The Hydrophobic Group

Lecithin (qv), a natural phosphoHpid possessing both hydrophilic and hydrophobic properties, is the most common emulsifier in the chocolate industry (5). The hydrophilic groups of the lecithin molecules attach themselves to the water, sugar, and cocoa soflds present in chocolate. The hydrophobic groups attach themselves to the cocoa butter and other fats such as milk fat. This reduces both the surface tension, between cocoa butter and the other materials present, and the viscosity. Less cocoa butter is then needed to adjust the final viscosity of the chocolate. 

Based on these observations in Figs. 8 and 9, it is suggested that the hydrophobic group modification (hy-drophobization) is an effective method for improving the immuno-stimulating activity of polyanionic polymers. 

The theory of hydrophobic interaction [70-72] indicates that hydrophobic residues tend to associate with one another so as to minimize the surface area exposed to the aqueous phase and thereby to release a maximum number of structured water molecules. Therefore, the steric fit between the hydrophobic groups may be an important factor for the hydrophobic association. It is reasonable to consider that aromatic hydrophobic groups may undergo tighter hydrophobic self-association because planar aromatic rings would sterically fit with each other to favor the release of structured water. 

Importance of the hydrophobic groups. The less hydrophobic the unpolar part of a molecule is, the higher the cmc. 

Influence of isomers. In a range of isomers the cmc and surface activity enlarge with increasing orientation of the hydrophobic group to the middle of the alkyl chain. 

Consequently, it is generally accepted that the chemical nature of the hydrophilic group affects biodegradability to a minor extent and that the hydrophobic group is the responsible for a ready biodegradation. 

In Eqs. (27) and (28), p is the contribution of the substrate water molecules, p that of the adsorbate polar head, and p that of the hydrophobic moiety of the adsorbed molecules. Consistently, 8i, 82, and 83 are the effective local permittivities of the free surface of water and of the regions in the vicinity of the polar head and of the hydrophobic group, respectively. The models have been used in a number of papers on adsorbed monolayers and on short-chain substances soluble in water. " Vogel and Mobius have presented a similar but more simplified approach in which p is split into two components only. " Recently some improvements to the analysis using Eq. (27) have been proposed. " An alternative approach suggesting the possibility of finding the values of the orientation angle of the adsorbate molecules instead of local permittivities has been also proposed.""... 

We will show several examples of the use of 2DLC for nonionic surfactants. The resulting resolution can be dramatically different depending on the two separation modes in the 2DLC system. As discussed previously, the separation of the hydrophobic groups can be accomplished with a reversed-phase column, and the separation of the... 

Micelles are the simplest possible structures. These are spherical entities in which the hydrophobic groups are directed towards the interior. Micelle formation occurs preferentially when the head groups are larger than the hydrophobic groups, as in fatty acids. 

A bilayer forms when two lipid layers come together the hydrophobic groups in the two single layers interact and exclude water. 

The hydrophobic group is usually a hydrocarbon chain and is generally called the tail, while the hydrophilic group, called the head, is an ionic group and very polar. Depending on the nature of the hydrophilic group, the surfactants are classified as ... 

In spite of the fact that keeping the hydrophobic groups from being in contact with the water can produce a decrease in the free energy of the system,... 

An example of the effectiveness of this equation is given by an aqueous HEUR gel made up of a polymer with Mn = 20 x 103 Daltons at a concentration of 30kgm-3 filled with a poly(styrene) latex with a particle diameter of 0.2 pm at q> = 0.2. The unfilled gel had a network modulus of 0.4 kPa, whilst the modulus of the filled gel was 0.7 kPa. Equation (2.68) predicts a value of 0.728 kPa. The poly(styrene) particles act as a non-interactive filler because the surface is strongly hydrophobic as it consists mainly of benzene rings and adsorbs a monolayer of HEUR via the hydrophobic groups, resulting in a poly(ethylene oxide) coating that does not interact with the HEUR network. This latter point was... 

Results from thermal denaturation and heat capacity studies have shown that the proteins are not necessarily completely unfolded in this process. The volume observations also suggest that the denatured state is not one in which all hydrophobic groups are exposed to water. But the results can also be understood from the effect of close polar and electrostatic groups interacting with the water structure surrounding the hydrophobic groups. The volume change is heavily... 

Reversed Phase This technique is based on hydrophobic regions on the surface of proteins and the hydrophobic groups covalently attached to the surface of the matrix. Organic solvents are required for elution. It is suitable for peptides and proteins up to 2.4x10" Da. 

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