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  • 1
    Electronic Resource
    Electronic Resource
    Immunocytochemical visualization of the centromeres during male and female meiosis in Lilium longiflorum (1997)
    Springer
    Chromosoma 106 (1997), S. 435-445 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Immunofluorescence staining with an antiserum raised against a presumptive meiotic histone, which has been shown to appear prior to male meiosis in liliaceous plants, preferentially stained the centromere (kinetochore) region of meiotic chromosomes in microsporocytes and megasporocytes. Using this antiserum, we were able clearly to visualize the centromeres at all important meiotic stages in microsporocytes, namely, the association and fusion of centromeres of homologous chromosomes at zygotene-pachytene in prophase I, the disjunction of the homologous centromeres at diplotene, the doubling of each centromere at metaphase I and nonseparation of the sister centromeres at anaphase I, by confocal laser scanning microscopy. Thus, this report provides a complete picture of the behavior of centromeres during meiosis in a eukaryote for the first time. This antiserum also decorated centromeres during female meiosis in cryo-sectioned megasporocytes, but did not stain the centromeres of mitotic chromosomes in root-tip meristem. From these observations, it is suggested that a meiosis-specific centromere protein is required for the meiosis-specific behavior of the centromere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050265
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  • 2
    Electronic Resource
    Electronic Resource
    A novel histone variant localized in nucleoli of higher plant cells (1999)
    Springer
    Chromosoma 108 (1999), S. 190-199 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract.  Immunofluorescence staining with antisera raised against p35, a basic nuclear protein that accumulates in the pollen nuclei of Lilium longiflorum, specifically stained the nucleoli in interphase nuclei of somatic tissues, including root and leaf, and in pachytene nuclei during meiotic division, whereas antisera raised against histone H1 uniformly stained the entire chromatin domain with the exception of the nucleoli in these nuclei. Further, p35-specific antisera stained the nucleoli in root and leaf nuclei of the monocotyledonous plants Tulipa gesneriana, Allium cepa and Triticum aestivum and of the dicotyledonous plants Vicia faba and Nicotiana tabacum. Thus, these novel antisera stained the nucleoli in cells of all higher plants examined, although the staining patterns within nucleoli were somewhat different among plant species and tissues. The full-length cDNA of p35 was cloned on the basis of the partial amino acid sequence. The deduced amino acid composition and amino acid sequence of p35 indicate that this nucleolar protein is a novel variant of histone Hl. Further, p35 was strongly bound to ribosomal DNA in vitro. The results of immunoblotting of histones extracted from each tissue of the various plant species with the nucleolus-specific antibodies also suggested the conservation of similar epitope(s) in both mono- and dicotyledonous plants. From these results, it is suggested that similar variants of histone Hl are specifically distributed in the nucleoli of all plant species and help to organize the nucleolar chromatin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050368
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  • 3
    Electronic Resource
    Electronic Resource
    Unusual core histones specifically expressed in male gametic cells of Lilium longiflorum (2000)
    Springer
    Chromosoma 108 (2000), S. 491-500 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. We have cloned three novel histone genes using antibodies that recognize only nuclei of the male gametic (generative and sperm) cells of Lilium longiflorum. The deduced amino acid sequence of each clone shows only between 40% and 50% identity with the H2A, H2B and H3 somatic core histones of other plant species. Transcripts of these genes were first detected in bicellular pollen soon after microspore mitosis, and their mRNAs, as revealed by in situ hybridization, were observed only in the cytoplasm of the generative cells. As expression of these three genes was specific to generative cells within the bicellular pollen, we designated the clones gH2A, gH2B and gH3. Immunocytochemistry further revealed that the proteins encoded by these genes accumulated in the elongating and condensing generative nucleus during development of bicellular pollen, and were most abundant in the two sperm nuclei within an elongated pollen tube. We therefore propose that these male gamete-specific core histones contribute to chromatin condensation of male gametes or to chromatin remodeling, and result in the repression of gene expression in male gametes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050401
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  • 4
    Electronic Resource
    Electronic Resource
    Scanning tunneling microscope study of microcrystalline silicon surfaces in air (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 427-429 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surfaces of microcrystalline silicon films prepared by the glow discharge method have been investigated by a scanning tunneling microscope (STM) in air. Grain-like structures of 30–80 nm size which correspond to transmission electron microscope data have been observed. The film surface was found to be geometrically rather flat but the structure was observed electrically, that is, the resistivity seemed to be inhomogeneous due to preferential oxidation. Also, degradation of STM images of a HF-etched microcrystalline silicon surface has been observed for the first time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100941
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  • 5
    Electronic Resource
    Electronic Resource
    A scanning tunneling microscopy/spectroscopy system for cross-sectional observations of epitaxial layers of semiconductors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1664-1667 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have constructed a new scanning tunneling microscope (STM) using two mechanical stages. One (z stage) is for approaching the tip to the sample surface and the other (x stage) is for one-dimensional movement of the sample to observe a specific area of the sample surface. The stages move so precisely that the distance between the tip and the sample is constant during the sample movement. It enables us to find the specific area quickly. Another feature of the STM is a novel data accessing method which realizes high-speed scanning tunneling spectroscopy (STS) measurement. A great deal of data are accessed at high speed by a personal computer equipped with 32-megabyte random access memory (RAM). Using this system, STM and STS measurements of cleaved (110) surfaces of Ga0.47In0.53 As/InP multiquantum wells were performed in air.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141129
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  • 6
    Electronic Resource
    Electronic Resource
    Imaging and probing electronic properties of self-assembled InAs quantum dots by atomic force microscopy with conductive tip (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 844-846 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atomic force microscopy with a conductive probe has been used to study both the topography and the electronic properties of 10-nm-scale self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy on n-type GaAs. The current flowing through the conductive probe normal to the sample surface is measured for imaging local conductance, while the deflection of cantilever is optically detected for disclosing geometrical structure. The conductance on InAs QDs is found to be much larger than that on the wetting layer, allowing imaging of QDs through measurements of local current. We attribute this change in conductance to the local modification of surface band bending associated with surface states on InAs QD surface. Mechanisms of electron transport through QDs are discussed based on current–voltage characteristics measured on QDs of various sizes. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123402
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrahigh vacuum atomic force microscope study of 10–30 nm scale GaAs ridge structure formation by molecular beam epitaxy (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 883-885 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The evolution of GaAs ridge structure formation by molecular beam epitaxy on a patterned substrate has been investigated using an ultrahigh vacuum atomic force microscope. It is found that the morphology of ridges can be quite irregular with random formation of various facets in the intermediate phase of growth, but self-smoothing processes of the lateral facets take place later on, leading to very sharp and smooth ridge structures in the end. The ridge top is quite sharp and straight with the height fluctuation of within 1–2 nm over the length of 1.4 μm. The role of the Ga atom flows from the side (111)B surfaces to the top (001) surface and their local modulations are considered to account for these observations. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118303
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  • 8
    Electronic Resource
    Electronic Resource
    Observation of the InP surface thermally cleaned in an arsenic flux using a scanning tunneling microscope (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1588-1590 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An InP surface thermally cleaned in an arsenic flux was observed using an ultrahigh-vacuum scanning tunneling microscope (UHV-STM). In the STM image, about 1.6 nm period lines of 0.8 nm width with two rows were observed along the [110] direction. This result suggests that the surface comprises two In-In dimers and two missing dimers per (4×2) cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106294
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  • 9
    Electronic Resource
    Electronic Resource
    An elastically bent silicon monochromator for a neutron diffractometer (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 32 (1999), S. 525-529 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A new type of elastically bent perfect Si (EBP-Si) monochromator for a neutron diffractometer dedicated to protein crystallography has been developed and successfully applied to two such diffractometers. It was experimentally demonstrated that the monochromatic neutron intensity increased and the beam was focused at the sample position when the monochromator was suitably bent. A specially designed bender for the EBP-Si monochromator, already applied to several diffractometers, is described. The distinctive features of the EBP-Si monochromator are summarized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889899003192
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  • 10
    Electronic Resource
    Electronic Resource
    Direct observation of deuterium migration in crystalline-state reaction by single-crystal neutron diffraction. II. 3–1 Photoisomerization of a cobaloxime complex (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 245-253 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Single crystal neutron diffraction analysis of photo-exposed(3-cyanopropyl-d2α,α)-[(R)-1-phenylethylamine-d11]bis(dimethylglyoximato-d14)cobalt(III) was carried out in order to clarify the mechanism of the crystalline-state photoisomerization of the 3-cyanopropyl group bonded to the Co atom in some cobaloxime complexes. Before irradiation the two H atoms bonded to the C1 atom of the 3-cyanopropyl group were exchanged with the D atoms such as —CH2CH2CD2CN. On exposure to a xenon lamp, the cell dimensions of the crystal were gradually changed. After 7 d exposure the change became insignificantly small. The structure was analyzed by neutron diffraction. The 3-cyanopropyl group was transformed to the 1-cyanopropyl group such as —CD(CN)C(H1/2,D1/2)2CH3 with retention of the single-crystal form. This indicates that one of the D atoms bonded to C1 migrates to either position bonded to C2. The other atoms of the complex remained unchanged. These results indicate that photoisomerization proceeded in two steps: the 3-cyanopropyl group was isomerized to the 2-cyanopropyl group in the first place and then the 2-cyanopropyl group was transformed to the 1-cyanopropyl group. Moreover, it was made clear that the second-step isomerization was irreversible, since one of the D atoms was retained. The disordered structure at C2 is estimated to be caused by the interconversion between the 1-cyanopropyl group produced and its dehydrogenated olefin after the photoisomerization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768199012008
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