CV
Flavio Maran
Flavio Maran obtained his Laurea Degree in Chemistry, Magna cum Laude, from the University of Padova in 1980. He took a faculty position in the same university in 1983. He is currently Professor of Physical Chemistry at the University of Padova where he leads the Electrochemistry Group and teaches physical chemistry, advanced physical chemistry, molecular electrochemistry, and electron transfer reactions to undergraduate and graduate chemistry and biotechnology students.
He has been a Visiting Scientist in Canada, USA, and Japan. Chairman of ECHEMS, the new organization for the development and support of electrochemical activities in emerging areas of research. Member of national and international chemical societies. Member of the Stirring Committee of the PhD School of Molecular Sciences of the University of Padova. Member of committees of the Electrochemical Society. Referee for many Peer Review International Journals and Reviewer of Research Projects for European and North-American Foundations. Organizer of scientific meetings and many international symposia on electrochemistry and electron transfer.
Sabrina Antonello
Sabrina Antonello was born in Italy in 1970. She was educated at the University of Padova, where she received her Laurea degree in Chemistry in 1996. She obtained her PhD in Chemistry in 2000 with a Thesis entitled "Dissociative Electron Transfers", which was awarded in 2001 as the best PhD thesis by the Electrochemistry Division of the Italian Chemical Society. She currently holds a Research Associate Fellowship at the University of Padova. Her research interests include electron transfer across interfaces and electrochemical microscopy techniques.
The Maran group is currently involved in collaborations with various research groups in Italy (e.g., Claudio Toniolo, Vincenzo Barone, University of Naples; ), Canada, USA, Japan, Denmark, and Spain.
Research Interests
The Maran group at the University of Padova carries out research in intramolecular dissociative electron-transfer reactions, electron-transfer reactions through biologically relevant bridges, charge-transfer processes across interfaces, and gold nanoclusters protected by peptide monolayers.
Intramolecular dissociative electron transfer
Predicting the rate of electron transfer (ET) reactions is one of the most significant and fascinating achievements of modern physical chemistry. Thanks to the Marcus theory of ET and subsequent refinements, the ET rates can be estimated using rather simple concepts, such as reaction driving force, reorganization energy, and electronic coupling between reactant and product states. In several chemical systems, the ET causes the cleavage of a bond, therefore leading to a dissociative ET (DET). Generally speaking, DETs are useful reactions in that they provide an elegant and chemically clean way to generate reactive species such as radicals and, depending on the fact that we deal with a reductive or oxidative process, bases or acids, and nucleophiles or electrophiles. At present, we have reached a valuable understanding of how the rate of heterogeneous and intermolecular DETs changes as a function of the reaction free energy. On the other hand, much less is known for intramolecular DETs. One of the purposes of our research is to assess to which extent the knowledge so far accumulated can be extended to intramolecular DETs. To address this problem, we are currently studying the activation and intramolecular DET in specifically devised donor-spacer-acceptor molecules, mostly using electrochemical techniques; to better understand the dynamics of these reactions, specific theoretical calculations are also carried out.
Electron-transfer reactions through biologically relevant bridges
Understanding how electrons are transferred in proteins is a challenging task requiring knowledge of many related aspects, such as the properties of the donor (D) and the acceptor (A), the effect of the surrounding medium, and the electronic coupling between the relevant states involved in the process. To study how fine details or specific aspects may tune electron transfer (ET) reactions in such complex environments and taking into account that the peptide chains are essential in assisting long-range ET in proteins, focusing on well defined D-peptide-A model molecules is a successful strategy adopted by several research groups. It has been proposed that long range ET through biological systems may occur by both the superexchange mechanism, a coherent tunneling mechanism in which ET between D and A occurs without transient occupation of the states of the bridge, and the electron hopping mechanism, whereelectron migration takes place by using electronic states that are localized onto the units forming the bridge itself. It is still unclear, however, whether this scheme is actually applicable to peptides and proteins. Our research is aimed at understanding this important issue, which rules the efficiency of long-range ET. We use electrochemical methods and quantum mechanical (QM) calculations to gain insights into this problem and to rationalize the physico-chemical effects modulating the rate of intramolecular ET in donor-peptide-acceptor systems in which the length of the oligopeptide spacer is varied and the nature of D and A changed. To investigate systematically how distance increase impact the electron tunneling, we are focusing on series of peptides having well-defined conformational preferences. These peptides are homo-oligomers based on the -aminoisobutyric acid (Aib) residue and are known for their propensity to form rigid 310-helices because of steric hindrance at the -carbon and the resulting restricted torsional freedom.
Charge-transfer processes across interfaces
Nature provides a variety of systems in which molecules self-assemble to form ordered sequences that are kept together by noncovalent forces. Membranes and self-assembled monolayers are particularly important examples of these systems. Charge transfer processes occurring at the interface between two immiscibile electrolyte solutions, or between solutions separated by a cellular membrane, or though self-assembled monolayers are issues of current active research. In particular, many studies have been directed to understand the role and mechanisms by which membrane-active peptides form channels. To study the mechanisms by which peptides act, different model membranes can be employed, such as solid-supported membranes and bilayer lipid membranes. Part of this project is to modify the interface or membrane by using suitably devised and well-characterized peptide systems capable of providing a better electrical connection between the two phases or, more generally, though the interphase. The goal eventually is to control the charge transfer between the two phases by understanding the mechanism of the transfer across the interface and the role of peptides generating charge-transfer channels. The above biomimetic membranes allow for the application of various powerful surface techniques, such as electrochemical methods and scanning probe microscopies. We will employ electrochemical techniques and scanning probe methods. In this connection, particular emphasis will be given to the use of the scanning electrochemical microscope (SECM), an instrument devised to study chemical and physical processes at high resolution near interfaces, and of the atomic force microscopy (AFM), which provides an exceptionally powerful and versatile tool to study the packing of self-assembled layers. We also will anchor peptides to metal electrodes by means of metal-sulfur bonds. The peptides forming the ensuing self-assembled monolayer will be composed by both non-coded and coded alpha-amino acids. This part of the project concerns the effects of the peptide length and secondary structure on the ET rate between the electrode and selected acceptor (or donor) species on the solution side of the self-assembled monolayer system.
Peptide protected gold nanoclusters
Controlling the electronic properties of nanometer-scale materials is one of the hottest areas of current research. In particular, several research groups are strongly focusing on the detailed understanding of the physical and chemical properties of monolayer-protected gold clusters (MPCs), which are relatively easy to fabricate and display high stability. The monolayer not only protects the core from particle aggregation but also furnishes a way to control the electrical, optical, magnetic, and chemical properties of the MPC itself. In addition, the ligands provide a scaffold to attach molecular groups carrying out specific functions, an issue of paramount relevance for the use of these systems in the area of devices, sensors, and for biomedical applications. Our group is interested in synthesizing and characterizing gold clusters protected by peptides decorated with groups displaying specific physico-chemical properties. Although the project has a fundamental character, the materials will be also chosen by keeping an eye on possible applications. A key aspect of this project is the use of thiolized peptides based on the alpha-aminoisobutiric acid (Aib) unit: even when short, the Aib oligopeptides form a rather robust secondary structure (310-helix). We wish to study i) the factors controlling the electronic communication with the gold core through the peptide monolayer; ii) the electrochemistry and photophysics of the so-devised particles; iiii) the possibility of obtaining complex structures in which the various MPCs are chemically connected in 1, 2, and 3D architectures.
Recent Selected Publications
1. "Intramolecular Dissociative Electron Transfer" Antonello, S.; Maran, F. Chem. Soc. Rev. 2005, In press. Reprint
2. "Evidence against the Hopping Mechanism as an Important Electron Transfer Pathway for Conformationally Constrained Oligopetides" Polo, F.; Antonello, S.; Formaggio, F.; Toniolo, C.; Maran, F. J. Am. Chem. Soc. 2005, 127, 492-493. Reprint
3. "Understanding Electron Transfer Across Negatively-Charged Aib Oligo-Peptides" Barone, V.; Antonello, S.; Formaggio, F.; Improta, R.; Maran, F. J. Phys. Chem. B 2005, 109, 1023-1033. Reprint
4. "ElectronTransfer to Sulfides: Heterogeneous Kinetics, C-S Bond Cleavage, and Self-protonation" Meneses, A. B.; Antonello, S.; Arévalo, M.-C.; Maran, F. Electrochim. Acta 2005, 50, 1207-1215.Reprint
5. "Synthesis and Characterization of a Series of Homopeptide Peroxyesters" Formaggio, F.; Crisma, M.; Scipionato, L.; Antonello, S.; Maran, F.; Toniolo, C. Org. Lett. 2004, 6, 2753-2756. Reprint
6. "Formation and Cleavage of Aromatic Disulfide Radical Anions" Antonello, S.; Daasbjerg, K.; Jensen, H.; Taddei, F.; Maran, F. J. Am. Chem. Soc. 2003, 125, 14905-14916. Reprint
7. "Anomalous Distance Dependence of Electron Transfer Across Peptide Bridges" Antonello, S.; Formaggio, F.; Moretto, A.; Toniolo, C.; Maran, F. J. Am. Chem. Soc. 2003, 125, 2874-2875. Reprint
8. "Insights into the Free Energy Dependence of Intramolecular Dissociative Electron Transfers" Antonello, S.; Crisma, M.; Formaggio, F.; Moretto, A.; Taddei, F.; Toniolo, C.; Maran, F. J. Am. Chem. Soc. 2002, 124, 11503-11513. Reprint
9. "Theoretical and Electrochemical Investigation on Dissociative Electron Transfers Proceeding Through the Formation of Loose Radical Anions: Reduction of Symmetrical and Unsymmetrical Disulfides" Antonello, S.; Benassi, R.; Gavioli, G.; Taddei, F; Maran, F. J. Am. Chem. Soc. 2002, 124, 7529-7538. Reprint
10. "Dissociative Electron Transfer" Maran, F.; Workentin, M. S. Interface 2002, 11, 44-49. Reprint
11. "Serendipitous Discovery of Peptide Dialkyl Peroxides" Moretto, A.; De Zotti, M.; Scipionato L.; Formaggio, F.; Crisma, M.; Toniolo, C.; Antonello, S.; Maran, F.; Broxterman, Q. B. Helv. Chim. Acta 2002, 85, 3099-3112. Reprint
12. "Nitroxyl Peptides as Catalysts of Enantioselective Oxidations" Formaggio, F.; Bonchio, M.; Crisma, M.; Peggion, C.; Mezzato, S.; Polese, A.; Barazza, A.; Antonello, S.; Maran, F.; Broxterman, Q. B.; Kaptein, B.; Kamphuis, J.; Vitale, R. M.; Saviano, M.; Benedetti, E.; Toniolo, C. Chem. Eur. J. 2002, 8, 84-93. Reprint
13. "Intramolecular, Intermolecular, and Heterogeneous Nonadiabatic Dissociative Electron Transfer to Peresters" Antonello, S.; Formaggio, F.; Moretto, A.; Toniolo, C.; Maran, F. J. Am. Chem. Soc. 2001, 123, 9577-9584.Reprint
14. "Kinetics and Mechanisms of the Dissociative Reduction of C-X and X-X Bonds (X = O, S)" Maran, F.; Wayner, D. D. M.; Workentin, M. S. Adv. Phys. Org. Chem. 2001, 36, p. 85-166.Reprint
15. "Nickel(I)(salen)-Electrocatalyzed Reduction of Benzyl Chlorides in the Presence of Carbon Dioxide" Gennaro, A.; Isse, A. A.; Maran, F. J. Electroanal. Chem. 2001, 507, 124-134.Reprint
16. "Reactivity of [Pd3(-OAc)3(,2-MeSCHCO2Et-C,S)3] in the Presence of Triphenylphosphine: A Model of the Early Steps of the Pd/PR3 Catalyzed Heck Reaction" Basato, M.; Sesto, B.; Zecca, M.; Valle, G.; Antonello, S.; Maran, F. J. Organomet. Chem. 2000, 601, 201-210.Reprint
17. "The Role and Relevance of the Transfer Coefficient in the Study of Dissociative Electron Transfers. Concepts and Examples from the Electroreduction of Perbenzoates" Antonello, S.; Maran, F. J. Am. Chem. Soc. 1999, 121, 9668-9676.Reprint
18. "Kinetics andTemperature Dependence of the Reduction of Dialkyl Peroxides. New Insights into the Dynamics of Dissociative Electron Transfer" Donkers, R. L.; Maran, F.; Wayner, D. D. M.; Workentin, M. S. J. Am. Chem. Soc. 1999, 121, 7239-7248.Reprint
19. "Evidence for Large Inner Reorganization Energies in the Reduction of Diaryl Disulfides: Toward a Mechanistic Link between Concerted and Stepwise Dissociative Electron Transfers?" Daasbjerg, K.; Jensen, H.; Benassi, R.; Taddei, F.; Antonello, S.; Gennaro, A.; Maran, F. J. Am. Chem. Soc. 1999, 121, 1750-1751.Reprint
20. "Mechanism of the Dissociative Electrooxidation of Oxalate in Aprotic Solvents" Isse, A. A.; Gennaro, A.; Maran, F. Acta Chem. Scand.1999, 53, 1013-1022.Reprint
Collaborazioni scientifiche
Sono in atto varie collaborazioni scientifiche nazionali ed internazionali. Quelle internazionali sono coi gruppi dei seguenti ricercatori:
Prof. M. S. Workentin, University of Western Ontario (London, Ontario, Canada)
Prof. M.-C. Arévalo, Universidad de La Laguna (La Laguna, Spagna)
Prof. K. Daasbjerg, Aarhus University (Aarhus, Danimarca)
Prof. J. Lessard, Université de Sherbrooke (Sherbrooke, Quebec, Canada)
Prof. J. Yoshida, Kyoto University (Kyoto, Giappone)
Quelle nazionali sono, in particolare, con:
Prof. F. Taddei, Università di Modena e Reggio Emilia
Prof. V. Barone, Università di Napoli "Federico II"
Prof. C. Toniolo, Università di Padova
Prof. Maria Anita Rampi, Università di Ferrara
Prof. Rolando Guidelli, Università di Firenze
Altre attività professionali
Componente di vari organi collegiali o professionali, sia in Italia che all'estero, e di varie iniziative scientifiche, tra cui:
-Collegio Docenti della Scuola di Dottorato in Scienze Chimiche, Università di Padova;
-Società Chimica Italiana (SCI), Electrochemical Society (ECS), International Society of Electrochemistry (ISE);
-Comitato direttivo della Division of Organic and Biological Electrochemistry (O&BE), ECS;
-Chairman dell'International Working Group on the International Promotion of Organic Electrochemistry (O&BE Division, ECS);
-Chairman dell'ECHEMS, gruppo internazionale di lavoro per la promozione e lo studio delle possibilità offerte dall'elettrochimica nell'ambito di settori caldi della ricerca contemporanea;
-Comitato New Materials and Nanotechnologies (ECS).
-Comitato per la valuazione di candidati a Habilitation à Diriger des Recherches (Francia);
-Commissario esterno per la PhD School of Chemistry, The Univeristy of Western Ontario (London, Ontario, Canada);
-Rappresentante per l'Elettrochimica Organica dell'Italian-German Workshop of Electrochemistry;
-Comitato di valutazione delle candidature per il Baizer Award (massimo riconoscimento mondiale nell'ambito dell'elettrochimica organica);
-Referee per numerose riviste scientifiche internazionali;
-Revisore di progetti di ricerca del National Science Foundation (USA), Natural Sciences and Engineering Research Council of Canada (Canada), INTAS (UE), Alban (UE).
-Co-editore di: Organic Electrochemistry - Manuel M. Baizer Award (Fifth International Symposium), The Electrochemical Society Volume Series: Pennington, NJ, 2002-10.
-Organizzatore o Chairman dei seguenti Simposi internazionali o Congressi:
Simposio 5th Manuel M. Baizer Award Symposium on Organic Electrochemistry, 201st ECS Meeting, Philadelphia (Pennsylvania-USA), 12-17 maggio 2002.
Simposio Electron Transfer Through Organic and Biological Bridges, 203rd ECS Meeting, Parigi (Francia), 27 aprile - 2 maggio 2003.
Simposio Electrochemistry Symposium in Honor of Michael Weaver,204th ECS Meeting, Orlando (Florida-USA), 12-17 ottobre 2003.
Simposio Electron Transfer Through Organic and Biological Bridges II, 207th ECS Meeting, Quebec City (Quebec-Canada), 15 - 20 maggio 2005;
Congresso Giornate dell'Elettrochimica Italiana GEI 2004, Padova, 5-9 settembre 2004.
1st ECHEMS Meeting, Venezia, 30 giugno - 3 luglio 2005.