- Amphiphile
Amphiphile (from the Greek αμφις, amphis: both and φιλíα,
philia : love, friendship) is a term describing achemical compound possessing bothhydrophilic andhydrophobic properties. 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 oflipid polymorphism . Organic compounds containing hydrophilic groups at both ends of aprolate molecule are called bolaamphiphilic. Common amphiphilic substances aresoap anddetergent .tructure and Properties
The
hydrophobic group is typically a largehydrocarbon moiety, such as a long chain of the form CH3(CH2)n, with n > 4. Thehydrophilic group falls into one of the following categories:
# Charged groups
#*Anionic . Examples, with the hydrophobic part of the molecule represented by an "R", are:
#**carboxylate s: RCO2-;
#**sulfate s: RSO4-;
#**sulfonate s: RSO3-.
#**phosphate s: The charged functionality inphospholipids .
#*Cationic . Examples:
#** amines: RNH3+.
# Polar, uncharged groups. Examples arealcohol s with large R groups, such as diacyl glycerol (DAG), and oligoethyleneglycol s with long alkyl chains.Often, amphiphilic species have several hydrophobic parts, several hydrophilic parts, or several of both.
Proteins and some blockcopolymers are 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.
Biological role
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.Although
phospholipids are principal constituents of biological membranes, there are other amphiphilic molecules, such ascholesterol andglycolipids , 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:
Surfactants are an example group of amphiphilic compounds. Their polar region can be eitherion ic, or non-ionic. Some typical members of this group are:sodium dodecyl sulfate (anion ic),Benzalkonium chloride (cation ic),Cocamidopropyl betaine (zwitterion ic) andoctanol (long chain alcohol, non-ionic).Many biological compounds are amphiphilic:
phospholipids ,cholesterol ,glycolipids ,fatty acids ,bile acids ,saponins , etc.External links
* [http://www.kibron.com/drug-discovery/physicochemical-profiling/study-on-fraction-absorbed/ Estimating intestinal permeability by surface activity profiling]
ee also
*
Hydrophile ,hydrophilic
*Wetting
* Freesurface energy
*Sodium dodecyl sulfate
*Surfactant
*Amphipathic lipids
*Polymorphism (biophysics)
*Abiogenesis#Possible Role of Bubbles
Wikimedia Foundation. 2010.