Strong, long-term temporal dynamics of an ecological network

Nature is organized into complex, dynamical networks of species and their interactions, which may influence diversity and stability. However, network research is, generally, short-term and depict ecological networks as static structures only, devoid of any dynamics. This hampers our understanding of how nature responds to larger disturbances such as changes in climate. In order to remedy this we studied the long-term (12-yrs) dynamics of a flower-visitation network, consisting of flower-visiting butterflies and their nectar plants. Global network properties, i.e. numbers of species and links, as well as connectance, were temporally stable, whereas most species and links showed a strong temporal dynamics. However, species of butterflies and plants varied bimodally in their temporal persistance: Sporadic species, being present only 1-2(-5) years, and stable species, being present (9-)11-12 years, dominated the networks. Temporal persistence and linkage level of species, i.e. number of links to other species, made up two groups of species: Specialists with a highly variable temporal persistence, and temporally stable species with a highly variable linkage level. Turnover of links of specialists was driven by species turnover, whereas turnover of links among generalists took place through rewiring, i.e. by reshuffling existing interactions. However, in spite of this strong internal dynamics of species and links the network appeared overall stable. If this global stability-local instability phenomenon is general, it is a most astonishing feature of ecological networks.     

Mycobacterium tuberculosis lineage influences innate immune response and virulence and is associated with distinct cell envelope lipid profiles

The six major genetic lineages of Mycobacterium tuberculosis are strongly associated with specific geographical regions, but their relevance to bacterial virulence and the clinical consequences of infection are unclear. Previously, we found that in Vietnam, East Asian/Beijing and Indo-Oceanic strains were significantly more likely to cause disseminated tuberculosis with meningitis than those from the Euro-American lineage. To investigate this observation we characterised 7 East Asian/Beijing, 5 Indo-Oceanic and 6 Euro-American Vietnamese strains in bone-marrow-derived macrophages, dendritic cells and mice. East Asian/Beijing and Indo-Oceanic strains induced significantly more TNF-α and IL-1β from macrophages than the Euro-American strains, and East Asian/Beijing strains were detectable earlier in the blood of infected mice and grew faster in the lungs. We hypothesised that these differences were induced by lineage-specific variation in cell envelope lipids. Whole lipid extracts from East Asian/Beijing and Indo-Oceanic strains induced higher concentrations of TNF-α from macrophages than Euro-American lipids. The lipid extracts were fractionated and compared by thin layer chromatography to reveal a distinct pattern of lineage-associated profiles. A phthiotriol dimycocerosate was exclusively produced by East Asian/Beijing strains, but not the phenolic glycolipid previously associated with the hyper-virulent phenotype of some isolates of this lineage. All Indo-Oceanic strains produced a unique unidentified lipid, shown to be a phenolphthiocerol dimycocerosate dependent upon an intact pks15/1 for its production. This was described by Goren as the 'attenuation indictor lipid' more than 40 years ago, due to its association with less virulent strains from southern India. Mutation of pks15/1 in a representative Indo-Oceanic strain prevented phenolphthiocerol dimycocerosate synthesis, but did not alter macrophage cytokine induction. Our findings suggest that the early interactions between M. tuberculosis and host are determined by the lineage of the infecting strain; but we were unable to show these differences are driven by lineage-specific cell-surface expressed lipids.     

FTIR 2D correlation spectroscopy of α₁ and α₂ fractions of an alkali-pretreated gelatin

An alkali-pretreated gelatin (pI~4.9) was fractionated by means of alcohol coacervation and semi-preparative gel chromatography. The thermal responses of the isolated α fractions, the coacervate and the total gelatin were investigated by 2D-correlation FTIR spectroscopy in the amide I band region (1600-1700 cm?1). The gelation temperature was the same for all examined samples (24.5°C) while the melting temperature of the α? fraction was lower (30°C) than that of the other samples (32.5°C). The 2D COS plots indicate that on cooling (gelation) the core sequence of conformational changes is the same for all samples. On heating, however, the α? fraction deviates from the α?-containing samples and shows an earlier disappearance of the triple helix signal in the event sequence. The lower melting temperature (less thermostable gelatin gel) of the α? fraction thus results from a different conformational cascade of the α? chains upon melting. In all samples the initial conformational changes take place in the β-turns, providing further evidence for the models proposed previously.     

Unusual packing of ET molecules caused by π-π stacking interactions with TRISPHAT molecules in two [ET][TRISPHAT] salts (ET = bis(ethylenedithio)tetrathiafulvalene, TRISPHAT = (tris(tetrachlorobenzenediolato)phosphate(V)))

The synthesis, structure and physical properties of two new radical salts formed with the organic donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) and a racemic mixture of the chiral anion (tris(tetrachlorobenzenediolato)phosphate(V)) (TRISPHAT) are reported. The structure of the salts (ET)₄[TRISPHAT]₄ · 3.5H₂O (1) and (ET)(TRISPHAT) · CH₂Cl₂ · CH₃CN (2) has been solved by X-ray single crystal diffraction. Unusual packings of ET molecules are obtained in the two structures. The electrical properties indicate that both compounds are insulators. This is in agreement with the isolation of the ET molecules and their complete ionization. On the other hand, the anisotropy of the ESR lines has been studied by Q-band ESR spectra.     

Habitat associations of species show consistent but weak responses to climate

Different vegetation types can generate variation in microclimates at local scales, potentially buffering species from adverse climates. To determine if species could respond to such microclimates under climatic warming, we evaluated whether ectothermic species (butterflies) can exploit favourable microclimates and alter their use of different habitats in response to year-to-year variation in climate. In both relatively cold (Britain) and warm (Catalonia) regions of their geographical ranges, most species shifted into cooler, closed habitats (e.g. woodland) in hot years, and into warmer, open habitats (e.g. grassland) in cooler years. Additionally, three-quarters of species occurred in closed habitats more frequently in the warm region than in the cool region. Thus, species shift their local distributions and alter their habitat associations to exploit favourable microclimates, although the magnitude of the shift (approx. 1.3% of individuals from open to shade, per degree Celsius) is unlikely to buffer species from impacts of regional climate warming.     

Reversible heat inactivation of copper sites precedes thermal unfolding of molluscan (Rapana thomasiana) hemocyanin

Hemocyanin (Hc) is a type-3 copper protein, containing dioxygen-binding active sites consisting of paired copper atoms. In the present study the thermal unfolding of the Hc from the marine mollusc Rapana thomasiana (RtH) has been investigated by combining differential scanning calorimetry, Fourier transform infrared (FTIR) and UV–vis absorption spectroscopy. Two important stages in the unfolding pathway of the Hc molecule were discerned. A first event, with nonmeasurable heat absorption, occurring around 60 °C, lowers the binding of dioxygen to the type-3 copper groups. This pretransition is reversible and is ascribed to a slight change in the tertiary structure. In a second stage, with midpoint around 80 °C, the protein irreversibly unfolds with a loss of secondary structure and formation of amorphous aggregates. Experiments with the monomeric structural subunits, RtH1 and RtH2, indicated that the heterogeneity in the process of thermal denaturation can be attributed to the presence of multiple 50 kDa functional units with different stability. In accordance, the irreversible unfolding of a purified functional unit (RtH2-e) occurred at a single transition temperature. At slightly alkaline pH (Tris buffer) the C-terminal β-sheet rich domain of the functional unit starts to unfold before the α-helix-rich N-terminal (copper containing) domain, triggering the collapse of the global protein structure. Even around 90 °C some secondary structure is preserved as shown by the FTIR spectra of all investigated samples, confirming the high thermostability of molluscan Hc.     

Synthesis and bioevaluation of 22-hydroxyacuminatine analogs

A series of 22-hydroxyacuminatine analogs was prepared by using different Friedländer condensations. Several of the new compounds were tested for antiproliferative activity on cancer cell lines and for topoisomerase I inhibitory activity.     

Drinking water is associated with weight loss in overweight dieting women independent of diet and activity

Background: Data from short‐term experiments suggest that drinking water may promote weight loss by lowering total energy intake and/or altering metabolism. The long‐term effects of drinking water on change in body weight and composition are unknown, however. Objective: This study tested for associations between absolute and relative increases in drinking water and weight loss over 12 months. Methods and Procedures: Secondary analyses were conducted on data from the Stanford A TO Z weight loss intervention on 173 premenopausal overweight women (aged 25–50 years) who reported <1 l/day drinking water at baseline. Diet, physical activity, body weight, percent body fat (dual‐energy X‐ray absorptiometry), and waist circumference were assessed at baseline, 2, 6, and 12 months. At each time point, mean daily intakes of drinking water, noncaloric, unsweetened caloric (e.g., 100% fruit juice, milk) and sweetened caloric beverages, and food energy and nutrients were estimated using three unannounced 24‐h diet recalls. Beverage intake was expressed in absolute (g) and relative terms (% of beverages). Mixed models were used to test for effects of absolute and relative increases in drinking water on changes in weight and body composition, controlling for baseline status, diet group, and changes in other beverage intake, the amount and composition of foods consumed and physical activity. Results: Absolute and relative increases in drinking water were associated with significant loss of body weight and fat over time, independent of covariates. Discussion: The results suggest that drinking water may promote weight loss in overweight dieting women.