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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 16 (1988), S. 231-241 
    ISSN: 1432-1017
    Keywords: Chromatin ; polynucleosomes ; chromatin condensation ; DNA ; flexibility ; molecular mobility ; ethidium ; fluorescence polarization ; divalent ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract We have studied the effects of Na+ (5–120 mM) and Mg2+ (0–6 mM) on the internal and overall flexibility of polynucleosome fragments from nucleasesolubilized chromatin from Ehrlich ascites cells. The mobility was monitored by the steady-state fluorescence polarization of the intercalated ethidium cation. The internal polynucleosome flexibility decreases continuously as the extended chromatin fragments are being compacted at increasing salt concentrations, and it can be further suppressed at ionic strengths above those where the 30 nm fiber is formed. The effect may be visualized as an initial formation of a loose 30 nm fiber that is further compacted at increasing ionic strengths. We observe several differences in the effects of Na+ and Mg2+ upon chromatin compaction. First, chromatin compacted by Mg2+ is less flexible than that compacted by Na+, suggesting a “tighter” chromatin structure with Mg2+. Second, Mg2+ affects the internal mobility in polynucleosome fragments shorter than 6–7 nucleosomes, which are too short to be compacted with Na+. Third, Mg2+ causes extensive macroscopic aggregation at concentrations above 0.2–0.3 mM, but the aggregation is uncorrelated with the intramolecular compaction. A quantitative evaluation of the overall polynucleosome “tumbling” mobility indicates that the compacted fragments possess more internal flexibility than do corresponding high molecular weight chromatin fibers. Finally, we note a correlation between the ethidium binding constant and the internal chromatin flexibility, possibly arising from lower torsional and “unwinding” flexibility of the linker DNA segments of compacted chromatin fibers.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1451-1456 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: By combining the time-of-flight or LIDAR principle with a Thomson backscatter diagnostic, spatial profiles of the electron temperature and density are measured in a magnetically confined fusion plasma. This technique was realized for the first time on the JET tokamak. A ruby laser (3-J pulse energy, 300-ps pulse duration, 0.5-Hz repetition rate) together with a 700-MHz bandwidth detection and registration system yields a spatial resolution of about 12 cm. A spectrometer with six channels in the wavelength range 400–800 nm gives a dynamic range of the temperature measurements of 0.3–20 keV. The stray light problem in the backscatter geometry is overcome by spectral discrimination and gating of the photomultipliers. A ruby filter in the spectral channel containing the laser wavelength allows calibration of the vignetting along the line of sight by means of Raman scattering, enabling the measurement of density profiles. The low level of background signal due to the short integration time for a single spatial point yields low statistical errors (ΔTe /Te ≈6%, Δne /ne ≈4% at Te =6 keV, ne =3×1019 m−3 ). Goodness-of-fit tests indicate that the systematic errors are within the same limits. The system is described and examples of measurements are given.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1070-1070 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Single Point Thomson Scattering System uses a multipulse ruby laser to measure Te and ne up to twenty times during a JET plasma pulse. The scattering volume is on the equatorial plane and, between plasma pulses, can be relocated to any one of seven specific points on a major radius. The collection system employs multimirror arrays and a triple prism spectrometer is used to eliminate stray laser light and disperse the scattered light. Novel features include two optoelectronic feedback systems which maintain alignment within the laser input and the collection systems. Sensitive components are located outside the biological shield, and those inside are compatible with remote handling procedures. The entire diagnostic can be remotely controlled via the JET computer system. Initial results from the diagnostic are presented.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 45 (1989), S. 562-566 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 45 (1989), S. 2012-2014 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 44 (1988), S. 502-504 
    ISSN: 1420-9071
    Keywords: Hexacyanoferrate(II) ; 134Cs ; cesium absorption ; biological half-life ; piglet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The efficacy of different hexacyanoferrates(II) in preventing the enteral absorption of134Cs was studied in piglets. As compared to the controls, oral application of134Cs together with KFe[Fe(CN)6], NH4Fe[Fe(CN)6], or Fe4[Fe(CN)6]3 resulted in a strong reduction of the134Cs-uptake by more than 97%. The decrease in enteral absorption depends on the dose of administered hexacyanoferrate(II), whereas differences between the compounds under study were small. The biological half-life of134Cs in non-hexacyanoferrate(II) treated piglets was 21.6±3.3 days (mean±SD).
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 8 (1987), S. 495-511 
    ISSN: 0192-253X
    Keywords: barley leaf development ; nuclear genes ; developmental control of transcription ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Groups of cDNA clones encoding abundant leaf proteins or derived from genes (gene families) with other features of interest have been selected from a barley leaf cDNA library. The characteriaztion of nine of the groups is summarized and includes information on the tissue specificity and light dependence of expression of their corresponding genes. Different types of control of gene expression are represented in the collection: leaf-specific expression, both stimulated and inhibited by light, constitutive expression, and expression that is maximal in one case in coleoptiles and in two cases in meristematic tissue. For the light-stimulated genes (gene families) encoding chloroplast proteins (Cab, RbcS, and plastocyanin), relative and absolute levels of messengers were determined as a function of cell age in sections of 7-day-old barley leaves grown under diurnal conditions. Key parameters of cell growth (protein, RNA, and DNA accumulation) were determined in the same leaf sections. The main conclusions of the expression studies are as follows: (1) Light is in no case a requirement for gene expression although it has significant stimulatory effect on some genes; (2) weak expression of some genes coding for chloroplast proteins was detected in the leaf-like, white coleoptiles, whereas expression in roots could not be detected; (3) The cab, rbcS, and plastocyanin genes are expressed very early during leaf cell differentiation, when the plastids morphologically are still in their amyloplast-amoeboid stages; (4) The expression of the cab, rbcS, and plastocyanin genes is not coordinated during leaf cell development.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1987), S. 117-118 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 305-310 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polycyclic peptide antibiotic, Nisin, has been analysed by plasma desorption mass spectrometry using two different sample preparation techniques and two versions of the commercial plasma desorption mass spectrometer, and a prototype with high resolving power. The spectra obtained allow identification of a major component and two minor analogues. Extensive fragmentation is observed in samples prepared by the electrospray technique, whereas only ions indicating the molecular weight are produced when the sample is adsorbed on nitrocellulose.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 1985-05-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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