Hydration interactions

Interchain Hydrogen-bonding Side-chain interaction Hydration Shell... 

For the interaction potentials provided by Eqs. (12) and (13) and various values of Kc, the average separation as a function of the external pressure is compared in Fig. 5 with experiment (Ref. [13]) for neutral lipid bilayers at different salt concentrations. Note that the force due to the confinement of the undulation is not simply additive to the other interactions (hydration... 

Keywords Hairy surface Double-layer interaction Hydration energy, Specific ion effect... 

Non-Ionics of the C E -type have a very typical solubility behaviour, which is related to the EO-water interaction, hydration for short. First, poly(ethylene oxide), (PEO)jj is fairly soluble in water at room temperature, but polylpropylene oxide) (PPO) is not (as expected), and neither is poly(methylene oxide) (PMO), (unexpected). This irregular trend reminds us that solubility is not only determined by hydration in solution, but also by the Gibbs energy in the crystalline phase, which will be related to the molecular packing therein. Based on this difference in solubility, and hence in adsorbability, surface active polymers of the PEO-PPO type have been synthesized [Pluronics]-, they have a wide scope of application. 

Polar molecule needs to be almost in contact with ion for substantial ion-dipole interaction. Hydrated compounds... 

These (or similar) interactions find their antecedents in the literature [74, 92, 142, 153, 179], The stronger the interaction of the anion with the hydroxyl group of the alcohol, the more activated the alcoholate will be for nucleophilic attack on the carboxyl carbon, which itself can be activated by a Lewis-type complex formed with a Lewis acidic cation. A third beneficial interaction with a basic anion may arise from strong interactions (hydration) with the water formed, which would drive the equilibrium reaction towards the product side [96-112],... 

Electrical double layer van der Waals Steric interaction Hydration/solvation interaction Polymeric bridging Hydrophobic interaction... 

It is important to realise that hydrophobic hydration is a physical consequence of rearrangement of the water stmcture around the solute, and is not primarily a result of direct attractive interactions between solute and water molecules. It is a hydration phenomenon totally distinct from the sort of attractive interaction hydration which occurs when a polar or charged solute is dissolved in water. 

Abstract. The stability of suspensions/emulsions is under consideration. Traditionally consideration of colloidal systems is based on inclusion only Van-der-Waals (or dispersion) and electrostatic components, which is refereed to as DLVO (Derjaguin-Landau-Verwey-Overbeek) theory. It is shown that not only DLVO components but also other types of the inter-particle forces may play an important role in the stability and colloidal systems. Those contributions are due to hydrodynamic interactions, hydration and hydrophobic forces, steric and depletion forced, oscillatory structural forces. The hydrodynamic and colloidal interactions between drops and bubbles emulsions and foams are even more complex (as compared to that of suspensions of solid particles) due to the fluidity and deformability of those colloidal objects. The latter two features and thin film formation between the colliding particles have a great impact on the hydrodynamic interactions, the magnitude of the disjoining pressure and on the dynamic and thermodynamic stability of such colloidal systems. 

The Macinnes, Debye-HUckel, and pH conventions describe the ionic activity as a function only of ionic strength. It is, however, not reasonable to expect the chloride ion, for example, always to have the same activity coefficient at a fixed temperature and ionic strength, regardless of the nature of the counter cation. Bjerrum (58) showed in 1920 that the behavior of electrolytes, including the minima observed in plots of In y+ vs. I, provides evidence for ion-solvent interactions. Hydration of the ions must be considered, and "single-parameter conventions are inadequate from the standpoint of solution theory. 

Fig. 4. Preferential interaction (hydration) parameter 1, as a function of reciprocal salt concentration l/w (1V3 in gram of salt/gram of water), for 1 bovine serum albumin and 2 aldolase solutions in guanidine HCl (lower scale) 3 NaDNA in NaCl and 4 CsDNA in CsCl solution (upper scale) [77R1].

Emulsions and microemulsions are dispersions of liquid in liquid. Therefore, an important feature is their interfacial fluidity and deformability, which distinguishes them from suspensions of solid particles. The stability of the latter is usually treated in the framework of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, " which accounts for the electrostatic and van der Waals interactions between solid particles. During recent years it was shown that other types of interparticle forces may often play an important role for the stability of dispersions—hydrodynamic interactions, hydration and hydrophobic forces, oscillatory structure forces, etc. - It was proven both experimentally and theoretically that steric and depletion " interactions may sometimes be a decisive factor for the dispersion stability. 

Hydrates are solid structures composed of water molecules joined as crystals that have a system of cavities. The structure is stable only if at least one part of the cavities contains molecules of small molecular size. These molecules interact weakly with water molecules. Hydrates are not chemical compounds rather, they are clathrates . 

The SPC/E model approximates many-body effects m liquid water and corresponds to a molecular dipole moment of 2.35 Debye (D) compared to the actual dipole moment of 1.85 D for an isolated water molecule. The model reproduces the diflfiision coefficient and themiodynamics properties at ambient temperatures to within a few per cent, and the critical parameters (see below) are predicted to within 15%. The same model potential has been extended to include the interactions between ions and water by fitting the parameters to the hydration energies of small ion-water clusters. The parameters for the ion-water and water-water interactions in the SPC/E model are given in table A2.3.2. 

The solute-solvent interaction in equation A2.4.19 is a measure of the solvation energy of the solute species at infinite dilution. The basic model for ionic hydration is shown in figure A2.4.3 [5] there is an iimer hydration sheath of water molecules whose orientation is essentially detemiined entirely by the field due to the central ion. The number of water molecules in this iimer sheath depends on the size and chemistry of the central ion ... 

A typical force curve showing the specific avidin-biotin interaction is depicted in figure Bl.20.10. The SFA revealed the strong influence of hydration forces and membrane undulation forces on the specific binding of proteins to membrane-bound receptors [81]. 

It will be noted that hydration enthalpy decreases with increasing ionic radius and increases very sharply with increase in ionic charge, these results being what we should expect for an electrostate interaction between a charged ion and the dipole of a water molecule (p, 44). 

A possible explanation of the hysteresis could be the non-equilibrium of the DNA hydration. In that case the value of hysteresis has to depend on the size of the experimental sample. However, such a dependence is not observed in the wide range of DNA film thicknesses (0.05-0.2 fmi) [14], [12]. Thus, hysteresis cannot be a macroscopic phenomenon and does reflect the molecular interaction of water and the biopolymer. 

Eisenstein, M., Shakked, Z.i Hydration patterns and intermolecnlar interactions in A-DNA crystal structures. Implications for DNA recognition. J. Mol. Biol. 248 (1995) 662-678... 

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