Cu2‐xS Surface Phases and Their Impact on the Electronic Structure of CuInS2 Thin Films – A Hidden Parameter in Solar Cell Optimization

The surface properties of CuInS₂ (CIS) thin‐film solar cell absorbers are investigated by a combination of electron and soft X‐ray spectroscopies. Spatially separated regions of varying colors are observed and identified to be dominated by either CuS or Cu₂S surface phases. After their removal by KCN etching, the samples cannot be distinguished by eye and the CIS surface is found to be Cu‐deficient in both regions. However, a significantly more pronounced off‐stoichiometry in the region initially covered by Cu₂S can be identified. In this region, the resulting surface band gap is also significantly larger than the E_g^Surf of the initially CuS‐terminated region. Such variations may represent a hidden parameter which, if overlooked, induces irreproducibility and thus prevents systematic optimization efforts.     

LmxMPK4, an essential mitogen-activated protein kinase of Leishmania mexicana is phosphorylated and activated by the STE7-like protein kinase LmxMKK5

The essential mitogen-activated protein kinase (MAP kinase), LmxMPK4, of Leishmania mexicana is minimally active when purified following recombinant expression in Escherichia coli and was therefore unsuitable for drug screening until now. Using an E. coli protein co-expression system we identified LmxMKK5, a STE7-like protein kinase from L. mexicana, which phosphorylates and activates recombinant LmxMPK4 in vitro. LmxMKK5 is comprised of 525 amino acids and has a calculated molecular mass of 55.9 kDa. The co-expressed, purified LmxMPK4 showed strong phosphotransferase activity in radiometric kinase assays and was confirmed by immunoblot and tandem mass spectrometry analyses to be phosphorylated on threonine 190 and tyrosine 192 of the typical TXY MAP kinase activation motif. The universal protein kinase inhibitor staurosporine reduced the phosphotransferase activity of co-expressed and activated LmxMPK4 in a dose-dependent manner. To our knowledge this is the first time that an in vitro activator of an essential Leishmania MAP kinase was identified and our findings form the basis for the development of drug screening assays to identify small molecule inhibitors of LmxMPK4 in the search for new therapeutic drugs against leishmaniasis.     

Temperature-dependent calcium-induced calcium release via InsP3 receptors in mouse olfactory ensheathing glial cells

Cooling can induce Ca(2+) signaling via activation of temperature-sensitive ion channels such as TRPM8, TRPA1 and ryanodine receptor channels. Here we have studied the mechanism of cooling-evoked Ca(2+) signaling in mouse olfactory ensheathing cells (OECs), a specialized type of glial cells in the olfactory nerve layer of the olfactory bulb. Reducing the temperature from above 30°C to 28°C and below triggered Ca(2+) transients that persisted in the absence of external Ca(2+), but were suppressed after Ca(2+) store depletion by cyclopiazonic acid. Cooling-evoked Ca(2+) transients were present in mice deficient of TRPM8 and TRPA1, and were not inhibited by ryanodine receptor antagonists. Inhibition of InsP(3) receptors with 2-APB and caffeine entirely blocked cooling-evoked Ca(2+) transients. Moderate Ca(2+) increases, as evoked by flash photolysis of NP-EGTA (caged Ca(2+)) and cyclopiazonic acid, triggered InsP(3) receptor-mediated Ca(2+) release at 22°C, but not at 31°C. The results suggest that InsP(3) receptors mediate Ca(2+)-induced Ca(2+) release in OECs, and that this Ca(2+) release is temperature-sensitive and can be suppressed at temperatures above 28°C.     

Organization of the superficial neuromast system in goldfish, Carassius auratus

Distribution, morphology, and orientation of superficial neuromasts and polarization of the hair cells within superficial neuromasts of the goldfish (Carassius auratus) were examined using fluorescence labeling and scanning electron microscopy. On each body side, goldfish have 1,800-2,000 superficial neuromasts distributed across the head, trunk and tail fin. Each superficial neuromast had about 14-32 hair cells that were arranged in the sensory epithelium with the axis of best sensitivity aligned perpendicular to the long axis of the neuromast. Hair cell polarization was rostro-caudal in most superficial neuromasts on trunk scales (with the exception of those on the lateral line scales), or on the tail fin. On lateral line scales, the most frequent hair cell polarization was dorso-ventral in 45% and rostro-caudal in 20% of the superficial neuromasts. On individual trunk scales, superficial neuromasts were organized in rows which in most scales showed similar orientations with angle deviations smaller than 45 degrees . In about 16% of all trunk scales, groups of superficial neuromasts in the dorsal and ventral half of the scale were oriented orthogonal to each other. On the head, most superficial neuromasts were arranged in rows or groups of similar orientation with angle deviations smaller than 45 degrees . Neighboring groups of superficial neuromasts could differ with respect to their orientation. The most frequent hair cell polarization was dorso-ventral in front of the eyes and on the ventral mandible and rostro-caudal below the eye and on the operculum.     

Amino acid sequence of the phosphorylation site of isocitrate dehydrogenase fromEscherichia coli

InEscherichia coli, NADP⁺-specific isocitrate dehydrogenase (EC 1.1.1.42) may undergo a phosphorylation catalyzed by a cAMP-independent protein kinase, with a concomitant decrease in catalytic activity. In this report, we describe the purification and amino acid sequence of a³²P-labeled peptide obtained from in vivo³²P-labeled isocitrate dehydrogenase. The³²P-labeled peptide was isolated from a tryptic digest and found to contain seven amino acids, including a single serine residue. Following automated Edman degradation and reversephase high-pressure liquid chromatography of the phenylthiohydantoin-amino acids, the sequence of this peptide was established to be-Ser(P)-Leu-Asn-Val-Ala-Leu-Arg.     

Acetyltransfer in natural product biosynthesis--functional cloning and molecular analysis of vinorine synthase

Vinorine synthase (EC 2.3.1.160) catalyses the acetyl-CoA- or CoA-dependent reversible formation of the alkaloids vinorine (or 11-methoxy-vinorine) and 16-epi-vellosimine (or gardneral). The forward reaction leads to vinorine, which is a direct biosynthetic precursor along the complex pathway to the monoterpenoid indole alkaloid ajmaline, an antiarrhythmic drug from the Indian medicinal plant Rauvolfia serpentina. Based on partial peptide sequences a cDNA clone was isolated and functionally expressed in Escherichia coli. The Km values of the native enzyme for gardneral and acetyl-CoA were determined to be 7.5 and 57 microM. The amino acid sequence of vinorine synthase has highest level of identity (28-31%) to that of Papaver salutaridinol acetyltransferase, Fragaria alcohol acyltransferase, and Catharanthus deacetylvindoline acetyltransferase involved in morphine, flavor, and vindoline biosynthesis, respectively. Vinorine synthase is a novel member of the BAHD superfamily of acyltransferases. Site-directed mutagenesis of 13 amino acid residues provided clear evidence that both, His160 and Asp164 of the consensus sequence HxxxD belong to the catalytic center. The mutations also showed that an amino acid triad is not characteristic of vinorine synthase. The experiments demonstrated the importance of the conserved motif SxL/I/VD near the N-terminus and the consensus sequence DFGWG near the C-terminal.     

Coping with flow: behavior, neurophysiology and modeling of the fish lateral line system

With the mechanosensory lateral line fish perceive water motions relative to their body surface and local pressure gradients. The lateral line plays an important role in many fish behaviors including the detection and localization of dipole sources and the tracking of prey fish. The sensory units of the lateral line are the neuromasts which are distributed across the surface of the animal. Water motions are received and transduced into neuronal signals by the neuromasts. These signals are conveyed by afferent nerve fibers to the fish brain and processed by lateral line neurons in parts of the brainstem, cerebellum, midbrain, and forebrain. In the cerebellum, midbrain, and forebrain, lateral line information is integrated with sensory information from other modalities. The present review introduces the peripheral morphology of the lateral line, and describes our understanding of lateral line physiology and behavior. It focuses on recent studies that have investigated: how fish behave in unsteady flow; what kind of sensory information is provided by flow; and how fish use and process this information. Finally, it reports new theoretical and biomimetic approaches to understand lateral line function.     

Benefit-of-doubt (BOD) scoring: A sequencing-based method for SNP candidate assessment from high to medium read number data sets

Identification of single nucleotide polymorphisms (SNPs) is a key element in sequence-based genetic analysis. Next generation sequencing offers a cost-effective basis to generate the necessary, large sequence data sets, and bioinformatic methods are being developed to process sequencing machine readouts. We were interested in detection of SNPs in a 350 kb region of an EMS-mutagenized Arabidopsis chromosome 3. The region was selectively analyzed using PCR-generated, overlapping fragments for Solexa sequencing. The ensuing reads provided a high coverage and were processed bioinformatically. In order to assess the SNP candidates obtained with a frequently used alignment program and SNP caller, we developed an additional method that allows the identification of high confidence SNP loci. The method can easily be applied to complete genome sequence data of sufficient coverage.     

Where am I and why? Synthesizing range biology and the eco‐evolutionary dynamics of dispersal

Although generations of researchers have studied the factors that limit the distributions of species, we still do not seem to understand this phenomenon comprehensively. Traditionally, species’ ranges have been seen as the consequence of abiotic conditions and local adaptation to the environment. However, during the last years it has become more and more evident that biotic factors – such as intra‐ and interspecific interactions or the dispersal capacity of species – and even rapidly occurring evolutionary processes can strongly influence the range of a species and its potential to spread to new habitats. Relevant eco‐evolutionary forces can be found at all hierarchical levels: from landscapes to communities via populations, individuals and genes. We here use the metapopulation concept to develop a framework that allows us to synthesize this broad spectrum of different factors. Since species’ ranges are the result of a dynamic equilibrium of colonization and local extinction events, the importance of dispersal is immediately clear. We highlight the complex interrelations and feedbacks between ecological and evolutionary forces that shape dispersal and result in non‐trivial and partially counter‐intuitive range dynamics. Our concept synthesizes current knowledge on range biology and the eco‐evolutionary dynamics of dispersal. Synthesis What factors are responsible for the dynamics of species' ranges? Answering this question has never been more important than today, in the light of rapid environmental changes. Surprisingly, the ecological and evolutionary dynamics of dispersal – which represent the driving forces behind range formation – have rarely been considered in this context. We here present a framework that closes this gap. Dispersal evolution may be responsible for highly complex and non‐trivial range dynamics. In order to understand these, and possibly provide projections of future range positions, it is crucial to take the ecological and evolutionary dynamics of dispersal into account.