Hydration state, internal

Regulation of Cellular Functions by the Internal Hydration State 196... 

REGULATION OF CELLULAR FUNCTIONS BY THE INTERNAL HYDRATION STATE... 

The burst pressure test characterizes the maximum internal pressnre, the vascnlar graft resists before failnre. The bnrst test is carried ont in the hydrated state nsing a setup similar to that of the pressure-diameter test that allows the system to achieve pressures higher than the physiological range (>2000 mm Hg). 

Quite recently, a series of pendant-type locally and densely sulfonated PESs were successfully obtained by a nucleophilic substitution reaction, followed by postsnlfo-nation using concentrated sulfuric acid (Figure 4.36) [45]. The polymers with lEC values ranging from 0.98 to 1.66 meq./g afforded considerable proton condnctivity and water absorption. The SPES with an lEC value of 1.66 meq./g showed a proton conductivity (0.131 S/cm) equal to Nation 117 at 100°C in fully hydrated state. Their excellent performance is attributed to the internal structure of the polymers, which formed a distinct phase separation between the hydrophilic and hydrophobic moieties observed by SAXS. 

Process. A typical indirect hydration process is presented in Eigure 1. In the process, propylene reacts with sulfuric acid (>60 wt%) in agitated reactors or absorbers at moderate (0.7—2.8 MPa (100—400 psig)) pressure. The isopropyl sulfate esters form and are maintained in the Hquid state at 20—80°C. Low propylene concentrations, ie, 50 wt %, can be tolerated, but concentrations of 65 wt % or higher are preferred to achieve high alcohol yields. Because the reaction is exothermic, internal cooling coils or external heat exchangers are used to control the temperature. 

Internal and External Phases. When dyeing hydrated fibers, for example, hydrophUic fibers in aqueous dyebaths, two distinct solvent phases exist, the external and the internal. The external solvent phase consists of the mobile molecules that are in the external dyebath so far away from the fiber that they are not influenced by it. The internal phase comprises the water that is within the fiber infrastmcture in a bound or static state and is an integral part of the internal stmcture in terms of defining the physical chemistry and thermodynamics of the system. Thus dye molecules have different chemical potentials when in the internal solvent phase than when in the external phase. Further, the effects of hydrogen ions (H" ) or hydroxyl ions (OH ) have a different impact. In the external phase acids or bases are completely dissociated and give an external or dyebath pH. In the internal phase these ions can interact with the fiber polymer chain and cause ionization of functional groups. This results in the pH of the internal phase being different from the external phase and the theoretical concept of internal pH (6). 

Figure 5 Time dependence of RMSD of atomic coordinates from canonical A- and B-DNA forms m two trajectories of a partially hydrated dodecamer duplex. The A and B (A and B coiTespond to A and B forms) trajectories started from the same state and were computed with internal and Cartesian coordinates as independent variables, respectively. (From Ref. 54.)...

Solvent effects also play an important role in the theory separating enthalpy and entropy into external and internal parts (134-136) or, in other terms, into reaction and hydration contributions (79). This treatment has been widely used (71, 73, 78, 137-141). The most general thermodynamic treatment of intermolecular interaction was given by Rudakov (6) for various states of matter and for solution enthalpy and entropy as well as for kinetics. A particular case is hydrophobic interaction (6, 89, 90). 

In conclusion, it is clear that a variety of stereoelectronic (internal) factors and external conditions favor a substantial positive charge in the transition state of diol epoxides as they undergo hydration or react with nucleophiles [115-118], Interpreting the reactivity of diol epoxides (or of numerous other electrophilic metabolites) in terms of toxification vs. detoxification is particularly difficult since toxicity depends as much on the nature of the endogenous nucleophile as on the intrinsic reactivity of the metabolites. 

The Proceedings of the International Gas Hydrate Conferences contain state-of-the-art descriptions of hydrates, at three year intervals ... 

Schaumann, G. E. (2005). Matrix relaxation and change of water state during hydration of peat. In A Selection of Papers from the Third International Conference Interfaces against Pollutions (IAP 2004), May 24-27, Julich, Germany. Colloids Surf. A Physicochem. Eng. Aspects 265(1-3), 163-170. 

The unterstanding of amphiphile association clearly must include detailed knowledge of the internal structure and dynamics, e.g., what is the conformation of the alkyl chains and what are their flexibility and packing conditions is the interior of micelles exclusively of hydrocarbon nature or is there any water penetration We will here consider the state of the hydrocarbon chains and defer a discussion of water penetration to the section on hydration. 

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