Internal electrostatic interactions

A key component of particle-based simulation methods involves the coupling of the dynamics of the charge carriers (ions) with the field of forces generated by the external boundary conditions as well as by the internal electrostatic interactions between the components of the system. This self-consistent coupling approach has been successfully employed for more than three decades in plasma simulations. The adjective self-consistent refers to the fact that the forces caused by the electrostatic interactions within the components of the system depend strictly on the spatial configuration of the components and must be updated continuously as the dynamics of the system evolves. 

Protein adsorption has been studied with a variety of techniques such as ellipsome-try [107,108], ESCA [109], surface forces measurements [102], total internal reflection fluorescence (TIRE) [103,110], electron microscopy [111], and electrokinetic measurement of latex particles [112,113] and capillaries [114], The TIRE technique has recently been adapted to observe surface diffusion [106] and orientation [IIS] in adsorbed layers. These experiments point toward the significant influence of the protein-surface interaction on the adsorption characteristics [105,108,110]. A very important interaction is due to the hydrophobic interaction between parts of the protein and polymeric surfaces [18], although often electrostatic interactions are also influential [ 116]. Protein desorption can be affected by altering the pH [117] or by the introduction of a complexing agent [118]. 

Int internal strain component Elec electrostatic interaction component vdW van der Waals interaction component. 

One area where the concept of atomic charges is deeply rooted is force field methods (Chapter 2). A significant part of the non-bonded interaction between polar molecules is described in terms of electrostatic interactions between fragments having an internal asymmetry in the electron distribution. The fundamental interaction is between the Electrostatic Potential (ESP) generated by one molecule (or fraction of) and the charged particles of another. The electrostatic potential at position r is given as a sum of contributions from the nuclei and the electronic wave function. 

The influence of pressure has also been used to tune the ST properties of these ID chain compounds. Application of hydrostatic pressure ( 6 kbar) on [Fe(hyptrz)3] (4-chlorophenylsulfonate)2 H20 (hyptrz=4-(3 -hydroxypro-pyl)-l,2,4-triazole) provokes a parallel shift of the ST curves upwards to room temperature (Fig. 5) [41]. The steepness of the ST curves along with the hysteresis width remain practically constant. This lends support to the assertion that cooperative interactions are confined within the Fe(II) triazole chain. Thus a change in external pressure has an effect on the SCO behaviour comparable to a change in internal electrostatic pressure due to anion-cation interactions (e.g. changing the counter-anion). Both lead to considerable shifts in transition temperatures without significant influence on the hysteresis width. Several theoretical models have been developed to predict such SCO behaviour of ID chain compounds under pressure [50-52]. Figure 5 (bottom) also shows the pressure dependence of the LS fraction, yLS, of... 

In addition, the direct electrostatic interaction between adsorbates has been treated . At intermediates distances of the order of a surface lattice constant, Norskov, Holloway, and Lang report that this interaction can give rise to substantial (> 0.1 eV) interaction energies, when both adsorbates in question induce electron transfer to or from the surface or have a large internal electron transfer. 

The elastic stress may be external or internal. External stresses are exerted on the chromatin during the cell cycle when the mitotic spindle separates chromosome pairs. The 30-nm fiber should be both highly flexible and extensible to survive these stresses. The in vitro experiments by Cui and Bustamante demonstrated that the 30-nm fiber is indeed very soft [66]. The 30-nm fiber is also exposed to internal stresses. Attractive or repulsive forces between the nucleosomes will deform the linkers connecting the nucleosomes. For instance, electrostatic interactions, either repulsive (due to the net charge of the nucleosome core particles) or attractive (bridging via the lysine-rich core histone tails [49]) could lead to considerable structural rearrangements. 

Ye, A. (2008). Complexation between milk proteins and polysaccharides via electrostatic interaction principles and applications - a review. International Journal of Food Science and Technology, 43, 406 115. 

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