N-linked oligosaccharides of cobra venom factor contain novel alpha(1-3)galactosylated Le(x) structures

Cobra venom factor (CVF), a nontoxic, complement-activating glycoprotein in cobra venom, is a functional analog of mammalian complement component C3b. The carbohydrate moiety of CVF consists exclusively of N-linked oligosaccharides with terminal alpha1-3-linked galactosyl residues, which are antigenic in human. CVF has potential for several medical applications, including targeted cell killing and complement depletion. Here, we report a detailed structural analysis of the oligosaccharides of CVF. The structures of the oligosaccharides were determined by lectin affinity chromatography, antibody affinity blotting, compositional and methylation analyses, and high-resolution (1)H-NMR spectroscopy. Approximately 80% of the oligosaccharides are diantennary complex-type, approximately 12% are tri- and tetra-antennary complex-type, and approximately 8% are oligomannose type structures. The majority of the complex-type oligosaccharides terminate in Galalpha1-3Galbeta1-4(Fucalpha1-3)GlcNAcbeta1, a unique carbohydrate structural feature abundantly present in the glycoproteins of cobra venom.     

Multiple mechanisms compensate to enhance tumor-protective CD8(+) T cell response in the long-term despite poor CD8(+) T cell priming initially: comparison between an acute versus a chronic intracellular bacterium expressing a model antigen

We evaluated CD8(+) T cell responses against the dominant CTL epitope, OVA(257-264), expressed by an acute (Listeria monocytogenes (LM) OVA) vs a chronic pathogen (Mycobacterium bovis bacillus Calmette-Guérin (BCG) OVA) to reveal the influence on CD8(+) T cell memory and consequent protection against a challenge with OVA-expressing tumor cells. Infection with lower doses of both pathogens resulted in stronger bacterial growth but weaker T cell memory indicating that memory correlates with pathogen dose but not with bacterial expansion. The CD8(+) T cell response induced by LM-OVA was helper T cell-independent and was characterized by a rapid effector response followed by a rapid, but massive, attrition. In contrast, BCG-OVA induced a delayed and weak response that was compensated for by a longer effector phase and reduced attrition. This response was partly dependent on CD4(+) T cells. CD8(+) T cell response induced by BCG-OVA, but not LM-OVA, was highly dependent on pathogen persistence to compensate for the weak initial CD8(+) T cell priming. Despite a stronger initial T cell response with LM-OVA, BCG-OVA provided more effective tumor (B16OVA) control at both local and distal sites due to the induction of a persistently activated acquired, and a more potent innate, immunity.     

Stark effect measurements on monomers and trimers of reconstituted light-harvesting complex II of plants

The electric-field induced absorption changes (Stark effect) of reconstituted light-harvesting complex II (LHCII) in different oligomerisation states-monomers and trimers-with different xanthophyll content have been probed at 77 K. The Stark spectra of the reconstituted control samples, containing the xanthophylls lutein and neoxanthin, are very similar to previously reported spectra of native LHCII. Reconstituted LHCII, containing lutein but no neoxanthin, shows a similar electrooptical response in the Chl a region, but the Stark signal of Chl b around 650 nm amounts to at most approximately 25% of that of the control samples. We conclude that neoxanthin strongly modifies the electronic states of the nearby Chl b molecules causing a large electrooptical response at 650 nm stemming from one or more Chls b in the control samples. Ambiguities about the assignment of several bands in the Soret region [Biochim. Biophys. Acta 1605 (2003) 83] are resolved and the striking difference in electric field response between the two lutein molecules is confirmed. The Stark effect in the carotenoid spectral region in both control and neoxanthin-deficient samples is almost identical, showing that the neoxanthin Stark signal is small and much less intense than the lutein Stark signal.     

Putting plant resistance traits on the map: a test of the idea that plants are better defended at lower latitudes

? It has long been believed that plant species from the tropics have higher levels of traits associated with resistance to herbivores than do species from higher latitudes. A meta-analysis recently showed that the published literature does not support this theory. However, the idea has never been tested using data gathered with consistent methods from a wide range of latitudes. ? We quantified the relationship between latitude and a broad range of chemical and physical traits across 301 species from 75 sites world-wide. ? Six putative resistance traits, including tannins, the concentration of lipids (an indicator of oils, waxes and resins), and leaf toughness were greater in high-latitude species. Six traits, including cyanide production and the presence of spines, were unrelated to latitude. Only ash content (an indicator of inorganic substances such as calcium oxalates and phytoliths) and the properties of species with delayed greening were higher in the tropics. ? Our results do not support the hypothesis that tropical plants have higher levels of resistance traits than do plants from higher latitudes. If anything, plants have higher resistance toward the poles. The greater resistance traits of high-latitude species might be explained by the greater cost of losing a given amount of leaf tissue in low-productivity environments.     

Variation in vegetative and flowering phenology in a forest herb caused by environmental heterogeneity

Timing of seasonal plant development can affect biotic interactions and plant fitness. Phenology is governed largely by temperature and may therefore be affected by global climate warming, making this an important area of research. Several factors in addition to temperature may cause differences in phenology. We studied the influence of local environment, plant size, and reproductive effort on shoot emergence and flowering time of 290 individuals of Actaea spicata (Ranunculaceae), distributed among 25 plots in four populations. We used multiple regression and structural equation models (SEM) to study causal relationships. Among plots, soil temperature and canopy cover explained 63% of the variation in shoot emergence. Soil temperature, slope, and canopy cover together explained 83% of the variation in flowering time. Within plots, small plants on steep south-facing slopes with high soil potassium concentrations emerged earlier in the year. Plants emerging earlier flowered earlier, but no environmental factors affected flowering time directly. We found no effects of reproductive effort. Our results support the view that flowering time of temperate forest herbs is constrained by several environmental factors acting indirectly through effects on shoot emergence time.