Volume, hydration

Nature of ion exchange resin. The absorption of ions will depend upon the nature of the functional groups in the resin. It will also depend upon the degree of cross-linking as the degree of cross-linking is increased, resins become more selective towards ions of different sizes (the volume of the ion is assumed to include the water of hydration) the ion with the smaller hydrated volume will usually be absorbed preferentially. 

Cation Ionic radius (A) Hydrated radius (A) Ionic volume (A3) Hydrated volume (A3) Exchange rate (s ) Transport number... 

After equilibration, the sample is applied to a GF/G filter under reduced pressure. The filter is dried under vacuum such that the sample equilibrates with the filter hydration volume. Reproducible sample application to the central part of the filter is facilitated by the use of a special adapter. 

Tabled shows the results for the regression analysis of dodecylsul-fate surfactants with different alkali counterions. The degree of surfactant ion/counterion association in the adsorption layer is evidently high (from 89.9% to 92.6% counterion coverage). There is also a correlation between the hydrated radius (volume) of the counterions and Coo. The decrease in the hydrated volume of the coimterions results in the higher value of Coo, and increases the attractive force between the molecules. A pictorial presentation...

Traditionally, the chemical potential of the standard hydrate is assumed to be at a given volume, independent of the hydrate guests. If the standard hydrate volume is not the volume of the equilibrium hydrate, there should be an energy change proportional to the difference in volume (AvH = v11 — 7). Note that, in the development of Equation 5.23, Av11 is assumed to be equal to zero (i.e., all hydrates of a given structure are at the same volume). 

Regressed Volumetric Thermal Expansion Parameters for Hydrate Volume (Divide by 3 to Get Linear Thermal Expansion Parameters)... 

Regressed Repulsive Constants and Guest Diameters for Hydrate Volume... 

Yousif et al. (1988) model. Rempel s model predicts a hydrate volume fraction of less than 1%, with a time period required of 2 x 105 years for a 1% accumulation of hydrates. 

Disaccharides can have similar utility to monosaccharides in DNA delivery polymers. Trehalose, a disaccharide composed of two glucose units linked via an a-(l—>1) glycosidic bond, has been shown to have cryo- and lyo-protective properties, attributed to an unusually large hydration volume [152]. As a function of these properties, trehalose has been shown to prevent aggregation and fusion of proteins and lipids [153]. Logically, incorporation of these features into a polymer backbone could afford similar characteristics to a DNA delivery system and may prevent aggregation of polyplexes in physiological serum concentrations and ionic... 

We can reasonably assume two major contributions to the difference in specific volume between the unfolded and folded states of a protein. The first contribution is that arising from the decrease in solvent-excluded volume when the tightly, but of course not perfectly, packed protein folded structure is disrupted. Water molecules enter this volume, thereby decreasing the overall volume of the protein solvent system. The magnitude of this contribution is a specific property of the protein, both in its folded and unfolded state. The second contribution arises from the change in the volume of the water molecules that hydrate the newly exposed protein surface area, relative to their volume in the bulk. Much of our present understanding of the contribution of differential hydration volume has come from recent studies of model compounds and proteins based on PPC. This technique, developed by Brandts and coworkers [17] and recently reviewed by us [16,18], is based on the measurement of the heat released or absorbed upon small (e.g., 0.5 MPa) pressure... 

Here we compare the thermodynamic parameters of trehalose, maltose and sucrose because they have the same chemical formula (C12H22O11) and mass (molecular weight 342.3), but different structures which could be responsible for their different hydration properties. The anomaly of hydration of trehalose is understood from the following observation [10]. Namely, the amount of water used for the preparation of 1.5 M trehalose solution is smaller than the amount used for the preparation of other sugar solutions. In a 1.5 M solution, trehalose itself occupies 37.5% of the volume of the solution. However, in a 1.5 M solution, sucrose occupies 13% and maltose occupies 14%. These data suggest that trehalose has a larger hydrated volume than the other sugars. This hypothesis can be demonstrated from various thermodynamic parameters as shown in Table 12.1. 

The individual HA molecules are present in solutions in random coil conformation and occupy large hydrated volume. This depends on the molecular mass of HA as well as on its concentration When the concentration increases, the motion of the molecular segments becomes more restricted [143]. As an important consequence, such crowded molecular system has significant viscous and elastic properties. The biological role of the HA in vitreous body and in the joint was interpreted according to these rheological properties [144]. 

Cation Ionic Radius (A) Hydrated Radius (A) Ionic Volume (A ) Hydrated Volume (A ) Exchange Rate (s ) Transport Number... 

Soak the resin before adding it to the column to allow it to reach its hydrated volume. 

A prolate shape also appears to explain better the hydrodynamic properties of iron-free (142) and of iron-saturated (143) transferrin. Ferric transferrin (a/b = 3) would, however, be more elongated than the iron-free form (a/b =2) while the effective hydrodynamic volume (Ve) would be higher for the iron complex than for the apoprotein. These results not only differ from those given in Table 3 for conalbumin but are also in partial disagreement with dielectric dispersion and viscosity measurements (144) which have indicated that human transferrin assumes a more spherical shape with iron-saturation, the axial ratio decreasing from 2.5 (apo) to 2.0 (ferric). This latter investigation also indicates a slight expansion (15.4 16.9) of the hydrated volume... 

Water hydration and counter-ion solvation of biological macro molecules considerably alter the translational and rotational dynamics ofbiological macromolecules. The effect can be correlated with a number of different solution properties of a given biological macromolecule such as the hydrated volume Vh- The term Vh is given by... 

Having now discussed hydrated volume, molecular shape and the frictional forces that oppose rotational and translational motion, we are now ready to discuss diffusion, the complete set of processes (including Brownian motion) that together bring about the bulk movement of biological macromolecules from one place to another in aqueous buffer solution. The processes that comprise diffusion are quantified by means of the concept of flux. Flux is defined as... 

Ion Ionic radius kf Hydrated radius(k) Ionic volume (A ) Hydrated volume (A ) Coordination number Water exchange rate(s ) ... 

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