Blue light regulates processes such as the development of plants and fungi and the behaviour of microbes. Two types of blue-light receptor flavoprotein have been identified: cryptochromes, which have partial similarity to photolyases, and phototropins, which are photoregulated protein kinases. The former have also been found in animals with evidence of essential roles in circadian rhythms. Euglena gracilis, a unicellular flagellate, abruptly changes its swimming direction after a sudden increase or decrease in incident blue light intensity, that is, step-up or step-down photophobic responses, resulting in photoavoidance or photoaccumulation, respectively. Although these photobehaviours of Euglena have been studied for a century, the photoreceptor molecules mediating them have remained unknown. Here we report the discovery and biochemical characterization of a new type of blue-light receptor flavoprotein, photoactivated adenylyl cyclase, in the photoreceptor organelle of Euglena gracilis, with molecular genetic evidence that it mediates the step-up photophobic response.
The structure of C6o molecules adsorbed on the Cu(l 1 l)-(l x 1) surface has been investigated by scanning tunneling microscopy (STM). Bias voltage dependent STM images of individual C6o molecules in the monolayer film showed unique intramolecular structures with a threefold symmetry. The observed images agree well with those calculated using the local density approximation. With charge transfer from the Cu(l 11) substrate to the monolayer film, the €50 molecule ratchets to threefold hollow sites. PACS numbers: 68.35.Bs, 61.16.Ch, 61.46,+w, 68.65.+g The investigation on carbon fullerenes discovered by Kroto et al. [1] has been a growing exciting field, since Kratschmer et al. [2] succeeded in the extraction and purification of C60 and other fullerenes. Discovery of superconductivity by Hebard et al. [3] in a K-doped fullerene sample, K3C60, added further excitement with promising practical applications [4]. Scanning tunneling microscopy (STM) has been successfully used to reveal the geometric and electronic structure of the fullerenes with molecular resolution. The nucleation and growth of C60 film and its structure on various substrates, such as Au(100) [5], (111) and (110) [6], Ag(lll) [7], highly oriented pyrolytic graphite (0001) [8], GaAs(llO) [9], and Si(l 11) [10], and (100) [11] have been major interests in STM studies. Investigations on other fullerene films, such as C70 [12], Cu [13], and SCC74/SC2C74 [14], and Sc 2 C 8 4 [15] on the Si (100)-(2x 1) surface have been reported using the FI-STM (field ion scanning tunneling microscope), elucidating the growth kinetics and geometric structures.The Cu(l 11) surface is one of the ideal surfaces for the growth of C60 film similar to the bulk [16], since the lattice mismatch is small (2%) between the nearest neighbor (nn) distance (10.0 A) of the bulk Ceo crystal and 4 times of the Cu-Cu nn distance (10.2 A). A recent study of C 60 adsorption on the Cu(lll), (110), and (100) surfaces using x-ray photoemission spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS) and other techniques [17] concluded the following: (1) The Cu substrate donates charge to the lowest unoccupied molecular orbital (LUMO) band of C60 as K does in K x C6o films and (2) single-domain epitaxy with a (4x4) superlattice and successive layer-bylayer growth can be achieved on the Cu(l 11) surface.In this Letter, we report the intramolecular structure of C60 molecules on the Cudll)-(lxl) surface using the FI-STM [18]. C60 molecules ratchet to hollow sites and are ordered due to the substrate-C6o and C60-C60 interactions. Observed intramolecular structure with a unique threefold symmetry agrees well with the charge density around the molecule calculated using the local density approximation (LDA). It was confirmed in the STM images and calculated charge density that excess charge on the molecule is present on top of the pentagonal rings.The experimental details of the extraction and purification of high-purity C60 powder (purity of 99.95%, the rest being C70) [19], a...
Gonad-stimulating substance (GSS) of starfish is the only known invertebrate peptide hormone responsible for final gamete maturation, rendering it functionally analogous to the vertebrate luteinizing hormone (LH). Here, we purified GSS of starfish, Asterina pectinifera, from radial nerves and determined its amino acid sequence. The purified GSS was a heterodimer composed of 2 different peptides, A and B chains, with disulfide cross-linkages. Based on its cysteine motif, starfish GSS was classified as a member of the insulin/insulin-like growth factor (IGF)/relaxin superfamily. The cDNA of GSS encodes a preprohormone sequence with a C peptide between the A and B chains. Phylogenetic analyses revealed that starfish GSS was a relaxin-like peptide. Chemically synthesized GSS induced not only oocyte maturation and ovulation in isolated ovarian fragments, but also unique spawning behavior, followed by release of gametes shortly after the injection. Importantly, the action of the synthetic GSS on oocyte maturation and ovulation was mediated through the production of cAMP by isolated ovarian follicle cells, thereby producing the maturationinducing hormone of this species, 1-methyladenine. In situ hybridization showed the transcription of GSS to occur in the periphery of radial nerves at the side of tube feet. Together, the structure, sequence, and mode of signal transduction strongly suggest that GSS is closely related to the vertebrate relaxin.gonadotropin ͉ gonad-stimulating substance ͉ insulin-like growth factor/relaxin superfamily ͉ 1-methyladenine ͉ in situ hybridization
Radioactive endohedral 7 Be@C 60 can be detected using radiochemical and radiochromatographic techniques in the final solvent. Such a 7 Be atom can penetrate into the C 60 cage to produce 7 Be@C 60 by a recoil process of the nuclear reactions. An ab initio molecular dynamics simulation was carried out to demonstrate that a direct insertion process is really possible. Both the experimental and the theoretical results were consistent with each other. [S0031-9007(96)01431-7]
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