Direct Correlation of the Organic Solar Cell Device Performance to the In‐Depth Distribution of Highly Ordered Polymer Domains in Polymer/Fullerene Films

This study correlates the device performance of organic solar cells and the electronic charge transport within polymer/fullerene films, directly to the optical order of the polymer. The optical order was measured by spectroscopic ellipsometry and evaluated by our previously derived model. We were able to determine the in‐depth distribution of higher and lower ordered poly(3‐hexylthiophene) (P3HT) domains within an [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) matrix. The over the film thickness integrated volume fraction of highly ordered P3HT domains could be directly correlated to the corresponding solar cell device performance. We are able to describe various thermally annealing conditions between room‐temperature and 200 °C.     

Membrane Permeation Induced by Aggregates of Human Islet Amyloid Polypeptides

Several neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases as well as nonneuropathic diseases such as type II diabetes and atrial amyloidosis are associated with aggregation of amyloid polypeptides into fibrillar structures, or plaques. In this study, we use molecular dynamics simulations to test the stability and orientation of membrane-embedded aggregates of the human islet amyloid polypeptide (hIAPP) implicated in type II diabetes. We find that in both monolayers and bilayers of dipalmitoylphosphatidylglycerol (DPPG) hIAPP trimers and tetramers remain inside the membranes and preserve their β-sheet secondary structure. Lipid bilayer-inserted hIAPP trimers and tetramers orient inside DPPG at 60° relative to the membrane/water interface and lead to water permeation and Na⁺ intrusion, consistent with ion-toxicity in islet β-cells. In particular, hIAPP trimers form a water-filled β-sandwich that induce water permeability comparable with channel-forming proteins, such as aquaporins and gramicidin-A. The predicted disruptive orientation is consistent with the amphiphilic properties of the hIAPP aggregates and could be probed by chiral sum frequency generation (SFG) spectroscopy, as predicted by the simulated SFG spectra.     

Membrane Permeation Induced by Aggregates of Human Islet Amyloid Polypeptides

Several neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases as well as nonneuropathic diseases such as type II diabetes and atrial amyloidosis are associated with aggregation of amyloid polypeptides into fibrillar structures, or plaques. In this study, we use molecular dynamics simulations to test the stability and orientation of membrane-embedded aggregates of the human islet amyloid polypeptide (hIAPP) implicated in type II diabetes. We find that in both monolayers and bilayers of dipalmitoylphosphatidylglycerol (DPPG) hIAPP trimers and tetramers remain inside the membranes and preserve their β-sheet secondary structure. Lipid bilayer-inserted hIAPP trimers and tetramers orient inside DPPG at 60° relative to the membrane/water interface and lead to water permeation and Na⁺ intrusion, consistent with ion-toxicity in islet β-cells. In particular, hIAPP trimers form a water-filled β-sandwich that induce water permeability comparable with channel-forming proteins, such as aquaporins and gramicidin-A. The predicted disruptive orientation is consistent with the amphiphilic properties of the hIAPP aggregates and could be probed by chiral sum frequency generation (SFG) spectroscopy, as predicted by the simulated SFG spectra.     

Degradation of barnacle nauplii: implications to chitin regulation in the marine environment

The exoskeleton of most invertebrate larval forms is made of chitin, which is a linear polysaccharide of β (1→4)-linked N-acetylglucosamine (GlcNAc) residues. These larval forms offer extensive body surface for bacterial attachment and colonization. In nature, degradation of chitin involves a cascade of processes brought about by chitinases produced by specific bacteria in the marine environment. Microbial decomposition of larval carcasses serves as an alternate mechanism for nutrient regeneration, elemental cycling and microbial production. The present study was undertaken to assess the influence of chitinase enzyme on the degradation of the nauplii of barnacle, Balanus amphitrite. The survival and abundance of bacteria during the degradation process under different experimental conditions was monitored. To the best of our knowledge, no such study is conducted to understand the degradation of larval exoskeleton using chitinase and its influence on bacteria. An increase in the chitinase activity with increase in temperature was observed. Scanning electron micrographs of chitinase treated nauplii showed scars on the surface of the barnacle nauplii initially and further disruption of the exoskeleton was observed with the increase in the treatment time. Bacterial abundance of the chitinase treated nauplii increased with the increase in enzyme concentration. Pathogenic bacteria such as Vibrio cholerae, V. alginolyticus, V. parahaemolyticus which were initially associated with the exoskeleton were absent after chitinase treatment, however, Bacillus spp. dominated subsequent to chitinase treatment and this might have important implications to marine ecosystem functioning.     

White sociology

ABSTRACT

This review essay considers central themes in Murji and Solomos’ rich edited collection with regard to the current orientation of Western sociological discipline to issues of racism.     

Decreased pCO(2) accumulation by eliminating bicarbonate addition to high cell-density cultures

High-density perfusion cultivation of mammalian cells can result in elevated bioreactor CO(2) partial pressure (pCO(2)), a condition that can negatively influence growth, metabolism, productivity, and protein glycosylation. For BHK cells in a perfusion culture at 20 x 10(6) cells/mL, the bioreactor pCO(2) exceeded 225 mm Hg with approximate contributions of 25% from cellular respiration, 35% from medium NaHCO(3), and 40% from NaHCO(3) added for pH control. Recognizing the limitations to the practicality of gas sparging for CO(2) removal in perfusion systems, a strategy based on CO(2) reduction at the source was investigated. The NaHCO(3) in the medium was replaced with a MOPS-Histidine buffer, while Na(2)CO(3) replaced NaHCO(3) for pH control. These changes resulted in 63-70% pCO(2) reductions in multiple 15 L perfusion bioreactors, and were reproducible at the manufacturing-scale. Bioreactor pCO(2) values after these modifications were in the 68-85 mm Hg range, pCO(2) reductions consistent with those theoretically expected. Low bioreactor pCO(2) was accompanied by both 68-123% increased growth rates and 58-92% increased specific productivity. Bioreactor pCO(2) reduction and the resulting positive implications for cell growth and productivity were brought about by process changes that were readily implemented and robust. This philosophy of pCO(2) reduction at the source through medium and base modification should be readily applicable to large-scale fed-batch cultivation of mammalian cells.     

Growth medium standardization and thermotolerance study of the freshwater microalga <Emphasis Type="Italic">Acutodesmus dimorphus—</Emphasis>a potential strain for biofuel production

Microalgal biomass seems to be one of the potential alternative feedstocks for the production of various types of biofuel. In the present study, first of all, suitable growth media and harvesting time were determined for the freshwater chlorophyte microalga Acutodesmus dimorphus. Cultivation of A. dimorphus in BG-11 medium for 15 days resulted in the highest biomass productivity with 24.60 % lipid and 22.78 % carbohydrate contents. Further, thermotolerance property of A. dimorphus was evaluated by heat stressing the cells at 45 °C and 50 °C up to 24 h and determining the cell mortality and pigment composition along with lipid and carbohydrate contents. Chlorophyll and carotenoid contents of cells significantly increased after heat stress at 45 °C. Increasing the heat stress from 8 to 24 h increased the dead cells by 3–4 % at both temperatures, which shows the thermotolerance of A. dimorphus. Lipid content of 27 % and carbohydrate content of 26–28 % even after 24 h of heat stress at 45 and 50 °C suggest A. dimorphus as a potential feedstock for biofuel production.     

Validation of fractal-like kinetic models by time-resolved binding kinetics of dansylamide and carbonic anhydrase in crowded media

Kinetic studies of biochemical reactions are typically carried out in a dilute solution that rarely contains anything more than reactants, products, and buffers. In such studies, mass-action-based kinetic models are used to analyze the progress curves. However, intracellular compartments are crowded by macromolecules. Therefore, we investigated the adequacy of the proposed generalizations of the mass-action model, which are meant to describe reactions in crowded media. To validate these models, we measured time-resolved kinetics for dansylamide binding to carbonic anhydrase in solutions crowded with polyethylene glycol and Ficoll. The measured progress curves clearly show the effects of crowding. The fractal-like model proposed by Savageau was used to fit these curves. In this model, the association rate coefficient k_a allometrically depends on concentrations of reactants. We also considered the fractal kinetic model proposed by Schnell and Turner, in which k_a depends on time according to a Zipf-Mandelbrot distribution, and some generalizations of these models. We found that the generalization of the mass-action model, in which association and dissociation rate coefficients are concentration-dependent, represents the preferred model. Other models based on time-dependent rate coefficients were inadequate or not preferred by model selection criteria.     

Anti-quorum sensing and antibiofilm potential of Alternaria alternata, a foliar endophyte of Carica papaya, evidenced by QS assays and in-silico analysis

In the present study, secondary metabolites from an endophytic fungus, Alternaria alternata, colonizing Carica papaya, demonstrated antiquorum sensing properties against Pseudomonas aeruginosa. This study reports the antagonistic effects of fungal crude extract of A. alternata against the various quorum sensing (QS) associated virulent factors such as percentage decrease in production of pyocyanin, alginate, chitinase and rhamnolipid; significant decrease in proteases activity such as LasA protease activity, staphylolytic activity, Las B elastase; and a marked decrease in biofilm formation and associated factors such as exopolysaccharide (EPS) production and cell surface hydrophobicity (CSH). Further, motility pattern i.e., swimming and swarming was also found to be inhibited. This down regulation of QS and associated factors are further supported by in-silico analysis of interaction between QS receptor LasR and bioactive molecules viz., sulfurous acid, 2-propyl tridecyl ester and 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester present in fungal crude extract, found based on GCMS analysis, sketches the modulating ability of QS expression. This is the first report on an endophytic fungus of C. papaya having a role in QS inhibition against P. aeruginosa and lays a platform to explore further the endophytes for potent therapeutic agents in QS.