Clusters mobile water

To summarise, the ranges and mean values of mobilities of decay product ions in air are similar to, or rather lower than, the mobilities of ordinary atmospheric positive ions. A possible common factor is the clustering of water molecules, but this would not account for the ageing effect observed by Fontan et al. (1969) since the clustering of water molecules normally occurs in less than a millisecond. Raes (1985) and Raes et al. (1985) have pointed out that air in laboratory apparatus often has appreciable concentrations of organic vapours, derived from the materials used, unless care is taken to exclude them. Trace molecules... 

At the 0.07 h discontinuity, the heat capacity function shifts from generally downward-trending to strongly upward-trending. This is expected for a two-dimensional condensation process—here, the formation of mobile water clusters from dispersed water associated with ionizable protein surface groups. This transition in the surface water is seen also in the IR spectroscopic properties (Fig. 38) and other proper-... 

This suggests enhanced clustering of water with stabilization of WAW. Only one signal of mobile water (other protons are not observed in the spectra) can be caused by fast (in the NMR timescale) exchange of water molecules from different structures (Emsley et al. 1965) because the amounts of water are enough to form multilayer coverage of the HGA particles, and the HGA powder is characterized by the textural porosity. 

A second system in which permeant/permeant interactions are inherently stronger than polymer/permeant interactions is that of water in hydrophobic polymers. Water is strongly hydrogen-bonded in the liquid state and consequently this leads to association or clustering of water molecules sorbed into the polymer. Once formed, these clusters of water, which may be quite stable, will probably be relatively less mobile than individual molecules. Consequently, if the proportion of clusters increases with increasing sorbed concentration C, as implied by this type of isotherm, then the diffusion coefficient D will decrease with increasing This behaviour contrasts sharply with that described above for highly swollen non-polar systems where D increases with C. 

In many cases, a protonated molecular ion (M - - H)+ is the only ion observed in a thermospray spectrum but if ammonium acetate buffer is used, depending upon the relative proton affinities of the species present, an ammonium adduct (M - - NH4)+ may be the predominant ion. In addition, clusters may be formed with components of the mobile phase. Although the thermospray ionization process involves less energy than conventional Cl, and very little intense fragmentation is usually observed, the presence of ions due to the elimination of small molecules, e.g. water, methanol and ketene, is not unknown. These latter ions are usually of relatively low intensity when compared to the protonated or... 

When the second-site revertants were segregated from the original mutations, the bci complexes carrying a single mutation in the linker region of the Rieske protein had steady-state activities of 70-100% of wild-type levels and cytochrome b reduction rates that were approximately half that of the wild type. In all these mutants, the redox potential of the Rieske cluster was increased by about 70 mV compared to the wild type (51). Since the mutations are in residues that are in the flexible linker, at least 27 A away from the cluster, it is extremely unlikely that any of the mutations would have a direct effect on the redox potential of the cluster that would be observed in the water-soluble fragments. However, the mutations in the flexible linker will affect the mobility of the Rieske protein. Therefore, the effect of the mutations described is due to the interaction between the positional state of the Rieske protein and its electrochemical properties (i.e., the redox potential of the cluster). 

When water undergoes self-ionization, a range of cationic species are formed, the simplest of which is the hydronium ion, HjO (Clever, 1963). This ion has been detected experimentally by a range of techniques including mass spectrometry (Cunningham, Payzant Kebarle, 1972), as have ions of the type H+ (HaO) with values of n up to 8. Monte-Carlo calculations show that HjO ions exist in hydrated clusters surrounded by three or four water molecules in the hydration shell (Kochanski, 1985). These ions have only a short lifetime, since the proton is highly mobile and may be readily transferred from one water molecule to another. The time taken for such a transfer is typically of the order of 10 s provided that the receiving molecule of water is correctly oriented. 

Ion exchange is actually a far more complicated process than the simple exchange of one cation for another or one anion for another, particularly for complex polyions such as proteins and oligonucleotides. Each ion of the stationary or mobile phase is surrounded by a cluster of counterions and water. When an ion in the mobile phase is transferred to the stationary phase, the cluster of counterions and water surrounding it is partially or completely displaced. A similar event occurs at the binding site of the stationary phase. Ions displaced from the stationary phase undergo the converse process. The... 

Luck, W.A.P. 1981. Structures of water in aqueous systems. In Water Activity Influences on Food Quality (L.B. Rockland and G.F. Stewart, eds), pp. 407 134. Academic Press, New York. Ludescher, R.D., Shah, N.K., McCaul, C.P., and Simon, K.V. 2001. Beyond Tg Optical luminescence measurements of molecular mobility in amorphous solid foods. Food Hydro colloids 15, 331-339. Ludwig, R. 2001. Water From cluster to the bulk. Angewandte Chem. Int. Ed. 40, 1808-1827. Maclnnes, W.M. 1993. Dynamic mechanical thermal analysis of sucrose solutions. In The Glassy State in Foods (J.M.V. Blanshard and PJ. Lillford, eds), pp. 223-248. Nottingham Univ. Press, Loughborough, Leicestershire. 

The solubility of an ionic dye in water normally increases with temperature, since the enhanced mobility favours electrostatic repulsion between ions rather than closer approach to form aggregates by means of the short-range attractive forces. Addition of a simple inorganic electrolyte, on the other hand, normally lowers the solubility limit at a given temperature. Such additions enhance the ionic character of the aqueous phase and help to stabilise the structure of dye aggregates by forming an electrical double layer within the sheath of clustered water molecules around them. 

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