FLUORESCENCE OF HOUSEFLY VISUAL PIGMENT

Abstract —The fluorescence of housefly photoreceptors was studied in vivo by using the deep pseudopupil technique. Whereas the rhodopsin R490 of the peripheral retinular cells fluoresces negligibly the metarhodopsin M580 fluoresces distinctly in the red. The newly discovered metarhodopsin M'is produced by intense blue light and can be reconverted into rhodopsin by intense long wavelength light. M'also fluoresces in the red; its excitation spectrum and emission spectrum peak at _max= 570 and 660 nm respectively.
Intense ultraviolet light irreversibly reduces the visual pigment fluorescence as well as the broad band autofluorescence (kmnx 470 nm) originating from non-visual pigments in the fly's eye.     

Strong inhibition of cholera toxin binding by galactose dendrimers

Galactose-containing dendrimers with long spacer arms inhibit cholera toxin binding as strongly as the natural ganglioside GM1 oligosaccharide does.     

Metallocene‐Catalyzed Gas‐Phase Ethylene Copolymerization: Kinetics and Polymer Properties

The influence of 1‐hexene is examined on the kinetics of ethylene copolymerization with a metallocene catalyst in gas phase. A model is derived, which is able to describe a large reaction rate increase due to a small amount of incorporated comonomer. This complexation model describes the measured reaction rates for ethylene and 1‐hexene, and the co‐monomer incorporation. Polymer properties were analyzed, such as comonomer weight fraction. The density, melting point, and molecular weight of the produced polymer decreased with increase in 1‐hexene gas concentration. The in situ 1‐hexene sorption is estimated and follows Henry's law, but seems much higher than reported in the literature.

     

1‐allyloxy‐2‐hydroxy‐propyl‐starch: Synthesis and characterization

New reactive unsaturated starch derivatives, 1‐allyloxy‐2‐hydroxy‐propyl‐starches (AHP‐starches), were synthesized by the reaction of waxy maize starch (WMS) and amylose‐enriched maize starch (AEMS) with allyl glycidyl ether in a heterogeneous alkaline suspension containing NaOH and Na₂SO₄. The degree of substitution (DS) was determined by ¹H NMR spectroscopy, and a DS of 0.20 ± 0.01 was found for both AHP‐WMS and AHP‐AEMS, respectively. The AHP derivatives of WMS and AEMS were further characterized with ¹H and ¹³C NMR. It was shown that the AHP substitution was located on the C‐6 hydroxyl group of the glucose residues in the starch. The substitution pattern of the AHP groups along the polymer chain was randomly clustered, as determined by enzymatic digestion using pullulanase, α‐amylase, and amyloglucosidase, followed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis of the digestion products. With X‐ray diffraction and scanning electron microscopy, no changes in the granular morphology and crystallinity between the unmodified starches and AHP‐starches were detected. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2734–2744, 2007     

Charged Higgs boson production in association with a top quark in MC@NLO

The European Physical Journal C - We discuss the calculation of charged Higgs boson production in association with a top quark in the MC@NLO framework for combining NLO matrix elements with a...     

In situ monitoring of desilication of MFI-type zeolites in alkaline medium

In situ pH and Attenuated Total Reflection (ATR) infrared techniques have been successfully applied in order to gain insights into the dissolution process connected to mesopore formation occurring upon alkaline treatment of ZSM-5 zeolites. Online pH measurements reveal a similar consumption of OH(-) ions in the initial stage of the reaction independent of the Si/Al ratio of the zeolite. In view of the greatly different mesoporosity development, the extraction of polymeric silica entities is anticipated, its structure depending on the framework Si/Al ratio. In agreement, ATR-IR experiments have confirmed dissolution of polymeric silicon-containing species that in the course of the alkaline treatment disintegrate into smaller entities. A direct relation between the type of porosity developed and the process of silicon extraction as measured in the liquid phase cannot be drawn.     

Chemoenzymatic synthesis of biotin-appended analogues of gangliosides GM2, GM1, GD1a and GalNAc-GD1a for solid-phase applications and improved ELISA tests

Biotinylated analogues of gangliosides GM2, GM1, GD1a and GalNAc-GD1a were synthesized in high yields using glycosyltransferases from Campylobacter jejuni. The presence of a biotin moiety in the aglycone part of these mimics allows for attachment of these materials onto various streptavidin-coated surfaces. Analysis of the interaction of biotin-appended GM1 with the B subunit of Escherichia coli heat-labile enterotoxin performed in a modified ELISA procedure shows the potential of this compound to replace the natural GM1 in toxin detection.     

Covalently attached saccharides on silicon surfaces

This paper presents the first functionalization of silicon surfaces with well-defined, covalently attached monolayers containing saccharides. Two methods were used to this aim: a thermal method (refluxing in mesitylene) and a recently developed, extremely mild photochemical method (irradiation with 447 nm at room temperature). The results were analyzed by FT-IR and angle-resolved X-ray photoelectron spectroscopy. The use of a two-dimensional detector in ARXPS allows for unparalleled, subnanometer resolution in the determination of the elemental composition of monolayers. Even for monolayers with a total thickness of only approximately 1.5 nm, a clear elemental depth profile can be obtained. Such analyses display for sialic acid-containing monolayers that the mild photochemical attachment does not destroy the (rather fragile) sialic acid moiety and that the sugar is present at the top of the monolayer and thus available for biological interactions.     

Spectral organization of ommatidia in flower-visiting insects

This article reviews recent advances of studies on the spectral organization of the compound eye in lepidopteran and hymenopteran insects. The compound eyes consist of ommatidia, which contain a set of photoreceptor cells. The common feature is that the ommatidia can be divided into three types, according to the combination of spectral classes of photoreceptors. Honeybees and nymphalid butterflies provide the simplest case with three photoreceptor classes having peak sensitivities in the ultraviolet (UV), blue (B), or green (G) wavelength region. These receptors populate the ommatidia in fixed combinations. In type I ommatidia, the main eight photoreceptors consist of one UV, one B, and six G receptors. Type II has two UV and six G receptors, and type III has two B and six G receptors. The organization is basically retained in all insect species studied so far, although some butterflies have more than six classes of spectral receptors, including those sensitive in the violet and red wavelength regions. To acquire these additional receptors, two distinct strategies are applied: the multiple opsin strategy, taken by the Japanese yellow swallowtail butterfly Papilio xuthus, and the filter strategy, used by the small white butterfly Pieris rapae.     

Thread-scalable evaluation of multi-jet observables

We have implemented the leading-color n-gluon amplitudes using the Berends–Giele recursion relations on a multi-threaded GPU. Speed-up factors between 150 and 300 are obtained compared to the CPU-based implementation of the same event generator. In this first paper, we study the feasibility of a GPU-based event generator with an emphasis on the constraints imposed by the hardware. Some studies of Monte Carlo convergence and accuracy are presented for PP→2,…,10 jet observables using of the order of 10¹¹ events.