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Alessandro Abbotto,
Erika Herrera Calderon,
Milind S. Dangate,
Filippo De Angelis,
Norberto Manfredi,
Claudio Maria Mari, Chiara Marinzi,
Edoardo Mosconi,
Michele Muccini,
Riccardo Ruffo,
Mirko Seri
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ABSTRACT: Two heteroarylene-vinylene donor−acceptor polymers, P(2,6-Py-V-EDOT) and P(2,5-Py-V-EDOT), containing vinylene-spaced simple donor (EDOT) and acceptor (pyridine) moieties, are presented. The central pyridine ring of the repeating unit is either 2,6- or 2,5-substituted, leading to different structural and electronic properties of the monomers. Polymers were obtained by either oxidative electropolymerization or Yamamoto coupling and fully characterized by NMR, UV−vis absorption, GPC, TGA, DSC, electrochemistry, and spectroelectrochemistry. Detailed ab initio computations have been performed for the monomers and model oligomers for analyzing their optical and electronic properties. GPC showed that isolated polymers obtained via Yamamoto poly coupling have low molecular weights, likely due to solubility issues. The electrochemical polymerizations led to p- and n-dopable polymers, with 2,5-Py-V-EDOT yielding more reversible n-doped process. The energetic positions revealed HOMO (−5.1 and −5.0 eV), LUMO (−3.4 eV), and narrow bandgap (1.6 and 1.7 eV) energies closely matching materials-design rules for optimized organic photovoltaic devices. Preliminary investigation in photovoltaic devices in combination with C71−PCBM afforded relatively modest power conversion efficiencies of 0.5% (AM 1.5G, 100 mW/cm2), which were attributed to the low molecular-weight of the polymers accessible via the chemical route.
11/2010;
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ABSTRACT: The first example of a heteroarylvinylene π-conjugated quaterpyridine Ru(II) sensitizer (N1044) was synthesized and used in dye-sensitized solar cells; the dye has an effective panchromatic absorption band, covering the entire visible spectrum up to the NIR region, and superior electrochemical characteristics (HOMO/LUMO and bandgap energies) with respect to previous representative Ru(II) bi- and quaterpyridine sensitizers. A record IPCE curve ranging from 360 to 920 nm has been measured with a maximum of 65% at 646 nm and still 33% efficiency at 800 nm; this leads to substantially increased photocurrent (19.2 mA cm(-2)) when compared to the prototype N719 Ru(II) sensitizer.
Dalton Transactions 11/2010; 40(1):234-42. · 3.84 Impact Factor
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The Journal of Physical Chemistry B 02/2010; · 3.70 Impact Factor
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ABSTRACT: Two dimers of a heteroaromatic quadrupolar (acceptor-donor-acceptor) chromophore have been synthesized with different interchromophoric distances. Optical spectra of dimers in solution show a red shift of the linear absorption band upon decreasing the interchromophore distance, while fluorescence and two-photon absorption spectra are only marginally affected by the interactions. A bottom up approach is adopted to describe the spectra: via a detailed spectroscopic analysis of the monomeric species in solution, we define an essential-state model for the isolated chromophore and use this information to set up a model for the dimers also accounting for interchromophore electrostatic interactions. To discriminate between static screening governed by the static dielectric constant and dynamical screening at optical frequencies, we first solve the problem in the mean-field approximation and then define the excitonic Hamiltonian on the resulting best excitonic basis. Along this line, the evolution of spectral properties with the interchromophore distance is properly rationalized.
The Journal of Physical Chemistry B 01/2010; 114(2):882-93. · 3.70 Impact Factor
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ABSTRACT: A novel heteroleptic ruthenium complex carrying a heteroaromatic-4,4'-pi-conjugated 2,2'-bipyridine [Ru(II)LL'(NCS)(2)] (L = 4,4'-bis[(E)-2-(3,4-ethylenedioxythien-2-yl)vinyl]-2,2'-bipyridine, L' = 4,4'-(dicarboxylic acid)-2,2'-bipyridine) was synthesized and used in dye-sensitized solar cells, yielding photovoltaic efficiencies of 9.1% under standard global AM 1.5 sunlight.
Chemical Communications 12/2008; · 6.17 Impact Factor
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Annalen der Chemie und Pharmacie 09/2008; 2008(30):5047 - 5054. · 3.10 Impact Factor
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Estuardo López-Vera,
Manuel B Aguilar,
Emanuele Schiavon, Chiara Marinzi,
Ernesto Ortiz,
Rita Restano Cassulini,
Cesar V F Batista,
Lourival D Possani,
Edgar P Heimer de la Cotera,
Francesco Peri,
Baltazar Becerril,
Enzo Wanke
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ABSTRACT: alpha-Conotoxins from marine snails are known to be selective and potent competitive antagonists of nicotinic acetylcholine receptors. Here we describe the purification, structural features and activity of two novel toxins, SrIA and SrIB, isolated from Conus spurius collected in the Yucatan Channel, Mexico. As determined by direct amino acid and cDNA nucleotide sequencing, the toxins are peptides containing 18 amino acid residues with the typical 4/7-type framework but with completely novel sequences. Therefore, their actions (and that of a synthetic analog, [gamma15E]SrIB) were compared to those exerted by the alpha4/7-conotoxin EI from Conus ermineus, used as a control. Their target specificity was evaluated by the patch-clamp technique in mammalian cells expressing alpha(1)beta(1)gammadelta, alpha(4)beta(2) and alpha(3)beta(4) nicotinic acetylcholine receptors. At high concentrations (10 microm), the peptides SrIA, SrIB and [gamma15E]SrIB showed weak blocking effects only on alpha(4)beta(2) and alpha(1)beta(1)gammadelta subtypes, but EI also strongly blocked alpha(3)beta(4) receptors. In contrast to this blocking effect, the new peptides and EI showed a remarkable potentiation of alpha(1)beta(1)gammadelta and alpha(4)beta(2) nicotinic acetylcholine receptors if briefly (2-15 s) applied at concentrations several orders of magnitude lower (EC(50), 1.78 and 0.37 nm, respectively). These results suggest not only that the novel alpha-conotoxins and EI can operate as nicotinic acetylcholine receptor inhibitors, but also that they bind both alpha(1)beta(1)gammadelta and alpha(4)beta(2) nicotinic acetylcholine receptors with very high affinity and increase their intrinsic cholinergic response. Their unique properties make them excellent tools for studying the toxin-receptor interaction, as well as models with which to design highly specific therapeutic drugs.
FEBS Journal 09/2007; 274(15):3972-85. · 3.79 Impact Factor
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Angewandte Chemie International Edition 02/2007; 46(18):3308-12. · 13.45 Impact Factor
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ABSTRACT: A mimetic of Lipid A with a beta-N(OMe) glycosidic linkage, four linear C-14 hydrophobic chains and without phosphate groups has been prepared together with its beta-O-linked analogue. Both these molecules were active in inhibiting the inflammatory action of Escherichia coli lipid A on MT2 macrophages in a dose-dependent manner, while they were completely devoid of inflammatory activity.
Bioorganic & Medicinal Chemistry 02/2006; 14(1):190-9. · 2.92 Impact Factor
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ABSTRACT: The design and synthesis of novel Ras inhibitors with a bicyclic scaffold derived from the natural sugar D-arabinose are presented. Molecular modelling showed that these ligands can bind Ras by accommodating the aromatic moieties and the phenylhydroxylamino group in a cavity near the Switch II region of the protein. All the synthetic compounds were active in inhibiting nucleotide exchange on p21 human Ras in vitro, and two of them selectively inhibited Ras-dependent cell growth in vivo.
ChemBioChem 11/2005; 6(10):1839-48. · 3.94 Impact Factor
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ABSTRACT: Chemical ligation approaches facilitate the chemoselective assembly of unprotected peptides in aqueous solution. Here, two photolabile auxiliaries are described that enlarge the applicability of native chemical ligation to non-cysteine targets. The auxiliaries, designed to allow reaction with thioester peptides, generate an amide bond between the two initial fragments. The o-nitrobenzyl tertiary benzylamide that is formed at the ligation junction can be transformed into a native amide group under mild photolysis conditions. The veratryl auxiliary was found to be excessively labile during peptide purification and ligation. However, the auxiliary based on the o-nitrobenzyl group shows all the necessary properties for a general application in routine peptide and protein synthesis. In addition, the auxiliary linked to the N-terminus can be efficiently photolyzed, suggesting a new approach for the generation of photocaged amines. Synthesis, solid phase introduction onto peptide chains, ligation properties and photolysis in water are described, and a careful study of compatibility of the method with potentially fragile peptide side chains is reported.
Bioorganic & Medicinal Chemistry 06/2004; 12(10):2749-57. · 2.92 Impact Factor
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ABSTRACT: Inhibiting the depalmitoylation of proteins disrupts cell survival signaling in tumor cells and leads to increased cell death. We chemically synthesized a non-hydrolyzable analog of the palmitoyl-cysteine thioester linkage (AcG-alpha-ketoamido-palmitoyl diamino propionate-VKIKK) (DAPKA) and showed that it inhibits palmitoyl:protein thioesterase (PPT1) in an in vitro assay using a specific fluorescent-based (4-methylumbelliferyl-beta-gluco-6-thiopalmitate) assay. We then showed that it killed cultured tumor cells and enhanced the killing of neurotumor cells by chemotherapeutic drugs such as etoposide and adriamycin. Overexpression of PPT1 protected against apoptosis induced by etoposide and the ketoamide and the inhibitory effect of the two was additive.
Cancer Letters 01/2003; 187(1-2):163-8. · 4.24 Impact Factor
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ABSTRACT: It has been proposed that chromogranin A (CgA), a protein secreted by many normal and neoplastic neuroendocrine cells, can play a role as a positive or a negative modulator of cell adhesion. The mechanisms that regulate these extracellular functions of CgA are unknown. We show here that plasmin can regulate the anti/pro-adhesive activity of CgA by proteolytic cleavage of the N-terminal domain. Limited proteolytic processing decreased its anti-adhesive activity and induced pro-adhesive effects in fibronectin or serum-dependent fibroblast adhesion assays. Cleavage of Lys(77)-Lys(78) dibasic site in CgA(1-115) was relatively rapid and associated with an increase of pro-adhesive effect. In contrast, antibodies against the region 53-90 enhanced the anti-adhesive activity of CgA and CgA(1-115). Structure-activity relationship studies showed that the conserved region 47-64 (RILSILRHQNLLKELQDL) is critical for both pro- and anti-adhesive activity. These findings suggest that CgA might work on one hand as a negative modulator of cell adhesion and on the other hand as a precursor of positive modulators, the latter requiring proteolytic processing for activation. Given the importance of plasminogen activation in tissue invasion and remodeling, the interplay between CgA and plasmin could provide a novel mechanism for regulating fibroblast adhesion and function in neuroendocrine tumors.
Journal of Biological Chemistry 12/2002; 277(48):45911-9. · 4.77 Impact Factor
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ABSTRACT: The first examples of di-branched di-anchoring organic sensitizers were synthesized and used in dye-sensitized solar cells leading to red-shifted IPCE maxima and increased photocurrent when compared to the corresponding mono-branched mono-anchoring dye, yielding power conversion efficiency of 5.7% (4.9% with ionic liquid electrolyte) with enhanced stability under 1 sun conditions from the dianchoring groups.
