Erythrocyte membranes proton

All of the authors imply that separation of water phases probably occurs at the cellular level. The semi-permeable nature of the cell membrane towards ions and solutes which are capable of relaxing water protons provides compartments in which relaxation rates can be significantly different, even when water transport across the membrane is very rapid. Indeed this property of whole tissue has been used in the development of an NMR method of determining water transport across erythrocyte membranes (11). 

Only in brush-border membranes of some specialised cells and in erythrocyte membranes there seems to be an Mg-ATPase, which can be stimulated by anions, but only to a minor degree. Moreover, the properties of the enzyme in these membranes differ considerably from those of the activities in the microsomal and mitochondrial fractions of most other tissues. The anion sensitivity of the ATPase activity in the brush-border membranes of placenta and small intestine is a property of the alkaline phosphatase [37,41] and that in erythrocytes is part of the (Ca -b Mg )-ATPase activity [33,34]. Although this does not definitely exclude a role of the enzyme in anion transport, no valid arguments in favour of a role of this enzyme in anion or proton transport have been advanced. 

For biological membranes the situation is more complex. The results from erythrocyte ghosts and lipids (13) suggest nonpolar association through lipid hydrocarbon chains. As a test of the technique a membrane in which the bilayer conformation has been demonstrated by some independent technique is desirable. I have argued earlier from calorimetric evidence that the membrane of M. laidlawii is such a system. NMR spectra of M. laidlawii membranes taken in this laboratory do not, however, show discernible hydrocarbon proton resonance. We must consider, then, why the two techniques of calorimetry and NMR do not agree. 

Although the majority of the lipids in M. laidlawii membranes appear to be in a liquid-crystalline state, the system possesses the same physical properties that many other membranes possess. The ORD is that of a red-shifted a-helix high resolution NMR does not show obvious absorption by hydrocarbon protons, and infrared spectroscopy shows no ft structure. Like erythrocyte ghosts, treatment with pronase leaves an enzyme-resistant core containing about 20% of the protein of the intact membrane (56). This residual core retains the membrane lipid and appears membranous in the electron microscope (56). Like many others, M. laidlawii membranes are solubilized by detergents and can be reconstituted by removal of detergent. Apparently all of these properties can be consistent with a structure in which the lipids are predominantly in the bilayer conformation. The spectroscopic data are therefore insufficient to reject the concept of a phospholipid bilayer structure or to... 

In erythrocytes, external oxidants such as ferricyanide increase glycolysis (Harrison et al., 1991). Since these cells have no mitochondria, the increase in glycolysis could increase lactate or pyruvate formation, and excretion of these acids could be a basis for proton movement across the plasma membrane. In cells with mitochondria, the transmembrane electron transport decreases available NADH, so lactate formation would be decreased with consequent accumulation of pyruvate. The pyruvate... 

In the bloodstream, ferric iron binds tightly to circulating plasma transferrin (TF) to form diferric transferrin (FeTF). Absorption of iron into erythrocytes depends on basolateral membrane receptor-mediated endocytosis of FeTF by transferrin receptor 1 (TfR 1). FeTF binds to TfR 1 on the surface of erythroid precursors. These complexes invaginate in pits on the cell surface to form endosomes. Proton pumps within the endosomes lower pH to promote the release of iron into the cytoplasm from transferrin. Once the cycle is completed,TF and TfR 1 are recycled back to the cell surface. TF and TfR 1 play similar roles in iron absorption at the basolateral membrane of crypt enterocytes (Parkilla et al., 2001 Pietrangelo, 2002). 

The equilibrium between plasma and red cells has been disturbed by the reactions described so far. The concentration of HCO3 has increased relatively more in the erythrocytes than in the plasma the pH of plasma has fallen relatively more than the pH of the erythrocytes and the non-difftisible ion concentration in the erythrocytes has fallen because of the increase in protonation of proteins and hemoglobin. The membrane potential of the erythrocytes therefore becomes less negative, and the distribution of all diffusible ions must change in accordance with the new membrane potential. The ion shifts that occur rapidly are a movement of HCO3 out of the erythrocytes and a movement of Cr into the erythrocytes to provide electrochemical balance. This shift of chloride ions is referred to as the chloride shift (Figure 46-9, reactions 6 and 7). As a result of these ion fluxes, the concentration of chloride in the venous plasma is about 1 mmol/L lower than that in the arterial plasma. 

P.J. Henderson, J.D.McGivan, and J.B. Chappell, Biocftem./., 111,521 (1969). The Action of Certain Antibiotics on Mitochondrial, Erythrocyte and Artificial Phospholipid Membranes The Role of Induced Proton Permeability. 

The control of surface functionality by proper selection of the composition of the LB films and/or the self-assembling (amphiphatic) molecular systems can mimic many functions of a biologically active membrane. An informative comparison is that between inverted erythrocyte ghosts (Dinno et al., 1991 Matthews et al., 1993) and their synthetic mimics when environmental stresses are imposed on both systems. These model systems can assist in mechanistic studies to understand the functional alterations that result from ultrasound, EM fields, and UV radiation. The behavior of carrier molecules and receptor site functionality must be mimicked properly along with simulating disturbances in the proton motive force (PMF) of viable cells. Use of ion/electron transport ionomers in membrane-catalyst preparations is beneficial for programs such as electro-enzymatic synthesis and metabolic pathway emulation (Fisher et al., 2000 Chen et al., 2004). Development of new membranes used in artificial organs and advances in micelle reaction systems have resulted from these efforts. 

J.H. Kim and J.-S. Yu, Erythrocyte-like hollow carbon capsules and their application in proton exchange membrane fuel cell, Phy. Chem. Chem. Pints. 12, 2010, 15301-15308. 

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