Article

The Permeability of the Erythrocyte-Like Cells of Phascolosoma gouldi

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Chapter
Abgehandelt werden in diesem Abschnitt im Tierkörper aufgefundene Verbindungen von Metallen (Fe, Cu, V, Zn) mit Proteinen, Peptiden oder Aminosäuren, in denen das Metall entweder stöchiometrisch an spezifische Liganden des Trägers oder an mit diesen verknüpften, abspaltbaren, nicht porphyrinartigen Gruppen* gebunden ist. Zu ersteren gehören Hämocyanine, Coeruloplasmin, Hämocuprein und Hepatocuprein, Hämerythrin, Eisen(III)-transferrin, die Metallverbindungen von Conalbumin sowie Ferrichrom und Zinkcysteinat ; zu letzteren das Hämovanadin. Eine Sonderstellung nehmen die hoch eisenhaltigen Systeme Ferritin und Hämosiderin ein.
Article
1.1. The molecular weight of hemerythrin from Phascolosoma gouldi is probably 120,000. There are 8 oxygen molecules and 19 iron atoms in each molecule of this size.2.2. The change in optical density at 800 mμ which occurs on oxygenation of the protein is not proportional to the degree of saturation.
Article
1.1. A modification of the osmotic lysis method, taking into account differences in osmotic resistance, is introduced. This method allows a more fundamental physicochemical interpretation of the permeability process and the calculation of permeability coefficients.2.2. Evidence is presented that the reflection coefficient for glycerol is near to one for human red blood cells as well as for pig red blood cells.3.3. The permeability coefficient proved to be independent of differences in lysis behaviour of erythrocytes, which were treated with isotonic solutions of different non-permeants.4.4. The osmotic resistance in NaCl solutions is strongly time dependent, whereas in sucrose solutions this parameter is time independent and gives the best approximation of the original osmotic resistance of the red blood cell.
Article
A model is put forward to describe the non-mediated transfer of non-electrolytes in terms of diffusion in homogeneous networks.
Article
The energy barrier model of a cellular membrane proposed by Danielli 1952 and modified by Zwolinski, Eyring & Reese 1949 is employed in conjunction with the equations derived from absolute reaction rate theory by the latter investigators. It is assumed, in agreement with Danielli, that the major barrier to entry of a slowly penetrating nonelectrolyte molecule into a lipid membrane is at the membrane-water interface rather than in the membrane itself. It is further assumed that the molecule passing from water into a lipid membrane goes through a partially vaporized or “exposed” state where a statistical fraction of the penetrating molecules is associated with neither water nor lipid.The peak free energy of activation for entry into the membrane, ΔFM∗, may be equated to (1 − γ), where γ is related to the fraction of the molecule exposed during passage, ΔFL and ΔFV are the Gibbs free energy changes on going from an aqueous phase to a lipid phase and from an aqueous phase to a vapor phase, respectively, and ΔFB∗ is an additional activation energy barrier which is assumed constant for similar molecules. For a molecule passing completely into a dissociated or a vapor state, γ = 1·0; for a molecule completely unexposed or entirely in contact with either one or both phases, γ = 0.The free energy values are evaluated as follows: in terms of the permeability constant at 20°C, Φ; ΔFL in terms of the olive oil : water partition coefficient, C; and ΔFV in terms of the vapor pressure of the pure solute at 20°C, P. The following equation is derived for determination of γ: .Graphs of log () versus log () illustrate that most oxygen containing nonelectrolytes, ranging from the slowly penetrating erythritol to the rapidly penetrating propanol, fall close to a straight line. The slope of the line, γ, is near 0·6 for animal cells (ox and rabbit erythrocytes, sipunculid worm hemolymph cells, sea urchin eggs and rat lymphocytes) and near 0·4 for an algal cell (Chara).
Article
Using unfertilized eggs of Arbacia punctulata as natural osmometers an attempt has been made to account for the course of swelling and shrinking of these cells in anisotonic solutions by means of the laws governing osmosis and diffusion. The method employed has been to compute permeability of the cell to water, as measured by the rate of volume change per unit of cell surface per unit of osmotic pressure outstanding between the cell and its medium. Permeability to water as here defined and as somewhat differently defined by Northrop is approximately constant during swelling and shrinking, at least for the first several minutes of these processes. Permeability is found to be independent of the osmotic pressure of the solution in which cells are swelling. Water is found to leave cells more readily than it enters, that is, permeability is greater during exosmosis than during endosmosis.
The permeability of the Arhacia egg to ammonium salts
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Le pouvoir oxyphorique du liquide coelomique et des hematies de Sipunculns nudus
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