scholarly journals An experimental test of new theoretical models for the electrokinetic properties of biological membranes. The effect of UO2++ and tetracaine on the electrophoretic mobility of bilayer membranes and human erythrocytes.

1986 ◽  
Vol 88 (6) ◽  
pp. 697-718 ◽  
Author(s):  
L Pasquale ◽  
A Winiski ◽  
C Oliva ◽  
G Vaio ◽  
S McLaughlin
Keyword(s):  
Sialic Acid ◽  
Zeta Potential ◽  
Charge Density ◽  
Electrophoretic Mobility ◽  
Classical Model ◽  
Theoretical Models ◽  
Human Erythrocytes ◽  
Hydrodynamic Drag ◽  
Diffuse Double Layer ◽  
Fixed Charges

For a large smooth particle with charges at the surface, the electrophoretic mobility is proportional to the zeta potential, which is related to the charge density by the Gouy-Chapman theory of the diffuse double layer. This classical model adequately describes the dependence of the electrophoretic mobility of phospholipid vesicles on charge density and salt concentration, but it is not applicable to most biological cells, for which new theoretical models have been developed. We tested these new models experimentally by measuring the effect of UO2++ on the electrophoretic mobility of model membranes and human erythrocytes in 0.15 M NaCl at pH 5. We used UO2++ for these studies because it should adsorb specifically to the bilayer surface of the erythrocyte and should not change the density of fixed charges in the glycocalyx. Our experiments demonstrate that it forms high-affinity complexes with the phosphate groups of several phospholipids in a bilayer but does not bind significantly to sialic acid residues. As observed previously, UO2++ adsorbs strongly to egg phosphatidylcholine (PC) vesicles: 0.1 mM UO2++ changes the zeta potential of PC vesicles from 0 to +40 mV. It also has a large effect on the electrophoretic mobility of vesicles formed from mixtures of PC and the negative phospholipid phosphatidylserine (PS): 0.1 mM UO2++ changes the zeta potential of PC/PS vesicles (10 mol % PS) from -13 to +37 mV. In contrast, UO2++ has only a small effect on the electrophoretic mobility of either vesicles formed from mixtures of PC and the negative ganglioside GM1 or erythrocytes: 0.1 mM UO2++ changes the apparent zeta potential of PC/GM1 vesicles (17 mol % GM1) from -11 to +5 mV and the apparent zeta potential of erythrocytes from -12 to -4 mV. The new theoretical models suggest why UO2++ has a small effect on PC/GM1 vesicles and erythrocytes. First, large groups (e.g., sugar moieties) protruding from the surface of the PC/GM1 vesicles and erythrocytes exert hydrodynamic drag. Second, charges at the surface of a particle (e.g., adsorbed UO2++) exert a smaller effect on the mobility than charges located some distance from the surface (e.g., sialic acid residues).

Negative surface charge near sodium channels of nerve: divalent ions, monovalent ions, and pH

1975 ◽  
Vol 270 (908) ◽  
pp. 301-318 ◽  
Keyword(s):  
Charge Density ◽  
Sodium Channel ◽  
Surface Charge ◽  
Diffuse Double Layer ◽  
Divalent Ions ◽  
Fixed Charges ◽  
Tenfold Increase ◽  
Monovalent Ions ◽  
Negative Surface ◽  
Negative Surface Charge

Evidence is given for a high density of negative surface charge near the sodium channel of myelinated nerve fibres. The voltage dependence of peak sodium permeability is measured in a voltage clamp. The object is to measure voltage shifts in sodium activation as the following external variables are varied: divalent cation concentration and type, monovalent concentration, and pH. With equimolar substitution of divalent ions the order of effectiveness for giving a positive shift is: Ba = Sr < Mg < Ca < Co ≈ Mn < Ni < Zn. A tenfold increase of concentration of any of these ions gives a shift of + 20 to + 25 mV. At low pH, the shift with a tenfold increase in Ca 2+ is much less than at normal pH, and conversely for high pH. Solutions with no added divalent ions give a shift of — 18 mV relative to 2 mM Ca 2+ . Removal of 7/8 of the cations from the calcium-free solution gives a further shift of — 35 mV. All shifts are explained quantitatively by assuming that changes in an external surface potential set up by fixed charges near the sodium channel produce the shifts. The model involves a diffuse double layer of counterions at the nerve surface and some binding of H+ ions and divalent ions to the fixed charges. Three types of surface groups are postulated: (1) an acid p K a = 2.88, charge density —0.9 nm -2 ; (2) an acid p K a = 4.58, charge density —0.58 nm -2 ; (3) a base p K a = 6.28, charge density + 0.33 nm -2 . The two acid groups also bind Ca 2+ ions with a dissociation constant K = 28 M. Reasonable agreement can also be obtained with a lower net surface charge density and stronger binding of divalent ions and H + ions.

scholarly journals High-concentration zeta potential measurements using light-scattering techniques

2010 ◽  
Vol 368 (1927) ◽  
pp. 4439-4451 ◽  
Author(s):  
Michael Kaszuba ◽  
Jason Corbett ◽  
Fraser Mcneil Watson ◽  
Andrew Jones
Keyword(s):  
Light Scattering ◽  
Zeta Potential ◽  
Electrophoretic Mobility ◽  
Electrostatic Interactions ◽  
Theoretical Models ◽  
High Concentration ◽  
Sample Concentration ◽  
High Concentrations ◽  
Laser Doppler Electrophoresis ◽  
Key Parameter

Zeta potential is the key parameter that controls electrostatic interactions in particle dispersions. Laser Doppler electrophoresis is an accepted method for the measurement of particle electrophoretic mobility and hence zeta potential of dispersions of colloidal size materials. Traditionally, samples measured by this technique have to be optically transparent. Therefore, depending upon the size and optical properties of the particles, many samples will be too concentrated and will require dilution. The ability to measure samples at or close to their neat concentration would be desirable as it would minimize any changes in the zeta potential of the sample owing to dilution. However, the ability to measure turbid samples using light-scattering techniques presents a number of challenges. This paper discusses electrophoretic mobility measurements made on turbid samples at high concentration using a novel cell with reduced path length. Results are presented on two different sample types, titanium dioxide and a polyurethane dispersion, as a function of sample concentration. For both of the sample types studied, the electrophoretic mobility results show a gradual decrease as the sample concentration increases and the possible reasons for these observations are discussed. Further, a comparison of the data against theoretical models is presented and discussed. Conclusions and recommendations are made from the zeta potential values obtained at high concentrations.

scholarly journals THE ELECTROPHORETIC MOBILITY OF HUMAN ERYTHROCYTES—WHOLE CELLS, GHOSTS, AND FRAGMENTS

1938 ◽  
Vol 22 (1) ◽  
pp. 1-5 ◽  
Author(s):  
W. H. Byler ◽  
H. M. Rozendaal
Keyword(s):  
Cell Surface ◽  
Electrophoretic Mobility ◽  
Human Erythrocytes ◽  
Red Cell ◽  
Chicken Serum ◽  
Whole Cells ◽  
Slow Change ◽  
Foreign Substance ◽  
Pure Salt

The electrophoretic mobility of human red cell ghosts decreases in the presence of chicken serum. The decrease is not directly due to the presence of adsorbed material but to a change which is catalyzed by the foreign substance. It is suggested that abnormal serum materials resulting from disease may serve as catalysts. Fragments of broken cells have the same mobility as whole cells at first, then decrease even in pure salt suspension, while the whole cells remain essentially unchanged for hours. The results suggest that the slow change of whole cells, the change of ghosts in the presence of foreign serum, and the change of fragments are all manifestations of the same modification of structure or composition of the cell surface.

The effects of electrolyte concentration, ion species and pH on the zeta potential and electrokinetic charge density of montmorillonite

Clay Minerals ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 853-861 ◽  
Author(s):  
E. E. Saka ◽  
C. Güler
Keyword(s):  
Zeta Potential ◽  
Charge Density ◽  
Negative Charge ◽  
Electrolyte Concentration ◽  
Great Influence ◽  
Electrolyte Solutions ◽  
Ionic Species ◽  
Positive Sign ◽  
Ion Species ◽  
Influence Of Ph

AbstractIn this study, the influence of pH, electrolyte concentration and type of ionic species (such as LiCl, NaCl, KCl, RbCl, CsCl, CaCl2, AlCl3) on the electrokinetic properties (zeta potential and electrokinetic charge density) of montmorillonite has been quantified. The zeta potential of montmorillonite particles did not change significantly with change in pH. The valencies of the ions have proven to have a great influence on the electrokinetic behaviour of the suspension. There is a gradual decrease in the zeta potential (from —24 mV to —12 mV) with increase in monovalent electrolyte concentration (from 10-4 M to 10-1 M). At any monovalent electrolyte concentration, the magnitude of the zeta potential increased with the electrolytes in the order Li+ > Na+ > K+ > Rb+ > Cs+. The zeta potential of the montmorillonite minerals in CaCl2 solutions illustrated the same behaviour as the monovalent cations. Less negative values were obtained for the CaCl2 electrolyte (∼–10 mV) due to the greater valence of the ions. A sign reversal was observed at an AlCl3 concentration of 5 x 10-4 M, and, at greater concentrations, zeta potential values had a positive sign (∼20 mV).The electrokinetic charge density of montmorillonite showed similar trends of variation in mono and divalent electrolyte solutions. Up to concentrations of ∼10-3 M, it remained practically constant at ∼0.5 x 10-3Cm-2, while for greater electrolyte concentrations the negative charge produced more negative values (–16 x 10-3Cm-2). The electrokinetic charge density of montmorillonite particles was constant at low AlCl3 concentrations, but at certain concentrations it increased rapidly and changed sign to positive.

The role of hemorheological disorders in the pathogenesis of hemorrhagic pancreonecrosis

2021 ◽  
Author(s):  
Н.П. Александрова ◽  
В.И. Карандашов ◽  
А.В. Варданян
Keyword(s):  
Sialic Acid ◽  
Shear Rate ◽  
Electrophoretic Mobility ◽  
Blood Viscosity ◽  
Proteolytic Enzymes ◽  
Biologically Active ◽  
Erythrocyte Aggregation ◽  
Control Group ◽  
Mechanical Resistance

Введение. Вопросы патогенеза острого панкреатита и панкреонекроза до настоящего времени остаются в центре внимания исследователей и клиницистов. До сих пор до конца не выяснена роль изменений в системе гемостаза и гемореологических нарушений в развитии этого заболевания. Цель исследования: установить роль гемореологических нарушений в патогенезе геморрагического панкреонекроза и изучить специфику механизма этих расстройств. Материалы и методы. Обследовано 29 пациентов с геморрагическим панкреонекрозом (12 женщин и 17 мужчин) в возрасте от 23 до 60 лет. Исследовали вязкость крови, показатель гематокрита, количество эритроцитов и их диаметр, агрегацию, электрофоретическую подвижность, деформируемость и механическую резистентность эритроцитов, белковый состав плазмы, содержание сиаловой кислоты в плазме и в эритроцитах, параметры липидного обмена, содержание кальция и фибриногена в крови,фибринолитическую активность крови и агрегационную активность тромбоцитов, гемокоагуляционная активность исследована методом тромбоэластографии. Для определения нормальных значений исследованных показателей было обследовано 15 практически здоровых лиц (7 женщин и 8 мужчин). Результаты. У больных панкреонекрозом самым грубым нарушениям подвергаются эритроциты: их механическая резистентность снижалась в 2 раза, объем увеличивался на 18,7%, деформируемость падала на 43,8%, количество снижалось на 8,75%, показатель гематокрита при этом оставался на уровне нормальных значений по причине увеличенного объема (сферичности) клеток; в 1,8 раза возрастала агрегация эритроцитов. Вязкость крови при скорости сдвига 1 c–1 увеличивалась в 3,3 раза, а при скорости сдвига 150 c–1 — в 1,58 раза по сравнению с нормой. Причиной повышения агрегации эритроцитов являлось снижение их электрофоретической подвижности на 35,9% из-за десиализации их мембран: концентрация сиаловой кислоты в клеточных мембранах была снижена на 20,8%, а содержание конъюгированной сиаловой кислоты в плазме увеличено в 2,25 раза по сравнению с нормальными значениями. Заключение. Гемореологические расстройства, которые возникают первоначально у больных геморрагическим панкреонекрозом как результат некротических изменений поджелудочной железы, с определенного, довольно раннего этапа сами становятся фактором патогенеза данного заболевания. Доминирующим фактором прогрессивного увеличения вязкости крови у больных панкреонекрозом является нарушение морфофункциональных и физико-химических свой ств эритроцитов на фоне высокой активности протеолитических ферментов, биологически активных аминов и крайней степени токсемии. Background. The pathogenesis of acute pancreatitis and pancreonecrosis is still the focus of researchers and clinicians. The role of hemorheological disorders in these diseases remain uncertain until now. Objectives: to define the role of hemorheological disorders in the pathogenesis of hemorrhagic pancreonecrosis and to study the specifics of the mechanism of these disorders. Patients/Methods. This study included 29 patients (12 women and 17 men, age of 23 to 60 years old) with hemorrhagic pancreatic necrosis. We examined blood viscosity, hematocrit and some erythrocyte properties as count, diameter, aggregation, electrophoretic mobility, deformability and mechanical resistance; other investigated parameters were plasma protein composition, plasma and erythrocytes sialic acid concentrations, lipids, total calcium and fibrinogen concentrations, blood fibrinolytic activity, platelets aggregation activity; total hemocoagulation activity was studied with thromboelastography. Control group contained 15 practically healthy individuals (7 women and 8 men). Results. Expressed disturbances of blood rheological properties, mostly in erythrocytes were detected in patients with pancreonecrosis. Red blood cells (RBC) showed 2-times decreasing of mechanical resistance, of their volume by 18.7%, of deformability by 43.8%, of count by 8.75%. Hematocrit remained normal level due to RBC increased volume (sphericity). RBC aggregation had been increased by 1.8 times. Blood viscosity at the shear rate of 1 s–1 was increased by 3.3 times and at the shear rate of 150 s–1 by 1.58 times. Raised erythrocyte aggregation was caused by a decrease of RBC electrophoretic mobility of 35.9%. Sialic acid concentration in RBC membranes was lower of 20.8% whereas conjugated sialic acid in plasma showed increasing by 2.25 times. Conclusions. RBC morphofunctional and physicochemical disturbances cause the increase in blood viscosity in patients with pancreonecrosis. It is distinguishing feature of hemorheological disorders in hemorrhagic pancreonecrosis developing, seems, due to high activity of proteolytic enzymes and biologically active amines. Of particular importance in hemorrhagic pancreonecrosis belong to platelet involving into intravascular coagulation.

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