Decrease In Surface Potential Research Articles

Studies on fragments of rod outer segments from bovine retinas.

Monolayers of fragments of our rod segments were formed at an air-water interface. The area of these particles was measured as a function of the pH of the aqueous phase. A maximum area was measured at pH 6.5. The film was characterised by measuring the decrease in surface pressure, after compression, and the half time required to reach constant pressure. At a pH between 6 and 7 the decrease in surface pressure was a minimum. Irradiation of films of fragments resulted in a decrease in surface potential of between 30 and 40 mV. The largest decrease occured at a pH between 6 and 6.5. A small decrease in surface pressure was also observed upon irradiation. Mixed films of fragments and phosphatidyl ethanolamine were examined. Irradiation of the mixed film resulted in a 70 mV decrease in surface potential.

The electrostatic basis of Mg++ inhibition of transmitter release.

The inhibition by Mg(++) of stimulus-evoked transmitter release is attributed to a decrease in surface potential, Psi(0), on the outer surface of the presynaptic terminal and hence a lower surface calcium concentration, [Ca(++)](0). Data on the frog neuromuscular junction are quantitatively fit by assuming that there is a negative charge density, sigma, on the outer surface of the presynaptic terminal of 6.5 x 10(13) charges per cm(2) and that simple diffuse double layer theory is applicable. No specific binding of Mg(++) or Ca(++) is required. Without any additional assumptions, the inhibitory effect of univalent cations is also quantitatively predicted.

Influence of the ionic composition of fluid medium on red cell aggregation.

The effects of ionic strength and cationic valency of the fluid medium on the surface potential and dextran-induced aggregation of red blood cells (RBC's) were investigated. The zeta potential was calculated from cell mobility in a microelectrophoresis apparatus; the degree of aggregation of normal and neuraminidase-treated RBC's in dextrans (Dx 40 and Dx 80) was quantified by microscopic observation, measurement of erythrocyte sedimentation rate, and determination of low-shear viscosity. A decrease in ionic strength caused a reduction in aggregation of normal RBC's in dextrans, but had no effect on the aggregation of neuraminidase-treated RBC's. These findings reflect an increase in electrostatic repulsive force between normal RBC's by the reduction in ionic strength due to (a) a decrease in the screening of surface charge by counter-ions and (b) an increase in the thickness of the electric double layer. Divalent cations (Ca(++), Mg(++), and Ba(++)) increased aggregation of normal RBC's in dextrans, but had no effect on the aggregation of neuraminidase-treated RBC's. These effects of the divalent cations are attributable to a decrease in surface potential of normal RBC's and a shrinkage of the electric double layer. It is concluded that the surface charge of RBC's plays a significant role in cell-to-cell interactions.

The interaction of 2,4-dinitrophenol with phospholipids at phospholipid-water interfaces

The effect of 2, 4-dinitrophenol, DNP, on monolayers of egg lecithin, hydrogenated egg lecithin, dipalmitoyl lecithin and mitochondrial lipids has been examined. Both the undissociated and dissociated forms of DNP bind to the phospholipid polar groups. Binding of the acid form leads to a decrease in monolayer surface potential and an expansion of the monolayer. The amount of penetration of the acid form into lecithin monolayers appears to depend on the London-Van der Waals attractions between the lecithin hydrocarbon chains. Binding of the 2,4-dinitro-phenolate anion is reflected in a decrease in surface potential for lecithin monolayers, and an increase in surface potential for mitochondrial lipid monolayers. The adsorption of dinitro-phenolate to egg lecithin has been further investigated by micro-electrophoresis of lecithin liposomes. It is suggested that binding of DNP to phospholipid-water interfaces is important in determining its action as an uncoupler of oxidative phosphorylation, and as a compound that increases the electrical conductance of artificial lipid membranes.

Chemisorption and incorporation of oxygen at a nickel surface

A continuous recording (static capacitor) device, with a response time of 0.1 s, has been used to measure the surface potential changes occurring during oxygen chemisorption on clean nickel films. At 77 and 90 °K, the surface potential is decreased to – 1.6 V, followed by an increase of 0.1 V at an oxygen pressure ofca. 10-2torr. This increase is the result of physical adsorption of oxygen molecules in a second layer. Oxygen doses added at higher temperatures cause a surface potential decrease, followed immediately by a slow decrease due to incorporation of oxygen in the metal lattice. The kinetics of the incorporation process are affected by the surface electric field formed by the oxygen-nickel double layer. Analysis of the kinetic curves, corrected for this field effect, shows that the average charge per oxygen atom is 0.3 ± 0.04 of an electronic charge. The experimental rate of incorporation is smaller, by a factor of approximately 10-12, than that calculated from the absolute rate equation and the use of the experimental value of the activation energy of 1 kcal/mole. This discrepancy is attributed to the very small probability of creating a low-energy barrier by the simultaneous movement apart of surface nickel atoms, allowing passage inwards of the oxygen adatoms. The calculated probability for this concerted motion is in agreement with the experimental value; the magnitude of the effective surface energy barrier is then evaluated as 7.3 ±1 kcal/mole. At temperatures between 350 and 403 °K, the kinetics of incorporation change, and their autocatalytic character corresponds to that of a nucleation and growth process. At these temperatures the surface potential increases to +0.7 V, and the adsorptive capacity is markedly reduced. These changes are attributed to the formation of oxide-like patches containing positively charged nickel atoms in their external surface.

Coacervating soap-electrolyte solutions: I. Charge properties. II. Generalized treatment of coacervating soap-electrolyte systems

The phenomenon of coacervation, i.e., separation of a homogeneous solution into two liquid layers on addition of an electrolyte to some association colloids, has been characterized previously. Comparison was made of the ionization patterns of several coacervating soap systems with those of noncoacervating systems at low added electrolyte concentrations. In noncoacervating systems, ionization increases with increasing electrolyte concentration and then levels off. In coacervating systems, ionization reaches a maximum at rather low electrolyte concentrations, followed by a rapid decrease in ionization with further additions of electrolyte. In the first case, the ionization is found to depend linearly on the square root of electrolyte concentration ( c ), whereas in the coacervating systems the ionization is proportional to ce − be , where b is a constant. These findings are explained in terms of (1) the constancy of the surface potential on addition of an electrolyte in noncoacervating systems and (2) a postulated decrease of the surface potential on addition of an electrolyte in coacervating systems. A generalized equation is developed, which gives the dependence of square root of micellar molecular weight on the reduced electrolyte concentration in the system. This equation is obeyed by several coacervating systems investigated and seems to be justified on the basis of the postulated decrease of surface potential on the addition of an electrolyte to a soap solution which forms coacervates.

アルミニウムの表面電位と塗膜の付着性に対するリン酸処理の影響

The surface potential of aluminium decreases and the adhesion of organic coatings to that metal increases in strength when its surface is chemically treated with a mixture of phosphoric acid and ethylalcohol, and there exists an approximately proportional relationship between the degree of decrease in surface potential and the degreee of increase in adhesive strength. The reason why the adhesive strength of organic coatings was increased by such a surface treatment of aluminium has been discussed.

ウイルスの血球凝集反応の本態に関する研究

In this communication a report is made on the mechanism of viral hemagglutination. The results are summarized as follows. I. ELECTROSTATIC CONSIDERATION OF THE VIRAI HEMAGGLUTINATION.The viral hemagglutination were distinguished into two processes, first, adherence of hemagglutinin to the surface of erythrocytes and, second, clot formation of those erythrocytes.The mechanism of the first process was different from other viruses, but the mechanism of the second process was in common with other hemagglutination.The second process was confirmed with various ionic formations of reaction medium, and then, it was nothing else but decrease of negative surface potential of erythrocytes. II. MEASUEMENT OF THE HEMAGGLUTINABILITY OF ERYTHROCYTES.The present author has observed that the erythrocytes disclosed nonspecific hemagglutination in hypertonic concentration of NaCl solution or CaCl2 solution. The nonspecific hemagglutination in hypertonic solution was utilized for measurement of the hemagglutinability.Hypertonic solution (16 times of isotonic concentration) of NaCl or CaCl2 solution was diluted serially twofold by mixing with distilled water and in each 1.0ml of this dilution was added 1 drop of 10% suspension of erythrocytes in normal saline and sedimentation was allowed to proceed at 4°C over night and the patterns were read (according to Salk).It was concluded by the method that hemagglutinability of trypsin and tannic acid treated erythrocytes was increased.

Adsorption and Surface Potential of Semi-conductors. Part 1. Photo-enhanced Adsorption of Oxygen and Change of Contact Potential of ZnS Phosphors with Illumination

When ZnS phosphor containing 10 -2 Mol% of Cu was irradiated in oxygen gas by light with wavelengths lying within the characteristic absorption band of the host crystal, photo-enhanced adsorption and increase of the surface potential (decrease of the work function) of the crystal were observed. If we assume that the lowering of the potential energy of adsorption of oxygen is equal to the increased amount of surface potential, the photo-enhanced adsorption can be explained semi-quantitatively. The change of the surface potential of ZnS with illumination, (Δc.p.) L , increased with pressures of oxygen and decreased with temperature.