Chitin (C8H13O5N)n (/ˈkaɪtɨn/ KY-tin)
is a long-chain polymer
of a N-acetylglucosamine, a derivative of glucose, and is
found in many places throughout the natural world. It is the main component of
the cell
walls of fungi,
the exoskeletons
of arthropods
such as crustaceans
(e.g., crabs, lobsters and shrimps) and insects, the radulae of molluscs, and the
beaks
and internal shells of cephalopods,
including squid
and octopuses.
The structure of chitin is comparable to the polysaccharide
cellulose,
forming crystalline nanofibrils or whiskers. In terms of function, it may be
compared to the protein keratin. Chitin has also proven useful for several medical
and industrial purposes. In butterfly wing scales, chitin is often organized
into stacks of nano-layers or nano-sticks made of chitin nanocrystals that
produce various iridescent colors by thin-film interference: similar, analogous
structures made of keratin are found in iridescent bird plumage.
Etymology
The English word "chitin" comes from the French
word chitine, which first appeared in 1821 and derived from the Greek
word χιτών (chiton), meaning covering.
A similar word, "chiton",
refers to a marine animal with a protective shell (also known as a "sea
cradle").
Chemistry, physical properties and biological function
The structure of chitin was solved by Albert
Hofmann in 1929.
Chitin is a modified polysaccharide
that contains nitrogen; it is synthesized
from units of N-acetylglucosamine (to be precise,
2-(acetylamino)-2-deoxy-D-glucose). These units form covalent β-1,4 linkages
(similar to the linkages between glucose units forming cellulose).
Therefore, chitin may be described as cellulose
with one hydroxyl
group on each monomer
replaced with an acetyl
amine group. This
allows for increased hydrogen bonding between adjacent polymers,
giving the chitin-polymer matrix increased strength.
In its unmodified form, chitin is translucent, pliable,
resilient, and quite tough. In arthropods, however, it is often modified, becoming
embedded in sclerotin,
a tanned proteinaceous
matrix, which forms much of the exoskeleton.
In its pure form, chitin is pliable and leathery in texture, but in most
invertebrates it occurs largely as a component of composite materials. Combined with calcium
carbonate, as in the shells of crustaceans
and molluscs,
chitin produces a much stronger composite. This composite material is much
harder and more stiff than pure chitin, and is tougher and less brittle than
pure calcium carbonate.Another difference between pure
and composite forms can be seen by comparing the flexible body wall between the
segments of a caterpillar (mainly chitin) to the stiff, light elytron of a beetle (containing
a large proportion of sclerotin).
Fossil record
For more on the preservation potential of chitin and other
biopolymers, see taphonomy.
Chitin was probably present in the exoskeletons of Cambrian
arthropods such as trilobites. The oldest preserved chitin dates to the Oligocene,
about 25 million years ago,
comprising a scorpion encased in amber.
Uses
Agriculture
Most recent studies point out that chitin is a good inducer
of defense mechanisms in plants. It
has also been assessed as a fertilizer that can improve overall crop yields. The EPA regulates
chitin for agricultural use within the USA. Chitosan is
prepared from chitin by deacetylation.
Industrial
Chitin is used in industry in many processes. Examples of
the potential uses of chemically modified chitin in food
processing include the formation edible films and as an additive to thicken
and stabilize foods and pharmaceuticals. It also acts as a binder in dyes, fabrics, and adhesives.
Industrial separation membranes and ion-exchange
media can be made from chitin. Processes to size and strengthen
paper employ
chitin and chitosan. Researchers have developed a method for using chitosan as a
reproducible form of biodegradable plastic and as a promising substrate for engineering human tissues by use of three-dimensional
bioprinting.
Medicine
Chitin's properties as a flexible and strong
material make it favorable as surgical
thread. Its biodegradibility means it wears away with time as the wound
heals. Moreover, chitin has been reported to have some unusual properties
that accelerate healing of wounds in humans.
Occupations associated with high environmental chitin
levels, such as shellfish processors, are prone to high incidences of asthma. Recent
studies have suggested that chitin may play a role in a possible pathway in human allergic disease. To be specific, mice
treated with chitin develop an allergic response, characterized by a build-up of interleukin-4-expressing
innate immune cells. In these treated mice, additional treatment with a chitinase
enzyme abolishes the response.
Biomedical research
Chitin may be employed for affinity purification of
recombinant protein. A chitin binding domain is genetically fused to a protein
of interest and then contacted to beads coated with chitin. The immobilized
protein is purified and released from the beads by cleaving off the chitin
binding domain.
SUBSCRIBERS - ( LINKS) :FOLLOW / REF / 2 /
findleverage.blogspot.com
Krkz77@yahoo.com
+234-81-83195664
No comments:
Post a Comment