Biological pH sensing based on surface enhanced Raman scattering through a 2-aminothiophenol-silver probe

We report pH sensing for biological applications based on surface enhanced Raman scattering (SERS) from silver nanoparticles functionalized with 2-aminothiophenol (2-aminobenzenethiol, 2-ABT). pH-dependent SERS spectra of the attached 2-ABT molecules enable one to sense the pH over the range of 3.0-8.0. We have performed the first demonstration of SERS detection in living cells kept in different pH buffer solutions and show that the pH sensitivity is retained in that case. Thus, the nanoparticles can be used as probes delivering spatially localized chemical information from biological environments and provide a new way to monitor chemical changes at cellular level.     

Analysis of age-associated changes in mitochondrial free radical generation by rat testis

Throughout spermatogenesis, mitochondria undergo a morphological and functional differentiation. Mitochondria are involved in the production of reactive oxygen species (ROS), considered one of the mediators of ageing. Particularly, lipid peroxidation is regarded as a major phenomenon by which ROS can impair cellular function. In the present study, we examined the production of superoxide anion, superoxide dismutase activity and the effect of Fe²⁺/ascorbate induced-lipid peroxidation on the respiratory chain activities of testis mitochondria throughout the process of spermatogenesis and ageing. Mitochondria from rat testes generated superoxide anion, mainly using NADH as substrate, which increased according to age. The activity of SOD is age-dependent and greatly stimulated during the first wave of spermatogenesis, but decreases in adulthood and old age. TBARS concentration was also markedly increased by ageing. The activity of mitochondrial respiratory chain complexes is differentially affected by oxidative stress induced by iron/ascorbate, succinate-dehydrogenase activity being less vulnerable than that of NADH-dehydrogenase and cytochrome c oxidase. The data suggest that ageing is accompanied by reduced activity of SOD, leading to excessive oxidative stress and enhanced lipid peroxidation that compromises the functionality of the electron transport chain. The data support the concept that mitochondrial function is an important determinant in ageing.     

Consequences of removing a keystone herbivore for the abundance and diversity of arthropods associated with a cruciferous shrub

Abstract. 1. The effect of the removal of Timarcha lugens (Chrysomelidae), one of the main herbivores of Hormathophylla spinosa (Cruciferae), on the abundance of co-occurring phytophagous insects, the abundance of non-phytophagous arthropods (detritivores, predators, and parasitoids), and the structure and diversity of the entire arthropod community, was studied for 3 years (1999–2001).
2. There was competition between T. lugens and co-occurring herbivores; the removal of T. lugens was correlated with an increase in the abundance of sap-suckers, flower-feeders, and, above all, folivores.
3. Timarcha lugens also had an indirect effect on arthropods belonging to other trophic levels; the abundance of predators increased significantly after the removal of T. lugens .
4. Community composition was affected by the experimental removal. In addition, the diversity of the overall community increased after removal of T. lugens .
5. The study demonstrated experimentally that T. lugens has a significant effect not only on other species belonging to the same trophic level, but also on the abundance of species belonging to higher trophic levels, and, consequently, on the entire structure and diversity of the complex community in which it is immersed.     

The role of phenotypic plasticity in shaping ecological networks

Plasticity-mediated changes in interaction dynamics and structure may scale up and affect the ecological network in which the plastic species are embedded. Despite their potential relevance for understanding the effects of plasticity on ecological communities, these effects have seldom been analysed. We argue here that, by boosting the magnitude of intra-individual phenotypic variation, plasticity may have three possible direct effects on the interactions that the plastic species maintains with other species in the community: may expand the interaction niche, may cause a shift from one interaction niche to another or may even cause the colonization of a new niche. The combined action of these three factors can scale to the community level and eventually expresses itself as a modification in the topology and functionality of the entire ecological network. We propose that this causal pathway can be more widespread than previously thought and may explain how interaction niches evolve quickly in response to rapid changes in environmental conditions. The implication of this idea is not solely eco-evolutionary but may also help to understand how ecological interactions rewire and evolve in response to global change.     

Assessment of different treatments for the concentration of three tomato fruit glycosidases from crude extracts

Ultrafiltration, (NH4)2SO4 addition to 80% saturation and lyophilization after desalting, were assessed as different methods for the concentration of tomato fruit - and -galactosidases and -L-arabinofuranosidase. Lyophilization was the most effective giving 95%, 82% and 75% recovery of enzyme activities, respectively. These enzymes are stable when preserved after lyophilization or in concentrated crude extracts at –20 or –50°C even after extended storage, either in the presence or absence of trehalose. © Rapid Science Ltd. 1998     

Biochemical changes in fermented melon (egusi) seeds (Citrullis vulgaris)

Summary Biochemical and sensory changes of Nigerian melon seeds fermented with fourBacillus strains isolated from African locust beans were studied. In all fermentations, the reducing sugar content doubled from a starting value of 45 mg/g. The total free amino acid content decreased for the first 40 h and then increased. WithB. licheniformis, B. subtilis andB. pumilis, there was a subsequent large increase in free amino acid content. The extracted oils in the fermentation product increased in saponification number and free acid content but decreased in iodine number. The sensory properties of theB. licheniformis product was similar to that of ogiri and that ofB. subtiis to Iru.     

Insights into a conformational epitope of Hev b 6.02 (hevein)

Hevein (Hev b 6.02) is a major IgE-binding allergen in natural rubber latex and manufactured products. Both tryptophans (Trp(21) and Trp(23)) of the hevein molecule were chemically modified with BNPS-skatole (2-nitrophenylsulfenyl-3-methyl-3(')-bromoindolenine); derivatized allergen failed to significantly inhibit binding of serum IgE in ELISA assays. Similarly, skin prick tests showed that hevein-positive patients gave no response with the modified allergen. Dot blot experiments carried out with anti-hevein mono- and polyclonal antibodies confirmed the importance of Trp(21) and Trp(23) for antibody-recognition, and demonstrated the specific cross-reactivity of other molecules containing hevein-like domains. We also report the structure of Hev b 6.02 at an extended resolution (1.5A) and compare its surface properties around Trp residues with those of similar regions in other allergens. Overall our results indicate that the central part of the protein, which comprises three aromatic and other acidic and polar residues, constitutes a conformational epitope.