Effect of an Electric Charge

At surfaces the effect of an electrical charge is much more pronounced than in bulk. There are two reasons for this. The first is that all the electrostatic lines of force, instead of radiating out spherically and symmetrically as is the case for an isolated point charge, are concentrated into the region 

The second factor is simply the high effective concentration of the charged groups attainable at the interface by virtue of the inability of the long-chain ions to escape into the bulk, due to strong forces of adsorption. The ions may consequently be packed more closely together than is ever possible in bulk solution. 

These two factors, each enhancing the effect of the electrical charge on the interface, are naturally very important in reactions occurring at 

Alexander and Rideal (30) found that the hydrolysis of a monolayer of ethyl palmitate on alkali became unusually slow as the reaction proceeded. They suggested that the reason for this decrease in rate lay in a reduced concentration of hydroxyl ions at the surface due to repulsion by the negative charge upon the interface, for which the palmitate ions formed in the saponification were responsible. 

The effect of the electric charge on the kinetics of surface reactions was investigated in detail by Davies (49) and by Davies and Rideal (21). They showed that the effect could be studied from two aspects the varia- 

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Mathematically, there is no difference between this treatment and that described later in Section V. If the soluble ion is negatively charged (s = —1) while the surface remains positive, the collision rate will be increased. Physically, this may be regarded as an attraction of the surface for the ions immediately below it, with the result that these do not move randomly but tend rather to oscillate continually between the surface and the liquid just below, till eventually chemical reaction occurs. The catalytic effect of an electric charge in the surface can, however, be treated more effectively by the method explained in Section V. 

FIG. 6 Effect of an electric field on the resultant number of solvent molecules permeating the membrane as a function of time for the case of charged solute molecules, and nonpolar homonuclear solvent molecules. R refers to the field being periodically reversed [26]. 

FIGURE 17.4 The effects of an electric field on nuclear radiation. The direction of deflection shows that a-rays are positively charged, p-rays negatively charged, and y-rays uncharged. 

When an electrostatic field of field strength E is applied, each type j of ion carrying charge ZjF (per mole) finds itself under the effect of an electric driving force... 

The energy dissipation of a system containing free charges subjected to electric fields Is well known but this Indicates a non-equilibrium situation and as a result a thermodyanmlc description of the FDE Is Impossible. Within the framework of interionic attraction theory Onsager was able to derive the effect of an electric field on the Ionic dissociation from the transport properties of the Ions In the combined coulomb and external fields (2). It is not improper to mention here the notorious mathematical difficulty of Onsager s paper on the second Wien effect. 

Effect of an electric field on a polar bond. A bond with a dipole moment (as in HF, for example) is either stretched or compressed by an electric field, depending on the direction of the field. Notice that the force on the positive charge ism the direction of the electric field (E), and the force on the negative charge is in the opposite direction. 

The effect of an electrical field on the absorption/emission of spectra of a probe such as fluorescein or a coumarin derivative. It is derived from the interaction of the induced dipole(s) in the probe interacting with the charged group. See Sitkoff, D., Lockhart, D.J., Sharp, K.A., and Honig, B., Calculation of electrostatic effects at the amino terminal of an helix, Biophys. J. 67,2251-2260,1994 Pierce, D.W. and Boxer, S.A., Stark effect spectroscopy of tryptophan, B/opfiyx. J. 68,1583-1591,1995 Klymchenko, A.S., Avilov, S.V., and Demchenko, A.P., Resolution of Cys and Lys labeling of a-crystalUn with site-sensitive fluorescent 3-hydroxyflavone dye. Anal. Biochem. 329, 43-57, 2004. 

Murphy, A.T. Adler, F.T. Penny, G.W. A theoretical analysis of the effects of an electric field on the charging of fine particles. Trans. AIEE 1959, 78, 318-326. 

The effect of an electric field in inducing an electric charge on a powder that is nominally nonconducting is illustrated in Figure 6, but has been known from... 

Capillary electrophoresis corresponds to an adaptation of the more general electrophoresis methodology. This separative technique is based upon the differential migration of the species, whether or not they carry an overall electric charge, present in the sample solution, under the effect of an electric field and when supported by an appropriate medium. 

The self-atom and atom-atom polarizabilities (nAA,nAB) defined using perturbation theory have been also employed to describe chemical reactivity [44], These quantities represent the effect of an electric field perturbation at one atom on the electronic charge at the same (nAA) or another atom (nAB), respectively. 

Electrophoretic methods are used to separate substances based on their charge-to-mass ratios, using the effect of an electric field on the charges of these substances. These techniques are widely used for charged colloidal particles or macro-molecular ions such as those of proteins, nucleic acids, and polysaccharides. There are several types of electrophoresis, zone electrophoresis being one of the most conunon. 

The transport of the three charged species (1 - surfactant, 2 - counterion, 3 - coion) with valence Zj under the effect of an electric potential is given by Eq. (7.75), which reads for the present situation. 

Most membrane proteins are electrically active. If a membrane-spanning protein has a conformational change that involves translocation or displacement of charges, or change in the molar electric moment (A Me), then a transmembrane electric field will shift its chemical equilibrium to favor states that have higher electric moments (Me). The quantitative relationships for the effect of an electric field on the chemical equilibrium represented by eq 5 are given in eqs 6-8 (13, 14) ... 

Fig. 3.1 The electrostatic potential of an electric charge of —ep dr at distance r from a point nucleus is given by V, but when the nucleus has a finite radius, the potential curve within the sphere is different. The shaded area indicates the effect of a change in the nuclear radius from to...

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