggest a general model for patterning and functionalization of bare metal surfaces with short chiral peptides.

• Tracking the chiral recognition of adsorbed dipeptides at the single-molecule level.

  Authors: Magalí Lingenfelder, Giulia Tomba, Giovanni Costantini, Lucio Colombi Ciacchi, Alessandro De Vita, Klaus Kern

  Angewandte Chemie (International ed. in English). 02/2007; 46(24):4492-5.