Amphiphile (from the Greek αμφις, amphis: both and φιλíα,
philia: love, friendship) is a term describing a chemical compoundpossessing both hydrophilicand hydrophobicproperties. Such a compound is called "amphiphilic" or "amphipathic." This forms the basis for a number of areas of research in chemistry and biochemistry, notably that of lipid polymorphism. Organic compounds containing hydrophilic groups at both ends of a prolatemolecule are called bolaamphiphilic. Common amphiphilic substances are soapand detergent.
tructure and Properties
hydrophobicgroup is typically a large hydrocarbonmoiety, such as a long chain of the form CH3(CH2)n, with n > 4. The hydrophilicgroup falls into one of the following categories:
# Charged groups
Anionic. Examples, with the hydrophobic part of the molecule represented by an "R", are:
phosphates: The charged functionality in phospholipids.
#** amines: RNH3+.
# Polar, uncharged groups. Examples are
alcohols with large R groups, such as diacyl glycerol (DAG), and oligo ethyleneglycols with long alkyl chains.
Often, amphiphilic species have several hydrophobic parts, several hydrophilic parts, or several of both.
Proteinsand some block copolymersare such examples.
Molecules of amphiphilic compounds have hydrophobic (usually of hydrocarbon nature) and hydrophilic (represented by either ionic or uncharged polar functional groups) structural regions.
As a result of having both hydrophobic and hydrophilic structural regions, some amphiphilic compounds may dissolve in water and to some extent in non-polar organic solvents.
When placed in an immiscible biphasic system consisting of aqueous and hydrophobic solvent the amphiphilic compound will partition the two phases. The balance between hydrophobic and hydrophilic natures defines the extent of partitioning.
Phospholipids, a class of amphiphilic molecules, are the main components of biological membranes. The amphiphilic nature of these molecules defines the way in which they form membranes. They arrange themselves into bilayers, by positioning their polar groups towards the surrounding aqueous medium, and their hydrophobic chains towards the inside of the bilayer, defining a non-polar region between two polar ones.
phospholipidsare principal constituents of biological membranes, there are other amphiphilic molecules, such as cholesteroland glycolipids, which are also included in these structures and give them different physical and biological properties.
Many other amphiphilic compounds strongly interact with biological membranes by insertion of hydrophobic part into the lipid membrane, while exposing the hydrophilic part to the aqueous medium, altering their physical behaviour and sometimes disrupting them.
Examples of amphiphiles
There are several examples of molecules that present amphiphilic properties:
Surfactantsare an example group of amphiphilic compounds. Their polar region can be either ionic, or non-ionic. Some typical members of this group are: sodium dodecyl sulfate( anionic), Benzalkonium chloride( cationic), Cocamidopropyl betaine( zwitterionic) and octanol(long chain alcohol, non-ionic).
Many biological compounds are amphiphilic:
phospholipids, cholesterol, glycolipids, fatty acids, bile acids, saponins, etc.
* [http://www.kibron.com/drug-discovery/physicochemical-profiling/study-on-fraction-absorbed/ Estimating intestinal permeability by surface activity profiling]
Sodium dodecyl sulfate
Abiogenesis#Possible Role of Bubbles
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