Protein lipophilic groups

The effect of chain length on surface tension arises from the fact that, as the hydrophobicity increases with each -CH2- group, the amphiphile molecule adsorbs more at the surface. This will thus be a general trend in more complicated molecules also, such as proteins and other polymers. In proteins, the amphiphilic property arises from the different kinds of amino acids (25 different amino acids). Some amino acids have lipophilic groups (such as phenylalanine, valine, leucine, etc.), while others have hydrophilic groups (such as glycine, aspartic acid, etc.) (Figure 3.4). 

A high complementarity of the surface properties. Lipophilic parts of the ligands are most frequently found to be in contact with lipophilic parts of the protein. Polar groups are usually paired with suitable polar protein groups to form hydrogen bonds or ionic interactions. 

Modification of the protein amine groups is the procedure most frequently used to produce antibody-liposome conjugates. Early procedures used crosslinking agents, such as l-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) (27,28) in the presence of preformed liposomes containing a lipophilic carboxylic acid. Condensing agents like these tend to form protein-protein polymers. Control of these reactions is typically difficult and complex, and as a result separation of the liposomes from protein polymers is a... 

Protein tertiary structure is also influenced by the environment. In water a globular protein usually adopts a shape that places its lipophilic groups toward the interior, with its polar groups on the surface, where they are solvated by water molecules. About 65% of the mass of most cells is water, and the proteins present in cells are said to be in their native state—the tertiary structure in which they express their biological activity. When the tertiary structure of a protein is disrupted by adding substances that cause the protein chain to unfold, the protein becomes denatured and loses most, if not all, of its activity. Evidence that supports the view that the tertiary structure is dictated by the primary structure includes experiments in which proteins are denatured and allowed to stand, whereupon they are observed to spontaneously readopt their native-state conformation with full recovery of biological activity. 

Emulsifiers to facilitate the formation/dispersion of oil drops (glycerides, proteins, lecithin, etc.). They are adsorbed on the periphery of oil drops (interface oil/aqueous phase), to decrease the surface tension of the drops and to form a barrier to prevent their coalescence. They are amphiphilic molecules including both hydrophilic and lipophilic groups. They may have a role of protection against oxidation. 

Surface plasmon resonance (SPR) allows monitoring label-free interactions between biomolecules in real time. In SPR measurements, one of the biomolecules is immobilized on a sensor surface and the other one is transported in solution across the surface. Binding of the second biomolecule will cause an increase in mass and a proportional increase in refractive index that can be monitored. Gold surfaces are the most commonly used ones and they can be modified or functionalized for the specific binding of particular molecules. For example, biotinylated surfaces enable the immobilization of streptavidin-labeled proteins, and surfaces modified with lipophilic groups allow the immobilization of vesicles creating membrane-like structures to study protein association and dissociation with membranes. 

Lefrancier, P., M. Petitou, M. Level, M. Derrien, J. Choay, and E. Lederer Synthesis of N-acetyl-muramyl-L-alanyl-D-glutamic ot-amide (MDP) or a-methyl ester derivatives, bearing a lipophilic group at the C-terminal peptide end. Int. J. Peptide Protein Res. 14, 437 (1979). 

The binding of a dmg to a protein depends on the inter-molecular forces described in Chapter 1. Thus electrostatic, dipole-dipole, hydrogen bonding, k-k interaction and van der Waals interactions, and even covalent bonding all play a part. The strength of van der Waals interaction depends on the availability of lipophilic groups within the protein. The amino acids with high... 

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