Optical Spectroscopy and Excited-State Dynamics of Eu3+-Doped Bismuth Borate Glasses Containing CuO

Bismuth borate glasses containing phosphors and luminescent rare-earths are of interest for applications in light-emitting devices. Herein, the influence of CuO impurities on red-emitting Eu³⁺-doped bismuth borate glasses of the 25Bi₂O₃-15BaO-10Li₂O-50B₂O₃ type was investigated by various spectroscopic methods. The glasses were prepared by the melt-quench technique and characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, UV/Vis optical absorption (OA), and photoluminescence (PL) spectroscopy including decay kinetics assessment. The XRD data confirmed the amorphous nature of the glasses whereas FT-IR spectra indicated the basic structural features of trigonal BO₃ units and BO₄ tetrahedra. The OA analysis showed that addition of CuO up to 0.5 mol% results in significant growth of the visible Cu²⁺ absorption band around 715 nm, with slight decrease in the optical band gap energies assessed through Tauc plots. A drastic PL quenching of Eu³⁺ ions emission was evidenced concurring with the detrimental effect of Cu²⁺. The assessment of the Eu³⁺ emission decay curves revealed significant lifetime decrease of the ⁵D₀ emitting state with increasing CuO concentration. An analysis of quenching constants was finally performed comparing results from integrated PL data with the emission decay rates. It is argued that the bismuth borate glass system supports an effective Eu³⁺→Cu²⁺ energy transfer (more so than phosphates) in connection with a strong spectral overlap between Eu³⁺ emission and Cu²⁺ absorption.     

Large Amplitude Torsions in Nitrotoluene Isomers Studied by Rotational Spectroscopy and Quantum Chemistry Calculations

Rotational spectra of ortho-nitrotoluene (2-NT) and para-nitrotoluene (4-NT) have been recorded at low and room temperatures using a supersonic jet Fourier Transform microwave (MW) spectrometer and a millimeter-wave frequency multiplier chain, respectively. Supported by quantum chemistry calculations, the spectral analysis of pure rotation lines in the vibrational ground state has allowed to characterise the rotational energy, the hyperfine structure due to the ¹⁴N nucleus and the internal rotation splittings arising from the methyl group. For 2-NT, an anisotropic internal rotation of coupled −CH₃ and −NO₂ torsional motions was identified by quantum chemistry calculations and discussed from the results of the MW analysis. The study of the internal rotation splittings in the spectra of three NT isomers allowed to characterise the internal rotation potentials of the methyl group and to compare them with other mono-substituted toluene derivatives in order to study the isomeric influence on the internal rotation barrier.     

Characterization of Calcium Oxalate Hydrates and the Transformation Process

Calcium oxalate can be found in humans as kidney stones and in cultural heritage as films in two crystallographic species, dihydrate (COD/weddellite) and/or monohydrate (COM/whewellite). Due to its instability, COD is transformed into COM. Studying this crystalline conversion provides information about the origin of the monohydrated species, which will help in the assessment of prevention measurements to avoid their formation. In the present study, the synthesis of calcium oxalate hydrate microcrystals has been carefully performed to avoid mixture of phases in the final products; the long and short range order structure of both species have been studied by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS), respectively. This structural information was considered in the density functional theory (DFT) computational study performed to assign the characteristic vibrational IR and Raman frequencies found. This detailed characterization allows an unambiguous assignment of the vibrations, thus providing the appropriate parameters required to monitor and characterize the transformation process.     

Aqueous extracts of Agave sisalana boles have prebiotic potential

Abstract

This work aimed at evaluating the prebiotic potential of the aqueous extract and crude polysaccharides from Agave sisalana boles by an in vitro screening. Crude polysaccharides were obtained from the aqueous bole extract by precipitation with acetone and resuspension in water. The liquid extract and the polysaccharide solution were then spray dried and submitted to thermal analysis and quantification of metabolites. Prebiotic activity was checked on probiotic strains belonging to the Lactobacillus genus using inulin, fructo-oligosaccharides, fructose and glucose as positive controls. The powder of A. sisalana bole extract, which has recently been identified as a rich source of inulin, exhibited higher potential of fermentation compared with crude polysaccharides.     

Exploring the Volatiles Released from Roots of Wild and Domesticated Tomato Plants under Insect Attack

Plants produce volatile organic compounds that are important in communication and defense. While studies have largely focused on volatiles emitted from aboveground plant parts upon exposure to biotic or abiotic stresses, volatile emissions from roots upon aboveground stress are less studied. Here, we investigated if tomato plants under insect herbivore attack exhibited a different root volatilome than non-stressed plants, and whether this was influenced by the plant’s genetic background. To this end, we analyzed one domesticated and one wild tomato species, i.e., Solanum lycopersicum cv Moneymaker and Solanum pimpinellifolium, respectively, exposed to leaf herbivory by the insect Spodoptera exigua. Root volatiles were trapped with two sorbent materials, HiSorb and PDMS, at 24 h after exposure to insect stress. Our results revealed that differences in root volatilome were species-, stress-, and material-dependent. Upon leaf herbivory, the domesticated and wild tomato species showed different root volatile profiles. The wild species presented the largest change in root volatile compounds with an overall reduction in monoterpene emission under stress. Similarly, the domesticated species presented a slight reduction in monoterpene emission and an increased production of fatty-acid-derived volatiles under stress. Volatile profiles differed between the two sorbent materials, and both were required to obtain a more comprehensive characterization of the root volatilome. Collectively, these results provide a strong basis to further unravel the impact of herbivory stress on systemic volatile emissions.     

Green Synthesis of Gold and Silver Nanoparticles Using Leaf Extract of Capsicum chinense Plant

So far, several studies have focused on the synthesis of metallic nanoparticles making use of extracts from the fruit of the plants from the genus Capsicum. However, as the fruit is the edible, and highly commercial, part of the plant, in this work we focused on the leaves, a part of the plant that is considered agro-industrial waste. The biological synthesis of gold (AuNPs) and silver (AgNPs) nanoparticles using aqueous extracts of root, stem and leaf of Capsicum chinense was evaluated, obtaining the best results with the leaf extract. Gold and silver nanoparticles synthesized using leaf extract (AuNPs-leaf and AgNPs-leaf, respectively) were characterized by UV-visible spectrophotometry (UV-Vis), Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR), X-ray Photoelectron Spectroscopy (XPS), Ultra Hight Resolution Scanning Electron Microscopy coupled to Energy-Dispersive X-ray spectroscopy (UHR-SEM-EDX) and Transmission Electron Microscopy (TEM), and tested for their antioxidant and antimicrobial activities. In addition, different metabolites involved in the synthesis of nanoparticles were analyzed. We found that by the use of extracts derived from the leaf, we could generate stable and easy to synthesize AuNPs and AgNPs. The AuNPs-leaf were synthesized using microwave radiation, while the AgNPs-leaf were synthesized using UV light radiation. The antioxidant activity of the extract, determined by ABTS, showed a decrease of 44.7% and 60.7% after the synthesis of the AuNPs-leaf and AgNPs-leaf, respectively. After the AgNPs-leaf synthesis, the concentration of polyphenols, reducing sugars and amino acids decreased by 15.4%, 38.7% and 46.8% in the leaf extract, respectively, while after the AuNPs-leaf synthesis only reducing sugars decreased by 67.7%. These results suggest that these groups of molecules are implicated in the reduction/stabilization of the nanoparticles. Although the contribution of these compounds in the synthesis of the AuNPs-leaf and the AgNPs-leaf was different. Finally, the AgNPs-leaf inhibited the growth of S. aureus, E. coli, S. marcescens and E. faecalis. All of them are bacterial strains of clinical importance due to their fast antibiotic resistance development.     

Indoxyl sulfate- and P-cresol-induced monocyte adhesion and migration is mediated by integrin-linked kinase-dependent podosome formation

Cardiovascular disease is an important cause of death in patients with chronic kidney disease (CKD). Protein-bound uremic toxins, such as p-cresyl and indoxyl sulfate (IS), are poorly removed during hemodialysis, leading to vascular endothelial dysfunction and leukocyte extravasation. These processes can be related to dynamic adhesion structures called podosomes. Several studies have indicated the role of integrin-linked kinase (ILK) in the accumulation of integrin-associated proteins in podosomes. Here, we investigated the involvement of ILK and podosome formation in the adhesion and extravasation of monocytes under p-cresol (pc) and IS exposure. Incubation of THP-1 human monocyte cells with these toxins upregulated ILK kinase activity. Together, both toxins increased cell adhesion, podosome formation, extracellular matrix degradation, and migration of THP-1 cells, whereas ILK depletion with specific small interfering RNAs suppressed these processes. Interestingly, F-actin colocalized with cortactin in podosome cores, while ILK was colocalized in podosome rings under toxin stimulation. Podosome Wiskott-Aldrich syndrome protein (WASP)-interacting protein (WIP) and AKT protein depletion demonstrated that monocyte adhesion depends on podosome formation and that the ILK/AKT signaling pathway is involved in these processes. Ex vivo experiments showed that both toxins induced adhesion and podosome formation in leukocytes from wild-type mice, whereas these effects were not observed in leukocytes of conditional ILK-knockdown animals. In summary, under pc and IS stimulation, monocytes increase podosome formation and transmigratory capacity through an ILK/AKT signaling pathway-dependent mechanism, which could lead to vascular injury. Therefore, ILK could be a potential therapeutic target for the treatment of vascular damage associated with CKD.Subject terms: Experimental models of disease, Atherosclerosis, Mechanisms of disease, Integrins, End-stage renal disease     

Comparison of the Effect of Hydrostatic and Dynamic High Pressure Processing on the Enzymatic Activity and Physicochemical Quality Attributes of ‘Ataulfo’ Mango Nectar

The effects of hydrostatic (HHP) and dynamic (HPH) high-pressure treatments on the activity of pectin methylesterase (PME) and polyphenol oxidase (PPO) as well as the physicochemical quality attributes of ‘Ataulfo’ mango nectar were assessed. HHP reduced PME relative activity by 28% at 100 MPa for 5 min but increased PPO activity almost five-fold. Contrarily, HPH did not affect PME activity, but PPO was effectively reduced to 10% of residual activity at 300 MPa and at three passes. Color parameters (CIEL*a*b*), °hue, and chroma were differently affected by each type of high-pressure processing technology. The viscosity and fluid behavior were not affected by HHP, however, HPH changed the apparent viscosity at low dynamic pressure levels (100 MPa with one and three passes). The viscosity decreased at high shear rates in nectar samples, showing a shear-thinning effect. The results highlight how different effects can be achieved with each high-pressure technology; thus, selecting the most appropriate system for processing and preserving liquid foods like fruit beverages is recommended.