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We study the emission properties of a high quality monolithic microcavity with an embedded ultrathin organic tetrakis(4-methoxyphenyl)porphyrin layer. Spectral and angle-resolved photoluminescence measurements show a well defined polarized doublet at detection angles larger than 15°. The splitting energy ranges up to 70 meV. The usual employed mechanism, based on the mismatch between the center of the mirror stop band and the wavelength of the microcavity, accounts only for a small fraction of the observed splitting. A transfer matrix model taking into account the optical anisotropy of the organic layer, has been employed to reproduce the observed experimental results. The anisotropy of the organic layer, confirmed by optical absorption spectroscopy, origins from a local molecular order as inferred by atomic force microscopy measurements. [ABSTRACT FROM AUTHOR]

Sodium intercalated manganese thiophosphate Na0.62Mn0.69PS3 powders have been synthesized by a two-step ion-exchange process. Dielectric measurements have been performed as a function of both temperature and frequency on the prepared samples in the 20–106 Hz frequency range over the 78–350 K temperature range by using the autobalancing bridge method. The temperature dependence of the dielectric constant imaginary part reveals the presence of a loss peak at the low temperatures together with a strong dispersion at the low frequencies and at the highest investigated temperatures. While the loss peak presence is characteristic for dipolar polarization processes, the strong low frequency dispersion at not very high temperatures, observed also in the dielectric constant real part, is typical for system with hopping charge carriers. A hypothesis about the nature of such carriers has been formulated on the basis of both the ion-exchange intercalation process and the comparison with the dielectric spectra previously observed for cesium intercalated manganese thiophosphate Cs0.46Mn0.77PS3 compounds. [ABSTRACT FROM AUTHOR]

Polycrystalline powders of Na2xMn1-xPS3 have been synthesized from layered MnPS3 material by successive ion-exchange intercalation of potassium and sodium ions. Their x-ray photoelectron spectroscopy (XPS) and x-ray excited Auger spectroscopy spectra have been measured at room temperature using Mg Kα (1253.6 eV) x-ray source. In particular, the Mn, P, and S 2p and Na 1s and 2p core-level regions and the Na Auger KL23L23 transition have been investigated. All the analyzed XPS core-level spectra display a single-peak structure, suggesting the absence of nonequivalent atoms of Na, Mn, P, and S. The manganese XPS spectrum shows, as observed in MnPS3 and in its cesium and potassium intercalation compounds, typical shake-up satellites, suggesting that the Mn–S bond is yet mainly ionic in nature. The comparison with the XPS spectra relative to MnPS3 and its potassium intercalation compound (K2xMn1-xPS3) does not emphasize any relevant difference in the binding energy positions of the investigated core levels, indicating that sodium ion intercalation process does not alter the electronic properties of pure host matrix. Moreover, Na 2p core levels are discrete and well localized in agreement with the hypothesis of a weak link between the guest (the Na+ ions) and the host lattice (the negatively charged Mn1-xPS3 sheets). Such a hypothesis finds confirmation by the calculation of the Na modified Auger parameter. [ABSTRACT FROM AUTHOR]

Cesium ions have been intercalated by ion exchange into layered manganese thiophosphate to produce Cs2xMn1-xPS3. Investigations have been conducted by x-ray diffraction analysis, IR absorption spectroscopy, x-ray photoemission spectroscopy (XPS), and dielectric spectroscopy. The XPS spectra, recorded at room temperature and at the Mn, P, and S 2p, Mn 3p, and Cs 3d and 4d core-level regions, indicate that no charge transfer occurs from guest species (Cs+) to pure host lattice (MnPS3). The presence of shake-up satellites at the Mn 2p and 3p core levels suggests that the cesium intercalation does not alter the nature of the Mn–S bond which is mostly ionic. Dielectric measurements, carried out between 260 and 375 K and in the 20 Hz–1 MHz frequency range, classify Cs2xMn1-xPS3 as hopping charge carrier systems. The nature of such carriers can be hypothesized on the basis of both the intercalation process by cationic substitution and the comparison with the observed dielectric response of the pure MnPS3. [ABSTRACT FROM AUTHOR]

Lithium intercalate thin films have been obtained from MnPS3 starting material and characterized by the x-ray photoelectron spectroscopy technique. The regions of Mn 2p and 3p, P and S 2p, and Li 1s core levels have been investigated. The analysis of the spectra has revealed the lack of nonequivalent atoms of Mn, P and S, and Li. The presence of shake-up-type satellites at the Mn 2p and 3p core levels suggests that Li2xMn1-xPS3 is a large-gap insulating Mn compound analogously to the parent MnPS3. After lithium intercalation no remarkable shift has been observed in the binding energy positions of the investigated core levels in comparison with the corresponding MnPS3 pure compound. On these bases, we assume that only an ion transfer accompanies the lithium intercalation process. [ABSTRACT FROM AUTHOR]

We have prepared novel nanohybrid Li2xMn1−xPS3/GO films consisting of graphene oxide (GO) and exfoliated MnPS3nanosheets via an easy mixing protocol at room temperature. These films were investigated by SEM and AFM, as well as XRD, Raman and XPS spectroscopies, obtaining information about the nature of the interaction between MnPS3and GO. In particular, the dark colour of the nanocomposite film and, more to the point, the analysis of (i) the C1s core level XPS spectra, (ii) the interlayer spacing obtained by XRD measurements and (iii) the increment in the intensity ratio ID/IGof the two bands typical of the carbon region of GO Raman spectra, suggest that a partial reduction of GO can be obtained right upon intercalation into Li2xMn1−xPS3. [ABSTRACT FROM PUBLISHER]

Kinetics of the growth of TPPS4 porphyrin J-aggregates slow down in the order H2SO4 ＞ HCl ＞ HBr ＞ HNO3 ＞ HClO4, in agreement with the Hofmeister series. The rate constants and the extent of chirality correlate with the structure-making or breaking abilities of the different anions with respect to the hydrogen bonding network of the solvent. [ABSTRACT FROM AUTHOR]

Li2xMn1-xPS3films have been synthesized by exfoliating MnPS3through the successive intercalations of K+and Li+ions. Their dielectric response has been measured from 80 to 350 K in the frequency range of (102–106) Hz. The obtained data have been analyzed in terms of both complex permittivityε*and theacconductivityσac. The frequency dependence ofσachas been interpreted in terms of the Jonscher’s law, whose exponentndecreases by increasing temperature. Thenvalues lie between 0.479 and 0.501 and are typical of materials in which theacconductivity is due to multiple hops of carriers. By analyzing theσdctemperature dependence, the observed dielectric response has been attributed to the intercalated lithium ions, and the Li2xMn1-xPS3films have been classified ashoppingcharge carrier systems. [ABSTRACT FROM AUTHOR]

Many essential biological molecules exist only in one of two possible mirror-image structures, either because they possess a chiral unit or through their structure (helices, for example, are intrinsically chiral), but so far the origin of this homochirality has not been unraveled. Here we demonstrate that the handedness of helical supramolecular aggregates formed by achiral molecules can be directed by applying rotational, gravitational and orienting forces during the self-assembly process. In this system, supramolecular chirality is determined by the relative directions of rotation and magnetically tuned effective gravity, but the magnetic orientation of the aggregates is also essential. Applying these external forces only during the nucleation step of the aggregation is sufficient to achieve chiral selection. This result shows that an almost instantaneous chiral perturbation can be transferred and amplified in growing supramolecular self-assemblies, and provides evidence that a falsely chiral influence is able to induce absolute enantioselection. [ABSTRACT FROM AUTHOR]

Aim: To design, manufacture and test a second generation leptin receptor (ObR) agonist glycopeptide derivative. The major drawback to current experimental therapies involving leptin protein is the appearance of treatment resistance. Our novel peptidomimetic was tested for efficacy and lack of resistance induction in rodent models of obesity and appetite reduction. Methods: The glycopeptide containing two additional non-proteinogenic amino acids was synthesized by standard solid-phase methods. Normal mice were fed with peanuts until their blood laboratory data and liver histology showed typical signs of obesity but not diabetes. The mice were treated with the peptidomimetic at 0.02, 0.1 or 0.5 mg/kg/day intraperitoneally side-by-side with 0.1 mg/kg/day leptin for 11 days. After termination of the assay, the blood cholesterol and glucose amounts were measured, the liver fat content was visualized and quantified and the remaining mice returned to normal diet and were allowed to mate. In parallel experiments normal rats were treated intranasally with the glycopeptide at 0.1 mg/kg/day for 10 days. Results: The 12-residue glycosylated leptin-based peptidomimetic E1/6-amino-hexanoic acid (Aca) was designed to target a principal leptin/ObR-binding interface. E1/Aca induced leptin effects in ObR-positive cell lines at picomolar concentrations and readily crossed the blood-brain barrier (BBB) following intraperitoneal administration. The peptide initiated typical leptin-dependent signal transduction pathways both in the presence and absence of leptin protein. The peptide also reduced weight gain in mice fed with high-fat peanut diet in a dose-dependent manner. Obese mice receiving peptide E1/Aca at a 0.5 mg/kg/day dose lost weight, corresponding to a net 6.5% total body weight loss, while similar mice treated with leptin protein did not. Upon cessation of the weight loss treatment, several obesity-related pathologies (i.e. abnormal metabolic profile and liver histology as well as infertility) normalized in peptide-, but not leptin-treated, mice. Peptide E1/Aca added intranasally to growing normal rats decelerated normal weight gain corresponding to a net 6.8% net total body weight loss with statistical significance. Conclusions: No resistance induction to peptide E1/Aca or toxicity in either obese or healthy rodents was observed, indicating the potential for widespread utility of the peptidomimetic in the treatment of leptin-deficiency disorders. We provide additional proof for the hypothesis that difficulties in current leptin therapies reside at the BBB penetration stage, and we document that by either glycosylation or intranasal peptide administration we can overcome this limitation. [ABSTRACT FROM AUTHOR]

Summary. Two Vero cell lines persistently infected with XJCl3 and Cl67 strains of Junin virus and named V3 and V7, respectively, have been characterized with respect to the presence and expression of the nucleoprotein (N) and the glycoprotein precursor (GPC) viral genes. After the acute phase of infection, where a marked CPE and high titers of virus were obtained, JV persistently infected cells became morphologically undistinguishable from Vero cells and virus production dropped to undetectable levels. V3 and V7 were resistant to the superinfection with antigenically related viruses. This fact could not be attributed to the presence of defective interfering particles or non-infectious virus in the supernatant. Expression of N was consistently detected in both cultures and accumulation of two degradation products of N was evident during the late passages. Although no G1 (main surface glycoprotein) expression was observed, a marked fusogenic capacity was detected in both cultures indicating at least, the synthesis of a GPC derived fusogenic glycoprotein. Cell lysates from V3 and V7 subjected to RT-PCR, using specific primers for N gene, or to a nested RT-PCR using specific primers for GPC (G1 region) confirmed the presence of both viral genes. No viral DNA sequences could be detected in JV persistently infected cells. [ABSTRACT FROM AUTHOR]

Examines the scaling properties of porphyrins and dendritic polymer systems. Molecule size of porphyrins; Growth of large diffusion-limited fractal aggregates; Fractal nature of dendrimers.

The planarity and electron delocalization of the 2, 2′:6′, 2″-terpyridine (terpy) moiety in salts of the type [Pt(terpy)Me]X leads to extensive stacking interactions in aqueous solution. UV/VIS, H NMR and resonance light scattering spectra provide evidence for the tendency of the complex to form large aggregates even under low ionic strength conditions. The interaction of the cationic complex with calf thymus DNA was investigated by spectroscopic techniques and mobility assays. At high r ratios the complex seems to form extended aggregates on the surface of the nucleic acid but at lower r evidence was obtained for intercalation. [ABSTRACT FROM AUTHOR]

The XJCl3 strain of Junin virus (JV) and the mouse-attenuated mutant Cl67 showed different GP 38 peptide mapping after limited proteolysis with ficin and papain; viral infectivity of both viruses also exhibited a different susceptibility to protease treatment. A correlation between envelope glycoprotein alteration and JV virulence in neonatal mice is proposed. [ABSTRACT FROM AUTHOR]

A light emitting structure consisting of two coupled microcavities has been realized and studied. One of the two cavities contains a luminescent organic thin film of tetrakis(4-methoxyphenyl)porphyrin, whereas the other microcavity is a dielectric structure coupled to the organic one by means of a LiF/ZnS Bragg mirror. Reflectivity spectra show the presence of two well defined cavity dips. We observe an energy splitting of the two cavity modes. Despite the fact that only one cavity contains the active layer, the photoluminescence spectra display two peaks with comparable intensities at the same energy of the reflectivity dips. These observations indicate the strong coupling of the two cavities. The comparison of the diagonalized effective Hamiltonian with the observed resonances further confirms the strong coupling. [ABSTRACT FROM AUTHOR]