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  • 1
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 76 (1983), S. 281-287 
    ISSN: 1432-1424
    Keywords: electron probe ; X-ray microanalysis ; bone marrow ; red blood cells ; transport ; membrane ; erythropoiesis ; hemoglobin ; blood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The change from high potassium dog erythroid cells to low potassium red blood cells during erythropoiesis was investigated by X-ray microanalysis of single cells. A correlation of morphology and composition, using freeze-dried cryosectioned preparations, showed that during normal erythropoiesis in dog bone marrow the switch from high potassium to low potassium occurs during the change from early to late nucleated erythroid cells, and in synchrony with the beginning of iron accumulation. In contrast, during rapid erythropoiesis in dogs with phenylhydrazine-induced anemia, the most prominent change in cation composition as well as the accumulation of iron occurs during the reticulocyte stage in the peripheral blood. The determination of the absolute amounts of sodium and potassium per cell in stress reticulocytes of peripheral blood indicated that the changeover from high potassium to low potassium actually occurs by the loss of cellular potassium during volume reduction, with little change in the amount of cellular sodium. This suggests that maturation may involve a selective change in potassium permeability. Lastly, it was observed that not all cells followed the predominant pathway with respect to change in morphology, membrane permeability and hemoglobin synthesis. One particular subpopulation appeared to follow a sequence which expressed the complete HK to LK transition before the accumulation of any iron; this implies the possibility of completing protein synthesis in a low potassium intracellular milieu.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 82 (1984), S. 137-143 
    ISSN: 1432-1424
    Keywords: rubidium uptake ; X-ray microanalysis ; bone marrow ; red blood cells ; transport ; membrane ; erythropoiesis ; hemoglobin ; blood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Rubidium uptake was measured in single erythroid and myeloid cells of rabbit by means of X-ray microanalysis. It was found in the nucleated bone marrow cells that after incubation in rubidium the sums of potassium and rubidium concentrations were similar to the original potassium concentrations, indicating that there was one-to-one replacement of potassium by rubidium. Although the nuclear potassium and rubidium concentrations were higher than those in the cytoplasm, the nuclear and cytoplasmic ratios of K/Rb were similar. This implies that the potassium in both compartments exchanged freely with rubidium. In the erythroid line of cells there was a continuous reduction of potassium transport activity during the maturation process as indicated by the decrease in rubidium uptake rates. The uptake was measured in seven groups of cell types that could be distinguished on the basis of morphology and chemical composition. The order of the groups from high to low rubidium uptake were: esosinophilic myelocyte 〉 early erythroblast and thinrimmed erythroblast 〉 late erythroblast 〉 early bone marrow red cell 〉 late bone marrow red cell 〉 peripheral blood red cell. Thus, there is a continuous decrease in rubidium transport as the erythroid cells mature.
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  • 5
    ISSN: 0392-6737
    Keywords: Mössbauer effect ; other γ-ray spectroscopy ; Other topics in biophysics and medical physics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary This paper describes a preliminary investigation of the mechanisms of Fe(II) oxidation and storage of Fe(III) in the bacterioferritin ofEscherichia coli (EcBFR). Using Mössbauer spectroscopy to examine the initial oxidation of iron by EcBFR we have confirmed that this ferritin exhibits «ferroxidase» activity and have shown that dimeric and monomeric iron species are produced as intermediates. We compare the characteristics of ferroxidase activity in EcBFR with those of human H-chain ferritin (HuHF) and discuss the different Mössbauer parameters of their dimeric iron with reference to the structures of their di-metal sites. In addition, we present preliminary findings suggesting that after an initial «burst», the rate of oxidation is greatly reduced, possibly due to blockage of the ferroxidase centre by bound iron. A new component, not found in HuHF and probably representing a small cluster of Fe(III) atoms, is reported.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 70-73 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Laue diffraction patterns have been recorded with synchrotron radiation for some very small crystals; in most of them the reflections are elongated radially. The Laue geometry is particularly sensitive to mosaic spread, and a relationship between mosaic spread and Laue spot extension is deduced. It appears that many very small crystals have a large mosaic spread (0.5-1° or more) which is probably the reason why they did not grow bigger.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Cryobiology 4 (1967), S. 85-89 
    ISSN: 0011-2240
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Bioenergetics 462 (1977), S. 153-160 
    ISSN: 0005-2728
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 993-1003 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the performance of GaAs/AlGaAs quantum-well infrared detectors exhibiting intersubband absorption in the 8–14 μm band. The dark current characteristics have been investigated as a function of barrier width and electron density in the well and compared with a model which takes into account thermionic emission and thermally assisted tunneling in the Wentzel–Kramers–Brillouin approximation. The model gives a good description of the data and is extended to predict the variation of detectivity and background limited operating temperature with structural parameters.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 3472-3480 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report photoluminescence measurements made on free-standing, lattice-matched GaAs/AlGaAs and pseudomorphic InGaAs/GaAs quantum boxes fabricated by laterally patterning quantum wells using electron-beam lithography and either reactive ion etching or ion beam milling. At temperatures below 10–20 K the luminescence efficiency of most of the GaAs quantum-box arrays tends to scale with the volume of quantum-well material remaining after processing even for the smallest boxes which have lateral dimensions of only 40–50 nm. These observations indicate that the surface recombination rate in GaAs submicron structures can be small relative to the radiative recombination rate at low temperatures. In contrast, radiative recombination in the InGaAs/GaAs quantum boxes is strongly quenched for lateral dimensions less than 500 nm. We suggest that this is because photoexcited carriers are laterally localized in the GaAs boxes by potentials of the order of a few meV, possibly associated with interface disorder or strain relaxation, and that such localization effects are smaller in the InGaAs boxes.
    Type of Medium: Electronic Resource
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