SpraySyn-A standardized burner configuration for nanoparticle synthesis in spray flames.

In many scientific communities, the definition of standardized experiments has enabled major progress in process understanding. The investigation of the spray-flame synthesis of nanoparticles at a well-defined standard burner by experiment and simulation makes it possible to produce a comprehensive data set with various established and novel measuring methods. In this work, we introduce the design of the SpraySyn burner as a new standard for a free-jet type burner that offers well-defined and simulation-friendly boundary conditions and geometries as well as accessibility for optical diagnostics. A combustible precursor solution is fed through a centrally located capillary and aerosolized with an oxygen dispersion gas flow. The spray flame is stabilized by a premixed flat methane/oxygen pilot flame fed via a porous bronze matrix surrounded by a stabilizing nitrogen coflow emanating through the same porous matrix, providing easy-to-calculate boundary conditions for simulations. This burner design enables the use of a wide choice of solvents, precursors, and precursor combinations. Best-practice operating instructions and parameters are given, and large-eddy simulations are performed demonstrating the suitability of the SpraySyn burner for computational fluid dynamics simulations. For ensuring reproducible operation across labs, we define a consumer-camera-based flame characterization scheme for the quantitative assessment of the flame geometry such as flame length, diameter, tilt angle, and photometric distribution of visible chemiluminescence along the center axis. These parameters can be used for benchmarking the pilot and spray flame by each user of the SpraySyn burner with the reference flames.

A trans-Atlantic examination of haddock Melanogrammus aeglefinus food habits.

The food habits of Melanogrammus aeglefinus were explored and contrasted across multiple north-eastern and north-western Atlantic Ocean ecosystems, using databases that span multiple decades. The results show that among all ecosystems, echinoderms are a consistent part of M. aeglefinus diet, but patterns emerge regarding where and when M. aeglefinus primarily eat fishes v. echinoderms. Melanogrammus aeglefinus does not regularly exhibit the increase in piscivory with ontogeny that other gadoids often show, and in several ecosystems there is a lower occurrence of piscivory. There is an apparent inverse relationship between the consumption of fishes and echinoderms in M. aeglefinus over time, where certain years show high levels of one prey item and low levels of the other. This apparent binary choice can be viewed as part of a gradient of prey options, contingent upon a suite of factors external to M. aeglefinus dynamics. The energetic consequences of this prey choice are discussed, noting that in some instances it may not be a choice at all.

Sexual size dimorphism in three North Sea gadoids.

Existing biological data on whiting Merlangius merlangus, cod Gadus morhua and haddock Melanogrammus aeglefinus from a long-term international survey were analysed to address sexual size dimorphism (SSD) and its effect on their ecology and management. Results show that SSD, with larger females of the same age as males, is a result of higher growth rates in females. A direct consequence of SSD is the pronounced length-dependent female ratio that was found in all three gadoids in the North Sea. Female ratios of the three species changed from equality to female dominance at specific dominance transition lengths of c. 30, 35 and 60 cm for M. merlangus, G. morhua and M. aeglefinus, respectively. An analysis by area for M. merlangus also revealed length dependence of female ratios. SSD and length-dependent female ratios under most circumstances are inseparable. Higher overall energy demand as well as a higher energy uptake rate must result from the observed SSD and dimorphism in growth rates. Potential processes related to feeding, locomotion and physiology are proposed that could balance the increased energy investment of females. Potential consequences of SSD and length dependency of female ratios are the reduction of the reproductive potential of a stock due to size-selective fishing and biased assessment of the true size of the female spawning stock that could distort decisions in fisheries management.

Loss of EphA4 impairs short-term spatial recognition memory performance and locomotor habituation.

EphA4 receptor (EphA4) tyrosine kinase is an important regulator of central nervous system development and synaptic plasticity in the mature brain, but its relevance to the control of normal behavior remains largely unexplored. This study is the first attempt to obtain a behavioral profile of constitutive homozygous and heterozygous EphA4 knockout mice. A deficit in locomotor habituation in the open field, impairment in spatial recognition in the Y-maze and reduced probability of spatial spontaneous alternation in the T-maze were identified in homozygous EphA4(-/-) mice, while heterozygo us EphA4(+/-) mice appeared normal on these tests in comparison with wild-type (WT) controls. The multiple phenotypes observed in EphA4(-/-) mice might stem from an underlying deficit in habituation learning, reflecting an elementary form of nonassociative learning that is in contrast to Pavlovian associative learning, which appeared unaffected by EphA4 disruption. A deficit in motor coordination on the accelerating rotarod was also demonstrated only in EphA4(-/-) mice--a finding in keeping with the presence of abnormal gait in EphA4(-/-) mice--although they were able to improve performance over training. There was no evidence for substantial changes in major neurochemical markers in various brain regions rich in EphA4 as shown by post-mortem analysis. This excludes the possibility of major neurochemical compensation in the brain of EphA4(-/-) mice. In summary, we have demonstrated for the first time the behavioral significance of EphA4 disruption, supporting further investigation of EphA4 as a possible target for behavioral interventions where habituation deficits are prominent.

Optimization models and the structure of the genetic code.

The codon assignment of the quasi-universal genetic code can be assumed to have resulted from the evolutionary pressures that prevailed when the code was still evolving. Here, we review studies of the structure of the genetic code based on optimization models. We also review studies that, from the structure of the code, attempt to derive aspects of the primordial circumstances in which the genetic code froze. Different rationales are summarized, compared with experimental data, discussed in the context of the transition from a RNA world to a DNA-protein world, and linked to the emergence of the last universal common ancestor.

Impact of non-ideal sorption on low-concentration tailing behavior for atrazine transport in two natural porous media.

The impact of non-ideal sorption on atrazine transport was investigated for two sandy porous media with 0.38% and 0.03% organic-carbon contents. In contrast to prior investigations, effluent atrazine concentrations were monitored over a range of five orders of magnitude to examine long-term elution behavior. As characterized by batch-experiments, atrazine experienced nonlinear sorption for both media. The results of the column experiments showed that atrazine exhibited extensive elution tailing (delayed approach to relative concentration of zero). This non-ideal transport was more pronounced for the medium with higher organic-carbon content. A mathematical model incorporating nonlinear, rate-limited sorption/desorption described by a continuous-distribution function was used to successfully simulate atrazine transport.

Genes affecting the activity of nicotinic receptors involved in Caenorhabditis elegans egg-laying behavior.

Egg-laying behavior in Caenorhabditis elegans is regulated by multiple neurotransmitters, including acetylcholine and serotonin. Agonists of nicotinic acetylcholine receptors such as nicotine and levamisole stimulate egg laying; however, the genetic and molecular basis for cholinergic neurotransmission in the egg-laying circuitry is not well understood. Here we describe the egg-laying phenotypes of eight levamisole resistance genes, which affect the activity of levamisole-sensitive nicotinic receptors in nematodes. Seven of these genes, including the nicotinic receptor subunit genes unc-29, unc-38, and lev-1, were essential for the stimulation of egg laying by levamisole, though they had only subtle effects on egg-laying behavior in the absence of drug. Thus, these genes appear to encode components of a nicotinic receptor that can promote egg laying but is not necessary for egg-laying muscle contraction. Since the levamisole-receptor mutants responded to other cholinergic drugs, other acetylcholine receptors are likely to function in parallel with the levamisole-sensitive receptors to mediate cholinergic neurotransmission in the egg-laying circuitry. In addition, since expression of functional unc-29 in muscle cells restored levamisole sensitivity under some but not all conditions, both neuronal and muscle cell UNC-29 receptors are likely to contribute to the regulation of egg-laying behavior. Mutations in one levamisole receptor gene, unc-38, also conferred both hypersensitivity and reduced peak response to serotonin; thus nicotinic receptors may play a role in regulating serotonin response pathways in the egg-laying neuromusculature.

Fields over unsharp coordinates.

It has been shown that space-time coordinates can exhibit only very few types of short-distance structures, if described by linear operators: they can be continuous, discrete, or "unsharp" in one of two ways. In the literature, various quantum gravity models of space-time at short distances point towards one of these two types of unsharpness. Here, we investigate the properties of fields over such unsharp coordinates. We find that these fields are continuous--but possess only a finite density of degrees of freedom, similar to fields on lattices. As a special case we recover the Shannon sampling theorem of information theory.

Assembly of Drosophila lamin Dm0 and C mutant proteins studied with the baculovirus system.

Despite extensive knowledge of the in vitro polymerization properties of nuclear lamins, it is still not well understood how the nuclear lamina assembles in vivo. To learn more about the relationship between in vitro and in vivo polymerization of nuclear lamins, we expressed Drosophila lamin Dm0, mutant proteins, having well defined alterations of their in vitro polymerization properties, in Sf9 cells using the baculovirus system. All lamin Dm0 mutants assembled into fibrillar aggregates indistinguishable in morphology from those assembled by the wild-type protein. However, in contrast to wild-type lamin Dm0, mutant proteins were extracted with buffers of physiological ionic strength and pH containing Triton X-100. These results indicate that various types of lamin dimer-dimer interactions can be disrupted without affecting the morphology of the lamin Dm0 polymer. However, all types of dimer-dimer interactions tested appear to be important for full polymer stability. In addition, we analyzed the polymer formation of two Drosophila lamin C mutants and found that a segment in the carboxy-terminal tail domain is required for assembly of lamin C paracrystals at the nuclear lamina.

Assembly of A- and B-type lamins studied in vivo with the baculovirus system.

We have expressed an A-type lamin (Xenopus lamin A), a probable A-type lamin (Drosophila lamin C), two B-type lamins (Xenopus lamin LI, Drosophila lamin Dmo), and two mutants of Xenopus lamin A in Sf9 cells. All proteins were synthesized at high levels resulting in formation of paracrystals with an axial repeat of 18.5-20.0 nm by A-type lamins; in contrast B-type lamins assembled into aggregates with a fibrillar ultrastructure. Of the four wild-type proteins analyzed only lamin Dmo was found in the nuclear compartment of Sf9 cells in association with the lamina whereas the three other lamins assembled into polymers localized in the cytoplasm as well as the nucleoplasm. The Xenopus lamin A mutant lacking the complete carboxy-terminal tail assembled in the cytoplasm into long filament bundles consisting of fibrils of less than 6 nm diameter. In vitro the non-helical amino-terminal head domain of lamins is required for the formation of 'head-to-tail' polymers. A lamin A mutant lacking this domain could be efficiently extracted from Sf9 cells with physiological buffers containing Triton X-100, demonstrating the importance of this domain for lamin assembly in vivo.

Chain termination codons and polymerase-induced frameshift mutations.

The consensus sequence for single-base deletions in non-reiterated runs during in vitro DNA-dependent DNA polymerisation is refined using data available in the literature. This leads to the observation that chain termination codons are hotspots for single-base deletions. The evolutionary implications are discussed in two models which differ in whether polymerases evolved while the genetic code emerged or after the genetic code was fixed. A possible answer to the question 'Why are stop codons just what they are?' is suggested.

Characterization and quantitation of three B-type lamins in Xenopus oocytes and eggs: increase of lamin LI protein synthesis during meiotic maturation.

We have previously shown that Xenopus oocytes, eggs, and early embryos contain lamins LII and LIII, and that portions of each are associated with distinct egg vesicle populations. We now report that a lamin similar or identical to the B-type lamin LI is also present in oocyte nuclei and in egg extracts. We have quantitated the three B-type lamins per oocyte nucleus, and have calculated relative ratios of LI:LIII = 1:100, and LII:LIII = 1:10. Similar to lamin LII, 5-15% of lamin LI is associated with egg membranes in a biochemically stable manner. Egg vesicles absorbed with lamin isoform-specific antibodies to magnetic beads indicate that lamin LI-associated egg membranes are of heterogenous morphology, and are independent from the lamin LII and LIII vesicle populations. Compared to other nuclear envelope proteins, the synthesis of lamin LI protein is specifically elevated during meiotic maturation, resulting in a 4- to 12-fold higher amount of lamin LI in eggs than is present in oocyte nuclei. Immunofluorescence and immunoblot analysis demonstrated that lamins LI, LII, and LIII are associated with the nuclear envelope formed on demembranated sperm when added to activated egg extract. These results strongly suggest that three different lamin-associated vesicle populations are involved in the formation of a nuclear envelope in egg extracts.

Truncated human P450 2D6: expression in Escherichia coli, Ni(2+)-chelate affinity purification, and characterization of solubility and aggregation.

Cytochrome P450 2D6 is one of the clinically important drug-oxidizing enzymes in human liver. We constructed an Escherichia coli expression vector to obtain large amounts of this microsomal hemoprotein in a form suitable for purification and further structural analysis. The N-terminal 25 amino acids, which presumably serve as a membrane anchor, were replaced by codons for a [His]6 tag to increase solubility and to allow for rapid purification by Ni(2+)-chelate affinity chromatography. P450 2D6 apoprotein was synthesized under practically all growth conditions, whereas formation of heme-containing holoenzyme strictly depended on addition of the heme precursor delta-aminolevulinic acid to the E. coli culture. The truncated P450 was purified from the soluble cytosolic fraction to electrophoretic homogeneity (7 nmol of P450/mg protein) by affinity chromatography on Ni(2+)-nitrilotriacetate-agarose. The purified protein exhibited a CO-reduced difference spectrum with a delta max at 450 nm and no detectable P420. Kinetic analysis revealed a Km value for bufuralol 1'-hydroxylation similar to the Km of the native full-length enzyme purified from human liver microsomes. To characterize the purified truncated protein with respect to hydrodynamic properties, we performed sedimentation velocity and sedimentation equilibrium analysis. These studies demonstrated that approximately 50% of the protein was in a highly aggregated state. Another 30% consisted of a single protein species with an approximated molecular weight of 200,000 and the residual 20% represented at least two other species with lower molecular weights. To prevent formation of such unexpectedly high aggregation states, purification was also performed in the presence of "nonaethyleneglycol monododecyl ether" (C12E9), a nonionic, chemically defined detergent often used in attempts to crystallize membrane proteins. Over 80% of this preparation was found to consist of a single protein species with a M(r) of 62,000 indicating a monomeric state. These data demonstrate that (i) N-terminal truncation of P450 2D6 does not principally interfere with heme incorporation and function of the enzyme, (ii) deletion of the hydrophobic N-terminus leads to a protein product which can be recovered largely from the soluble E. coli fraction, and (iii) this soluble truncated protein is highly aggregated unless detergents are added to maintain it in a monomeric state.

Thermocrispum gen. nov., a new genus of the order Actinomycetales, and description of Thermocrispum municipale sp. nov. and Thermocrispum agreste sp. nov.

Ten strains of thermophilic actinomycetes were isolated from waste and mushroom composts, as well as from the air of compost plants and a refuse incineration plant in Germany. These organisms produce white aerial mycelia and form hyphae with so-called pseudosporangia that fragment into rod-like structures. The organisms have type III cell walls (meso-diaminopimelic acid and whole-cell sugar type C), the phospholipid type is type PII, and mycolic acids are not present. The major menaquinone is MK-9(H4), and the fatty acids are mainly iso- and anteiso-branched fatty acids, hydroxy fatty acids, and 10-methyl-branched fatty acids. The guanine-plus-cytosine content of the DNA is 69 to 73 mol%. The chemotaxonomic markers (especially whole-cell sugar type C) and 16S ribosomal DNA sequence data indicated that these organisms represent a new genus of the order Actinomycetales, for which the name Thermocrispum is proposed. On the basis of phylogenetic and phenotypic data, this new genus is closely related to members of the family Pseudonocardiaceae and related taxa and contains two species: Thermocrispum municipale sp. nov. and Thermocrispum agreste sp. nov. The type species of the genus is T. municipale, with type strain MKD 35 (= DSM 44069), and the type strain of T. agreste is CHB 77 (= DSM 44070).

Pneumocandins from Zalerion arboricola. I. Discovery and isolation.

HPLC bioautography of the directed biosynthesis of Zalerion arboricola led to the discovery of pneumocandin B0 (L-688,786), a new antifungal and anti-Pneumocystis carinii lipopeptide. Isolation techniques were developed to separate this component from pneumocandin A0 (L-671,329) in fermentations of a mutant of Zalerion arboricola. A number of related compounds were also isolated, which differ from pneumocandins A0 and B0 in the hydroxylation patterns on the ornithine, homotyrosine, and proline.

Occurrence of sialic acids in Drosophila melanogaster.

Sialylated oligosaccharides, which are cell type-specific and developmentally regulated, have been implicated in a variety of complex biological events. Their broad functional importance is reflected by their presence in a wide variety of phyla extending from Echinodermata through higher vertebrates. Here, sialic acids are detected throughout development in an insect, Drosophila. Homopolymers of alpha 2,8-linked sialic acid, polysialic acid, are developmentally regulated and only expressed during early Drosophila development.

Restricticin, a novel glycine-containing antifungal agent.

Restricticin (1) is a naturally-occurring antifungal agent which contains triene, pyran and glycine ester functionalities and is unrelated to any previously known family of natural products. This unstable compound, as well as its corresponding N,N-dimethyl derivative (2), have been produced and isolated from both solid and liquid fermentations of Penicillium restrictum. The desglycyl hydrolysis product, restrictinol (3), was produced via the hydrolysis of pure restricticin and as an artifact of the isolation of restricticin.