Ionic repulsion

Ionic repulsion between anionic samples and the resin causes poor resolution. As shown in Fig. 4.17, the addition of only 0.01 M NaNO, results in normal elution and peak shape for an anionic polymer, sodium polyacrylate. 

In the case of functional polymers such as nylon, the molecular size can increase because ionic functional groups contained in the molecule repel each other. To decrease ionic repulsion, sodium trifluoroacetate should be added to HFIP. 

A second surface modification has been reported by Yamamoto et al. These workers added stearic acid to their carbon paste mixture. This produced an electrode which was relatively insensitive to ascorbic acid and DOPAC relative to dopamine. It is theorized that this electrode works because of electrostatic repulsion of the anionic ascorbate and DOPAC by surface stearate groups. Ionic repulsion has also been employed by covering the surface of the working electrode with an anionic polymer membrane. Gerhardt et al. used Nafion, a hydrophobic sulfonated perfluoro-polymer, to make a dopamine selective electrode. This electrode exhibited selectivity coefficients as large as 250 1 for dopamine and norepinephrine over ascorbic acid, uric acid, and DOPAC. 

Several types of interaction can be probed with AFM (i) Van der Waals forces and ionic repulsion, (ii) magnetic and electrostatic forces, (iii) adhesion and frictional forces and (iv) the elastic and plastic properties of the surface. In terms of the interactions relevant to electrochemistry, only those interactions typified in (i) will be considered. 

All in all, affinity and potency of an agonist at a particular mGluR subtype seem to correlate with the nature of its interactions with Lobe I and II and to what extent it is capable of stabilizing the closed ATD. Selectivity, on the other hand, arises from sterical hindrance or ionic repulsion between the distal acidic group of the agonist and side chains of distal residues present in some mGluR subtypes but not in others. The Y74/R57/K74 residue in mGluRl/2/4 appears to be a particular important determinant of selectivity. The side... 

THE EFFECT OF IONIC REPULSION AMONG HYDROPHILIC GROUPS ON THE AGGREGATION STRUCTURE OF MONOLAYER... 

Since cations and anions have opposite charges, is negative. The force between two anions will yield a positive value of . We see how a positive value of implies an inter-ionic repulsion and a negative value implies an inter-ionic attraction. 

Dispersants function through various mechanisms. For water-based systems the preferred mechanism is stabilisation by ionic repulsion. A repulsion force layer is formed around the mineral particle. To maintain the suspension stability, the thickness of this layer around each particle has to be increased with increasing particle size. Layer decay is more frequent with the use of small particles, which results in higher proneness to partial flocculation. Also a uniform layer is necessary for effective stabilisation of all dispersed particles. AMP-95 helps to achieve all these requirements. 

Phosphatidic Acid Monolayers. Phosphatidic acid, prepared from egg lecithin by the action of phospholipase D, forms considerably more expanded monolayers than egg lecithin, presumably because of ionic repulsion between the phosphate groups in the phosphatidic acid mono-layers (42). Phosphatidic acid monolayers showed about four times more increase in surface potential when CaCl2 is substituted for NaCl in the subsolution than did egg lecithin monolayers (43). This again supports the conclusion that the trimethylammonium group competes with Ca2+ for the anionic phosphate group in egg lecithin monolayers (Figure 1A). 

Since coiled chains of proteins are known to uncurl because of ionic repulsions when ionization occurs, Reid (1957) suggested that excited state dissociation acts as a trigger in rapid biological processes. The 7-azaindole dimer, which undergoes photo-induced double proton transfer (see Section 4), has similarities to the adenine-thymine and guanine-cytosine base pairs of DNA. Its excited state proton transfers have been proposed as possible mechanisms of mutagenesis (Ingram and El-Bayoumi, 1974). 

Micellar size is larger with lipids having longer hydrocarbon chains, since the hydrocarbon-volume-to-head ratio is higher and the attractive forces between the tails (van der Waals forces) are greater than the ionic repulsive forces between the head groups. 

The molecular size of the PSS depends on the type of the buffer counterion. The effective charge of the PSS decreases in the series Li+/Na+/K+/Cs+ due to the increasing affinity to the sulfo groups. The decrease in the effective charge leads to a decrease in the radius of gyration of the PSS due to a decrease in ionic repulsion. The consequent increase of the mobility has been observed with PSS with uncoated capillaries in the counter electroosmotic mode [25]. 

The structure of lithium fluoride, (a) Represented by a ball-and-stick model. Note that each Li+ ion is surrounded by six F ions, and each F ion is surrounded by six Li+ ions, (b) Represented with the ions shown as spheres. The structure is determined by packing the spherical ions in a way that both maximizes the ionic attractions and minimizes the ionic repulsions. 

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