Demis Paolucci

Electron transfer between cytochrome C and p66Shc generates reactive oxygen species that trigger mitochondrial apoptosis

Reactive oxygen species (ROS) are potent inducers of oxidative damage and have been implicated in the regulation of specific cellular functions, including apoptosis. Mitochondrial ROS increase markedly after proapoptotic signals, though the biological significance and the underlying molecular mechanisms remain undetermined. P66Shc is a genetic determinant of life span in mammals, which regulates ROS metabolism and apoptosis. We report here that p66Shc is a redox enzyme that generates mitochondrial ROS (hydrogen peroxide) as signaling molecules for apoptosis. For this function, p66Shc utilizes reducing equivalents of the mitochondrial electron transfer chain through the oxidation of cytochrome c. Redox-defective mutants of p66Shc are unable to induce mitochondrial ROS generation and swelling in vitro or to mediate mitochondrial apoptosis in vivo. These data demonstrate the existence of alternative redox reactions of the mitochondrial electron transfer chain, which evolved to generate proapoptotic ROS in response to specific stress signals.

Functionalised single wall carbon nanotubes/polypyrrole composites for the preparation of amperometric glucose biosensors

Ferrocenyl-functionalised SWNTs are coupled to glucose oxidase within an amphiphilic polypyrrole matrix for the amperometric catalytic detection of glucose.

Singling out the Electrochemistry of Individual Single-Walled Carbon Nanotubes in Solution

Bandgap fluorescence spectroscopy of aqueous, micelle-like suspensions of SWNTs has given access to the electronic energies of individual semiconducting SWNTs, while substantially lower is the success achieved in the determination of the redox properties of SWNTs as individual entities. Here we report an extensive voltammetric and vis-NIR spectroelectrochemical investigation of true solutions of unfunctionalized SWNTs and determine the standard electrochemical potentials of reduction and oxidation as a function of the tube diameter of a large number of semiconducting SWNTs. We also establish the Fermi energy and the exciton binding energy for individual tubes in solution. The linear correlation found between the potentials and the optical transition energies is quantified in two simple equations that allow one to calculate the redox potentials of SWNTs that are insufficiently abundant or absent in the samples.

Liquid-crystalline fullerene–ferrocene dyads

The 1,3-dipolar cycloaddition reaction was used to assemble fullerene, ferrocene and a second-generation liquid-crystalline cyanobiphenyl-based dendrimer. The targeted compound displayed an enantiotropic smectic A phase from 40 to 135 °C. The d-layer spacing was determined by X-ray diffraction, and was found to be independent of temperature with a value of 95 A. Molecular modeling and structural considerations suggested partial bilayer organization of the mesogenic molecular units within the smectic layers. Oxidation or reduction processes of the basic components (ferrocene, fullerene, dendrimer) were investigated by electrochemical techniques, and were in agreement with the structure. Photoinduced electron transfer from ferrocene to fullerene was identified, most likely with a “through space” mechanism.

Donor-acceptor nanoensembles of soluble carbon nanotubes{

Donor-acceptor nanoensembles, prepared via electrostatic interactions of single wall carbon nanotubes and porphyrin salts, give rise to photoinduced intra-complex charge separation that lasts tens of microseconds.

Anion recognition by functionalized single wall carbon nanotubes

Amidoferrocenyl-functionalised single wall carbon nanotubes (Fc-SWNT) are efficient exoreceptors for the redox recognition of H2PO4-.

Growth of p- and n-Dopable Films from Electrochemically Generated C60 Cations

The formidable electron-acceptor properties of C60 contrast with its difficult oxidations. Only recently it has become possible to achieve reversibility of more than one electrochemical anodic process versus the six reversible cathodic reductions. Here we exploit the reactivity of electrochemical oxidations of pure C60 to grow a film of high thermal and mechanical stability on the anode. The new material differs remarkably from its precursor since it conducts both electrons and holes. Its growth and properties are consistently characterized by a host of techniques that include atomic force microscopy (AFM), Raman and infrared spectroscopies, X-ray-photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS), scanning electron microscopy and energy-dispersive X-ray analysis (SEM-EDX), matrix-assisted laser desorption/ionization (MALDI), and a variety of electrochemical measurements.

A light-harvesting fluorinated fullerene donor-acceptor ensemble; long-lived charge separation.

In a first example of a trannulene-based donor-acceptor dyad visible light photoexcitation generates a long-lived (870 ns) charge-separated state.

Two concomitant polymorphs that interconvert via crystal-to-crystal phase transitions, and single crystals obtained by heteromolecular seeding

The organometallic salt [(η5-C5H5)2Fe][AsF6] crystallises as a mixture of two concomitant polymorphs, a trigonal and a monoclinic form, which interconvert via fully reversible solid-to-solid phase transitions. Single crystals of the two forms have been obtained by heteromolecular seeding.

A remarkable water-soluble (molecular) alloy with two tuneable solid-to-solid phase transitions

The organometallic cations [(η5-C5H5)2Co]+ and [(η5-C5H5)2Fe]+ are fully miscible in the solid state and form the mixed crystalline material [(η5-C5H5)2Cox Fe1−x][PF6], which undergoes two fully reversible phase transitions that can be tuned by varying the molar ratio of the two cations; the water-soluble organometallic salt thus possesses the behaviour of a molecular alloy.