Publications

Abstract An understanding of the mechanism of action of antimicrobial peptides is fundamental to the development of new and more active antibiotics. In the present work, we use a wide range of techniques (SANS, SAXD, DSC, ITC, CD, and confocal and electron microscopy) in order to fully characterize the interaction of a cecropin A-melittin hybrid antimicrobial peptide, CA(1-7)M(2-9), of known antimicrobial activity, with a bacterial model membrane of POPE/POPG in an effort to unravel its mechanism of action. We found that CA(1-7)M(2-9) disrupts the vesicles, inducing membrane condensation and forming an onionlike structure of multilamellar stacks, held together by the intercalated peptides. SANS and SAXD revealed changes induced by the peptide in the lipid bilayer thickness and the bilayer stiffening in a tightly packed liquid-crystalline lamellar phase. The analysis of the observed abrupt changes in the repeat distance upon the phase transition to the gel state suggests the formation of an L-gamma phase. To the extent of our knowledge, this is the first time that the L-gamma phase is identified as part of the mechanism of action of antimicrobial peptides. The energetics of interaction depends on temperature, and ITC results indicate that CA(1-7)M(2-9) interacts with the outer leaflet. This further supports the idea of a surface interaction that leads to membrane condensation and not to pore formation. As a result, we propose that this peptide exerts its antimicrobial action against bacteria through extensive membrane disruption that leads to cell death.

Abstract Pseudomonas aeruginosa is one of the most dreaded human pathogens, because of its intrinsic resistance to a number of commonly used antibiotics and ability to form sessile communities (biofilms). Innovative treatment strategies are required and that can rely on the attenuation of the pathogenicity and virulence traits. The interruption of the mechanisms of intercellular communication in bacteria (quorum sensing) is one of such promising strategies. A cobalt coordination compound (Co(HL)(2)) synthesized from (E)-2-(2-(pyridin-2-ylmethylene) hydrazinyl)-4-(p-tolyl) thiazole (HL) is reported herein for the first time to inhibit P. aeruginosa 3-oxo-C12-HSL-dependent QS system (LasI/LasR system) and underling phenotypes (biofilm formation and virulence factors). Its interactions with a possible target, the transcriptional activator protein complex LasR-3-oxo-C12-HSL, was studied by molecular modeling with the coordination compound ligand having stronger predicted interactions than those of co-crystallized ligand 3-oxo-C12-HSL, as well as known-binder furvina. Transition metal group 9 coordination compounds may be explored in antipathogenic/antibacterial drug design.

Abstract Steady-state and time-resolved fluorescence techniques were used to study excited-state proton transfer (ESPT) to water of the reversible photoacid 2-naphthol-8-sulfonate (2N8S) in acetonitrile/water mixtures. In acetonitrile-rich mixtures, up to chi(water) <= 0.12, we found a slow ESPT process on the order of nanoseconds. At Xwater chi(water) approximate to 0.15, the RO- fluorescence band intensity is at the minimum, whereas at chi(water) approximate to 0.030, it is at the maximum. The steady-state fluorescence spectra of these mixtures show that the intensity of the RO- fluorescence band at chi(water) approximate to 0.030 is about 0.24 of that of the ROH band. We explain this unusual phenomenon by the presence of water clusters that exist in the acetonitrile-rich CH3CN/H2O mixtures. We propose that a water bridge forms between the 2-OH and 8-sulfonate by preferential solvation of 2N8S, and this enables the ESPT process between the two sites of the molecular structure of 2N8S. In mixtures of chi(water) >= 0.25, the ESPT process takes place to water clusters in the bulk mixture. The higher the chi(water) in the mixture, the greater the ESPT rate constant. In neat water, the rate constant is rather small, 4.5 X 10(9) s(-1). TD-DFT calculations show that a single water molecule can bridge between 2-OH and 8-sulfonate in the excited state. The activation energy for the ESPT reaction is about 9 kcal/mol, and the RO-(S-1) species is energetically above the ROH(S-1) species by about 1.6 kcal/mol.

Abstract Foodborne microbial diseases are still considered a growing public health problem worldwide despite the global continuous efforts to ensure food safety. The traditional chemical and thermal-based procedures applied for microbial growth control in the food industry can change the food matrix and lead to antimicrobial resistance. Moreover, currently applied disinfectants have limited efficiency against biofilms. Therefore, antimicrobial photodynamic therapy (aPDT) has become a novel alternative for controlling foodborne pathogenic bacteria in both planktonic and sessile states. The use of aPDT in the food sector is attractive as it is less likely to cause antimicrobial resistance and it does not promote undesirable nutritional and sensory changes in the food matrix. In this review, aspects on the antimicrobial photodynamic technology applied against foodborne pathogenic bacteria and studied in recent years are presented. The application of photodynamic inactivation as an antibiofilm strategy is also reviewed.

Abstract A procedure for the physical vapor deposition (PVD), in high-vacuum conditions, for high purity and crystalline methylammonium lead halide perovskite thin films is described. This procedure and methodology can be used to fabricate high-performance hybrid organic-inorganic materials that have recently emerged as the next-generation photovoltaic technology. PVD of methylammonium iodide and lead iodide to produce lead halide perovskite thin films was optimized according to the equilibrium vapor pressures of corresponding precursors evaporated from Knudsen effusion cells. Optical properties of perovskite thin films were characterized by UV-Vis-NIR and fluorescence spectroscopy. The high crystallinity of vapor-deposited thin films on glass, indium fin oxide, fluorine-doped fin oxide, and TiO2 surfaces was proved by scanning electron microscopy and X-ray diffraction. This vapor deposition approach leads to the production of very pure, crystalline and high stable perovskite thin films.

Abstract Anthocyanins are potential food colorants due to their color, low toxicity and biological properties. However, the low chemical stability of anthocyanins has limited their use. In this work, the thermal stability of cyanidin-3-O-glucoside (cy3glc) (major blackberry anthocyanin) and blackberry purees through molecular inclusion with beta-cyclodextrin (beta-CD) was assessed. Complexation with beta-CD showed a thermal stabilization of cy3glc, resulting on a decrease of the degradation rate constant (k) and in several alterations in the cy3glc-beta-CD DSC thermogram. To assess the bioaccessibility of blackberry anthocyanins, the stability of blackberry purees through simulated in vitro digestion was also studied. Despite the rapid degradation of anthocyanins observed within the first minutes of simulated intestinal digestion, complexation with beta-CD allowed anthocyanins degradation to be slowed down. The results obtained demonstrate the ability of beta-CD to increase blackberry anthocyanins thermal stability and also to decrease the rate of degradation of these pigments under simulated gastrointestinal conditions.

Abstract Aromatic diamines and naphthyl-substituted benzidines (BDB, TPB, TPD, NPB, alpha-NPD, beta-NPB, TNB) are listed as one of the best series available of hole transport materials used as thin films in organic electronics (OLEDs, OPVs). High-quality, homogeneous and compact thin films (ae 300 nm of thickness) of this compound series were prepared by a physical vapor deposition procedure. SEM and XRD characterizations evidence the amorphous nature of the thin films of NPB, alpha-NPD, beta-NPB and TNB, prepared onto ITO and gold surfaces by a controlling mass flow rate. The semiconducting behavior of this class of pi-conjugated materials was investigated through UV-vis characterization by the determination of optical band gaps (ae 3 eV). According to DSC, SEM and XRD analyses, the materials evidenced an amorphous structure and high thermal stability in the glassy state. Analyzing the melting properties, the ratio T (g)/T (m) = 2/3 was observed for TPB and NPB, which have a higher molecular symmetry, while T (g)/T (m) = 3/4 was observed for the asymmetric beta-NPB and TPD. The first accurate measurements of the vapor pressures and thermodynamic properties of phase transition were obtained for the most common hole transport material (NPB) in OLEDs. The relative stability of the crystalline phases of the diamine derivatives (BDB, TPB, NPB) was found to be enthalpically driven, increasing linearly with the molar volume of the compound.

Abstract The present work presents an extensive literature survey and analysis of the heat capacity and thermodynamic properties of fusion, vaporization, and sublimation for the linear hydrocarbons and several terminally substituted homologous series. The successive introduction of methylene groups on the relative stability of the solid and liquid phases is analyzed and discussed based on the chain length dependence of the enthalpies, entropies, and Gibbs energies of phase transition. An oddeven alternation is observed in the fusion and sublimation equilibria. The improved packing patterns of even-numbered n-alkanes is reflected in higher values of melting temperatures and thermodynamic properties of phase transition. Molar heat capacities in liquid phase of n-alkanes derivatives exhibit a linear dependence with the chain length by an increment of 31 +/- 2 JK(-1)mol(-1) per methylene group (-CH2-). A contribution of 4.95 kJmol(-1) per methylene group (value corrected for 298.15 K) is derived for the increment of the enthalpy of vaporization. A constant value for the specific enthalpy of vaporization is observed for long chain compounds: 360 Jg(1). As predictable, the enthalpy of vaporization is higher for groups that can form hydrogen-bonding interactions than for plain hydrocarbons. Concerning the monohalogenated alkanes, a clear increasing of enthalpy of vaporization for the larger halogen groups is observed. Moreover, the thermodynamic results indicate that along the fusion of n-alkanes and n-alkanols, there is a decrease of around 40% in the magnitude of intermolecular interactions.

Abstract The biological effects attributed to nitric oxide ((NO)-N-center dot) and nitroxyl (HNO) have been extensively studied, propelling their array of putative clinical applications beyond cardiovascular disorders toward other age-related diseases, like cancer and neurodegenerative diseases. In this context, the unique properties and reactivity of the N-O bond enabled the development of several classes of compounds with potential clinical interest, among which (NO)-N-center dot and HNO donors, nitrones, and nitroxides are of particular importance. Although primarily studied for their application as cardioprotective agents and/or molecular probes for radical detection, continuous efforts have unveiled a wide range of pharmacological activities and, ultimately, therapeutic applications. These efforts are of particular significance for diseases in which oxidative stress plays a key pathogenic role, as shown by a growing volume of in vitro and in vivo preclinical data. Although in its early stages, these efforts may provide valuable guidelines for the development of new and effective N-O-based drugs for age-related disorders. In this report, we review recent advances in the chemistry of NO and HNO donors, nitrones, and nitroxides and discuss its pharmacological significance and potential therapeutic application.