Mechanisms water interactions

VI. MECHANISM OF INTERACTION OF WATER-SOLUBLE POLYMERS WITH IONS IN AQUEOUS SOLUTION... 

Pavlov, A.R., Revina, A.A., Dupin, A.M., Baldyrev, A.A., Yaropolow, A.I. (1993). The mechanism of interaction of camosine with superoxide radicals in water solutions. Biochem. Biophys. Acta 1157,304-314. 

Soil-Water Interactions Mechanisms and Applications, Second Edition, Revised and Expanded, Shingo Iwata, Toshio Tabuchi, and Benno P. Warkentin... 

Interface and colloid science has a very wide scope and depends on many branches of the physical sciences, including thermodynamics, kinetics, electrolyte and electrochemistry, and solid state chemistry. Throughout, this book explores one fundamental mechanism, the interaction of solutes with solid surfaces (adsorption and desorption). This interaction is characterized in terms of the chemical and physical properties of water, the solute, and the sorbent. Two basic processes in the reaction of solutes with natural surfaces are 1) the formation of coordinative bonds (surface complexation), and 2) hydrophobic adsorption, driven by the incompatibility of the nonpolar compounds with water (and not by the attraction of the compounds to the particulate surface). Both processes need to be understood to explain many processes in natural systems and to derive rate laws for geochemical processes. 

It is important to propose molecular and theoretical models to describe the forces, energy, structure and dynamics of water near mineral surfaces. Our understanding of experimental results concerning hydration forces, the hydrophobic effect, swelling, reaction kinetics and adsorption mechanisms in aqueous colloidal systems is rapidly advancing as a result of recent Monte Carlo (MC) and molecular dynamics (MO) models for water properties near model surfaces. This paper reviews the basic MC and MD simulation techniques, compares and contrasts the merits and limitations of various models for water-water interactions and surface-water interactions, and proposes an interaction potential model which would be useful in simulating water near hydrophilic surfaces. In addition, results from selected MC and MD simulations of water near hydrophobic surfaces are discussed in relation to experimental results, to theories of the double layer, and to structural forces in interfacial systems. 

In this article, we suggest that a modified superheated-liquid model could explain many facts, but the basic premise of the model has never been established in clearly delineated experiments. The simple superheated-liquid model, developed for LNG and water explosions (see Section III), assumes the cold liquid is prevented from boiling on the hot liquid surface and may heat to its limit-of-superheat temperature. At this temperature, homogeneous nucleation results with significant local vaporization in a few microseconds. Such a mechanism has been rejected for molten metal-water interactions since the temperatures of most molten metals studied are above the critical point of water. In such cases, it would be expected that a steam film would encapsulate the water to... 

Chemical and biological effects of ionizing radiation are thought to occur through two main mechanisms direct interaction of the radiation with food components and living cells in materials exposed to it, and indirect action from radiolytic products, such as the radicals formed from water molecules (see Chap. 12). 

Although liquid water is usually looked upon as a single, unvarying substance, its structure near surfaces may be quite different from that of free water. Interaction between water molecules and an immediately adjacent surface orients these molecules, and this orientation can extend for several molecular diameters into the bulk liquid. A very clear and succinct description of this mechanism was given by Henniker (1949) Although the powerful... 

Water binding varies with the number and type of polar groups (5 ). Other factors that affect the mechanism of protein-water interactions include protein conformation and environmental factors that affect protein polarity and/or conformation. Conformational changes in the protein molecules can affect the nature and availability of the hydration sites. Transition from globular to random coil conformation may expose previously buried amino acid side chains, thereby making them available to interact with aqueous medium. Consequently, an unfolded conformation may permit the protein to bind more water than was possible in the globular form ( ). 

Besides interacting with suspended particles, a chemical also undergoes direct exchange at the sediment surface by diffusion and advection into the hyporheic zone. Furthermore, resuspension followed by exchange between water and particles also adds to the sediment-water interaction. These processes have been extensively discussed in Chapter 23, especially in Box 23.2. There we concluded that the effect from the different mechanisms can be combined into a flux of the form (see Eq. 23-25) ... 

On Mechanisms of Interaction of Ca++ with Dipalmitoyl Lecithin at the Air-Water Interface... 

To date, the only sorbent used reportedly for coating the stir bar is poly-dimethylsiloxane (PDMS), although the use of stir bars coated with polar sorbents is predicted for the future [141]. Using this sorbent, the primary mechanism of interaction with organic solutes is via absorption or partitioning into the PDMS coating such that the distribution constant [equation (2.37)] between PDMS and water (APDMs/w) is proposed to be proportional... 

Teppen et al. [89] have used a flexible model for clay minerals that allows full movement of the M-O-M bonds in the clay structure, where M represents Si, Al, or other cations in the octahedral sheet. This model was used in MD simulations of interactions of hydrated clay minerals with trichloroethene [90, 91]. The simulations suggest that at least three distinct mechanisms coexist for trichloroethene sorption on clay minerals [90], The most stable interactions of trichloroethene with clay surfaces are by full molecular contact, coplanar with the basal surface. The second type more reversible, less stable is adsorption through single-atom contact between one chlorine atom and the surface. In a third mechanism, trichloroethene interacts with the first water layer and does not interact with clay surface directly. Using MC and MD simulation the structure and dynamics of methane in hydrated Na-smectite were studied [92], Methane particles are solvated by approximately 12-13 water molecules, with six oxygen atoms from the clay surface completing the coordination shell. 

These considerations lead us to a conclusion that nerve excitation is a very slow process and the membrane does not contain elements which has a frequency response of MHz or GHz. The only molecular species which may have such a frequency response are water molecules. However, the role of water in nerve excitation is totally unknown and does not offer, at present, any evidence for the possible mechanism of interaction between micro-waves and nerve membranes. 

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