Pani-Ag/PVA nanocomposite: Gamma induced changes in the thermal and optical characteristics

The gamma (γ) induced modifications in the synthesized Pani-Ag/PVA nanocomposite (NCP) thermal and optical characteristics have been depicted. The induced effect was investigated applying X-ray diffraction, differential scanning calorimetry, and UV-spectroscopy. Further, the color intensity (ΔE) of the irradiated NCP and blank has been estimated. The γ radiation decreases the optical band gap value from 2.65 to 1.54 eV owing to the randomly amorphous dominance in the irradiated NCP. Moreover, γ radiation induced noticeable defects generation, splitting the crystals, leading to depressed melting temperature.     

Polyelectrolyte complexes IV. Interpolyelectrolyte complexes between some polycations with N,N-dimethyl-2-hydroxypropyleneammonium chloride units and poly(sodium styrenesulfonate) in dilute aqueous solution

We report first on the interpolyelectrolyte complex formation (PEC) between one polycation of integral type having about 95 mol% of N,N-dimethyl-2-hydroxypropyleneammonium chloride units in the backbone (PCA₅) and poly(sodium styrenesulfonate) (NaPSS), in dependence on the polyion concentrations and the mixing order. The PEC formation was qualitatively followed by viscometry, conductometry and UV-spectroscopy. Quasi-soluble PECs could be formed in the polyion concentration range of 0.1-1.0 unit mM. A complex stoichiometry close to 1:1 was found by both the qualitative measurements on the formation of quasi-soluble PEC in dilute aqueous solutions (when PCA₅ concentration was lower than the overlap concentration, C<C^∗) and elemental analyses of the insoluble PEC formed at the high polycation concentration (50 unit mM, C?C^∗). The influence of the ionic strength on the PECs stability was followed by the subsequent addition of NaCl up to an ionic strength of 3.5 M on the reaction mixture, after the PECs formation with three polycations different by both the content of quaternary ammonium salt groups in the backbone and the degree of branching (PCA₅, PCA₂₀ and PCT₂₀). No dissociation of PECs into the original components was evidenced irrespective of the polycation structure and the mixing order.     

Antamanide Analogs as Potential Inhibitors of Tyrosinase

The tyrosinase enzyme, which catalyzes the hydroxylation of monophenols and the oxidation of o-diphenols, is typically involved in the synthesis of the dark product melanin starting from the amino acid tyrosine. Contributing to the browning of plant and fruit tissues and to the hyperpigmentation of the skin, leading to melasma or age spots, the research of possible tyrosinase inhibitors has attracted much interest in agri-food, cosmetic, and medicinal industries. In this study, we analyzed the capability of antamanide, a mushroom bioactive cyclic decapeptide, and some of its glycine derivatives, compared to that of pseudostellarin A, a known tyrosinase inhibitor, to hinder tyrosinase activity by using a spectrophotometric method. Additionally, computational docking studies were performed in order to elucidate the interactions occurring with the tyrosinase catalytic site. Our results show that antamanide did not exert any inhibitory activity. On the contrary, the three glycine derivatives AG9, AG6, and AOG9, which differ from each other by the position of a glycine that substitutes phenylalanine in the parent molecule, improving water solubility and flexibility, showed tyrosinase inhibition by spectrophotometric assays. Analytical data were confirmed by computational studies.