Amphipathic, amphiphilic molecules

The out-of-plane orientation of chromophores can be more easily controlled in LB films as compared with the in-plane orientation. Many chromophores are known to show anisotropic orientation in the surface normal direction. The molecular structure of chromophores and their position in amphiphile molecules, the surface pressure, the subphase conditions are among those affect their out-of-plane orientation. The out-of-plane orientation has been studied by dichroic ratio at 45° incidence, absorbance ratio at normal and 45° incidence, and incident angle dependence of p-polarized absorption [3,4,27,33-41]. The evaluation of the out-of-plane orientation in LB films is given below using amphipathic porphyrin (AMP) as an example [5,10,12]. 

Lipid bilayer Amphipathic (or amphiphilic) molecules contain both hydrophilic (water-... 

The repertoire of membrane lipids is extensive, perhaps even bewildering, at first sight. However, they possess a critical common structural theme membrane lipids are amphipathic molecules (amphiphilic molecules). A membrane lipid contains both a hydrophilic and a hydrophobic moiety. 

Amphiphilic Molecule with both hydrophobic and hydrophilic regions, synonymous with amphipathic. Anesthetic additivity Phenomenon where half-doses of two unrelated anesthetic drugs provide the full effect of amnesia. 

Another example where the amphipathic feature of the molecules plays an important role is the case of some thermotropic ionic calamitic liquid crystals such as ditholium salts [64]. In spite of their rod-like shape, these compounds exhibit columnar mesophases with supramolecular organization similar to that of amphiphilic molecules. In this case, it is clear that the driving force for the supramolecular organization is the amphipathic character of the molecules... 

Proteins are by nature amphipathic or amphiphilic molecules that is, they contain both a hydrophobic (nonpolar) and a hydrophilic (polar) moiety. However, natural proteins per se are not used as commercial surfactants. Rather, proteins are modified by chemical or enzymatic means to products with surface-active properties. The use of modified proteins based on casein, soybean, albumen, collagen, or keratin is not new [5]. The Maywood Chemical Company introduced commercial protein-based surfactants (PBS) in the United States in 1937. They were primarily condensation products of fatty acids with hydrolyzed proteins [5], Renewed interest in PBS has occurred not only as products based on renewable raw materials (i.e., proteins and fatty acids), but also as a solution to waste disposal for animal and vegetable protein byproducts [5], Among the commercial PBS, the following trade names have been active Crotein, Lexein, Magpon Polypeptide, Protolate, Sol-U-Teins, and Super Pro. 

It follows from study of the kinetics of transfer of ions across the phase boundary between two immiscible electrolyte solutions (see chapter 9) that ion-exchanger ions, where the ion is as nearly as possible symmetrically surrounded by hydrophobic groups on all sides, are especially suitable. Amphiphilic (amphipathic) substances, in whose molecules the hydrophobic part is separated from the hydrophilic part, are less suitable because they have a tendency to become adsorbed on the membrane/water phase boundary, thus retarding ion transfer across this boundary. 

Molecules that contain both polar and apolar groups are called amphipathic or amphiphilic. This group includes soaps (see p.48), phospholipids (see p. 50), and bile acids (see p. 56). 

A special group of lipids that possess both hydrophilic and hydrophobic (lipophilic) parts are termed as amphiphiles or amphipathics and are also referred to as surfactants. They adsorb at surfaces or interfaces and change the interfacial free energy associated with the building of an interface. A surfactant molecule consists of two distinct chemical groups (i) the head which is hydrophilic (water-loving) and (ii) the tail which is hydrophobic (water-fearing). 

Some compounds, like short-chain fatty acids, are amphiphilic or amphipathic, i.e., they have one part that has an affinity for the nonpolar media (the nonpolar hydrocarbon chain) and one part that has an affinity for polar media such as water (the polar group). The energetically most favourable orientation for these molecules is at surfaces or interfaces so that each part of the molecule can reside in an environment for which it has the greatest affinity (see Figure 3.18). These molecules that form... 

Amphipathic Molecule with both hydrophobic and hydrophilic regions, synonymous with amphiphilic. 

Amphipathic Having both lyophilic and lyophobic groups (properties) in the same molecule, as in most surfactants. Also referred to as amphiphilic. 

Molecules that have both hydrophUic and hydrophobic characteristics often form spherical self-assembled structures called micelles (Fig. 12-2). These enclose hpids and interact with the surrounding wate" at their surface they are also called detergents. Household detergents, such as washing-up hquid and soap, dissolve hydrophobic oils within the hydrophobic core of their micelles. Molecules that have both hydrophobic and hydrophUic characteristics are variously caUed amphiphilic, amphi-phobic, and amphipathic (Greek amphi, both sides as in amphitheater in which the audience sits on both sides of the stage). 

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