scholarly journals The Surface of the Washed Human Erythrocyte as a Polyanion

1960 ◽  
Vol 44 (2) ◽  
pp. 251-268 ◽  
Author(s):  
G. V. F. Seaman ◽  
D. H. Heard
Keyword(s):  
Ionic Strength ◽  
Cell Membrane ◽  
Human Erythrocyte ◽  
Negative Charge ◽  
Physical Adsorption ◽  
Structural Instability ◽  
Carboxyl Groups ◽  
Charge Reduction ◽  
Tosyl Chloride ◽  
Phosphate Groups

The electrokinetic behaviour of normal erythrocytes is compared with that of trypsin-, N-bromosuccinimide-, and tosyl-treated erythrocytes. Reduction in the net negative charge with reduction in ionic strength of the suspending medium and also on treatment with N-bromosuccinimide and trypsin is discussed using a porous non-rigid polyanion as a model for the periphery of the cell membrane. It is deduced from the equivalent binding of chloride and thiocyanate ions and the absence of any effect on treatment of red cells with tosyl chloride, that normal, N-bromosuccinimide- and trypsin-treated cells are polyanionic in character. Reduction in erythrocyte charge on treatment with N-bromosuccinimide or trypsin is probably not due to the removal of phosphate groups from the interface, nor to physical adsorption of N-bromosuccinimide or trypsin. The charge reduction is probably produced by bond fission with possibly a net disappearance of carboxyl groups from the electrophoretic plane of shear either by loss from, or reorientation of, the membrane. The loss or reorientation of material associated with these carboxyl groups does not lead to any basic change in the character of the surface of the cell, nor to any obvious structural instability. The biconcave discoid form is maintained and there is no significant hemolysis of the erythrocytes even after contact with a solution of trypsin for 24 hours.

Interactions of polynucleotides and their components

1968 ◽  
Vol 23 (1) ◽  
pp. 25-30 ◽  
Author(s):  
J. Clauwaert ◽  
J. Stockx
Keyword(s):  
Ionic Strength ◽  
Inductive Effect ◽  
Large Range ◽  
Electrostatic Attraction ◽  
Screening Off ◽  
Electron Withdrawal ◽  
New Treatment ◽  
Ribose Moiety ◽  
Phosphate Groups ◽  
Electron Attraction

The pK' values of the current bases, nucleosides, nucleotides, nucleotide derivatives and poly U have been determined over a large range of ionic strength. The pK' shifts of the monomers due to variations in ionic strength can be accounted for qualitatively and quantitatively by means of the relationThe collision diameters of uracil, uridine, uridine cyclic -2':3'-phosphate and 3' (2') -uridylic acid were determined. The introduction of phosphate affects the charge, resulting into differences in activity coefficient between nucleotides and their corresponding nucleosides and bases. A substitution of -H by ribose at N(3) of uracil or cytosine or at N(9) of adenine or guanine results into an electron withdrawal from the bases with lowering of the pK' value. 2'-Deoxyribose exhibits a weaker electron attraction. Introducing -CH3 at C(5) of uracil yields electrons to the base and the pK values of various thymine derivatives are about 0.5 pH units higher than those of the corresponding uracil derivatives. A phosphate group on C2 or C3 results in an electrostatic attraction of the dissociable proton, so that the pK' is increased at low ionic strengths; at higher ionic strengths screening off occurs and the pK' values of the nucleotides become almost the same as those of the corresponding nucleosides. The site of substitution on the ribose moiety is important: C2'-O-phosphate seems to exert a stronger electrostatic attraction on - NH3⊕ groups than C3'-O-phosphate, whereas C5'-O-phosphate exerts in addition an inductive effect that is dependent on the presence of - OH on C2. The electrostatic influence of the phosphate groups on the uracil moiety in UpU, UpC and CpUpC runs roughly parallel to that found in cyclic-2':3'-nucleotides. The pK' shifts experienced in poly U are related to the polyelectrolyte character of this polymer. A new treatment for the evaluation of the electrostatic potential of polynucleotides (poly U) is proposed that is based on the usual rodlike (polyelectrolyte) model.

Pseudopodium Induction by the Action of Quaternary Ammonium Ions on Amoeba Proteus

1969 ◽  
Vol 4 (1) ◽  
pp. 17-24
Author(s):  
J. E. BREWER ◽  
L. G. E. BELL
Keyword(s):  
Cell Membrane ◽  
Cell Surface ◽  
Quaternary Ammonium ◽  
Amoeba Proteus ◽  
Carboxyl Groups ◽  
Ammonium Ions ◽  
Quaternary Nitrogen ◽  
Quaternary Ammonium Ions ◽  
Ammonium Compounds ◽  
Long Chain

Some aliphatic long-chain quaternary ammonium compounds and choline derivatives have been examined for their ability to induce pseudopodia from Amoeba proteus. The reaction involved in pseudopodium induction is believed to be between the quaternary nitrogen cations and polysaccharides on the cell surface. Not all of the carboxyl groups of the polysaccharide are involved in this reaction. The mechanism of pseudopodium induction is discussed in terms of changes in the surface charge and the permeability of the cell membrane.

scholarly journals The human erythrocyte anion transport protein, band 3. Characterization of exofacial alkaline titratable groups involved in anion binding/translocation.

1992 ◽  
Vol 100 (2) ◽  
pp. 301-339 ◽  
Author(s):  
P J Bjerrum
Keyword(s):  
Ionic Strength ◽  
Binding Site ◽  
Transport System ◽  
Human Erythrocyte ◽  
Binding Constant ◽  
Anion Transport ◽  
High Ionic Strength ◽  
Anion Binding ◽  
Asymmetry Factor ◽  
Sensitive Group

Chloride self-exchange across the human erythrocyte membrane at alkaline extracellular pH (pHO) and constant neutral intracellular pH (pH(i)) can be described by an exofacial deprotonatable reciprocating anion binding site model. The conversion of the transport system from the neutral to the alkaline state is related to deprotonation of a positively charged ionic strength- and substrate-sensitive group. In the absence of substrate ions ([ClO] = 0) the group has a pK of approximately 9.4 at constant high ionic strength (equivalent to approximately 150 mM KCl) and a pK of approximately 8.7 at approximately zero ionic strength. The alkaline ping-pong system (examined at constant high ionic strength) demonstrates outward recruitment of the binding sites with an asymmetry factor of approximately 0.2, as compared with the inward recruitment of the transport system at neutral pHO with an asymmetry factor of approximately 10. The intrinsic half-saturation constant for chloride binding, with [Cli] = [Clo], increased from approximately 30 mM at neutral to approximately 110 mM at alkaline pHO. The maximal transport rate was a factor of approximately 1.7 higher at alkaline pHO. This increase explains the stimulation of anion transport, the "modifier hump," observed at alkaline pHO. The translocation of anions at alkaline pHO was inhibited by deprotonation of another substrate-sensitive group with an intrinsic pK of approximately 11.3. This group together with the group with a pK of approximately 9.4 appear to form the essential part of the exofacial anion binding site. The effect of extracellular iodide inhibition on chloride transport as a function of pHO could, moreover, be simulated if three extracellular iodide binding constants were included in the model: namely, a competitive intrinsic iodide binding constant of approximately 1 mM in the neutral state, a self-inhibitor binding constant of approximately 120 mM in the neutral state, and a competitive intrinsic binding constant of approximately 38 mM in the alkaline state.

Functionalization of gold nanoparticles with nanobodies through physical adsorption

2017 ◽  
Vol 9 (23) ◽  
pp. 3430-3440 ◽  
Author(s):  
Julie Goossens ◽  
Hla Sein ◽  
Shaohong Lu ◽  
Magdalena Radwanska ◽  
Serge Muyldermans ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Ionic Strength ◽  
Protein Engineering ◽  
Physical Adsorption ◽  
Adsorption Behaviour ◽  
First Time

The physical adsorption behaviour of nanobodies to gold nanoparticles is described for the first time in an extensive manner including parameters such as pI, ionic strength and several protein engineering strategies. The generated nanobody-gold conjugates are functional.

scholarly journals Stimulating Effect of Terfenadine on Erythrocyte Cell Membrane Scrambling

2016 ◽  
Vol 38 (4) ◽  
pp. 1425-1434 ◽  
Author(s):  
Elena Signoretto ◽  
Michela Castagna ◽  
Abdulla Al Mamun Bhuyan ◽  
Florian Lang
Keyword(s):  
Cell Membrane ◽  
Human Erythrocyte ◽  
Haemoglobin Concentration ◽  
Annexin V ◽  
Human Erythrocytes ◽  
Forward Scatter ◽  
Erythrocyte Surface ◽  
Suicidal Death ◽  
Phosphatidylserine Translocation ◽  
Surface Signaling

Background/Aims: The antihistaminic drug Terfenadine may trigger apoptosis of tumor cells, an effect unrelated to its effect on histamine receptors. Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal death of erythrocytes characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Signaling triggering eryptosis include increase of cytosolic Ca2+ activity ([Ca2+]i), oxidative stress, and ceramide. The present study explored, whether Terfenadine is capable to trigger eryptosis. Methods: Flow cytometry was employed to estimate phosphatidylserine abundance at the erythrocyte surface from annexin-V-binding, cell volume from forward scatter, [Ca2+]i from Fluo3-fluorescence, abundance of reactive oxygen species (ROS) from 2′,7′-dichlorodihydrofluorescein (DCF) diacetate dependent fluorescence, and ceramide abundance at the human erythrocyte surface utilizing specific antibodies. Hemolysis was quantified from haemoglobin concentration in the supernatant. Results: A 48 hours exposure of human erythrocytes to Terfenadine (≥ 5 µM) significantly increased the percentage of annexin-V-binding cells and triggered hemolysis without significantly modifying the average forward scatter. Terfenadine (7.5 µM) significantly increased Fluo3-fluorescence, but did not significantly modify DCF fluorescence or ceramide abundance. The effect of Terfenadine on annexin-V-binding was significantly blunted but not abolished by removal of extracellular Ca2+. Exposure of human erythrocytes to Ca2+ ionophore ionomycin (1 µM, 15 min) triggered annexin-V-binding, an effect augmented by Terfenadine pretreatment (10 µM, 48 hours). Conclusions: Terfenadine triggers phospholipid scrambling of the human erythrocyte cell membrane, an effect in part due to entry of extracellular Ca2+ and in part due to sensitizing human erythrocyte cell membrane scrambling to Ca2+.

scholarly journals Erythrocyte adducin: a calmodulin-regulated actin-bundling protein that stimulates spectrin-actin binding.

1987 ◽  
Vol 105 (6) ◽  
pp. 2837-2845 ◽  
Author(s):  
S M Mische ◽  
M S Mooseker ◽  
J S Morrow
Keyword(s):  
Ionic Strength ◽  
Erythrocyte Membrane ◽  
Human Erythrocyte ◽  
Actin Binding ◽  
Protein 4.1 ◽  
Calcium Dependent ◽  
High Affinity ◽  
Putative Role ◽  
Cross Bridges ◽  
Dependent Mechanism

Adducin is an erythrocyte membrane skeletal phosphoprotein comprised of two related subunits of 105,000 and 100,000 Mr. These peptides form a functional heterodimer, and the smaller of the two binds calmodulin in a calcium-dependent fashion. Although this protein has been physicochemically characterized, its function remains unknown. We have examined the interaction of human adducin with actin and with human erythrocyte spectrin using sedimentation, electrophoretic, and morphologic techniques. Purified adducin binds actin at physiologic ionic strength and bundles it into arrays of laterally arranged filaments, the adducin forming cross-bridges between the filaments at 35.2 /- 3.8 (2 SD) nm intervals. The stoichiometry of high affinity adducin binding to actin at saturation is 1:7, corresponding to a dimer of adducin for every actin helical unit. Adducin also promotes the binding of spectrin to actin independently of protein 4.1. At saturation, each adducin promotes the association of one spectrin heterodimer. The formation of this ternary spectrin-actin-adducin complex is independent of the assembly path, and the complex exists in a readily reversible equilibrium with the free components. The binding of adducin to actin and its ability to stimulate spectrin-actin binding is down-regulated by calmodulin in a calcium-dependent fashion. These results thus identify a putative role for adducin, and define a calcium- and calmodulin-dependent mechanism whereby higher states of actin association and its interaction with spectrin in the erythrocyte may be controlled.

scholarly journals Role of the reticulum in the stability and shape of the isolated human erythrocyte membrane

1982 ◽  
Vol 92 (3) ◽  
pp. 714-721 ◽  
Author(s):  
Y Lange ◽  
RA Hadesman ◽  
TL Steck
Keyword(s):  
Ionic Strength ◽  
Erythrocyte Membrane ◽  
Human Erythrocyte ◽  
Time Course ◽  
Isotonic Saline ◽  
Human Erythrocyte Membrane ◽  
Wide Range ◽  
Cell Stability ◽  
Mechanically Stabilized ◽  
Low Ionic Strength

In order to examine the widely held hypothesis that the reticulum of proteins which covers the cytoplamsic surface of the human erythrocyte membrane controls cell stability and shape, we have assessed some of its properties. The reticulum, freed of the bilayer by extraction with Triton X-100, was found to be mechanically stable at physiological ionic strength but physically unstable at low ionic strength. The reticulum broke down after a characteristic lag period which decreased 500-fold between 0 degrees and 37 degrees C. The release of polypeptide band 4.1 from the reticulum preceded that of spectrin and actin, suggesting that band 4.1 might stabilize the ensemble but is not essential to its integrity. The time-course of breakdown was similar for ghosts, the reticulum inside of ghosts, and the isolated reticulum. However, at very low ionic strength, the reticulum was less stable within the ghost than when free; at higher ionic strength, the reverse was true. Over a wide range of conditions the membrane broke down to vesicles just as the reticulum disintegrated, presumably because the bilayer was mechanically stabilized by this network. The volume of both ghosts and naked reticula varied inversely and reversibly with ionic strength. The volume of the naked reticulum varied far more widely than the ghost, suggesting that its deformation was normally limited by the less extensible bilayer. The contour of the isolated reticulum was discoid and often dimpled or indented, as visualized in the fluorescence microscope after labeling of the ghosts with fluoroscein isothiocyanate. Reticula derived from ghosts which had lost the ability to crenate in isotonic saline were shriveled, even though the bilayer was smooth and expanded. Conversly, ghosts crenated by dinitrophenol yielded smooth, expanded reticula. We conclude that the reticulum is a durable, flexible, and elastic network which assumes and stabilizes the contour of the membrane but is not responsible for its crenation.

scholarly journals Activities of potassium and sodium ions in rabbit heart muscle.

1975 ◽  
Vol 65 (6) ◽  
pp. 695-708 ◽  
Author(s):  
C O Lee ◽  
H A Fozzard
Keyword(s):  
Ionic Strength ◽  
Cell Membrane ◽  
Activity Coefficient ◽  
Heart Muscle ◽  
Extracellular Fluid ◽  
Rabbit Heart ◽  
Mean Value ◽  
Sodium Ions ◽  
K Activity ◽  
External K

Activities (a) of intracellular K and Na in rabbit ventricular papillary muslces were determined with cation-selectivve glass microelectrodes and concentrations (C) were estimated with flame photometry. The CK and aK of the muscles were 134.9 +/- 3.1 mM (mean value +/- SE) and 82.6 mM, respectively, at 25 degrees C. The corresponding CNa and aNa were 32.7 +/- 2.7 and 5.7, respectively. The apparent intracellular activity coefficients for K (gammaK) and Na (gammaNa) were 0.612 and 0.175, respectively. Similar results were obtained at 35 +/- 1 degree C. gammaK was substantially lower than the activity coefficient (0.745) of extracellular fluid (Tyrode's solution), which might be expected on the basis of a different intracellular ionic strength. gammaNa was much lower than that of extracellular fluid, and suggest that much of the Na was compartmentalized or sequestered. For external K concentrations greater than 5 mM, the resting membrane potentials agreed well with the potential differences calculated from the K activity gradients across the cell membrane as a potassium electrode. These results emphasize that potassium equilibrium potentials in heart muscle should be calculated by activities rather than concentrations.

scholarly journals The efficiency of nano-TiO2 and γ-Al2O3 in copper removal from aqueous solution by characterization and adsorption study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fatemeh Ezati ◽  
Ebrahim Sepehr ◽  
Fatemeh Ahmadi
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Ph Value ◽  
Physical Adsorption ◽  
Geochemical Modeling ◽  
Low Cost ◽  
Background Electrolyte ◽  
Isotherm Models ◽  
Batch Adsorption ◽  
Equilibrium Data

AbstractWater pollution is a major global challenge given the increasing growth in the industry and the human population. The present study aims to investigate the efficiency of TiO2 and γ-Al2O3 nanoadsorbents for removal of copper (Cu(II)) from aqueous solution as influenced by different chemical factors including pH, initial concentration, background electrolyte and, ionic strength. The batch adsorption experiment was performed according to standard experimental methods. Various isotherm models (Freundlich, Langmuir, Temkin, and Dubinin–Radushkevich) were fitted to the equilibrium data. According to geochemical modeling data, adsorption was a predominant mechanism for Cu(II) removal from aqueous solution. Calculated isotherm equations parameters were evidence of the physical adsorption mechanism of Cu(II) onto the surface of the nanoparticles. The Freundlich adsorption isotherm model could well fit the experimental equilibrium data at different pH values. The maximum monolayer adsorption capacity of TiO2 and γ-Al2O3 nanosorbents were found to 9288 and 3607 mg kg−1 at the highest pH value (pH 8) and the highest initial Cu(II) concentration (80 mg L−1) respectively. Copper )Cu(II) (removal efficiency with TiO2 and γ-Al2O3 nanoparticles increased by increasing pH. Copper )Cu(II) (adsorption deceased by increasing ionic strength. The maximum Cu(II) adsorption (4510 mg kg−1) with TiO2 nanoparticles was found at 0.01 M ionic strength in the presence of NaCl. Thermodynamic calculations show the adsorption of Cu(II) ions onto the nanoparticles was spontaneous in nature. Titanium oxide (TiO2) nanosorbents could, therefore, serve as an efficient and low-cost nanomaterial for the remediation of Cu(II) ions polluted aqueous solutions.

scholarly journals Protease activity in the human erythrocyte: localization to the cell membrane

Blood ◽  
1979 ◽  
Vol 53 (5) ◽  
pp. 875-882
Author(s):  
SK Ballas ◽  
ER Burka
Keyword(s):  
Cell Membrane ◽  
Proteolytic Activity ◽  
Human Erythrocyte ◽  
Protease Activity ◽  
Cell Membranes ◽  
Generating System

Proteolytic activity in the mature human erythrocyte was localized to the cell membrane. This activity, which could not be ascribed to contaminating leukocytes in the suspension, was totally absent from the soluble portion of the cell and was more active against hemoglobin subunits than against tetrameric hemoglobin molecules. Pulse-chase experiments confirmed that the membrane proteolytic activity was more active in degrading beta chains that alpha chains. The activity could be extracted from erythrocyte cell membranes, but not from membrane- free hemolysate, by exposure to 0.75-M KSCN. The activity of the protease was dependent on time and temperature and did not require ATP or an energy-generating system for activity.

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