Water in living cells

A review of water in biology, including discussion of the physical structure of liquid water, its interaction with biomolecules, and the state of water in living cells. 

NMR proton relaxation times for water in living tissues are found to be shorter than in ordinary water, and the lines correspondingly broader. Some workers have interpreted this fact as indicating that water in living cells may be in a semicrystalline state, rather than a liquid state the... 

The distribution of various types of water inside the living cells is a question that cannot be answered yet, especially because in many cells marked changes have been noted in the state of intracellular water as a result of biological activity. The possibility that water in living cells may differ structurally from bulk water has incited a search for parameters of cell water that deviate numerically from those of bulk water. 

Many pieces of experimental evidence exist in support of the AI hypothesis and against the membrane-pump theory. The reader must consult the aforementioned monograph for a full discussion. Here I shall limit our discussion to two issues the adsorbed state of and the bulk phase water in living cells. 

Drying. The living tree holds much water in its cells. A southern pine log, 5 m long and 0.5 m in diameter, for example, may weigh as much as 1000 kg and contain 47% or 0.46 m (16 fE) water. 

The covalent bond is the strongest force that holds molecules together (Table 2-1). Noncovalent forces, while of lesser magnitude, make significant contributions to the structure, stability, and functional competence of macromolecules in living cells. These forces, which can be either attractive or repulsive, involve interactions both within the biomolecule and between it and the water that forms the principal component of the surrounding environment. 

FIGURE3.7 The potential window for the redox chemistry of life. Redox chemistry in living cells is approximately limited by the standard potentials for reduction and oxidation of the solvent water at neutral pH. Approximate standard reduction potentials are also indicated for the commonly used oxidant ferricyanide and reductants NADH and dithionite. 

Contrary to the accumulated knowledge on the static or quasi-static characteristics of thin lipid films at air/water interface, less attention has been paid to the dynamical or nonequilibrium behavior of the film. Studies on the dynamical characteristics of thin lipid films may be quite important, because the life phenomena are maintained under nonequilibrium conditions. According to the modern biochemistry [11,12], thin lipid membrane in living cells is not a rigid wall but a thermally fluctuating barrier with high fluidity. In the present section, we will show that thin lipid film exhibits the various interesting dynamical tc-A characteristics, such as the "overshoot hump", the "zero surface pressure", and the "flat plateau". 

In living cells, water is the predominant solvent. It is therefore not surprising that scientific studies of enzymes have been carried out mainly in aqueous media. Often qnite dilute solutions of substrates and enzymes in aqueous buffers have been studied. However, one should bear in mind that high concentrations of proteins, other biopolymers and low molecular weight compounds are present around the enzymes in living cells. Furthermore, some enzymes are associated with membrane stmctures containing mainly hydrophobic lipids. Accordingly, some of the non-conventional ... 

Miwa and Yamamoto (31) described a simple and rapid method with high accuracy and reliability for the determination of C8 0-C22 6 fatty acids, which occur in esterified forms in dietary fats and oils and in living cells [the biological effects of routinely consumed fats and oils are of wide interest because of their impact on human health and nutrition (28,29), in particular, the ratio of cu-3 polyunsaturated fatty acid to w-6 polyunsaturated fatty acids (w-3/cu-6) seems to be associated with atherosclerosis and breast and colon cancers (30)]. They report improved separation of 29 saturated and mono- and polyunsaturated fatty acids (C8-C22), including cis-trans isomers and double-bond positional isomers, as hydrazides formed by direct derivatization with 2-nitrophenylhydrazine hydrochloride (2-NPH HC1) of saponified samples without extraction. The column consisted of a J sphere ODS-M 80 column (particle size 4 /xm, 250 X 4.6-mm ID), packed closely with spherical silica encapsulated to reach a carbon content of about 14% with end-capped octadecyl-bonded-spherical silica (ODS), maintained at 50°C. The solvent system was acetonitrile-water (86 14, v/v) maintained at pH 4-5 by adding 0.1 M hydrochloric acid with a flow rate of 2.0 ml/min. Separation was performed within only 22 min by a simple isocratic elution (Fig. 6). The resolution of double-bond positional isomers, such as y-linolenic ( >-6) and a-linolenic acid ( >-3) hydrazides and w-9, >-12, and >-15 eicosenoic acid hydrazides was achieved by use of this column. 

Lucifer Yellow probes are water-soluble to at least 1.5%. The absorbance maximum of the derivatives occurs at about 426—428 nm with an emission peak at about 530—535 nm, in the yellow region of the spectrum. The quantum yield of Lucifer dyes is about 0.25. The good intensity of luminosity from these dyes makes possible detection of small quantities of labeled molecules intracellularly. The fluorescent conjugates are readily visible in living cells at concentrations that are nontoxic to cell viability. The low molecular weight and water solubility of these dyes allow passage of labeled compounds from one cell to another, potentially revealing molecular relationships... 

Although there were some differences on the effects of temperature and pressure according to each particular compound, the free bases of hyoscyamine (1), scopolamine (2), and pseudoephedrine (6) were all found to be highly soluble in supercritical CO,. However, the hydrochloride salts of these compounds were scarcely extracted by pure CO, under any conditions employed. These results were consistent with preliminary evidence indicating that these alkaloids are not extracted from plant materials by pure CO,. This means that the alkaloids in living cells in the plant are not in the form of their free bases but rather as water-soluble salts in the cell vacuole [40]. Therefore, it was necessary to develop a procedure to enhance the solubilities of alkaloidal salts in CO,. 

Bioindicators. Water-soluble, colorless tetrazolium salts can be reduced to water-insoluble, deeply colored formazans. The reduction of tetrazolium salts in plant tissue at pH 7.2 was first demonstrated in 1941 [77], Tetrazolium salts have since been used in biochemistry, cytochemistry, and histochemistry because of the great sensitivity of this reaction. They can be used to detect biological redox systems in blood serum, in living cells, tissues, tumors, and bacteria. Tetrazolium Blue [167429-81-7] (48) is a particularly sensitive reagent. 

Long-chain aliphatic hydrocarbons and derivatives originating in living cells. Some lipids, such as fatty acids, are also surfactants. Simple lipids tend to be hydrocarbon-soluble but not water-soluble. Examples fatty acids, fats, waxes. 

O respiration the biochemical reaction in living cells that produces energy from the reaction ol glucose and oxygen to produce carbon dioxide and water... 

Barer R (1953) Determination of dry mass, thickness, solid and water concentration in living cells Nature 172 1098... 

In contrast to non-enzymatic chemical reactions, enzymatic reactions occur under rather mild physiological conditions, that is to say at moderate temperatures, reasonable pH values, and in aqueous solution. Evolution has taken place in an environment with water as one of the major components. Therefore, biochemical reactions in living cells occur in a dilute aqueous medium. 

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