Electrostatic repulsion effect

Surfactants tend to concentrate in the lamella at a gas-liquid interface. With the drainage of the lamella, the inner and outer interfaces come closer together, and the electrostatic repulsion caused by the ionic groups of the surfactant prevents further drainage, so foam stabilization occurs. 

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CV measurements showed that the reversible eleetrode reaetion of the [Fe(CN)6]" redox eouple was suppressed to some extent by the treatment with the DNA. The addition of the anti-DNA antibody further suppressed the redox reaetion thus decreasing the magnitudes of the CV peak currents. This is most likely caused by a steric hindrance of the bulky protein, which binds to the DNA double strands on the electrode surface, to mainly reduce the effective area of the electrode. The electrostatic repulsive effect may also contribute to the electrode response, since the isoelectric point of mouse IgM is commonly in the range of 4.5 to 7.0. Figure 11 shows the relationship between the decrease in the anodic peak current (A/p ) and the antibody concentration. As seen in this figure, the electrode system responded to the anti-DNA antibody in the concentration range of 1 — 100 nM. For the case of the mouse IgM, which does not interact with double-stranded DNA, the present system gave almost no response. The sensor did not respond to other serum proteins as well (data not shown). 

In Table 3 is a compilation of some of the rate constants which have been determined for various flavin semiquinone reactions. Note that whereas many of these reactions are quite rapid (at or near diffusion control), others are relatively slow. Of particular interest (see below) is the reaction of Oj with FH-, which is too slow to measure (due to the competing disproportionation). Note also that side chain and electrostatic repulsion effects can be seen in some of these reactions. 

In solutions of low nucleophilicity, multiply charged electrophiles can frequently exhibit deep-seated rearrangements and fragmentation reactions. These reactions often stem from the electrostatic repulsive effects involving the charge centers, and they have precluded the observation of... 

These distonic superelectrophiles (145-147) have been characterized by low-temperature H NMR (and 13C NMR in the case of 147) from FSO3H-SbFs solution. Dication 146 was also studied by calorimetric studies to determine the heat of diprotonation of 2,5-hexanedione.48 It was found that the heat of diprotonation for the y-diketones (like 2,5-hexanedione) is about 5 kcal/mol less than expected, when compared to twice the heat of protonation of acetone or other monoketones. The destabilization of dication 146 by 5 kcal/mol can be the result of electrostatic effects, and it can be considered evidence for the superelectrophilic character of such dications. When 2,6-admantanedione is reacted in FSO3H—SbFj solution, the dication 148 is formed as a persistent species, observable by and 13C NMR.12 The carboxonium carbons of 148 are observed at Z I3C 247.7, while the mono-cationic species (149) has a carboxonium carbon at 513C 267.1. These 13C NMR data were interpreted as evidence for the increasing importance of the carboxonium-type resonance structure (148a) due to electrostatic repulsive effects. Some examples of aromatic diketones (i.e., diacetylbenzenes) have also been reported to produce bis-carboxonium dications in their protonation reactions in superacids.47... 

This is due to steric and electrostatic repulsive effects that result when oligonucleotide molecules are too densely spaced on the support. Secondly, ar-... 

Alternatively, the continued adsorption, even in the presence of electrostatic repulsive effects, may indicate strong specific binding between colloid-metal centres and membrane functional groups. Once the flux has declined to 2 - 20"/o of its initial value, electrokinetic interactions could increase rejection. 

Humic acids, a class of naturally occurring organic polyelectrolytes found 1n soil and natural waters, have been the subject of considerable study with Sephadex SEC (34-36). Unfortunately, both electrostatic repulsive effects and hydrophobic adsorption influence the chromatography on Sephadex of these complex polyacids. Since the first effect is diminished and the second increased by added salt, solvents that eliminate non-steric effects have apparently not been identified (36). 

Polymer composition/ionic content (high-charge density usually gives greater viscosity per unit weight of polymer due to electrostatic repulsion effects). 

It should be noted that the potential assodated with the reversible oxidation of the ferrocene subunit of 8 (0.37 V vs Fc+/Fc) is about 170 mV more positive than that observed for the oxidation of N,N-diethyl-ferrocene-sulphonamide, which has been taken as a reference system (Ej values vs Fc /Fc for all the mentioned systems are displayed in the potential diagram in Fig. 4). This potential increase should be ascribed to the electrostatic repulsive effects exerted by the adjacent Ni cation on the ferrocene subunit, which makes the Fc/Fc oxidation process remarkably more difficult. On the contrary, very small or nil electrostatic repulsive effects are observed in the oxidation process involving the cyclam fragment of 8, whose Ex/2 potential is only slightly more positive than that observed for the oxidation of the reference system ArS02[Ni (cyclam)]2+ (see Fig. 4). In this connection, it should be considered that the increase of the positive electrical charge of the redox active metal centre (from 2+ to 3-I-) takes place under a much more moderate... 

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