Stabilization of the monoolein Pn3m cubic structure on trehalose glasses

Trehalose is known to protect some organisms from various stresses due to drought and high temperature. To explore the molecular mechanism of the protective function, the mesomorphic properties of the monoolein-water system, dried in the presence of trehalose, were studied by X-ray diffraction. While, in pure water, two bicontinuous inverse cubic structures (the Pn3m and Ia3d phases) and a lamellar Lα phase exist as a function of concentration, only the Pn3m cubic phase has been detected in concentrated trehalose solutions or in trehalose glasses, even under extremely dry conditions. Depending on the sugar concentration, or after glass dehydration, the Pn3m cubic unit cell decreases to very low values, much below the smaller one observed in pure water. However, as no phase transitions occur, a simple osmotic mechanism can be excluded. An additional stabilization of the lipid phase, arising from interfacial free energy changes due to trehalose-water-lipid direct interactions, and large enough to affect the energetic balance between the Pn3m and the Ia3d cubic phases, evidently occurs. Moreover, no differences in the Pn3m cubic structure were observed when the sugar platelets convert to the glassy state; no apparent structural modifications that can be related to mechanical pressure exerted on the lipid phase have been detected. Received: 5 October 1998 / Accepted: 13 November 1998     

32Phosphorus transfer in systems of fish and amphipods exploiting detritus particles

Detrital size preferences of the fish Mugil sp. and the amphipod Echinogammarus veneris were determined in the laboratory by ³²P. Three different size-classes of leaf-detritus particles, inoculated with a fungus, were offered separately in 24-h experiments. Detritus ³²P increased with particle size, depending on the growth of microflora. Both species preferred the largest size-class. In mixed-species experiments, ³²P uptake by Mugil was significantly less than when it was alone. A similar ³²P transfer was measured in Mugil fed on the largest particles, previously utilized by E. veneris. This indicates that the feeding activity of the amphipod indirectly affects the detrital utilization by Mugil sp. It is suggested that the influence might depend on the microbial impoverishment and the change in the particle size.     

Recognizing and interpreting vegetational belts: New wine in the old bottles of a von Humboldt's legacy

Since von Humboldt, recognizing and using elevational subdivisions is at the core of biogeographical and ecological studies in mountain ecosystems. However, despite the large use of vegetational belts, their conceptual definition and practical identification appear to be surprisingly loose and inconsistent. Many authors use variations in climatic conditions to identify elevational belts. These belts are useful to set a framework for ecological studies but cannot be considered a surrogate of vegetational belts, because factors different from climate play a major role in determining the distribution of plant assemblages. Vegetation physiognomy can be used to identify ‘biome‐type’ belts that are useful for comparisons across geographical areas with different floras. However, to properly reflect ecological conditions at local scale, vegetational belts should be based on species composition. One of the most effective statistical approaches for this purpose is the use spatially constrained cluster analysis. The use of indicator species analysis may be also recommended to identify the species that most characterize vegetational belts. This can help researchers to identify belts in the field. Since species identification can be difficult, some authors use plant functional types for belt delimitation. Plant functional types can be helpful to trace the adaptative responses of vegetation along elevational gradients, but cannot be recommended as a standard way to identify belts. In general, criteria to identify vegetational belts can be based on both vegetation structure (namely physiognomy and structural parameters) and/or species composition, depending on the scale and the aim of the analyses, and they should be clearly stated.     

Real-Time Insights into Biological Events: In-Cell Processes and Protein-Ligand Interactions

FlowNMR has the aim of continuously monitoring processes that occur in conditions that are not compatible with being carried out within a closed tube. However, it is sample intensive and not suitable for samples, such as proteins or living cells, that are often available in limited volumes and possibly low concentrations. We here propose a dialysis-based modification of a commercial flowNMR setup that allows for recycling the medium while confining the sample (proteins and cells) within the active volume of the tube. This approach is demonstrated in the specific cases of in-cell NMR and protein-based ligand studies.     

Structure and I2/I redox catalytic behaviour of PEDOT-PSS films electropolymerized in aqueous medium: Implications for convenient counter electrodes in DSSC

The present paper focuses on the impact of different electro-synthesis processes, used to produce poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) systems in aqueous medium, on the polymer backbone and its electro-catalytic activity.FE-SEM and micro-Raman spectroscopy were used to analyze the samples obtained by varying the conditions of the electro-polymerization processes. The I₂/I⁻ redox behaviour of various PEDOT-PSS layers has been comparatively examined in relation to the surface morphology and structural characteristics of the polymer. A response similar to that of a conventional Pt electrode has been revealed for the films produced by chronoamperometric technique.The study has demonstrated that the polymer structure plays an important role in the electro-activity, providing a possibility to improve the redox performance of PEDOT-PSS films by a proper choice of the synthesis methods. Moreover, the use of aqueous solution as a reaction medium can be welcomed as a sustainable chemistry way involving the use of environmentally friendly chemicals.     

Chemoecological study of the invasive alga Caulerpa taxifolia var. distichophylla from the Sicilian coast

Aquatic Ecology - Marine invasive species and their bioactive metabolites have become critical ecological issues in the Mediterranean Sea. In particular, the highly invasive green algae Caulerpa...     

The R-Ras/RIN2/Rab5 complex controls endothelial cell adhesion and morphogenesis via active integrin endocytosis and Rac signaling

During developmental and tumor angiogenesis, semaphorins regulate blood vessel navigation by signaling through plexin receptors that inhibit the R-Ras subfamily of small GTPases. R-Ras is mainly expressed in vascular cells, where it induces adhesion to the extracellular matrix (ECM) through unknown mechanisms. We identify the Ras and Rab5 interacting protein RIN2 as a key effector that in endothelial cells interacts with and mediates the pro-adhesive and -angiogenic activity of R-Ras. Both R-Ras-GTP and RIN2 localize at nascent ECM adhesion sites associated with lamellipodia. Upon binding, GTP-loaded R-Ras converts RIN2 from a Rab5 guanine nucleotide exchange factor (GEF) to an adaptor that first interacts at high affinity with Rab5-GTP to promote the selective endocytosis of ligand-bound/active β1 integrins and then causes the translocation of R-Ras to early endosomes. Here, the R-Ras/RIN2/Rab5 signaling module activates Rac1-dependent cell adhesion via TIAM1, a Rac GEF that localizes on early endosomes and is stimulated by the interaction with both Ras proteins and the vesicular lipid phosphatidylinositol 3-monophosphate. In conclusion, the ability of R-Ras-GTP to convert RIN2 from a GEF to an adaptor that preferentially binds Rab5-GTP allows the triggering of the endocytosis of ECM-bound/active β1 integrins and the ensuing funneling of R-Ras-GTP toward early endosomes to elicit the pro-adhesive and TIAM1-mediated activation of Rac1.     

δ1-Pyrroline-5-carboxylate reductase as a new target for therapeutics: inhibition of the enzyme from Streptococcus pyogenes and effects in vivo

Compounds able to interfere with amino acid biosynthesis have the potential to inhibit cell growth. In both prokaryotic and eukaryotic microorganisms, unless an ornithine cyclodeaminase is present, the activity of δ¹-pyrroline-5-carboxylate (P5C) reductase is mandatory to proline production, and the enzyme inhibition should result in amino acid starvation, blocking in turn protein synthesis. The ability of some substituted derivatives of aminomethylenebisphosphonic acid and its analogues to interfere with the activity of the enzyme from the human pathogen Streptococcus pyogenes was investigated. Several compounds were able to suppress activity in the micromolar range of concentrations, with a mechanism of uncompetitive type with respect to the substrate P5C and non-competitive with respect to the electron donor NAD(P)H. The actual occurrence of enzyme inhibition in vivo was supported by the effects of the most active derivatives upon bacterial growth and free amino acid content.     

Oleoylethanolamide protects human sperm cells from oxidation stress: studies on cases of idiopathic infertility

N-acylethanolamides are naturally occurring hydrophobic molecules usually present in a very small amount in many mammalian tissues and cells. The presence of N-acylethanolamides has also been demonstrated in human reproductive tracts and fluids, although their biological effects and molecular mechanisms of action are not yet completely elucidated. It is known that some N-acylethanolamides, such as oleoylethanolamide, have antioxidative properties. The aim of this study was to test whether oleoylethanolamide could protect sperm cells from reactive oxygen species-induced oxidative damage in cases of idiopathic infertility, because the excessive generation of these radicals was associated with this pathology. Our results show that 2.5 nM oleoylethanolamide in vitro supplementation significantly reduces DNA strand breaks both in fertile and infertile subjects. Moreover, oleoylethanolamide increases kinematic parameters, such as curvilinear velocity and amplitude of lateral head displacement and hyperactivation, both in the presence and in the absence of oxidative stress. Results of this study support the hypothesis of a possible protective action of oleoylethanolamide against reactive oxygen species, which could explain its beneficial effects on in vitro capacitated spermatozoa.     

Ribosome-inactivating proteins in edible plants and purification and characterization of a new ribosome-inactivating protein from Cucurbita moschata

The basic protein fraction of tissue extracts from 40 edible plants inhibited cell-free protein synthesis and released adenine from herring sperm DNA, thus having adenine glycosylase activity. This suggested the presence of ribosome-inactivating proteins (RIPs) in the plant extracts. This indication was further strengthened by the presence of the two activities after a partial chromatographic purification of three extracts, including that from Lycopersicon esculentum (tomato), which had very low activity. From the extract of Cucurbita moschata (pumpkin), the most active one, a glycoprotein of 30,665 Da was purified which had the properties of a RIP, in that (i) it inhibited protein synthesis by a rabbit reticulocyte lysate with IC₅₀ (concentration giving 50% inhibition) 0.035 nM (1.08 ng ml⁻¹) and by HeLa, HT29 and JM cells with IC₅₀ in the 100 nM range, (ii) deadenylated hsDNA and other polynucleotidic substrates, and (iii) depurinated yeast rRNA at a concentration of 0.1 ng ml⁻¹, all values being comparable to those of other RIPs. The C. moschata RIP gave a weak cross-reaction only with an antiserum against dianthin 32, but not with antisera against other RIPs, and had superoxide dismutase, antifungal and antibacterial activities.