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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 6 (1973), S. 508-510 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Reassociation kinetics of DNA from the macronucleus of the ciliate, Tetrahymena pyriformis GL, has been studied. The genome size determined by the kinetic complexity of DNA was found to be 2.0×108 base pairs (or 1.2×1011 daltons). About 90% of the macronuclear DNA fragments 200–300 nucleotides in length reassociate at a rate corresponding to single-copy nucleotide sequences, and 7–9% at a rate corresponding to moderate repetitive sequences; 3–4% of such DNA fragments reassociate at C0t practically equal to zero. To investigate the linear distribution of repetitive sequences, DNA fragments of high molecular weight were reassociated and reassociation products were treated with Sl-nuclease. DNA double-stranded fragments were then fractionated by size. It has been established that in the Tetrahymena genome long regions containing more than 2000 nucleotides make up about half of the DNA repetitive sequences. Another half of the DNA repetitive sequences (short DNA regions about 200–300 nucleotides long) intersperse with single-copy sequences about 1,000 nucleotides long. Thus, no more than 15% of the Tetrahymena genome is patterned on the principle of interspersing single-copy and short repetitive sequences. Most of the so called “zero time binding” or “foldback” DNA seem to be represented by inverted self-complementary (palindromic) nucleotide sequences. The conclusion has been drawn from the analysis of this fraction isolated preparatively by chromatography. About 75% of the foldback DNA is resistant to Sl-nuclease treatment. The Sl-nuclease resistance is independent of the original DNA concentration. Heat denaturation and renaturation are reversible and show both hyper and hypochromic effects. The majority of the inverted sequences are unique and about 20% are repeated tens of times. According to the equilibrium distribution in CsCl density gradients the average nucleotide content of the palindromic fraction does not differ significantly from that of total macronuclear DNA. It was shown that the largest part of this fraction of the Tetrahymena genome are not fragments of ribosomal genes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 74 (1979), S. 105-124 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The arrangement of repetitive and single-copy DNA sequences has been studied in DNA of some species of Echinodermata — sea urchin, starfishes and sea-cucumber. Comparison of the reassociation kinetics of short and long DNA fragments indicates that the pattern of DNA sequence organization of all these species is similar to the so called “Xenopus pattern” characteristic of the genomes of most animals and plants. However, substantional variations have been found in the amount of repetitive nucleotide sequences in DNA of different species and in the length of DNA regions containing adjacent single-copy and repetitive sequences. Measurements of the size of S1-nuclease resistant reassociated repetitive DNA sequences show a variability of ratios between long and short repetitive DNA sequences of different species. — The degree of divergence of short and long repetitive DNA sequences and single-copy DNA was studied by molecular hybridization of the sea urchin Strongylocentrotus intermedius 3H-DNA with the DNA of other species and by determination of the thermostability of the hybridized molecules so obtained. All three fractions of S. intermedius DNA contain sequences homologous to DNA of the other echinoderm species studied. The results obtained suggest that short repetitive DNA sequences are those which have been most highly conserved throughout the evolution of Echinodermata. A new hypothesis is proposed to explain the nature of the evolutionary changes in DNA sequence interspersion patterns.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-4978
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The radius of gyration of mononucleosomes determined by X-ray small-angle scattering is 4.35 nm. The maximum dimension determined from the distance distribution function and the volume amount to 12.9 nm and 370 nm3, respectively. For a particular fraction of polynucleosomes a mean radius of gyration 16 nm, a maximum dimension 65 nm, and a mean volume 25,240 nm3 is obtained.The shape is approximated by an elongated cylinder having a diameter of 28 nm. A polynucleosome is built up from 69 nucleosomes, on the average. The distance of neighbouring nucleosomes in the polynucleosome amounts to 5.2 nm. Moreover, this distance shows that the nucleosomes in the polynucleosome are very closely packed.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4978
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-4978
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A comparative study of the condensation of reconstituted complexes of circular SV40 DNA with core histones from calf thymus and sea urchin sperm was performed using sedimentation and electron microscopic techniques. It is shown that in low ionic strength solutions both types of complexes are similar to native ‘minichromosomes’. In the region from 0.08 to 0.16 M NaCl the complexes of SV40 DNA with thymus histones form small compact particles. By contrast, the compaction of the SV40 DNA complexes with sperm histones results in the formation of giant intermolecular associates. The results obtained may mean that histone H2B of sea urchin sperm participates in the formation of a higher order structure in sperm chromatin.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chemical and petroleum engineering 24 (1988), S. 565-566 
    ISSN: 1573-8329
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-9066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Conclusions 1. The number of simultaneously growing dendrites determined by plotting profilometer records of basis metal surfaces is in good agreement with the value obtained with an electron microscope, which is of the order of 106 per 1 cm2 of cathode surface [5]. 2. The character of growth of a dispersed deposit is largely determined by the conditions under which hydrogen evolution takes place on the electrode surface. The magnitude of hydrogen evolution polarization, which is determined by the nature of the basis material and the true surface of the electrode (its profile), controls the character of current density variation on the tips of dendrites, i.e., the rate of their growth. The greater the hydrogen overvoltage on a given material (vitreous carbon) and the smaller the active surface of the material (a gauze electrode) the higher is the rate of growth of dendrites, resulting in the formation of finer powders.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Powder metallurgy and metal ceramics 17 (1978), S. 899-900 
    ISSN: 1573-9066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Conclusions 1. Statistical mathematical models have been obtained describing the dependence of the particle size (amount of the+0.045-mm fraction) and apparent density of copper powders on the basic parameters of the electrodeposition process. 2. The mathematical models provide a close approximation to the real industrial process within the process parameter ranges for which they were obtained. 3. The properties of electrodeposited copper powders can be controlled, and a suitable method has been developed for the selection of process parameters enabling copper powders of predetermined properties to be obtained. The method has been tested under pilot-plant conditions and adopted at the Uralélektromed' Combine.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of alcohol-water solvents on the conformation of native DNA was studied by the methods of flow birefrigence and viscometry. Conformational transitions of DNA were observed at low alcohol concentrations corresponding to the destruction of the water spatial structure. A change in the secondary structure of the DNA molecule was observed at high ethanol concentrations and is discussed in the paper.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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