Thin layers of in-plane anisotropic materials can support ultraconfined polaritons, whose wavelengths depend on the propagation direction. Such polaritons hold potential for the exploration of ...fundamental material properties and the development of novel nanophotonic devices. However, the real-space observation of ultraconfined in-plane anisotropic plasmon polaritons (PPs)-which exist in much broader spectral ranges than phonon polaritons-has been elusive. Here we apply terahertz nanoscopy to image in-plane anisotropic low-energy PPs in monoclinic Ag
Te platelets. The hybridization of the PPs with their mirror image-by placing the platelets above a Au layer-increases the direction-dependent relative polariton propagation length and the directional polariton confinement. This allows for verifying a linear dispersion and elliptical isofrequency contour in momentum space, revealing in-plane anisotropic acoustic terahertz PPs. Our work shows high-symmetry (elliptical) polaritons on low-symmetry (monoclinic) crystals and demonstrates the use of terahertz PPs for local measurements of anisotropic charge carrier masses and damping.
The presence of sulfated polysaccharides in
of seaweeds is considered to be a consequence of the physiological adaptation to the high salinity of the marine environment. Recently, it was found that ...sulfated polysaccharides were present in certain freshwater
species and some vascular plants.
(Ulvophyceae, Chlorophyta) is one of the largest genera of green algae that are able to grow in both, seas and freshwater courses. Previous studies carried out on the water-soluble polysaccharides of the marine species
established the presence of sulfated xylogalactoarabinans constituted by a backbone of 4-linked β-L-arabinopyranose units partially sulfated mainly on C3 and also on C2 with partial glycosylation, mostly on C2, with terminal β-D-xylopyranose or β-D-galactofuranose units. Besides, minor amounts of 3-, 6- and/or 3,6-linked β-D-galactan structures, with galactose in the pyranosic form were detected. In this work, the main water soluble cell wall polysaccharides from the freshwater alga
were characterized. It was found that this green alga biosynthesizes sulfated polysaccharides, with a structure similar to those found in marine species of this genus. Calibration of molecular clock with fossil data suggests that colonization of freshwater environments occurred during the Miocene by its ancestor. Therefore, the presence of sulfated polysaccharides in the freshwater green macroalga
could be, in this case, an adaptation to transient desiccation and changes in ionic strength. Retention of sulfated polysaccharides at the cell walls may represent a snapshot of an evolutionary event, and, thus constitutes an excellent model for further studies on the mechanisms of sulfation on cell wall polysaccharides and environmental stress co-evolution.
Poly(amide-triazole) and poly(ester-triazole) synthesized from d-galactose as a renewable resource were applied for the synthesis of nanoparticles (NPs) by the emulsification/solvent evaporation ...method. The NPs were characterized as stable, spherical particles, and none of their components, including the stabilizer poly(vinyl alcohol), were cytotoxic for normal rat kidney cells. These NPs proved to be useful for the efficient encapsulation of cilostazol (CLZ), an antiplatelet and vasodilator drug currently used for the treatment of intermittent claudication, which is associated with undesired side-effects. In this context, the nanoencapsulation of CLZ was expected to improve its therapeutic administration. The carbohydrate-derived polymeric NPs were designed taking into account that the triazole rings of the polymer backbone could have attractive interactions with the tetrazole ring of CLZ. The activity of the nanoencapsulated CLZ was measured using a matrix metalloproteinase model in a lipopolysaccharide-induced inflammation system. Interestingly, the encapsulated drug exhibited enhanced anti-inflammatory activity in comparison with the free drug. The results are very promising since the stable, noncytotoxic NP systems efficiently reduced the inflammation response at low CLZ doses. In summary, the NPs were obtained through an innovative methodology that combines a carbohydrate-derived synthetic polymer, designed to interact with the drug, ease of preparation, adequate biological performance, and environmentally friendly production.
In this work we present experimental results on the behavior of diamond at megabar pressure. The experiment was performed using the PHELIX facility at GSI in Germany to launch a planar shock into ...solid multi-layered diamond samples. The target design allows shock velocity in diamond and in two metal layers to be measured as well as the free surface velocity after shock breakout. As diagnostics, we used two velocity interferometry systems for any reflector (VISARs). Our measurements show that for the pressures obtained in diamond (between 3 and 9 Mbar), the propagation of the shock induces a reflecting state of the material. Finally, the experimental results are compared with hydrodynamical simulations in which we used different equations of state, showing compatibility with dedicated SESAME tables for diamond.
Herein we report the design, synthesis and characterization of novel 1,2,4-triazole
d-ribose derivatives, as well as their synthetic precursors.
The antitumoral activity against T cell lymphoma cell ...line of these products was studied. Structures containing a 1,2,4-triazolic ring linked by sulfur to the carbohydrate moiety showed a moderate antiproliferative activity. The presence of the second heterocyclic ring did not show significant changes in their biological activity. Meanwhile, structures with 3-thiobenzyl-5-substituted-1,2,4-triazole ring linked by nitrogen leads to compounds with a biphasic behavior, stimulating cell proliferation at low concentrations and inhibiting it at higher ones. An increment in the polarity was associated with a decrease in the activity of the evaluated compounds.
A preliminary antitumoral screening pointed the 1,2,4-triazolic structures linked to protected sugars as promising leaders for further studies.
Novel 1,2,4-triazole
d-ribose derivatives were synthesized and their antitumoral activity on a T cell lymphoma cell line was evaluated.
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► Synthesis of novel 1,2,4-triazole
d-ribose derivatives. ► Antitumoral activity on a T cell lymphoma cell line was evaluated. ► Triazole ring linked by sulfur to protected sugar shows antiproliferative activity. ► The antiproliferative activity decreases as polarity increase. ► Isoxazoline ring, as a second heterocycle has no relevance in the activity.
In this work, we present experimental results on the behavior of liquid water at megabar pressure. The experiment was performed using the HIPER (High-Intensity Plasma Experimental Research) laser ...facility, a uniaxial irradiation chamber of GEKKO XII (GXII) at the Institute of Laser Engineering (ILE), and the PHELIX at GSI (GSI Helmholtz Centre for Heavy Ion Research), a single-beam high-power laser facility, to launch a planar shock into solid multilayered water samples. Equation-of-state data of water H2O are obtained in the pressure range 0.50–4.6 Mbar by tuning the laser-drive parameters. The Hugoniot parameters (pressure, density, etc.) and the shock temperature were simultaneously determined by using VISAR and SOP as diagnostic tools and quartz as the standard material for impedance mismatch experiments. Finally, our experimental results are compared with hydrodynamic simulations tested with different equations of state, showing good compatibility with tabulated SESAME tables for water.
Sequential extraction of tetrasporic
Pterocladiella capillacea with water at room temperature and then at 50
°C led to the isolation of two products that were each fractionated with cetrimide to give ...a soluble fraction and a precipitate. The precipitates were then subjected to fractional solubilization in solutions of increasing sodium chloride concentration. The whole treatment yielded two major fractions in each case, one soluble in the cetrimide medium and the other soluble in 0.5 M NaCl, which were further fractionated by anion-exchange chromatography. Structural analysis, carried out by methylation, desulfation–methylation,
13C NMR spectroscopy and determination of the absolute configuration of the 2,6-di-
O-methylgalactose units in the permethylated products, indicated the presence of xylogalactans, with low content of 3,6-anhydrogalactose and low molecular weight. These polysaccharides varied in the level of xylopyranosyl and sulfate substitution, primarily on the 6-position of the 3-linked β-
d-galactopyranosyl and on the 3-position of the 4-linked α-galactopyranosyl units. Moreover, herein we report, for the first time, the presence of 3-substituted, 4-linked
d-galactopyranosyl residues in an alga belonging to the Gelidiales.
Sequential extraction of
Pterocladiella capillacea with water at room temperature and then at 50
°C gave two products, which by thorough fractionation and further structural analysis, afforded evidence of the presence of 3-substituted, 4-linked
d-galactopyranosyl units in polysaccharides from this seaweed.
A sulphated galactan (SG) with low molecular weight (app. 2800) was isolated from extracts of Cryptopleura ramosa, a red seaweed from the South American coasts. The compound was a selective inhibitor ...of HSV-1 and HSV-2 replication in Vero cells with 50% inhibitory concentrations (IC50) in the range 1.6-4.2 micrograms/ml and a 50% cytotoxic concentration (CC50) of 476 micrograms/ml. SG was also effective against HSV-1 in cells of neural origin such as murine astrocytes. The mode of action of SG could be ascribed to an inhibitory action on virus adsorption. Furthermore, SG did not inhibit the blood coagulation process at concentrations highly exceeding the IC50.
In view of the economic and technical limitations associated with diluted aqueous suspensions of cellulose nanofibrils, in the present contribution sorbitol was assayed as capping agent in the drying ...of bacterial nanocellulose (BNC) for the first time. The effect of different sorbitol:BNC mass ratios (1:1, 3:1 and 5:1), drying strategies (freeze-drying versus oven-drying), and redispersion methods (high-speed homogenization and mechanical stirring) on the water redispersibility of dried BNC was studied. Sedimentation, specific surface area and rheology assays all demonstrated the suitability of sorbitol for significantly limiting irreversible hydrogen bonding between adjacent cellulose nanofibrils during dehydration, leading to redispersed BNC suspensions with characteristics similar to those of never-dried ones. In the case of freeze-dried samples, results showed that the lowest sorbitol:BNC mass ratio assayed (i.e., 1:1) was enough to prevent irreversible hydrogen bonding between adjacent cellulose fibrils, whereas for oven-dried BNC samples full redispersion was achieved by mechanical stirring when sorbitol:BNC mass ratios of at least 3:1 were used. The feasibility of easily removing sorbitol from the dried product upon redispersion was also verified.
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•Sorbitol was used for the first time as capping agent in the drying of BNC.•Sorbitol addition proved to be successful in the prevention of BNC hornification.•A 1:1 sorbitol:BNC ratio was required to successfully redisperse freeze-dried samples.•A 3:1 sorbitol:BNC ratio was required to successfully redisperse oven-dried samples.•Sorbitol could be easily removed by washing with water at room temperature.
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