Solvatochromic Modeling of Laurdan for Multiple Polarity Analysis of Dihydrosphingomyelin Bilayer

The hydration properties of the interface between lipid bilayers and bulk water are important for determining membrane characteristics. Here, the emission properties of a solvent-sensitive fluorescence probe, 6-lauroyl-2-dimethylamino naphthalene (Laurdan), were evaluated in lipid bilayer systems composed of the sphingolipids D-erythro-N-palmitoyl-sphingosylphosphorylcholine (PSM) and D-erythro-N-palmitoyl-dihydrosphingomyelin (DHPSM). The glycerophospholipids 1-palmitoyl-2-palmitoyl-sn-glycero-3-phosphocholine and 1-oleoyl-2-oleoyl-sn-glycero-3-phosphocholine were used as controls. The fluorescence properties of Laurdan in sphingolipid bilayers indicated multiple excited states according to the results obtained from the emission spectra, fluorescence anisotropy, and the center-of-mass spectra during the decay time. Deconvolution of the Laurdan emission spectra into four components based on the solvent model enabled us to identify the varieties of hydration and the configurational states derived from intermolecular hydrogen bonding in sphingolipids. Sphingolipids showed specific, interfacial hydration properties stemming from their intra- and intermolecular hydrogen bonds. Particularly, the Laurdan in DHPSM revealed more hydrated properties compared to PSM, even though DHPSM has a higher T_m than PSM. Because DHPSM forms hydrogen bonds with water molecules (in 2NH configurational functional groups), the interfacial region of the DHPSM bilayer was expected to be in a highly polar environment. The careful analysis of Laurdan emission spectra through the four-component deconvolution in this study provides important insights for understanding the multiple polarity in the lipid membrane.     

Characterizing the host and symbiont proteomes in the association between the Bobtail squid, Euprymna scolopes, and the bacterium, Vibrio fischeri

The beneficial symbiosis between the Hawaiian bobtail squid, Euprymna scolopes, and the bioluminescent bacterium, Vibrio fischeri, provides a unique opportunity to study host/microbe interactions within a natural microenvironment. Colonization of the squid light organ by V. fischeri begins a lifelong association with a regulated daily rhythm. Each morning the host expels an exudate from the light organ consisting of 95% of the symbiont population in addition to host hemocytes and shed epithelial cells. We analyzed the host and symbiont proteomes of adult squid exudate and surrounding light organ epithelial tissue using 1D- and 2D-polyacrylamide gel electrophoresis and multidimensional protein identification technology (MudPIT) in an effort to understand the contribution of both partners to the maintenance of this association. These proteomic analyses putatively identified 1581 unique proteins, 870 proteins originating from the symbiont and 711 from the host. Identified host proteins indicate a role of the innate immune system and reactive oxygen species (ROS) in regulating the symbiosis. Symbiont proteins detected enhance our understanding of the role of quorum sensing, two-component signaling, motility, and detoxification of ROS and reactive nitrogen species (RNS) inside the light organ. This study offers the first proteomic analysis of the symbiotic microenvironment of the adult light organ and provides the identification of proteins important to the regulation of this beneficial association.     

The conformations of the O-specific polysaccharides of Shigella dysenteriae type 4 and Escherichia coli O159 studied with molecular mechanics (MM3) filtered systematic search

The branched O-antigens of Escherichia coli O159 and Shigella dysenteriae type 4 are structurally related and are known to show cross-reactivity with antibodies. In the present study, conformational analyses were performed on these two O-antigens using molecular mechanics MM3(96) with filtered systematic search. The results show very strong steric restrictions for the trisaccharide at the branch point of the E. coli O159 antigen, especially for the β-d-GlcNAc-(1 → 3)-β-d-GlcNAc linkage of the main chain. For the type 4 O-antigen the calculations show essentially a single conformation with respect to the α-d-GlcNAc-(1 → 3)-α-d-GlcNAc linkage of the main chain and three different favoured conformations for the fucose branch. Consecutive repeating units of the S. dysenteriae type 4 and E. coli O159 O-antigens form linear extended chains with significant flexibility between the branches. Comparative calculations carried out with the SWEET server indicate that our method of filtered systematic search is a superior method in the case of branched, constrained oligosaccharides. Based on the results of the MM3 calculations, we propose that the common epitope explaining the cross-reactivity comprises the fucose branch, the downstream GlcNAc and part of the uronic acid.     

Diversity and partitioning of bacterial populations within the accessory nidamental gland of the squid Euprymna scolopes

Microbial consortia confer important benefits to animal and plant hosts, and model associations are necessary to examine these types of host/microbe interactions. The accessory nidamental gland (ANG) is a female reproductive organ found among cephalopod mollusks that contains a consortium of bacteria, the exact function of which is unknown. To begin to understand the role of this organ, the bacterial consortium was characterized in the Hawaiian bobtail squid, Euprymna scolopes, a well-studied model organism for symbiosis research. Transmission electron microscopy (TEM) analysis of the ANG revealed dense bacterial assemblages of rod- and coccus-shaped cells segregated by morphology into separate, epithelium-lined tubules. The host epithelium was morphologically heterogeneous, containing ciliated and nonciliated cells with various brush border thicknesses. Hemocytes of the host's innate immune system were also found in close proximity to the bacteria within the tubules. A census of 16S rRNA genes suggested that Rhodobacterales, Rhizobiales, and Verrucomicrobia bacteria were prevalent, with members of the genus Phaeobacter dominating the consortium. Analysis of 454-shotgun sequencing data confirmed the presence of members of these taxa and revealed members of a fourth, Flavobacteria of the Bacteroidetes phylum. 16S rRNA fluorescent in situ hybridization (FISH) revealed that many ANG tubules were dominated by members of specific taxa, namely, Rhodobacterales, Verrucomicrobia, or Cytophaga-Flavobacteria-Bacteroidetes, suggesting symbiont partitioning to specific host tubules. In addition, FISH revealed that bacteria, including Phaeobacter species from the ANG, are likely deposited into the jelly coat of freshly laid eggs. This report establishes the ANG of the invertebrate E. scolopes as a model to examine interactions between a bacterial consortium and its host.     

Kinetics of phosphate limited algal growth

The kinetics of phosphate limited growth of two green algae Chorella pyrenoidosa and Selenastrum capricornutum have been studied in chemostats. Several kinetic models which express the specific growth rate as a function of the intracellular phosphours content have been examined, and one of the models was found to be significantly better than the other models. The principles of this model were described in a recent paper by Nyholm. The kinetics of phosphate uptake have been investigated by adding pulses of phosphate to the chemostats. The uptake by phosphours deficient cells could be described by Michaelis–Menten kinetics for phosphate concentrations below approximately 500 μg P/liter. Further, with the assumption of a discontinuous adjustment of the uptake rate at the onset of phosphours deficiency, a complete kinetic model for growth and phosphate removal is proposed. The mean cell size and the contents of chlorophyll and RNA per unit dry weight have been measured for C. pyrenoidosa as a function of the dilution rate.     

Dynamics of phosphate limited algal growth: Simulation of phosphate shocks

A simulation model is suggested which describes transient growth of the green alga Chlorella pyrenoidosa after exposure of phosphate limited chemostatic cultures to phosphate shocks. The specific growth rate is related to an internal concentration of functional phosphorus. The model includes a metabolic activity functional as suggested by Powell (1969), and it is assumed that phosphate taken up by the cells passes through an intermediate pool of not functional phosphorus which is thought to inhibit growth. Comparisons are made with a simpler model described previously.     

A Geospatial Comparison of Distributed Solar Heat and Power in Europe and the US

The global trends for the rapid growth of distributed solar heat and power in the last decade will likely continue as the levelized cost of production for these technologies continues to decline. To be able to compare the economic potential of solar technologies one must first quantify the types and amount of solar resource that each technology can utilize; second, estimate the technological performance potential based on that resource; and third, compare the costs of each technology across regions. In this analysis, we have performed the first two steps in this process. We use physical and empirically validated models of a total of 8 representative solar system types: non-tracking photovoltaics, 2d-tracking photovoltaics, high concentration photovoltaics, flat-plate thermal, evacuated tube thermal, concentrating trough thermal, concentrating solar combined heat and power, and hybrid concentrating photovoltaic/thermal. These models are integrated into a simulation that uses typical meteorological year weather data to create a yearly time series of heat and electricity production for each system over 12,846 locations in Europe and 1,020 locations in the United States. Through this simulation, systems composed of various permutations of collector-types and technologies can be compared geospatially and temporally in terms of their typical production in each location. For example, we see that silicon solar cells show a significant advantage in yearly electricity production over thin-film cells in the colder climatic regions, but that advantage is lessened in regions that have high average irradiance. In general, the results lead to the conclusion that comparing solar technologies across technology classes simply on cost per peak watt, as is usually done, misses these often significant regional differences in annual performance. These results have implications for both solar power development and energy systems modeling of future pathways of the electricity system.     

The validity of obesity based on self-reported weight and height: Implications for population studies

Objective: To validate self‐reported information on weight and height in an adult population and to find a useful algorithm to assess the prevalence of obesity based on self‐reported information. Research Methods and Procedures: This was a cross‐sectional survey consisting of 1703 participants (860 men and 843 women, 30 to 75 years old) conducted in the community of Vara, Sweden, from 2001 to 2003. Self‐reported weight, height, and corresponding BMI were compared with measured data. Obesity was defined as measured BMI ≥ 30 kg/m². Information on education, self‐rated health, smoking habits, and physical activity during leisure time was collected by a self‐administered questionnaire. Results: Mean differences between measured and self‐reported weight were 1.6 kg (95% confidence interval, 1.4; 1.8) in men and 1.8 kg (1.6; 2.0) in women (measured higher), whereas corresponding differences in height were ?0.3 cm (?0.5; ?0.2) in men and ?0.4 cm (?0.5; ?0.2) in women (measured lower). Age and body size were important factors for misreporting height, weight, and BMI in both men and women. Obesity (measured) was found in 156 men (19%) and 184 women (25%) and with self‐reported data in 114 men (14%) and 153 women (20%). For self‐reported data, the sensitivity of obesity was 70% in men and 82% in women, and when adjusted for corrected self‐reported data and age, it increased to 81% and 90%, whereas the specificity decreased from 99% in both sexes to 97% in men and 98% in women. Discussion: The prevalence of obesity based on self‐reported BMI can be estimated more accurately when using an algorithm adjusted for variables that are predictive for misreporting.     

Peptides in lipid bilayers: the power of simple models

Interactions between proteins and lipids lie at the heart of virtually all membrane processes, but on a molecular level they are still poorly understood. Nowadays, simple model systems comprising designed transmembrane peptides in synthetic lipid bilayers are increasingly being recognized as powerful tools to uncover basic principles of protein-lipid interactions. Such model systems enable detailed analysis of how the properties of lipids influence the structure and dynamics of transmembrane helices, how these helices are anchored at the lipid-water interface, and how the length and composition of transmembrane segments influence the organization and dynamics of membrane lipids. In addition, well-characterized model systems have proven useful to refine computational approaches and to develop new techniques for studies of protein-lipid interactions.     

Airway cellularity, lipid laden macrophages and microbiology of gastric juice and airways in children with reflux oesophagitis

Background and methods

Human metapneumovirus (hMPV) is a recently discovered respiratory virus associated with bronchiolitis, pneumonia, croup and exacerbations of asthma. Since respiratory viruses are frequently detected in patients with acute exacerbations of COPD (AE-COPD) it was our aim to investigate the frequency of hMPV detection in a prospective cohort of hospitalized patients with AE-COPD compared to patients with stable COPD and to smokers without by means of quantitative real-time RT-PCR.

Results

We analysed nasal lavage and induced sputum of 130 patients with AE-COPD, 65 patients with stable COPD and 34 smokers without COPD. HMPV was detected in 3/130 (2.3%) AE-COPD patients with a mean of 6.5 × 10⁵ viral copies/ml in nasal lavage and 1.88 × 10⁵ viral copies/ml in induced sputum. It was not found in patients with stable COPD or smokers without COPD.

Conclusion

HMPV is only found in a very small number of patients with AE-COPD. However it should be considered as a further possible viral trigger of AE-COPD because asymptomatic carriage is unlikely.