Electrostatic interactions with

In the absence of dyes, APA- and AdPA-grafted silica bind La(III) with, respectively, 0.20 and 0.27 mmol/g sorption capacity, resulting in formation of 1 2 (La L) complexes. 50% of introduced cation is bonded at pH=5 (APA), pH=6.1 (AdPA) and complete adsorption occurs at pH=6 (APA), pH=6.5 (AdPA). The grafted support in absence of La adsorbs the chosen dyes at pH<4 due to the electrostatic interaction with the -NH, groups on the surface, present as a result of grafting procedure. The adsorption of dyes at pH>4 is insignificant. 

Thus the potential difference at the interface between a metal and electrolyte solution is due to both the charges at the interface (electrostatic potential difference) and the surface dipole layers the latter is referred to as the surface or adsorption potential difference. On the basis of the above considerations it might appear that adsorption at a metal surface with an excess charge is solely due to electrostatic interaction with charged species in the solution, i.e. if the metal surface has an excess negative charge the cations... 

The second part of lanosterol biosynthesis is catalyzed by oxidosqualene lanosterol cyclase and occurs as shown in Figure 27.14. Squalene is folded by the enzyme into a conformation that aligns the various double bonds for undergoing a cascade of successive intramolecular electrophilic additions, followed by a series of hydride and methyl migrations. Except for the initial epoxide protonation/cyclization, the process is probably stepwise and appears to involve discrete carbocation intermediates that are stabilized by electrostatic interactions with electron-rich aromatic amino acids in the enzyme. 

Second in penetrating power is (3 radiation. These fast electrons can penetrate about 1 cm into flesh before their electrostatic interactions with the electrons and nuclei of molecules bring them to a standstill. 

In the same manner, the rc-electron densities of the monomer and the cation are affected. Substituents, which decrease the electron density at the P-C-atom, that is, the place of the primary attack on the double bond, increase the positive charge at the a-C-atom of the cation and therefore its electrostatic interaction with a negative reaction centre (qa(cation) = —2.08 + 2.53qp(monomer) r = 0.93 n = 13). The previous equation shows that the electron density of the cation is more influenced than that of the monomer (Aqp(monomer) = 0.1 and Aqjcation) = 0.25).. 

Salts of fatty acids are classic objects of LB technique. Being placed at the air/water interface, these molecules arrange themselves in such a way that its hydrophilic part (COOH) penetrates water due to its electrostatic interactions with water molecnles, which can be considered electric dipoles. The hydrophobic part (aliphatic chain) orients itself to air, because it cannot penetrate water for entropy reasons. Therefore, if a few molecnles of snch type were placed at the water surface, they would form a two-dimensional system at the air/water interface. A compression isotherm of the stearic acid monolayer is presented in Figure 1. This curve shows the dependence of surface pressure upon area per molecnle, obtained at constant temperature. Usually, this dependence is called a rr-A isotherm. 

The ions in solution are subject to two types of forces those of interaction with the solvent (solvation) and those of electrostatic interaction with other ions. The interionic forces decrease as the solution is made more dilute and the mean distance between the ions increases in highly dilute solutions their contribution is small. However, solvation occurs even in highly dilute solutions, since each ion is always surrounded by solvent molecules. This implies that the solvation energy, which to a first approximation is independent of concentration, is included in the standard chemical potential and has no influence on the activity. 

In 1910, Georges Gouy (1854-1926) and independently, in 1913, David L. Chapman (1869-1958) introduced the notion of a diffuse electrical double layer at the surface of electrodes resulting from a thermal motion of ions and their electrostatic interactions with the surface. 

The EFG parameters Vzz and described by (4.42a) and (4.42b) do not represent the actual EFG felt by the Mossbauer nucleus. Instead, the electron shell of the Mossbauer atom will be distorted by electrostatic interaction with the noncubic distribution of the external charges, such that the EFG becomes amplified. This phenomenon has been treated by Stemheimer [54—58], who introduced an anti-shielding factor (1 —y 00) for computation of the so-called lattice contribution to the EFG, which arises from (point) charges located on the atoms surrounding the Mossbauer atom in a crystal lattice (or a molecule). In this approach,the actual lattice contribution is given by... 

Certain kinds of metal ions bind to the DNA double strands by an electrostatic interaction with the phosphate group(s) or by complex formation with the sugar moiety or the nucleic... 

As an alternative to peptidic inhibitors, which display electrostatic interactions with the active site, covalent inhibitors have also been described recently. Such peptides bear a functional group that can react reversibly with the catalytic serine of the protease. These include aldehydes, a-ketoacid derivates, lactams and boronates. 

The reactions and compound presented in this chapter support the notion that the formation of o-QMs from the parent phenols is a quite complex process. In the case of the oxidation by Ag20 but also likely in other oxidations, a zwitterionic intermediate is involved that can be stabilized intermolecularly, for example, by electrostatic interaction with other suitable zwitterions, or intramolecularly by neighboring groups or inductive/mesomeric effects. By stabilizing the zwitterionic intermediate and destabilizing the o-QM, the energetic gap between these two intermediates is lowered and... 

Comparison of solution pH with the pKa of a side chain informs about the protonation state. A unique pKa, termed the standard or model pKa, can be experimentally determined for each ionizable side chain in solution when it is incorporated in a model compound, often a blocked amino acid residue [73] (Table 10-1). In a protein environment, however, the pKa value of an ionizable side chain can substantially deviate from the standard value, due to desolvation effects, hydrogen bonding, charge-charge, charge-dipole, and other electrostatic interactions with the... 

In compounds (II) and (III) (Table 2) a very short O-O distance is observed, which is due to the formation of strong hydrogen bonds in [H(H20)2] + cations, whereas in compound (I) the 0-0 distance is about 0.3 A longer (Table 1 and papers [44,73,74,101]). In compounds (I) and (II) in contrast to (III), the Brax atoms are simultaneously bonded by way of an electrostatic interaction with two octanuclear fragments, thus forming in the crystals of these compounds endless chains. 

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