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Monica CASELLI

Ricercatore Universitario
Dipartimento di Scienze Chimiche e Geologiche - Sede Dipartimento di Scienze Chimiche e Geologiche

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Pubblicazioni

2023 - Influence of chirality on the aggregation of a new A-π-D-π-A small molecule with a benzodithiophene core: Spectroscopic and morphological investigations [Articolo su rivista]
Parenti, Francesca; Capelli, Raffaella; Mucci, Adele; Mortalò, Cecilia; Paolicelli, Guido; Pigani, Laura; Vanossi, Davide; Caselli, Monica
abstract

2021 - Intrinsic Fluorescence of the Active and the Inactive Functional Forms of Human Thymidylate Synthase [Articolo su rivista]
Vitiello, Simone; Caselli, Monica; Pavesi, Giorgia; Santucci, Matteo; Ferrari, Stefania; Costi, Maria Paola; Ponterini, Glauco
abstract

The observables associated with protein intrinsic fluorescence – spectra, time decays, anisotropies – offer opportunities to monitor in real time and non-invasively a protein‘s functional form and its interchange with other forms with different functions. We employed these observables to sketch the fluorometric profiles of two functional forms of human thymidylate synthase (hTS), a homodimeric enzyme crucial for cell proliferation and thus targeted by anticancer drugs. The protein takes an active and an inactive form. Stabilization of the latter by peptides that, unlike classical hTS inhibitors, bind it at the monomer/monomer interface offers an alternative inhibition mechanism that promises to avoid the onset of drug resistance in anticancer therapy. The fluorescence features depicted herein can be used as tools to identify and quantify each of the two protein forms in solution, thus making it possible to investigate the kinetic and thermodynamic aspects of the active/inactive conformational interchange. Two examples of fluorometrically monitored interconversion kinetics are provided.

2019 - Excited-state intramolecular proton transfer in a bioactive flavonoid provides fluorescence observables for recognizing its engagement with target proteins [Articolo su rivista]
Vanossi, D.; Caselli, M.; Pavesi, G.; Borsari, C.; Linciano, P.; Costi, M. P.; Ponterini, G.
abstract

A benzothiophene-substituted chromenone with promising activity against Leishmania and Trypanosoma species exhibits peculiar fluorescence properties useful for identifying its complexes with target proteins in the microorganism proteomes. The emission spectra, anisotropy and time profiles of this flavonoid strongly change when moving from the free to the protein-bound forms. The same two types of emission are observed in organic solvents and their mixtures with water, with the relative band intensities depending on the solvent ability to establish hydrogen bonds with the solute. The regular emission prevails in protic solvents, while in aprotic solvents the anomalously red-shifted emission occurs from a zwitterionic tautomeric form, produced in the excited state by proton transfer within the intramolecularly H-bonded form. This interpretation finds support from an experimental and theoretical investigation of the conformational preferences of this compound in the ground and lowest excited state, with a focus on the relative twisting about the chromenone-benzothiophene interconnecting bond. An analysis of the absorption and emission spectra and of the photophysical properties of the two emitting tautomers highlights the relevance of the local microenvironment, particularly of the intra- and intermolecular hydrogen bonds in which this bioactive compound is involved, in determining both its steady-state and time-resolved fluorescence behaviour.

2019 - Optoelectronic Properties of A‐π‐D‐π‐A Thiophene‐Based Materials with a Dithienosilole Core: An Experimental and Theoretical Study [Articolo su rivista]
Parenti, Francesca; Caselli, Monica; Vanossi, Davide; Buffagni, Mirko; Imperato, Manuel; Pigani, Laura; Mucci, Adele
abstract

Two A‐π‐D‐π‐A thiophene based small molecules, with a central dithienosilole core and dicyanovinyl end groups were synthesized. These compounds differ only for the presence of alkyl and alkylsulfanyl chains, respectively, on thiophene beta positions. The computational data together with the spectroscopic and electrochemical findings (obtained by means of absorption, steady‐state/time‐resolved emission techniques and cyclic voltammetry) revealed that both molecules possess low electronic and optical band gaps, broad absorption spectra and a good stability both in p and n‐doping states, properties that make them suitable for optoelectronic applications. In either compounds the HOMO‐LUMO transition involves an intramolecular charge transfer from the electron‐donor dithienosilole unit to the two terminal electron‐acceptor DCV groups. A marked positive emission solvatochromism was observed for both molecules and was interpreted on the basis of the symmetry breaking in the S1 excited state. The two synthesized compounds were also compared to their shorter precursors and to similar oligothiophenes to understand how the nature of the building block influences the characteristics of the final materials. Furthermore, it was possible to better understand the contribution of the sulfur atom in modulating the optical properties of the small molecules studied.

2018 - Thiophene based A-D-A small molecules with a dithienosilole core: synthesis, theoretical calculations and optoelectronic properties [Abstract in Atti di Convegno]
Parenti, Francesca; Buffagni, Mirko; Caselli, Monica; Mucci, Adele; Pigani, Laura; Vanossi, Davide; Zambon, Alfonso
abstract

Polythiophenes are conjugated materials finding application in many optoelectronic devices.1 Recently, much attention has been devoted to oligothiophenes, the shorter analogous compounds of these polymers. These semiconductor materials are structurally well-defined, monodisperse, free of defects and often possess higher polarizability and charge mobility with respect to the corresponding polymers.2 Thiophene-based small molecules3 are well studied as photoactive materials in organic solar cells. In particular, molecules with A-π-D-π-A architecture, formed by a central electron donating building block (D) and two terminal electron accepting groups (A) linked by π-conjugated bridges, show a low energy absorption band making them suitable as active layers in organic solar cells.4,5 Little modifications of the backbone, i.e. by changing the length of the alkyl substituents or the type of the functional groups, will often result in remarkable modification of the band gap and other optical properties. Here, we present the theoretical calculations, the synthesis and the characterization of two A-π-D-π-A small molecules E1 and E2, where the central unit is a dithienosilole, the terminal units are methyldicyanovinyl functionalized thiophene rings and the π-bridges are alkyl or alkylsulfanyl functionalized thiophene rings, respectively. The aim of this research is to study the structural, electronic and optical properties of these molecules to better understand the role of the sulfur atom of the alkylsulfanyl chains and to gain insight on the properties of these materials in view of their application in optoelectronic and photovoltaic devices

2017 - Novel oligothiophenes with reduced HOMO-LUMO band gap for Optoelectonics [Abstract in Atti di Convegno]
Parenti, Francesca; Buffagni, Mirko; Zambon, Alfonso; Caselli, Monica; Vanossi, Davide; Mucci, Adele
abstract

Here we present the synthesis of A-π-D-π-A thiophene-based oligomers (Figure 1); in the design of these materials we incorporated both electron-donor and electron-acceptor groups by having a central donor dithienosilole, two terminal methyldicyanovinyl acceptor groups and two bithienyl units, functionalised with alkyl or alkylsulfanyl chains, as π-bridges.

2016 - Excitation-Energy Transfer Paths from Tryptophans to Coordinated Copper Ions in Engineered Azurins: a Source of Observables for Monitoring Protein Structural Changes [Articolo su rivista]
DI ROCCO, Giulia; Bernini, Fabrizio; Borsari, Marco; Martinelli, Ilaria; Bortolotti, Carlo Augusto; Battistuzzi, Gianantonio; Ranieri, Antonio; Caselli, Monica; Sola, Marco; Ponterini, Glauco
abstract

The intrinsic fluorescence of recombinant proteins offers a powerful tool to detect and characterize structural changes induced by chemical or biological stimuli. We show that metal-ion binding to a hexahistidine tail can significantly broaden the range of such structurally sensitive fluorescence observables. Bipositive metal-ions as Cu2+, Ni2+ and Zn2+ bind 6xHis-tag azurin and its 6xHis-tagged R129W and W48A-R129W mutants with good efficiency and, thereby, quench their intrinsic fluorescence. Due to a much more favourable spectral overlap, the 6xHis-tag/Cu2+ complex(es) are the most efficient quenchers of both W48 and W129 emissions. Based on simple Förster-type dependence of energy-transfer efficiency on donor/acceptor distance, we can trace several excitation-energy transfer paths across the protein structure. Unexpected lifetime components in the azurin 6xHis-tag/Cu2+ complex emission decays reveal underneath complexity in the conformational landscape of these systems. The new tryptophan emission quenching paths provide additional signals for detecting and identifying protein structural changes.

2016 - Optical and photophysical properties of anisole and cyanobenzene-substituted perylene diimides [Articolo su rivista]
Pagoaga, Bernard; Mongin, Olivier; Caselli, Monica; Vanossi, Davide; Momicchioli, Fabio; BLANCHARD DESCE, Mireille; Lemercier, Gilles; Hoffmann, Norbert; Ponterini, Glauco
abstract

One- and two-photon absorption cross-sections and spectra and the photophysical properties of eight perylenetetracarboxy-3,4:9,10-diimide (PDI) derivatives are reported and analyzed. The investigated compounds are characterized by direct binding of the phenyl rings of the substituents to the bay positions of the perylene core. They have been designed to test the effects of differences in the electronic nature – electron donating (anisole) or accepting (cyanobenzene) – and binding topology (cis or trans, meta or para disubstitution or tetrasubstitution) of the bay substituents on the above optical and photophysical observables. (TD)DFT and Hu¨ckel MO calculations have provided theoretical information on the ground-state geometries, the MOs and the electronic spectra of several model compounds. For tetrasubstituted and cis disubstituted derivatives, strong steric interactions in the bay area determined the preferred conformations, with perylene cores distorted near the substituted bay(s) and a 42–441 twisting of the substituent rings relative to the core, quite irrespective of the electronic nature of the substituents. On the other hand, in trans-disubstituted PDI steric hindrance in the bay areas was much weaker and similar in the cyanobenzene and the anisole derivatives. So, the large differences found in the conformational preferences were completely attributable to electronic effects. With electron-accepting cyanobenzene, the substituent rings were found normal to the central planar perylene core, thus enabling the assignment of the moderate spectroscopic effects to inductive interactions. The DFT analysis of the PDI trans-disubstituted with electron-donating anisoles gave quite strongly distorted perylene-core geometries and less twisted (591) substituent rings. The corresponding increased substituent/core conjugative interactions resulted in new CT allowed electronic transitions and an extremely pronounced solvent-polarity dependence of the emission spectra and intensities. All anisole substituted PDI feature a very fast radiationless decay path in polar solvents, likely related to a relaxation to a charge-separated configuration in the lowest excited-state.

2016 - SiO2-CaO-P2O5 bioactive glasses: A promising curcuminoids delivery system [Articolo su rivista]
Nicolini, Valentina; Caselli, Monica; Ferrari, Erika; Menabue, Ledi; Lusvardi, Gigliola; Saladini, Monica; Malavasi, Gianluca
abstract

In this paper, we report the study of the loading and the release of curcuminoids by bioactive glasses (BG) and mesoporous bioactive glasses (MBG). Through a detailed spectroscopic study, it was possible to determine the amount and the type of molecules released in water and in simulated body fluid (SBF). In particular, curcumin and K2T21 show a good ability to be released in di-keto and keto-enolic form, depending from the pH. However, after 24 h, the amount of pristine curcumin release is very low with a consequent increment of degradation products derived by curcuminoids. The presence of -OH groups on curcuminoids is a fundamental pre-requisite in order to obtain a high loading and release in polar solution such as water and SBF. The substrate on which we loaded the drugs does not seem to affect significantly the loading and the release of the drugs. The environment, instead, affects the release: for all the drugs, the release in SBF, buffered at pH of 7.4, is slightly worse than the release in water (basic pH values).

2015 - Porphyrin-based electrostatically self-assembled multilayers as fluorescent probes for mercury(II) ions: a study of the adsorption kinetics of metal ions on ultrathin films for sensing applications [Articolo su rivista]
Caselli, Monica
abstract

The electrostatic multilayer self-assembly technique was employed to prepare fluorescent probes for mercury(II) ions. Films showing an appreciable fluorescence emission were obtained by alternate adsorption of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) with polyelectrolytes. Fluorescence intensity quenching, arising from the coordinative interaction between the porphyrin and mercury ions, was monitored as a function of time. The response mechanism was studied on the basis of kinetic and equilibrium models for adsorption. The adsorption process of mercury ions on porphyrin-based films was described by the pseudo-second-order equation and the kinetic parameters were correlated with the initial concentrations of the metal ions in aqueous solution. The kinetic approach was evaluated as an alternative to monitoring the sensing responses at equilibrium.

2013 - A comparative study of two amphiphilic merocyanines: from monomers to aggregates in Langmuir and Langmuir–Blodgett mixed films [Articolo su rivista]
LODI, ANDREA; MOMICCHIOLI, Fabio; CASELLI, Monica; G., Giancane; PONTERINI, Glauco
abstract

The Langmuir–Blodgett (LB) films with J aggregates of the amphiphilic MC2 merocyanine have been deeply investigated for more than two decades, mainly because of their interest for applications in photonic devices. To extend the excitation/emission wavelength range, we have studied an homologous dye, MC1, based on a shorter merocyanine chromophore, aiming at checking the ability of this compound to arrange into J aggregates within stable LB films. In this comparative MC1/MC2 investigation, we have addressed the structural and spectroscopic properties of the monomers in solution, the thermodynamic and morphological properties of the Langmuir monolayers at the air–water interface and the spectroscopic and photophysical properties, and the structural features thence obtainable, of the aggregates in the LB films. 1H NMR experiments have shown that, in chloroform solutions, both dyes adopt planar conformations with the hydrophilic and hydrophobic groups pointing to opposite directions. Strongly attractive interactions are exhibited by both dyes towards arachidic acid in monolayers at the air– subphase interface, with a maximum stability for the 1 : 2 MC(1/2) : AA mixture. Relatively homogeneous LB multilayers have been obtained from 1 : 4 and 1 : 2 MC : AA mixtures with good transfer ratios. Absorption and emission of the LB films of MC1 are dominated by J aggregates, while those of MC2 show some H aggregate contributions too. The J aggregates of both compounds exhibit a tendency to align with the transition dipoles along the film dipping direction, only slightly tilted relative to the substrate surface; however, this tendency is more pronounced for the MC1 J aggregates. Overall, MC1 yields slightly more stable monolayers and more solid multilayers compared to MC2.

2013 - A proteomic approach to investigate the mechanism of action of anticancer peptides [Relazione in Atti di Convegno]
Genovese, Filippo; Gualandi, Alessandra; Taddia, Laura; Caselli, Monica; Ponterini, Glauco; Ferrari, Stefania; Marverti, Gaetano; R., Guerrini; M., Pela'; Pavesi, Giorgia; C., Trapella; Costi, Maria Paola
abstract

Many efforts to improve survival of patients affected by Ovarian Cancer (OC) have focused on more effective systemic therapies and on the search for new therapeutic targets. One of the molecular targets for OC is human Thymidylate Synthase (hTS), a homodimeric enzyme essential for DNA biosynthesis. The main goal of our research is to identify compounds able to inhibit hTS by interfering with its dimerization, without causing its over-expression and the onset of cellular drug resistance against the traditional hTStargeted compounds. We have recently discovered some peptides which specifically target the hTS dimer interface and inhibit the enzyme by stabilizing its di-inactive form [1]. These molecules have been recently investigated for their SAR profile. LR, our lead compound, inhibits the intracellular enzyme in both cisplatin (cDDP)-sensitive and -resistant ovarian cancer cells without causing protein overexpression, thus showing a potential for overcoming the limits of OC chemotherapy. This work aims at setting up a proteomic approach able to provide information on the changes in the protein expression profile induced in OC cells by treatment with LR with respect to a well-known folate antimetabolite, Pemetrexed (PTX) and identify key proteins that are involved in its mechanism of action.

2012 - Aggregation behaviour of a water-soluble ammonium-functionalizedpolythiophene: Luminescence enhancement induced by bile-acid anions [Articolo su rivista]
R., Cagnoli; Caselli, Monica; Libertini, Emanuela; Mucci, Adele; Parenti, Francesca; Ponterini, Glauco; Schenetti, Luisa
abstract

The water-soluble poly{trimethyl-[7-(3-thienylsulfanyl)heptyl]ammonium iodide-co-thiophene} (PTNDMe3) forms aggregates whose size span a large range of values, depending on solvent, concentrationand film formation conditions. Larger aggregates were detected by atomic force microscopy and dynamic light scattering, smaller ones by DOSY NMR, UVevisible and fluorescence. All techniques indicate a reduced aggregation of PTNDMe3 in DMSO relative to water and a marked de-aggregation of PTNDMe3 in water following addition of bile-acid anions such as deoxycholate and ursodeoxycholate.The latter effect shows itself through a very large enhancement of the polymer photoluminescence likely caused by disruption of aggregated non-emissive exciton traps. A tailored combination of electrostaticand hydrophobic interactions between the polymer and the bile-acid anions seems to be necessary to achieve this effect. These observations suggest that this polythiophene might provide a basis for the development of fluorescent sensors suitable for the detection of medium-sized amphiphilic biomolecules.

2012 - Proteomic Approach to the Detection of the Mechanism of Action of Anticancer Peptides [Abstract in Rivista]
Genovese, Filippo; Gualandi, Alessandra; Taddia, Laura; Caselli, Monica; Ponterini, Glauco; Marverti, Gaetano; Pirondi, Silvia; R., Guerrini; M., Pela'; Pavesi, Giorgia; C., Trapella; Costi, Maria Paola
abstract

A label-free quantitative proteomic approach has been undertaken to study the effects of the peptide on the proteins involved in the modulated metabolic pathways, in particular those involved in the folate metabolism. Structure-activity relationships (SAR) have been performed to improve the lead peptide pharmacodynamics. All the compounds have been assayed and a protein profile set was studied to mark and validate their behavior as inhibitor of OC cell growth.

2010 - Dimer-monomer equilibrium of human thymidylate synthase monitored by fluorescenceresonance energy transfer. [Articolo su rivista]
Genovese, Filippo; Ferrari, Stefania; Guaitoli, Giambattista; Caselli, Monica; Costi, Maria Paola; Ponterini, Glauco
abstract

An ad hoc bioconjugation/fluorescence resonance energy transfer (FRET) assay has been designed to spectroscopically monitor the quaternary state of human thymidylate synthase dimeric protein. The approach enables the chemoselective engineering of allosteric residues while preserving the native protein functions through reversible masking of residues within the catalytic site, and is therefore suitable for activity/oligomerization dual assay screenings. It is applied to tag the two subunits of human thymidylate synthase at cysteines 43 and 43' with an excitation energy donor/acceptor pair. The dimer-monomer equilibrium of the enzyme is then characterized through steady-state fluorescence determination of the inter-subunit resonance energy transfer efficiency.

2010 - Probing solute–solvent hydrogen bonding with fluorescent water-soluble curcuminoids [Articolo su rivista]
Caselli, Monica; Ferrari, Erika; Imbriano, Carol; Pignedoli, Francesca; Saladini, Monica; Ponterini, Glauco
abstract

Glycosylated water-soluble curcuminoids (C1–C3, first scheme of this article) differing in the 3,3-ringsubstituents (–OH, –OCH3 and H) equilibrate between the di-keto and the keto–enol forms. The formerare well observable in the absorption spectra in water, but their emissions are always negligible. Theketo–enol forms of C1–C3 exhibit a broad range of fluorescence quantum yields in different solvents,organic and water: formation of solute–solvent hydrogen bonds through the 3,3-ring substituents maychange the radiationless S1-state decay constant by up to a factor 200. Such a fluorescence quenchingmechanism is extremely efficient in water and, for C1, in accepting organic media. On the contrary, noeffects traceable to intermolecular hydrogen bonds involving the central -dicarbonyl moiety have beenobserved. So, fluorescence of these curcuminoids may probe the hydrogen bonding ability, particularly asacceptor, of their microenvironments, including hydrophilic/hydrophobic domains in complex biologicalsystems. Interaction of C1 and C2 with bovine serum albumin results in emission enhancements inverseto the quantum yields of the curcuminoids in water. The observations support the idea that, although thecurcuminoid microenvironment within its complex with the protein is less polar and hydrogen bondingthan water itself, residual water/ligand hydrogen bonds are active in enhancing radiationless transitions.Finally, fluorescence confocal images of HCT116 cells treated with C1–C3 suggest the apparently smallstructural differences to affect, besides their fluorescence behaviour, their interactions and fate withinliving cells.

2009 - Photodegradation of organic pesticides in the environment [Articolo su rivista]
Caselli, Monica
abstract

Reactions induced by absorption of light contribute to the degradation of many chemical compounds in the environment. A critical overview on the current research activity concerning direct and indirect photodegradation processes of organic pesticides in the aquatic environment and on soil is reported.

2008 - "Aminoalkylsulfanyl substituted polithiophene: an aggregation study" [Abstract in Atti di Convegno]
Parenti, Francesca; Cagnoli, Rita; Caselli, Monica; Libertini, Emanuela; Mucci, Adele; Pinetti, Diego; Ponterini, Glauco; L., Preti; Schenetti, Luisa
abstract

The aggregation properties of poly{trimethyl-[7-(3-thienylsulfanyl)heptyl]ammonium iodide-co-thiophene} (PTN+Me3) (Fig.1) were investigated through NMR, AFM, light scattering and fluorescence spectroscopy.

2008 - Aminoalkylsulfanyl Substituted Polythiophene: an Aggregation Study [Relazione in Atti di Convegno]
Parenti, Francesca; Pinetti, Diego; Ponterini, Glauco; Preti, Lisa; Schenetti, Luisa; Cagnoli, Rita; Caselli, Monica; Libertini, Emanuela; Mucci, Adele
abstract

The aggregation behaviour of poly{trimethyl-[7-(3-thienylsulfanyl)heptyl]ammonium iodide-co-thiophene} (PTN+Me3) was investigated through NMR, atomic force microscopy (AFM), dynamic light scattering (DLS), UV-Vis and fluorescence spectroscopy. The interaction with sodium ursodesoxycholate (NaUDC) causes a marked enhancement of fluorescence emission.

2008 - Make sense of nanochemistry and nanotechnology [Articolo su rivista]
Ambrogi, Paola; Caselli, Monica; M., Montalti; M., Venturi
abstract

A class in a Scientific-Technological Lyceum (age 17) decided to produce a PowerPoint presentation to introduce nanochemistry and nanotechnology to the students in lower grades. Because the subject is very new, there was nothing in the School textbooks and, therefore, the students had to cooperate in order to find materials, to use ICT sources and to take decisions, such as selecting information and choosing slide layouts. Furthermore, the Cooperative Learning methodology was employed to solve the problem of setting up the presentation. To make nanochemistry and nanotechnology a reality for the students, they used a link between these new frontiers of Chemistry and subjects currently tackled at the Secondary School level. This was the quantitative determination of Ca2+ ions by using calcein, a luminescent chemosensor, in which well known concepts, such as chemical equilibrium and stability constants of coordination compounds, are involved. The educational aims of the project were to promote both content knowledge and social skills in Secondary School students. The activity created a good class atmosphere and also led to the retention of content knowledge.

2008 - Strategies to Reduce Inter-chain Aggregation and Fluorescence Quenching in Alternated Multilayers of a Polythiophene [Articolo su rivista]
Lodi, Andrea; Caselli, Monica; Zanfrognini, Barbara; Cagnoli, Rita; Mucci, Adele; Parenti, Francesca; Schenetti, Luisa; Ponterini, Glauco
abstract

Electrostatically self-assembled multilayers of a fluorescent carboxyalkylsulfanyl polythiophene and poly(diallyldimethylammonium) were prepared using the layer-by-layer deposition approach and were structurally characterized by linear dichroism and atomic-force microscopy. Steady-state measurements revealed that fluorescence was quenched relative to the solution behaviour. The emission quantum yield was found to increase upon decreasing the polymer concentration in the dipping solution as well as by codepositing polythiophene with another polyanion, poly(sodium-4-styrenesulfonate). Fluorescence quenching was therefore attributed to the formation of non-emitting inter-chain aggregate exciton traps.Intercalation of polythiophene layers with non-emitting polymers having larger energy gaps did not result in enhanced fluorescence, thus suggesting negligible polythiophene aggregation and exciton migration across different layers. At best, we could obtain quantum yields around 0.1–0.15, about half the solution value but almost two orders of magnitude larger than found with cast or spin-cast films.

2007 - Electronic spectra and fluorescence properties of multichromophoric sulfonylureas [Articolo su rivista]
Baraldi, Ivan; Caselli, Monica; Ponterini, Glauco; Vanossi, Davide
abstract

The multichromophoric character of two sulfonylurea herbicides, SMT and BNS, has been investigated in its manifestations in the electronic absorption spectra and in some fluorescence properties through a combined experimental and theoretical approach. After a theoretical analysis of the most stable structures of these flexible systems, the UV absorption spectra of the two multichromophoric compounds have been analysed both experimentally and theoretically, and most transitions have been assigned to individual chromophores, also by comparison with four suitable reference compounds (5-8). Finally, some experimental information concerning the fluorescence spectra and quantum yields have been analysed with reference to the contributions from single fluorophores and the role of low-lying n -> pi* states. (c) 2006 Elsevier B.V. All rights reserved.

2007 - Solvent-dependent host-guest complexation of two homologous merocyanines by a water-soluble calyx[8]arene. Spectroscopic analysis and structural calculations [Articolo su rivista]
A., Lodi; Caselli, Monica; A., Casnati; Momicchioli, Fabio; F., Sansone; Vanossi, Davide; Ponterini, Glauco
abstract

The sulfonated calixarene I8C12 acts as a host for homologous merocyanines Mc1 and Mc2 in organic solvents, exhibiting neither selectivity towards the guest dyes nor solvent dependence of the complexation equilibria. In water, on the contrary, only the lower homologue, Mc1, is solubilized in the presence of the calixarene. A combination of UV–visible and fluorescence spectroscopic and photophysical analysis and MD structural simulation of the calixarene-dye complexes was employed to account for the observations, and suggests that a radical change in the complexation mode occurs upon moving from an organic to an aqueous environment.

2005 - Light-induced degradation of metsulfuron-methyl in water [Articolo su rivista]
Caselli, Monica
abstract

Photodegradation of metsulfuron-methyl, a sulfonylurea herbicide, has been investigated in aqueous solution at different pH and excitation wavelengths. The efficiency of the process has been evaluated through quantum yield determinations. The identification of the photoproducts indicates that the major photochemical pathway is initiated by C-S bond dissociation followed by involvement of water to yield the main final products; the behaviour in water is shown to differ markedly from that in an organic environment. © 2004 Elsevier Ltd. All rights reserved.

2004 - Consequences of H-dimerization on the photophysics and photochemistry of oxacarbocyanines [Articolo su rivista]
Caselli, Monica; L., Latterini; Ponterini, Glauco
abstract

The photophysical/photochemical behaviour of the monomers and the H dimers of four oxacarbocyanines (dyes D-G in the scheme) was investigated in water. In contrast with the usually observed effect of H dimerization, the dimers of dyes D-G were found to fluoresce with efficiencies comparable to or larger than those of the corresponding monomers. Analysis of the decay paths of the lowest excited singlet state showed, however, that dimerization causes a decrease of the radiative rate constants and an enhancement of intersystem crossing to the triplet manifold, as expected from application of exciton theory to a model H dimer. Twisting about one of the polymethine bonds contributes to the decay from the spectroscopic minimum of monomers, though yielding a rather small amount of a distorted cis isomer. The process is inhibited in dimers, likely due to a pronounced increase of activation energy connected with a loss of van der Waals attractive energy at the twisted geometry.

2004 - Induction of phase I and phase II enzyme activities by UVB and xenobiotics in normal human keratinocytes. [Abstract in Rivista]
Benassi, Luisa; Magnoni, Cristina; Bertazzoni, Giorgia; Caselli, Monica; Seidenari, Stefania; Giannetti, Alberto
abstract

The function of the skin is to provide a barrier for protection against the external environment. Relatively little is known about the overall role of CYP450 in the metabolism of xenobiotics or endogenous cellular compounds in the skin. The aim of this study was to analyse the expression and induction of several drugs metabolizing enzymes. To this purpose both phase I and phase II enzymes activities were studied in normal human keratinocytes in culture after exposure to UVB radiation and to classical cytochrome inducers: β-naphthoflavone (BNF), 3-methylcholanthrene (MC), phenobarbital (PB). We investigated 7-ethoxyresorufìn O-deethylase (EROD) and 7-pentoxyresorufìn O-depenthylase activities (PROD). Normal human keratinocytes were cultured with mitomycin-treated 3T3 cells in Dulbecco’s modified Eagle’s medium/Ham’s F12. At confluence cells were incubated with inducers or irradiated with different doses of UVB. The microsomal fraction was studied by western-blot analysis. The MC-induced EROD activity was up to fourfold higher when compared with BNF induced activity. UVB exposure resulted in a dose-dependent (25-75 mJ) and time dependent (6-24 h) induction of CYP450 1A1. Immunoblotting assay showed expression for CYP450 1B1 not only keratinocytes but also in melanocytes. Proadifen, an inhibitor of CYP450-monooxygenase, led to a significant decrease in EROD activity. The results of the present study clearly show that irradiation with UVB is capable of modifying the activity of CYP450 isoenzymes in keratinocytes. The phase II enzyme gluthatione S transferase activity (GST) was induced by UVB and PB. These experimental findings stress the value of epidermal cell culture for pharmaco-toxicological studies of topical agents used in dermatology.

2003 - Induction of cytochrome P450 enzyme activity by UVB and xenobiotics in normal human keratinocites. [Abstract in Rivista]
Bertazzoni, Giorgia; Benassi, Luisa; Magnoni, Cristina; Caselli, Monica
abstract

The function of the skin is to provide a barrier for protection against the external environment. Relatively little is known about the overall role of CYP450 in the metabolism of xenobiotics or endogenous cellular compounds in the skin. The aim of this study was to analyse the expression and induction of several drugs metabolizing enzymes involved in either phase I or phase II reactions, in proliferanting human keratinocytes after exposure to UVB radiation and to three classical cytochrome inducers such as: β-naphthoflavone (BNF), 3-methylcholanthrene (MC), phenobarbital (PB). We investigated 7-ethoxyresorufìn O-deethylase (EROD) and 7-pentoxyresorufìn O-depenthylase activities (PROD). Normal human keratinocytes were cultured with mitomycin-treated 3T3 cells in Dulbecco’s modified Eagle’s medium/Ham’s F12. At confluency cells were incubated with inducers or irradiated with different doses of UVB. The microsomal fraction was studied by western-blot analysis. The MC-induced EROD activity was up to 4 fold higher when compared with BNF induced activity. UVB exposure resulted in a dose-dependent (25-75 mJ) and time dependent (6-24 h) induction of CYP450 1A1. Immunoblotting assay showed expression for CYP450 1B1 for both keratinocytes and melanocytes. Proadifen, an inhibitor of CYP450-monooxygenase, led to a significant decrease in EROD activity. The results of the present study clearly show that irradiation with UVB is capable of modifying the activity of CYP450 isoenzymes in keratinocytes. The phase II enzyme gluthatione S transferase activity (GST) was induced by UVB and PB. These experimental findings stress the value of epidermal cell culture for pharmaco-toxicological studies of topical agents used in dermatology.

2003 - Induzione dell'attività degli enzimi di fase I e II nei cheratinociti umani normali. [Abstract in Atti di Convegno]
Benassi, Luisa; Bertazzoni, Giorgia; Magnoni, Cristina; Caselli, Monica; Seidenari, Stefania
abstract

La cute può essere considerata come un effettivo distretto di biotrasformazione di composti chimici. Lo scopo di questo lavoro è stato analizzare l'espressione dei sistemi enzimatici per il metabolismo di fase I e fase II nei cheratinociti umani in proliferazione dopo irradiazione con raggi UVB e dopo esposizione a tre classici induttori: beta-naphthoflavone (BNF), 3-methylcholantrene (MC), phenobarbital (PB). Cheratinociti umani normali sono stati coltivati con fibroblasti 3T3 mitomicinati in Dulbecco's modified Eagle's medium/Ham's F12. A subconfluenza le cellule sono state incubate con gli induttori o irradiate a differenti dosi di UVB. La fase I è stata analizzata con attività 7-ethoxyresorufin O-deethylase (EROD) e 7-pentoxyresorufin O-depenthylase (PROD). la frazione microsomiale è stata studiata mediante analisi western blot. L'attività EROD indotta dall'MC era più alta di 4 volte rispetto al BNF. L'esposizione a raggi UVB risultava dose dipendente (50-75 mJ) e tempo dipendente (6-24h). L'attività della glutatione-S-transferasi(GST), enzima di fase II determinato con cinetica enzimatica, veniva significativamente espressa con UVB e PB. Questi risultati dimostrano il ruolo della cute nel metabolismo esogeno e la possibilità di utilizzare colture di cellule epidermiche per studi farmacotossicologici di agenti topici usati in dermatologia.

2002 - Dimerization of green sensitizing cyanines in solution. A spectroscopic and theoretical study of the bonding nature [Articolo su rivista]
Baraldi, Ivan; Caselli, Monica; Momicchioli, Fabio; Ponterini, Glauco; Vanossi, Davide
abstract

The bonding nature in cyanine-dye aggregates has been investigated by studying dimerization in solution of 3, 3'-disulfopropyl-4,5,4',5'-dibenzo-9-ethyloxacarbocyanine (D) and three other oxacarbocyanine analogues (E, F, G) used as photographic sensitizers in the green spectral region. Quantitative information on the monomer-dimer equilibrium of dye D in different solvents and of its analogues (E, F, G) in water was obtained by measurement of the absorption spectrum as a function of dye concentration and of temperature. Dimerization was found to be generally driven by enthalpic factors traceable to strong attractive van der Waals interactions between the two large and highly polarizable dye molecules. Entropic contributions to DeltaG(0) usually favour dissociation but are smaller than the enthalpic ones. The visible absorption spectrum of the dimer consists in a classic two-branched exciton band with a marked splitting (1600 cm(-1) in water). The experimental observations were the subject of a theoretical study including classical molecular dynamics (MD) and Monte Carlo (MC) calculations of the dimer structure and comparative analysis of monomer and dimer spectra by the CS INDO CI method. Computer simulations led to three similar H-type structures, the most stable of which is characterized by a distance of 4.7 Angstrom between the planes of the chromophores and an endoendo configuration of the sulfopropyl substituents. The calculated dimer spectrum was clearly interpreted in terms of exciton model but a quantitative agreement with the two-maximum exciton band could be obtained only by assuming substantial deviation of the long molecular axes from parallelism. On the basis of normal coordinate calculations it is suggested that such configurations may occur with a high probability in virtue of twisting vibrational motions of extremely low frequency. (C) 2002 Elsevier Science B.V. All rights reserved.

2002 - Induction of cytochrome P450 enzyme activity by UVB and xenobiotics in normal human keratinocytes and melanocytes [Abstract in Rivista]
Benassi, Luisa; Bertazzoni, Giorgia; Magnoni, Cristina; Caselli, Monica; Seidenari, Stefania
abstract

Cytochrome P450 (CYP450) play a major role in the bioactivation of procarcinogenesis in target tissue and the expression of this enzyme i san important determinant of human susceptibility to cancer. Relatively little is known about the overall role of CYP450 in the metabolism of xenobiotics or endogenous cellular compounds in the skin. The aim of this study was to analyse the expression of cytochrome enzymes in proliferanting human keratinocytes and melanocytes after exposure to UVB radiation and to three classical cytochrome inducers such as: β-naphthoflavone (BNF), 3-methylcholanthrene (MC), phenobarbital (PB). We investigated 7-ethoxyresorufìn O-deethylase (EROD) (which is CYP450 1A1 dependent) and 7-pentoxyresorufìn O-depenthylase activities (PROD) (CYP450 2B1 dependent)activities. Normal human keratinocytes were cultured with mitomycin-treated 3T3 cells in Dulbecco’s modified Eagle’s medium/Ham’s F12 or with KGM serum-free medium. Melanocytes were grown in medium 154. At confluency cells were incubated with inducers or irradiated with different doses of UVB. At different times after treatments, cells were harvested for in vitro measurement of CYP450 induction. The microsomal fraction was studied by western-blot analysis. Low, but measurable levels of CYP activity were detected in both basal and differentianting keratinocytes. The MC-induced EROD activity was up to 4 fold higher when compared with BNF induced activity. UVB exposure resulted in a dose-dependent (10-75 mJ) and time dependent (4-24 h) induction of CYP450 1A1 for keratinocytes and CYP450 2B1 for melanocytes. Immunoblotting assay showed expression for CYP450 1B1 for both keratinocytes and melanocytes. Proadifen, an inhibitor of CYP450-monooxygenase, led to a significant decrease in EROD activity. The results of the present study clearly show that irradiation with UVB is capable of modifying the activity of CYP450 isoenzymes not only in keratinocytes but also in melanocytes.These experimental findings stress the value of epidermal cell culture for pharmaco-toxicological studies of topical agents used in dermatology.

2001 - Irradiation-wavelength dependent photochemistry of the bichromophoric sulfonylurea chlorsulfuron [Articolo su rivista]
Caselli, Monica; Ponterini, Glauco; M., Vignali
abstract

The photochemistry of the bichromophoric sulfonylurea chlorsulfuron has been investigated at different irradiation wavelengths and environmental conditions. The identified products indicate that different reaction paths are followed, depending whether the benzene or the triazine component chromophores are excited. In the first case, the chlorine atom is substituted by hydrogen or hydroxyl in water; in the second one three competitive photodegradation paths may be followed, the most efficient one being the cleavage of the S-N bond in the sulfonylurea bridge. Photodegradation quantum yield measurements, combined with laser flash photolysis experiments have shown that, while both singlet and tripler states contribute to all photolytic paths in deaerated solution, quenching by oxygen makes the triplet contribution negligible in samples equilibrated with air. (C) 2001 Elsevier Science B.V. All rights reserved.

1995 - PHOTOISOMERIZATION OF ASYMMETRIC INDOBENZIMIDAZOLO CYANINE DYES [Articolo su rivista]
Tatikolov, As; Derevyanko, Na; Ishchenko, Aa; Baraldi, Ivan; Caselli, Monica; Momicchioli, Fabio; Ponterini, Glauco
abstract

The isomerization kinetics of three indobenzimidazolo polymethine cyanines have been investigated and compared with the corresponding properties of the parent symmetric dyes. A significant alternation of the pi bond orders in the polymethine chain was found in the ground states (S-0) of the asymmetric dyes. A similarly alternant behaviour was exhibited by the calculated S-0 potential energy barriers for twisting around the polymethine chain bonds of the asymmetric carbocyanine, whereas uniform barriers were found for the symmetric parent compounds. The experimentally observed sequence of back-isomerization activation energies was interpreted on the basis of these theoretical results. It was suggested by some spectral and kinetic fluorescence properties, and it was confirmed by the calculated polymethine-chain pi bond orders of the lowest singlet excited slates (S-1) that the electronic asymmetry induced by the different terminal heterocycles was strongly reduced upon excitation of these dyes to their S-1 states. In spite of this, the trans-cis photoisomerization of asymmetric cyanines occurred invariably around those bonds having the highest pi bond orders in the ground state. A tentative theoretical explanation of this systematic behaviour is reported.

1995 - Theoretical and photophysical study of photoisomerism of cyanine dyes : bisphenylaminopentamethine cyanine (BPPC) [Articolo su rivista]
Baraldi, Ivan; Carnevali, A.; Caselli, Monica; Momicchioli, Fabio; Ponterini, Glauco; Berthier, G.
abstract

The trans-cis photoisomerism of BPPC was investigated as part of a comprehensive, both theoretical and experimental, study on the photophysical and photochemical properties of cyanines having pentamethine cyanine as a common chromophore. In this work the determination of the trans → cis photoisomerization and thermal back isomerizatkm kinetics in alcohols was combined with CS INDO CI calculations of S0 and S1 potential energy curves for the paths leading to mono-cis isomers, where the dielectric solvent effects were taken into account by the simple virtual charge model. In agreement with the indications of a previous steady-state spectroscopy study, it was concluded that irradiation of BPPC into the visible absorption region gives rise to formation of the C(3)–C(4) cis planar isomer, already observed with the parent chromophore (BMPC), and an additional isomer, N(1)-C(2) cis, peculiar to BPPC. The role of the solute-solvent interactions is discussed with reference to the purely intramolecular model previously proposed for the cyanine photoisomerization.

1994 - A condensed thiadiazolo-pyrimidine as a new efficient fluorophore. Theoretical and experimental investigation of the electronic spectra and photophysics [Articolo su rivista]
Baraldi, Ivan; Carnevali, A.; Caselli, Monica; Costi, Maria Paola; Pecorari, P.; Ponterini, Glauco; Rinaldi, M.
abstract

A recently synthesized condensed thiadiazolo-pyrimidine (MTP) has been found to exhibit a very intense fluorescence emission in aprotic solvents. The origins of such an unusual property for a compound containing many different heteroatoms (four nitrogens, two sulphurs and one oxygen) have been investigated by a combined theoretical and experimental approach. The nature and peculiarity of the MTP chromophore have been analysed using both computed electron densities and crystallographic data from the literature. The singlet and triplet spectra have been measured and calculated, and a good agreement has been found between the two sets of results. On this basis, we have attempted to interpret the rather peculiar photophysical behaviour of MTP.

1993 - Concerning medium polarity effects on the photophysics andphotochemistry of TICT-forming dyes [Articolo su rivista]
Momicchioli, Fabio; Baraldi, Ivan; A., Carnevali; Caselli, Monica; Ponterini, Glauco
abstract

Mechanism and dynamics of the excited state relaxation in compounds able to form TICT states were investigated from a theoretical point of view with special reference to the dielectric solvent effects. The study included 4-dimethylamino-4’-cyanostilbene (DCS) and Michler’s Hydrol Blue (MHB), which are thought to involve emitting and non-emitting TICT states, respectively. It was found that in DCS the formation ofTICT states, by twisting either the dimethylamino or the dimethylanilino groups, may in principle be induced by the solvent polarity but requires extreme conditions. InMHB, both calculations and new fluorescence quantum-yield measurements in a variety of solvents indicated that the TICT-state formation is essentially controlled by the solvent viscosity.

1993 - Modelling of the cis-trans partitioning in the photoisomerizations of cyanines and stilbene derivatives [Articolo su rivista]
Caselli, Monica; Momicchioli, Fabio; Ponterini, Glauco
abstract

In the course of photoisomerization, polymethine cyanines as well as stilbene and its derivates decay from the S1 potential energy minimum, corresponding to the perpendicular geometry, to yield either cis or trans ground-state molecules. The fraction of cis isomers obtained, alpha, spans a larger range of values for symmetric cyanines than for stilbene derivatives. It is argued that such different behaviour for the two classes of compounds should be traceable to the electronically different nature of their S1 perp species. Making use of radiationless transition theory results, it is shown that the relative location of the S1 minimum and S0 maximum along the internal rotation coordinate is crucial to the evaluation of alpha: even small differences between these critical twisting angles, which are more reasonably expected for polymethine cyanines than for stilbene-like compounds, may cause strong deviations from equipartitioning (alpha = 0. 5 ).

1992 - PHOTOISOMERIZATION DYNAMICS OF 3,3'-DIETHYL OXACARBOCYANINE - INTRAMOLECULAR AND SOLVENT VISCOSITY EFFECTS [Articolo su rivista]
Ponterini, Glauco; Caselli, Monica
abstract

The dynamics of photoisomerization and of ground-state back isomerization of 3,3'-diethyl oxacarbocyanine (DOC) in linear alcohols are analyzed. Intramolecular activation energies are obtained and compared with those of the corresponding dicarbocyanine (DODCI) in an attempt at establishing the consequence of the polymethine chain lengthening on the isomerization dynamics. The activation energy for the photoisomerization of DOC is slightly lower than that of DODCI, whereas the reverse is found for the ground-state back isomerization. The coupling of the internal twisting coordinate with solvent drag is analyzed within the framework of the hydrodynamic Kramers model. Although this approach does not provide a fully satisfactory description of the experimental points, it has been taken as a reference model: the parameters obtained from the data fitting have been assigned a semi-quantitative significance and a number of possible reasons of breakdown of the hydrodynamic Kramers description have been considered and qualitatively discussed.

1989 - Rotamerism in 2,2’-binaphthyl. A study based on fluorescence analysis and CS-INDO/CI calculations [Articolo su rivista]
Baraldi, Ivan; M. C., Bruni; Caselli, Monica; Ponterini, Glauco
abstract

The torsional isomerism of 2-2’-binaphthyl in the ground state and lowest excited singlet states has been investigated theoretically and experimentally. The combined results of a fluorescence steady-state and time-resolved analysis and of CS-INDO/CI calculations showed that this molecule exists in the ground state in two rotameric forms in which the naphthyls are rotated around the interconnecting quasi-single bond by different angles. The absorption spectrum of 2-2’-binaphthyl was assigned and resolved into the individual spectra of the two rotamers. The fluorescence spectra, lifetimes and quantum yields of the two isomers at room temperature were also derived. The effects of solvent viscosity increase and of temperature decrease on the measured fluorescence lifetimes were found to be small. Lastly, a discussion of the rotational behaviour of this molecule as opposed to that of other biaryls is offered on the basis of the calculated torsional energy curves.