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  • 1
    Keywords: NUCLEOSOME CORE PARTICLES ; Repeat length ; DNA DOUBLE HELICES ; SYNAPTONEMAL COMPLEX
    Abstract: Chromatin domains formed in vivo are characterized by different types of 3D organization of interconnected nucleosomes and architectural proteins. Here, we quantitatively test a hypothesis that the similarities in the structure of chromatin fibers (which we call "structural homology") can affect their mutual electrostatic and protein-mediated bridging interactions. For example, highly repetitive DNA sequences in heterochromatic regions can position nucleosomes so that preferred inter-nucleosomal distances are preserved on the surfaces of neighboring fibers. On the contrary, the segments of chromatin fiber formed on unrelated DNA sequences have different geometrical parameters and lack structural complementarity pivotal for stable association and cohesion. Furthermore, specific functional elements such as insulator regions, transcription start and termination sites, and replication origins are characterized by strong nucleosome ordering that might induce structure-driven iterations of chromatin fibers. We propose that shape-specific protein-bridging interactions facilitate long-range pairing of chromatin fragments, while for closely-juxtaposed fibers electrostatic forces can in addition yield fine-tuned structure-specific recognition and pairing. These pairing effects can account for some features observed for mitotic and inter-phase chromatins.
    Type of Publication: Journal article published
    PubMed ID: 23860914
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biological physics 10 (1982), S. 43-50 
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The use of electrical fields to guide, hold and fuse cells is described. The electrical fusion process consists of two steps: the cells are collected to form pearl-chains between Pt electrodes by the action of dielectrophoresis, then a brief DC pulse is applied, such that the breakdown voltage of the membranes is briefly exceeded and cell-to-cell juncture of the membranes occurs around the pore formed by the pulse. Giant fused cells (diameter up to 100 m) can be formed by the electrically mediated fusion of mouse 3T3 fibroblast cells, provided that pronase is added just before field application.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biological physics 10 (1982), S. 31-42 
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Systems of linear inhomogeneous rate equations for reaction-diffusion kinetics are solved utilizing a Green's integral operator technique. The general theory for the eigenvalues and eigenfunctions of n-component linear systems undergoing diffusion and reaction is derived. The time development of temporal oscillations of the system's reactants is studied. Systemic homogeneity is related to a quantity defined as redundancy. The latter is a function of the system's entropy and a correlation is made between redundancy and noise. It is hypothesized that this correlation may provide a tie between the time development of noise and the time development of pathology in living systems.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biological physics 10 (1982), S. 65-73 
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The hazard of ambient cigarette smoke to nonsmokers is studied by comparing the average dose of exposure to ambient smoke of nonsmokers with the dose of exposure to primary smoke of smokers with due consideration of the possible nonlinear effect on low-density exposures. The maximum risk is estimated by assuming a linear response. The result is that the effect of ambient smoke is 1/13 of that due to primary smoke. Based on the meager information on the nonlinear effect, a minimum estimate is obtained which reduces the risk of ambient smoke to 1/60 of that of primary smoke. Thus the ambient smoke is estimated to cause an excess of deaths between 50,000 and 10,000 a year in a population of 220,000,000, or to reduce the life expectancy by an amount between 225 days and 48 days.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Various aminoglycoside antibiotics—tobramycin "analytical standard"; tobramycin, gentamycin, kanamycin, and amikacin, all containing preservatives added in pharmaceutical preparations; and streptomycin—without preservatives—yield in aqueous solutions a conductance peak when titrated against a heparin aqueous solution, indicating the formation of a charge transfer complex, which subsequently dissociates. At the volume ratio corresponding to the peak, a colloidal suspensoid forms which is possibly a micellar complex stabilized by the ions produced by the dissociation of the complex. The clinical significance of this interaction is suggested by preliminary microbiological tests. The possible effects of plasma protein binding and dissociation of the complexes here reported in tissues, however, were not studied. In the interaction with heparin, the aminoglycoside antibiotics appear to act as electron acceptors, though heparin is reported to act as an acceptor against chlorpromazine, which is well known to be a strong electron donor. There appears to be an interaction between nonpreserved tobramycin and the preservative added for the pharmaceutical preparation, which would explain the difference in titration behavior between the antibiotic alone and the antibiotic with preservative. Conductance titrations of heparin against penicillin and cloxacillin, which are not aminoglycosides, show no evidence of complexation or any other interaction. No suspensoid forms.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biological physics 10 (1982), S. 102-102 
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biological physics 10 (1982), S. 75-84 
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The density of individualArtemia cysts has been determined by sedimentation velocity measurements at unit gravity. Dried cyst (〈 0.02 g H2O/g dry weight) densities,ρ s were obtained by successive sedimentation in two nonpenetrating organic solvents. This removes geometric terms from the equation relating density to sedimentation velocity. Hydrated cysts (≈ 1.68 g H2O/g dry weight) were sedimented in 0.0750 m NaCl to obtain their density (ρ c). Values ofρ s,ρ c, and their ratios were found to be independent of cyst volume; therefore, the weight fraction of water in hydrated cysts is very nearly the same in cysts of greatly different size. It can be concluded that measurement of the water content of large populations of these cysts accurately reflects the water content of individual cysts, a point which has been assumed in previous work on this system. Ifρ s does not change appreciably when dried cysts are fully hydrated then the density of their water,ρ w, can be calculated to be 1.022 g/cm3 (±0.0011 ρ). That value is significantly higher than the density of pure water and is very close to estimates ofρ w in skeletal muscle and amphibian oocytes obtained by others. However, the assumption thatρ s is independent of hydration is open to serious criticism, for all these studies. Consequently, conclusions and interpretations derived from such measurements must be considered to be tentative and uncertain.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Nuclear relaxation studies were performed on Mn2+ and Co2+-substituted human carbonic anhydrase C (HCAC) to determine the active site configurations of the products ofp-nitrophenylacetate hydrolysis. Metal-ligand distances calculated from the magnitudes of the paramagnetic effect on longitudinal nuclear relaxation rates indicate direct coordination of the phenolic oxygen ofp-nitrophenol to the enzyme-bound Mn2+ in the ternary HCAC-Mn2+-p-nitrophenol complex. The Mn2+ top-nitrophenol distances in the quaternary HCAC-Mn2+-acetate-p-nitrophenol and HCAC-Co2+-p-nitrophenol-acetate complexes are also consistent with coordination ofp-nitrophenol to the enzyme-bound metal via the phenolic oxygen. However, the orientation of the aromatic ring ofp-nitrophenol appears to be different for the Co2+ and Mn2+-enzymes. The carboxyl carbon of acetate is in the range of innersphere distances expected for direct coordination of a carboxyl oxygen to the enzyme-bound Mn2+, and the acetate molecule is folded around the metal. Although direct coordination of acetate to the metal in the HCAC-Co2+-p-nitrophenol-acetate complex cannot be inferred from our data, weak innersphere complexation with a somewhat longer Co2+-carboxyl oxygen bond distance is not excluded. We found small but significant differences in the arrangement of the products at the active sites of the Co2+ and Mn2+-enzymes which may be responsible for the differences in their reactivities in the hydrolysis reaction.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The isolated midgut of Lepidopteran larvae actively transports potassium from the hemolymph side to the lumen side when chamber-mountedin vitro. Active potassium transport is not affected by ouabain and is not dependent on sodium. A long controversy has existed over the fraction of the midgut cells that participate in active transport of potassium. One set of investigators demonstrated that only a small fraction of the tissue potassium was involved in the pool of potassium involved in active transport whereas a separate set of workers found that virtually all of the exchangeable potassium was thus involved. The results presented in this paper show that the insect's diet affects whether some or all the cells are in the pool, known formally as a transport pool. Leaf-reared insects are characterized by a small pool whereas diet-reared insects are characterized by a large pool. These results are shown to correlate with the pool size results of previous investigators.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biological physics 10 (1982), S. 111-112 
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Type of Medium: Electronic Resource
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