Bound water molecule definition

Water in food products can be described as being free or bound. The definition of what consitiutes bound water is far from clear (see Fennema, 1985) but it can be considered as that part of the water in a food which does not freeze at — 40°C and exists in the vicinity of solutes and other non-aqueous constituents, has reduced molecular mobility and other significantly altered properties compared with the bulk water of the same system (Fennema, 1985). The actual amount of bound water varies in different products and the amount measured is often a function of the assay technique. Bound water is not permanently immobilized since interchange of bound water molecules occurs frequently. 

The amino acid residue that bridges the two-metal sites is shown in italic boldface. When the symbol H2O is given this may represent from one to three metal-bound water molecules. R is the distance between the metal atoms. When Trp is listed as a ligand, the a-amino and a amide carbonyl are the ligands. See footnote of Table 1 for the definitions of other terms. 

This chapter has given an overview of the structure and dynamics of lipid and water molecules in membrane systems, viewed with atomic resolution by molecular dynamics simulations of fully hydrated phospholipid bilayers. The calculations have permitted a detailed picture of the solvation of the lipid polar groups to be developed, and this picture has been used to elucidate the molecular origins of the dipole potential. The solvation structure has been discussed in terms of a somewhat arbitrary, but useful, definition of bound and bulk water molecules. 

Water in skeletal carbonates bound Hp and OH , 106-107,109 liquid Hp in fluid inclusions, 106 Water molecules at day interface, modes of reorientation, 403-404 Water self-diffusion coefficient, measurement, 404-405 Weathering, definition, 4 Wintergreen, triboluminescent spectra, 255259... 

The hydrate contains water as an integral part of the crystalline structure of the compound. When salt crystallizes from an aqueous solution, the number of water molecules bound to the metal ion are characteristic of the metal and are in a definite proportion. Thus when copper sulfate crystallizes from water, the blue salt copper(II) sulfate pentahydrate, CuS04-5H20, forms. As indicated by the formula, 5 waters of hydration are bound to the copper(II) ion in copper sulfate. Notice how the formula is written—the waters of hydration are separated from the formula of the salt by a dot. 

Here, we adopt a definition of dynamic hydration numbers based on the average number of water molecules that are bounded to the ion with enough strength to participate in its diffusive motion. - To quantify the concept, the following expression is used ... 

Two interrelated topics that bear most directly on the description of the hydration shell—i.e., the bound water layer(s)—are the definition of the shell and its thickness. The problem of how the bound water can be sufficiently precisely defined is discussed elsewhere [11,37,51] and we shall not pursue it further here. It is clear, however, that the extent to which water is affected by a nearby surface is a function of the distance between them, namely the thickness of the hydration shell. Second-layer water (and, obviously, multilayer water) is much less perturbed than the water adjacent to the surface. We have used several methods to evaluate the thickness of the interphasal water layer in system A (as revealed by the low-temperatme behavior of water) [2,11] and found it to be about 0.5 nm. Virtually the same value has been assessed for the thickness of the bound water layer on many organic and inorganic substrates [37,52-57]. As 0.5-0.6 nm is the thickness of two water molecules [45], we may envisage two monolayers of interphasal (or boimd) water that are loosely associated with the substrate. We have shown that Aw/eo = 3 for system A at a total water content of 30 wt%. 

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