Water at biological interfaces

The INS spectra of the totally hydrated species resembles that of ice Ih, see Fig.9.10, when the contribution from the dry sample is subtracted. However, at modest degrees of hydration the INS spectrum of the samples show significant differences from ice Ih. Using a simple model, where the water present was treated as either interfacial or bulk in nature, 

In DNA the transition from interfacial to bulk water occurs after ca 1 layer but grana membranes retain interfacial water up to ca 2 layers on each surface. Similarly the water in close contact with gelatine and chitosan did not have the ice Ih structure [43]. 

The INS from water on other biologically relevant samples has been compared to the INS of high-density ice [44]. Beyond the assessment of the extent of interfacial water and its possible nature the interpretation of the INS data is very difficult and several papers focus on the physics of the glass transition found in these systems [45]. Only modest progress has been made with more quantitative biological approaches involving modelling [46]. 

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Drost-Hansen, W. (1971). Structure and properties of water at biological interfaces. In Chemistry of the Cell Interface, (Brown, H. D ed.), Vol. 2, pp. 1-184, Academic Press, New York. 

Drost-Hansen, W. (1978). Water at biological interfaces—structural and functional aspects. Phys. Chem. Liq. 7, 243-348. 

Drost-Hansen, W. (1971). Structure and properties of water at biological interfaces. In Chemistry of the Cell Interface, Part B (Brown, H. D., ed.), pp. 1-184, Academic Press, New York. Drost-Hansen, W. Clegg, J. S. (eds). (1979). Cell-Associated Water, Academic Press, New York. Franks, F. Mathias, S. (eds.) (1982). Biophysics of Water, John Wiley Sons, New York. 

Goodfellow JM, Howell PL, Elliott R (1986) Water at biomolecule interfaces. In Moras D, Drenth J, Strandberg B, Suck D, Wilson K (eds) Crystallography in molecular biology. Plenum, New York, pp 167-177... 

So far there have been few in-depth MD simulations of water at the interfaces of cells. As indicated earlier, the results of general studies and Spectroscopic data suggest that much of the water in biological cells is affected by the interface. The fact that the... 

After briefly reviewing the spectral consequences that result for the formation of H-bonds ( 9.1) the extensive body of work on water is presented ( 9.2), including water in minerals ( 9.2.1), its protonated species ( 9.2.2), the ices ( 9.2.3) and water at bio-interfaces ( 9.2.4). The next section ( 9.3) covers proton transfer, which is important for systems, across all the scientific disciplines from Materials Science to Biology. This section includes the dicarboxylates as models ( 9.3.1), proton conductors ( 9.3.2) and unusual species ( 9.3.3). 

The popular applications of the adsorption potential measurements are those dealing with the surface potential changes at the water/air and water/hydrocarbon interface when a monolayer film is formed by an adsorbed substance. " " " Phospholipid monolayers, for instance, formed at such interfaces have been extensively used to study the surface properties of the monolayers. These are expected to represent, to some extent, the surface properties of bilayers and biological as well as various artificial membranes. An interest in a number of applications of ordered thin organic films (e.g., Langmuir and Blodgett layers) dominated research on the insoluble monolayer during the past decade. 

Interfacial water molecules play important roles in many physical, chemical and biological processes. A molecular-level understanding of the structural arrangement of water molecules at electrode/electrolyte solution interfaces is one of the most important issues in electrochemistry. The presence of oriented water molecules, induced by interactions between water dipoles and electrode and by the strong electric field within the double layer has been proposed [39-41]. It has also been proposed that water molecules are present at electrode surfaces in the form of clusters [42, 43]. Despite the numerous studies on the structure of water at metal electrode surfaces using various techniques such as surface enhanced Raman spectroscopy [44, 45], surface infrared spectroscopy [46, 47[, surface enhanced infrared spectroscopy [7, 8] and X-ray diffraction [48, 49[, the exact nature of the structure of water at an electrode/solution interface is still not fully understood. 

Thermodynamics of adsorption at liquid interfaces has been well established [22-24]. Of particular interest in view of biochemical and pharmaceutical applications is the adsorption of ionic substances, as many of biologically active compounds are ionic under the physiological conditions. For studying the adsorption of ionic components at the liquid-liquid interface, the polarized liquid-liquid interface is advantageous in that the adsorption of ionic components can be examined by strictly controlling the electrical state of the interface, which is in contrast to the adsorption studies at the air-water or nonpolar oil-water interfaces [25]. 

An interesting vertical profile of the metabolite concentrations was observed the compounds showed a tendency to accumulate at the two-phase boundaries of air-freshwater and freshwater-saline water (the halocline). Thus, concentration maxima were observed at depths of 0 and 2 m (see Fig. 6.4.1) [6]. The observed distribution may result from either the physicochemical properties of these compounds (surface activity and hydrophobicity), or their formation at the interface due to increased biological activity. For the parent surfactants a similar but less pronounced vertical distribution pattern was observed (with maxima at 0 and 2 m of 17 and 9 xg L 1, respectively) [5],... 

A panel discussion at the end of the book describes the potential biological hazards of drinking water and the needs and applications of the analytical methods presented in the book. This panel discussion is essential to the reader s understanding of the often complex chemistry-toxicology-water treatment-regulators interface. We hope that the reader will enjoy the panel discussion, not only for the technical content, but also for insight into the personal philosophies of the participants. 

It is commonly stated that the first readily observable event at the interface between a material and a biological Quid is protein or macromolecule adsorption. Clearly other interactions precede protein adsorption water adsorption and possibly absorption (hydration effects), ion bonding and electrical double layer formation, and the adsorption and absorption of low molecular weight solutes — such as amino acids. The protein adsorption event must result in major perturbation of the interfacial boundary layer which initially consists of water, ions, and other solutes. 

One type of lipid that is dominant in biological interfaces is lecithin, and lecithin-water systems have therefore been examined extensively by different physical techniques. Small s binary system (3) for egg lecithin-water is presented in Figure 2. The lamellar phase is formed over a large composition range, and, at very low water content, the phase behavior is quite complex. Their structures as proposed by Luzzati and co-workers (4) are either lamellar with different hydrocarbon chain packings or based on rods both types are discussed below. 

It is well established that acid-base equilibria and consequently pXa values can be subject to considerable variations in dependence of environment, namely, the polarity and dielectric constant of the solvent, solvation properties, and so on. This aspect is of particular significance in biological processes that occur at the interface of water and biomolecule aggregates. For example, variations in pXa values of amino acid side chains in proteins as well as local conditions in the... 

This bacterial production occurs in the pore fluids of sediments and in stagnant basins (seas, lakes, rivers and fiords). At the interface between anoxic and oxic waters the H2S can be oxidized. This oxidation is frequently coupled to changes in the redox state of metals (1.2) and non-metals (2). Another major interest in the H-jS system comes from an attempt to understand the authigenic production of sulfide minerals as a result of biological or submarine hydrothermal activity and the transformation and disappearance of these minerals due to oxidation (4). For example, hydrothermally produced H2S can react with iron to form pyrite, the overall reaction given by... 

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