What is Killing Organic Photovoltaics: Light‐Induced Crosslinking as a General Degradation Pathway of Organic Conjugated Molecules

In view of a rapid development and increase in efficiency of organic solar cells, reaching their long‐term operational stability represents now one of the main challenges to be addressed on the way toward commercialization of this photovoltaic technology. However, intrinsic degradation pathways occurring in organic solar cells under realistic operational conditions remain poorly understood. The light‐induced dimerization of the fullerene‐based acceptor materials discovered recently is considered to be one of the main causes for burn‐in degradation of organic solar cells. In this work, it is shown that not only the fullerene derivatives but also different types of conjugated polymers and small molecules undergo similar light‐induced crosslinking regardless of their chemical composition and structure. In the case of conjugated polymers, crosslinking of macromolecules leads to a rapid increase in their molecular weight and consequent loss of solubility, which can be revealed in a straightforward way by gel permeation chromatography analysis via a reduction/loss of signal and/or smaller retention times. Results of this work, thus, shift the paradigm of research in the field toward designing a new generation of organic absorbers with enhanced intrinsic photochemical stability in order to reach practically useful operation lifetimes required for successful commercialization of organic photovoltaics.     

Ultrastructural study of cat zona pellucida during oocyte maturation and fertilization

The mammalian zona pellucida (ZP) is an extracellular glycoprotein structure formed around growing oocytes, ovulated eggs and preimplantation embryos. The specific functions of ZP are highly determined by its morphological structure. Studies on cat oocytes during maturation and after fertilization were undertaken, using routine transmission (TEM) and scanning electron microscopy (SEM). Two basic ZP layers – outer with rough spongy appearance and inner with smaller fenestrations and smooth fibrous network – were visible. Deposits, secreted by oviductal cells formed new layer, the so called oviductal ZP. After fertilization outer ZP showed rougher meshed network due to fusion between filaments as a consequence from sperm penetration while the inner was smoother with melted appearance. The presented data on the SEM and TEM characteristics of cat oocytes, together with our previous studies on carbohydrate distribution suggest that during oocyte maturation and fertilization ZP undergoes structural and functional rearrangements related to sperm binding and penetration.     

Rotation screen prevents fish damage in hydroelectric power stations

Downstream migrations of fish over a rotation screen were studied at a hydroelectric power station in Hadamar/Hessen, Germany. This study monitored and evaluated the functionality and efficiency of the rotation screen in order to prevent fish from entering the Kaplan turbine. During one autumn and two spring tests, a total of 1,629 specimens representing 25 species including eel and salmon smolt migrated over the screen. The smallest fish (dace, bleak, three-spined stickleback, and perch) from standard lengths ≤30 mm were carried by scoop buckets mounted on the rotation screen. The tests confirmed in all cases that the migration activity of fish depended unambiguously on the diurnal cycle (P < 0.05). Guest editors: R. L. Welcomme & G. Marmulla Hydropower, Flood Control and Water Abstraction: Implications for Fish and Fisheries     

Expression of the pyranose 2-oxidase from Trametes pubescens in Escherichia coli and characterization of the recombinant enzyme

cDNA-encoding pyranose 2-oxidase (P2O) from Trametes pubescens was sequenced and cloned into Escherichia coli strain BL21/DE3 on a multicopy plasmid under the control of trc promoter. The synthesis of P2O was studied in a batch culture in M9-based mineral medium: the enzyme was synthesized constitutively at 28 °C in amount corresponding to 8% of the cell soluble protein (0.6 U mg⁻¹). Only small portion of P2O (11%) was in the form of non-active inclusion bodies. Purified recombinant enzyme has similar physico-chemical and kinetic parameters with other P2Os. When compared to the expression of p2o of Trametes ochracea, a ratio of the mature enzyme to inclusion bodies found in the same E. coli host at 28 °C is as much as nine times higher. The finding makes the enzyme from T. pubescens preferable for the large-scale production by recombinant bacteria. The difference in amino acid sequences of the P2O from T. ochracea and T. pubescens may explain the favourable trait of the latter enzyme regarding protein folding.     

The Effect of a Spinal Cord Hemisection on Changes in Nitric Oxide Synthase Pools in the Site of Injury and in Regions Located Far Away from the Injured Site

1. The present study was designed to examine the nitric oxide synthase activities (constitutive and inducible) in the site of injury in response to Th10-Th11 spinal cord hemisection and, to determine whether unilateral disconnection of the spinal cord influences the NOS pools on the contra- and ipsilateral sides in segments located far away from the epicentre of injury.2. A radioassay detection was used to determine Ca²⁺-dependent and inducible nitric oxide synthase activities. Somal, axonal and neuropil neuronal nitric oxide synthase was assessed by immunocytochemical study. A quantitative assessment of neuronal nitric oxide synthase immunoreactivity was made by an image analyser. The level of neuronal nitric oxide synthase protein was measured by the Western blot analysis.3. Our data show the increase of inducible nitric oxide synthase activity and a decrease of Ca²⁺-dependent nitric oxide synthase activity in the injured site analysed 1 and 7 days after surgery. In segments remote from the epicentre of injury the inducible nitric oxide synthase activity was increased at both time points. Ca²⁺-dependent nitric oxide synthase activity had decreased in L5-S1 segments in a group of animals surviving for 7 days. A hemisection performed at thoracic level did not cause significant difference in the nitric oxide synthase activities and in the level of neuronal nitric oxide synthase protein between the contra- and ipsilateral sides in C6-Th1 and L5-S1 segments taken as a whole. Significant differences were observed, but only when the spinal cord was analysed segment by segment, and/or was divided into dorsal and ventral parts. The cell counts in the cervicothoracic (C7-Th1) and lumbosacral (L5-S1) enlargements revealed changes in neuronal nitric oxide synthase immunoreactivity on the ipsilateral side of the injury. The densitometric area measurements confirmed the reduction of somal, neuropil and axonal neuronal nitric oxide synthase immunoreactive staining in the ventral part of rostrally oriented segments.4. Our findings provide evidence that the changes in nitric oxide synthase pools are limited not only to impact zone, but spread outside the original lesion. The regional distribution of nitric oxide synthase activity and neuronal nitric oxide synthase immunoreactivity, measured segment by segment shows that nitric oxide may play a significant role in the stepping cycle in the quadrupeds.     

Re-localization of nuclear DNA helicase II during the growth period of bovine oocytes

Nuclear DNA helicase II (NDH II) is the bovine homolog of human RNA helicase A. The aim of this study was to compare NDH II localization between somatic cells (bovine embryonal fibroblasts) and female germ cells (oocytes), with the main focus on the dynamic changes in the redistribution of NDH II during the growth phase of the bovine oocytes. The fine granular staining of NDH II was spread in the whole nucleoplasm of fibroblasts, excluding the reticulated nucleoli. In contrast, the large reticulated nucleoli of the growing oocytes isolated from early antral follicles exhibited strong positivity for NDH II together with the immunostaining signals of upstream binding factor (UBF) and RNA polymerase I subunit (PAF53), documenting the high synthetic activity of these nucleoli. At the time of termination of oocyte growth, NDH II was preferentially located at the nucleolar periphery together with proteins of fibrillar centres. In fully grown oocytes, NDH II was still present in the thin periphery shell around the compact nucleolar core. The semiquantitative RT-PCR revealed that the average signal of NDH II mRNA in fully grown oocytes was only at 40% level in comparison with growing oocytes. Western blot analysis further confirmed that a 140 kD NDH II protein was abundant in growing oocytes, while the signal was substantially weaker in fully grown oocytes. The significant decrease in NDH II gene expression and in NDH II mRNA translation correlates with a termination of the oocyte growth. Altogether, the results demonstrate that NDH II expression parallels the activity of ribosomal RNA biosynthesis in the bovine growing oocytes.     

Is Active Management the Key to the Conservation of Saproxylic Biodiversity? Pollarding Promotes the Formation of Tree Hollows

Trees with hollows are key features sustaining biodiversity in wooded landscapes. They host rich assemblages of often highly specialised organisms. Hollow trees, however, have become rare and localised in Europe. Many of the associated biota is thus declining or endangered. The challenge of its conservation, therefore, is to safeguard the presence of hollow trees in sufficient numbers. Populations of numerous species associated with tree hollows and dead wood are often found in habitats that were formed by formerly common traditional silvicultural practices such as coppicing, pollarding or pasture. Although it has been occasionally mentioned that such practices increase the formation of hollows and the availability of often sun-exposed dead wood, their effect has never been quantified. Our study examined the hollow incidence in pollard and non-pollard (unmanaged) willows and the effect of pollarding on incremental growth rate by tree ring analysis. The probability of hollow occurrence was substantially higher in pollard than in non-pollard trees. Young pollards, especially, form hollows much more often than non-pollards; for instance, in trees of 50 cm DBH, the probability of hollow ocurrence was ∼0.75 in pollards, but only ∼0.3 in non-pollards. No difference in growth rate was found. Pollarding thus leads to the rapid formation of tree hollows, a habitat usually associated with old trees. It is therefore potentially a very important tool in the restoration of saproxylic habitats and conservation of hollow-dependent fauna. If applied along e.g. roads and watercourses, pollarding could also be used to increase landscape connectivity for saproxylic organisms. In reserves where pollarding was formerly practiced, its restoration would be necessary to prevent loss of saproxylic biodiversity. Our results point to the importance of active management measures for maintaining availability, and spatial and temporal continuity of deadwood microhabitats.     

Amyloid aggregation of lysozyme: The synergy study of red wine polyphenols

The amyloidoses are diseases associated with nonnative folding of proteins and characterized by the presence of protein amyloid aggregates. The ability of quercetin, resveratrol, caffeic acid, and their equimolar mixtures to affect amyloid aggregation of hen egg white lysozyme in vitro was detected by Thioflavin T fluorescence assay. The anti‐amyloid activities of tested polyphenols were evaluated by the median depolymerization concentrations DC₅₀ and median inhibition concentrations IC₅₀. Single substances are more efficient (by at least one order) in the depolymerization of amyloid aggregates assay than in the inhibition of the amyloid formation with IC₅₀ in 10^?4 to 10^?5M range. Analyzed mixture samples showed synergic or antagonistic effects in both assays. DC₅₀ values ranged from 10^?5 to 10^?8M and IC₅₀ from 10^?5 to 10^?9M, respectively. We observed that certain mixtures of studied polyphenols can synergistically inhibit production of amyloids aggregates and are also effective in depolymerization of the aggregates. Synergic or antagonistic effects of studied mixtures were correlated with protein–small ligand docking studies and AFM results. Differences in these activities could be explained by binding of each polyphenol to a different amino acid sequence within the protein. Our results indicate that synergic/antagonistic anti‐amyloid effects of studied mixtures depend on the selective binding of polyphenols to the known amyloidogenic sequences in the lysozyme chain. Our findings of the effective reduction of amyloid aggregation of lysozyme by polyphenol mixtures in vitro are of the utter physiological relevance considering the bioavailability and low toxicity of tested phenols. Proteins 2013; © 2012 Wiley Periodicals, Inc.     

Bioconversion of Agave tequilana fructans by exo-inulinases from indigenous Aspergillus niger CH-A-2010 enhances ethanol production from raw Agave tequilana juice

Agave tequilana fructans are the source of fermentable sugars for the production of tequila. Fructans are processed by acid hydrolysis or by cooking in ovens at high temperature. Enzymatic hydrolysis is considered an alternative for the bioconversion of fructans. We previously described the isolation of Aspergillus niger CH-A-2010, an indigenous strain that produces extracellular inulinases. Here we evaluated the potential application of A. niger CH-A-2010 inulinases for the bioconversion of A. tequilana fructans, and its impact on the production of ethanol. Inulinases were analyzed by Western blotting and thin layer chromatography. Optimal pH and temperature conditions for inulinase activity were determined. The efficiency of A. niger CH-A-2010 inulinases was compared with commercial enzymes and with acid hydrolysis. The hydrolysates obtained were subsequently fermented by Saccharomyces cerevisiae to determine the efficiency of ethanol production. Results indicate that A. niger CH-A-2010 predominantly produces an exo-inulinase activity. Optimal inulinase activity occurred at pH 5.0 and 50 °C. Hydrolysis of raw agave juice by CH-A-2010 inulinases yielded 33.5 g/l reducing sugars, compared with 27.3 g/l by Fructozyme^® (Novozymes Corp, Bagsværd, Denmark) and 29.4 g/l by acid hydrolysis. After fermentation of hydrolysates, we observed that the conversion efficiency of sugars into ethanol was 97.5 % of the theoretical ethanol yield for enzymatically degraded agave juice, compared to 83.8 % for acid-hydrolyzed juice. These observations indicate that fructans from raw Agave tequilana juice can be efficiently hydrolyzed by using A. niger CH-A-2010 inulinases, and that this procedure impacts positively on the production of ethanol.     

The peripheral chimerism of bone marrow–derived stem cells after transplantation: regeneration of gastrointestinal tissues in lethally irradiated mice

Bone marrow–derived cells represent a heterogeneous cell population containing haematopoietic stem and progenitor cells. These cells have been identified as potential candidates for use in cell therapy for the regeneration of damaged tissues caused by trauma, degenerative diseases, ischaemia and inflammation or cancer treatment. In our study, we examined a model using whole-body irradiation and the transplantation of bone marrow (BM) or haematopoietic stem cells (HSCs) to study the repair of haematopoiesis, extramedullary haematopoiesis and the migration of green fluorescent protein (GFP⁺) transplanted cells into non-haematopoietic tissues. We investigated the repair of damage to the BM, peripheral blood, spleen and thymus and assessed the ability of this treatment to induce the entry of BM cells or GFP⁺lin⁻Sca-1⁺ cells into non-haematopoietic tissues. The transplantation of BM cells or GFP⁺lin⁻Sca-1⁺ cells from GFP transgenic mice successfully repopulated haematopoiesis and the haematopoietic niche in haematopoietic tissues, specifically the BM, spleen and thymus. The transplanted GFP⁺ cells also entered the gastrointestinal tract (GIT) following whole-body irradiation. Our results demonstrate that whole-body irradiation does not significantly alter the integrity of tissues such as those in the small intestine and liver. Whole-body irradiation also induced myeloablation and chimerism in tissues, and induced the entry of transplanted cells into the small intestine and liver. This result demonstrates that grafted BM cells or GFP⁺lin⁻Sca-1⁺ cells are not transient in the GIT. Thus, these transplanted cells could be used for the long-term treatment of various pathologies or as a one-time treatment option if myeloablation-induced chimerism alone is not sufficient to induce the entry of transplanted cells into non-haematopoietic tissues.