Hydrophobic molecule

Biological molecules generally exist in an aqueous (hydrophilic) environment and must be physically compatible with it. What makes a molecule hydrophobic... 

Figure 5.1 (a) The aggregation of surfactant molecules showing the increase of entropy due to the liberation of water molecules. Hydrophobic forces are the main factors for the association of surfactant molecules, (b) The analogy with two droplets of oil in water. 

Cyclodextrin Organic molecule Hydrophobic/ van der Waals Cavitate (ct-cyclodextrin) (p-hydroxybenzoic acid)... 

A typical globular protein adopts a unique minimum energy conformation that is compact with few or no internal water molecules. Hydrophobic (nonpolar) R groups tend to be on the inside (away from water) and most hydrophilic (polar) R groups tend to be on the outside where they can be solvated by hydrogen bonding with H20. In the case of enzymes (proteins that catalyse specific chemical reactions) there may be special structural features of which the best known are active site depressions or grooves on the surface that bind the chemical substrates of the enzyme-catalysed reaction. 

Cholesterol ((3(3)-cholest-5-en-3-ol) is a major non-phospholipid component of animal membranes and is the principal sterol of animals. Cholesterol is also amphipathic, the 3-hydroxy being polar and the rest of the molecule hydrophobic. Cholesterol can insert into phospholipid bilayers, lowering membrane permeability and lowering the melting point of membranes (i.e. making the membranes less ordered and more fluid). 

It is important that the theories and discussions above have considered simple models - hard spheres - of small-molecule hydrophobic solutes. As noted above, this is partly because that problem historically has been regarded as a basic puzzle of hydrophobic phenomena. The tools developed in this book have provided a compelling analysis of that basic puzzle. 

Anomalies of Water and Polyamorphism Hydrogen Bond Network Dynamics of Water Molecules Hydrophobic Hydration and Interaction Ion Hydration... 

Before doing so let us briefly discuss the notions of hydrophilicity and hydro-phobicity. These names are used for macroscopic surfaces and for (parts of) molecules to indicate affinity for water, and we shall follow this custom. It is noted that the two phenomena are tsqjiCcdly collective, i.e. involving many molecules. In a vacuum, a water molecule attracts any molecule, hydrophobic or not, and this is also true for a drop of water and a drop of oil. In wetting science, the surface of a substance is called hydrophilic when a water droplet on it spreads or forms drops with a (very) low contact cuigle. Can these notions be made quantitative ... 

In the retro-Diels-Alder reaction of anthracenedione [42], the volume of activation is small. Acceleration in water cannot come from a change in the hydration shell of the molecule. Hydrophobic interactions are negligible and aqueous acceleration is caused by the hydrogen-bond donating ability of water, which stabilizes the polarized activated complex. The Gibbs energy of activation displays a fair linear correlation with the Ej parameter. Hexafluoroisopropanol with an Ej value of 65.3 is even more efficient as a solvent than water Ej= 63.1) which appears to be less polar [41]. 

Abstract Sulfur sols are colloidal solutions of elemental sulfur or of sulfur-rich compounds. The particles in these solutions have diameters of O.l-l.O iim and consist either of Ss molecules (hydrophobic sulfur sols) or of chain-like sulfur compounds with hydrophilic end groups like sulfonate or functionalized organic groups (hydrophilic sulfur sols). Both types of sols are stabilized by the negative charge of the particles which results in mutual repulsion. Therefore, cations and especially multivalent cations are able to precipitate the sol particles. While hydrophilic sulfur sols can be prepared with sulfur concentrations of up to 600 g hydrophobic sols are much more dilute (<0.1 g 1 ). Sols of these types occur both in industrial desulfurization plants where sulfide is oxidized to elemental sulfur as well as in cultures of certain oxidizing sulfur bacteria. 

Ionic Interactions Hydrogen Bonds van der Waals Forces THERMAL PROPERTIES OF WATER SOLVENT PROPERTIES OF WATER Hydrophilic Molecules Hydrophobic Molecules Amphipathic Molecules Osmotic Pressure IONIZATION OF WATER Acids, Bases, and pH... 

Solvation of non-polar and apolar molecules - hydrophobic effects... 

The term hydrophobic hydration means the first of the above, that is, the interaction between one solute moleeule and the surrounding water molecules. Hydrophobic hydration can be quantified by measuring the free energy of transfer of a non-polar molecule from its neat liquid state to water. It is straightforward to... 

Like soaps, synthetic detergents combine hydrophilic and hydrophobic regions in the same molecule. Hydrophobic regions are generally alkyl groups or... 

Water with Two Solute Molecules Hydrophobic Hydrophilic Phenomena... 

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