Water in Biological Materials

Water behaves differently in different environments. Properties of water in heterogenous systems such as living cells or food remain a field of debate. Water molecules may interact with macromolecular components and supramolecular structures of biological systems through hydrogen bonds and electrostatic interactions. Solvation of biomolecules such as lipids, proteins, nucleic acids, or saccharides resulting from these interactions determines their molecular structure and function. 

Various physical techniques, i.e., nuclear magnetic resonance (NMR), x-ray diffraction, and chemical probes (exchange of H by D), indicate that there is a layer of water bound to protein molecules, phospholipid bilayers, and nucleic acids, as well as at the surface of the cell membranes and other organelles. 

Water associated at the interfaces and with macromolecular components may have quite different properties from those in the bulk phase. Water can be expected to form locally ordered structures at the surface of water-soluble, as well as water-insoluble, macromolecules and at the boundaries of the cellular organelles. Biomacromolecules generally have many ionized and polar groups on their surfaces and tend to align near polar water molecules. This ordering effect exerted by the macromolecular surface extends quite far into the surrounding medium. 

According to the association-induction theory proposed by Ling (1962), fixed charges on macromolecules and their associated counterions constrain water molecules to form a matrix of polarized multilayers having restricted motion, compared with pure water. The monolayer of water molecules absorbed on the polar sorption site of the molecule is almost immobilized and thus behaves, in many respects, like part of the solid or like water in ice. It has different properties than additional water layers defined as multilayers have. The association-induction theory has been shared by many researchers for many years. Unfortunately, elucidation of the nature of individual layers of water molecules has been less successful, due to the complexity of the system and lack of appropriate techniques. 

Measurements of the diffusion coefficients of globular protein molecules in solution yield values for molecular size that are greater than the corresponding radii determined by x-ray crystallography. The apparent hydrodynamic radius can be calculated from the Stokes-Einstein relation  

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Grant, E.H. "Determination of Bound Water in Biological Materials." In Proc. Workshop Physical Bases of Electromagnetic Interactions with Biological Systems, University of Maryland, 1979, p. 113. 

NMR imaging is increasingly used to study structures and processes in solid materials. In some instances, the material being imaged is a liquid that penetrates a solid substance—for example, water and oil in sandstone. Here the methods are similar to those that we have already described for imaging water in biological materials, with parameters adjusted according to the nature and size of the samples. 

However, in many technologically important situations, water is not in its bulk form but instead is attached to some substrates or filling small cavities. Common examples are water in porous media, such as rock or sandstones, and water in biological material as in the interior of cells or attached to surfaces of biological macromolecules and membranes. This is what we define here as the confined or the interfacial water. 

Mashimo, S., Kuwabara, S., Yagihara, S., and Higasi, K. 1997. Dielectric relaxation time and structure of bound water in biological materials. Journal of Physical Chemistry 91 6337-6338. 

Dielectric spectroscopy and scattering studies on the structural relaxation in many different materials have assumed that the normal T-dependence of the relaxation time of a liquid will closely resemble that of propylene glycol (PG), that is, both bulk water and confined PG relax in the same manner, and with an apparent continuity. The main relaxation time of PG exhibits a thermal behavior that differs from that proposed for bulk and confined water. Confined water relaxation times seem substantiaiiy altered when compared to bulk water (which evidently is not the case in confined EG). It also shows an apparent FSC. In addition, an even more dramatic change in the T-dependence of water confined in nanoporous MCM-41 is clearly evident. These results are not unique in that they simply exhibit the typical behavior of supercooled water in biological materials and in other confined environments. Thus, we consider both bulk and confined ethylene glycol (EG, OHCH2CH2OH). Figure 17 shows the EG dielectric relaxation times studied. 

A method for sample preparation allows determination of total tin and tributyltin ions in biological materials. End analysis by ETAAS, using a tungstate-treated graphite tube, allows LOD for tributyltin Sn of 0.4 ng/g79. An alternative method for sea water uses in situ concentration of Sn hydrides on a zirconium-coated graphite tube, followed by ETAAS absolute LOD 20 and 14 pg for tributyltin ion and total Sn, respectively, with corresponding RSD of 5.6 and 3.4%80. 

Analytical methods for detection of nickel in biological materials and water include various spectrometric, photometric, chromatographic, polarographic, and voltametric procedures (Sunder-man et al. 1984 WHO 1991). Detection limits for the most sensitive procedures — depending on sample pretreatment, and extraction and enrichment procedures — were 0.7 to 1.0 ng/L in liquids, 0.01 to 0.2 pg/m3 in air, 1 to 100 ng/kg in most biological materials, and 12 pg/kg in hair (WHO 1991 Chau and Kulikovsky-Cordeiro 1995). 

No methods for determining chlorine dioxide in biological materials were located. Most studies concerning human health effects measure the concentrations of chlorine dioxide in the air or in water. The measurement of chlorine dioxide in biological materials is not commonly used because of the rapid conversion of chlorine dioxide to chlorine-containing metabolites, such as chlorite and chloride ions. 

Stoeppler M. 1980. Analysis of nickel in biological material and natural waters. In Nriagu JO, ed. Nickel in the environment. New York, NY John Wiley and Sons, Inc., 661-821. 

Methods for tracking nanotubes in biological materials are needed to measure the rate of nanotube transport, distance of penetration from places of introduction at inhalation, with food and water, and implantation of nanotubes ... 

This case represents a composite typical manufacturing process for a mediumsized protein produced by microbial cells. The key process steps are listed in Table 15.5. The overall yield from fermentation to API ranges from 15 to 30% with no recycle or recovery of used materials. Shown in Table 15.6, this composite process confirms the large usage of water in biologies manufacture 10000 to 20000 kg of water for every kg of protein produced. The amounts of organic solvents could be... 

There is little need or opportunity to measure BCME in biological samples because of its rapid hydrolysis in water to yield formaldehyde and chloride. The abundance of chloride and, to a lesser extent, of formaldehyde, in biological materials precludes use of these hydrolysis products as an index of exposure to BCME. Therefore, the analysis of BCME in biological samples from exposed humans is virtually impossible. 

Organo-tin compounds have been used as catalysts, stabilisers for plastics and biocides. Tributyltin (TBT) species are very effective biocides, and have been incorporated as active agents in antifouling compounds for marine applications. However, TBT has seriously affected other marine organisms such as oysters, crabs and fish even at parts per billion and lower concentrations in water. Consequendy, the determinations of low levels of TBT and dibutyl tin (DBT), its less toxic primary degradation product in water and in biological materials, are very important. 

Abbasi, S.A. (1989) Sub-microdetermination of antimony (III) and antimony (V) in natural and polluted waters and total antimony in biological materials by flameless AAS following extractive separation with N-p-methoxyphenyl-2-furylacrylohydroxamic acid. Anal. Letts, 22, 237-255. 

Finally, the question of the structure of biological water is one of far-reaching importance. Some workers in the last few decades have suggested that water in biological systems is special but our answer is that this special structure is so readily explicable that no mystery exists. Biological cells are sized on the micron scale and contain much soiid material. The surface-to-volume ratio inside such cells is very large. Most of the waters in cells are in fact surface waters. In this sense, biologicai water is special but only because it has lost the netted-up properties of bulk water and adopted the individual two-dimensional structure of water at all surfaces. 

Due to the high sensitivity, activation analysis is one of the most important methods for determination of microcomponents, in particular trace elements, in materials of high purity (e.g. in semiconductors), in water, in biological samples and in minerals. The main fields of apphcation are ... 

Abbasi conducted a submicro determination (down to 10 ppb levels) of Sb(III) and Sb(V) in natural and polluted waters and biological materials. The Sb(III) and Sb(V) concentrations obtained were as follows surface sample of reservoir water 0 and 0, near-bottom sample of reservoir water 0.17 and 0.16 ppb, sea water (India) 0 and 0.28 ppb, and polluted water (rubber industry) 0.85 and 1.91 ppb. Total antimony concentrations of goat liver and frog muscle were 0.094 and 0.027 ppb, respectively . ... 

Strontium determinations in soils, sea water, etc., have the same topicality as similar determinations in biological materials. The strontium and barium content of a number of soils and plants has been determined by Bowen and Dymond (5). They found that strontium was preferentially absorbed with respect to calcium by plants from most of the )ils considered while barium was taken up much less readily. 

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