Manganese Defective Clustering: Influence on the Spectroscopic Features of Ceria-Based Nanomaterials.

The influence of manganese modification on the spectroscopic features of manganese-doped CeO2 systems synthesized by the microwave-assisted hydrothermal route and their correlation with the presence of O defective structures were verified, focusing on their interaction with poisonous atmospheres. Raman and electron paramagnetic resonance studies confirmed the presence of defective clusters formed by dipoles and/or quadrupoles. The number of paramagnetic species was found to be inversely proportional to the doping concentration, resulting in an increase in the Mn2+ signal, likely due to the reduction of Mn3+ species after the interaction with CO. X-ray photoelectron spectroscopy data showed the pure system with 33% of its cerium species in the Ce3+ configuration, with an abrupt decrease to 19%, after the first modification with Mn, suggesting that 14% of the Ce3+ species are donating one electron to the Mn2+ ions, thus becoming nonparamagnetic Ce4+ species. On the contrary, 58% of the manganese species remain in the Mn2+ configuration with five unpaired electrons, corroborating the paramagnetic feature of the samples seen in the electron paramagnetic resonance study.

Bacterioruberin extracts from a genetically modified hyperpigmented Haloferax volcanii strain: antioxidant activity and bioactive properties on sperm cells.

AIMS: To examine the antioxidant activity of Bacterioruberin (Bctr)-rich extracts isolated from a hyperpigmented, genetically modified Haloferax volcanii strain (HVLON3) and to investigate the effect on cold-sensitive ram sperm cells. METHODS AND RESULTS: The strain HVLON3 produces higher Bctr amounts than most haloarchaea (220 ± 13 mg g-1 DW). HVLON3-Bctr extract has higher antioxidant activity than ß-carotene (threefold) as evaluated using 2,2 diphenyl-1-picrylhydrazyl combined with Electron Paramagnetic Resonance analysis (EC50 4·5 × 10-5  mol l-1 vs 13·9 × 10-5  mol l-1 respectively). Different concentrations of HVLON3-Bctr extracts were assayed on ram sperm after freezing/thawing and physiologically relevant parameters were examined. Extracts containing 7 and 20 µmol l-1 Bctr significantly improved cell viability (P < 0·0001), total and progressive motility (P < 0·0001) and sperm velocities (P = 0·0172 for curvilinear velocity VCL, P = 0·0268 for average path velocity VAP and P = 0·0181 for straight line velocity VSL) and did not affect other parameters evaluated. CONCLUSIONS: HVLON3 is an excellent source of natural microbial C50 carotenoids with applicability in Biotechnology, Biomedical and Veterinary fields. HVLON3 Bctr extract improves the quality of cryopreserved ram sperm cells and could be applied to increase insemination yields. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides an insight on the bioactive properties of a bioproduct derived from haloarchaea (carotenoids) which are so far underexploited.

Photophysicochemical characterization of mycosporine-like amino acids in micellar solutions.

The properties and photochemical and photophysical behavior of the mycosporine-like amino acids (MAAs) shinorine and porphyra-334 were experimentally evaluated in solutions of direct ionic micelles as simple biomimicking environments. The preferential partition of the natural molecules in the aqueous phase of sodium dodecyl sulfate (SDS) or cetyltrimethylammonium chloride (CTAC) micellar systems is confirmed. Although the proton dissociation of the carboxylic groups in the MAAs is slightly inhibited in CTAC solutions, the molecules are predicted to be in the form of zwitterions in all the explored media around physiological pH. The increase in the fluorescence quantum yield, emission lifetime and stationary anisotropy in the presence of CTAC micelles suggest electrostatic attractions of the MAAs with the surface of the cationic micelles. Consistently, the triplet-triplet absorption spectra in CTAC solutions reveal the typical environmental features of the micellar interface, while in the presence of SDS they are similar to those determined in neat water. Finally, the photostability of the MAAs increases in the micellar systems, more noticeably in the case of CTAC. It is concluded that the ability of the two MAAs to act as UV screens is susceptible to the influence of electrostatic interactions with organized microheterogeneous environments.

Confocal Raman spectroscopy: In vivo biochemical changes in the human skin by topical formulations under UV radiation.

A new approach to the study of the effects on human skin of mycosporine-like amino acids (MAAs) and gadusol (Gad) incorporated in polymer gel is proposed in this work. The depth profile and photoprotector effects of Pluronic F127® gels containing each of the natural actives were evaluated by in vivo confocal Raman spectroscopy aiming at the analysis of the biochemical changes on human skin. Hierarchical cluster analysis (HCA) showed that the data corresponding to different depths of the skin, from surface to 4 µm, and from 6 to 16 µm, remained in the same cluster. In vivo Raman spectra, classified into five different layers of epidermis according to their similarities, indicated that the amount of Gad gel increased by about 26% in the outermost layer of the stratum corneum (SC) and that MAAs gel at 2 µm depth was 103.4% higher than in the outermost layer of the SC. Variations in the SC of urocanic acid at 1490-1515 cm(-1) and 1652 cm(-1) and histidine at 1318 cm(-1) were calculated, before and after UV exposure with or without gels. With the application of gels the vibrational modes that correspond to lipids in trans conformation (1063 and 1128 cm(-1)) increased with respect to normal skin, whereas gauche conformation (1085 cm(-1)) disappeared. Our studies suggest that gels protected the skin against the stress of the natural defense mechanism caused by high levels of UV exposure.

The photoprotector mechanism of mycosporine-like amino acids. Excited-state properties and photostability of porphyra-334 in aqueous solution.

The photostability and photophysical parameters of an aqueous solution of the mycosporine-like amino acid (MAA) porphyra-334 have been determined. The excited-singlet state lifetime, measured by time-correlated single photon counting, was 0.4 ns. Laser flash photolysis experiments at 355 nm did not show any transient species. The triplet state of porphyra-334 was sensitized by triplet-triplet energy transfer. The T-T absorption spectrum was determined and the maximal absorption coefficient at 440 nm was estimated to be 1 x 10(4) M(-1) cm(-1). In this way an upper limit for the intersystem crossing quantum yield was determined. The very low quantum yield of fluorescence (phiF = 0.0016) and triplet formation (phiT < 0.05) together with a photodecomposition quantum yield of 2-4 x 10(-4), in the absence and the presence of oxygen respectively, can be explained by a very fast internal conversion process. These results support the photoprotective role assigned to this MAA in living systems.