Polymer backbone

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Backbone chain
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IUPAC definition for a main chain (backbone) in polymer chemistry

In

polythiophenes) in thin films and in solution. Crystallization in its turn affects the optical properties of the polymers, its optical band gap and electronic levels.[2]

Organic polymers

Formation of polystyrene, a polymer with an organic backbone.

Common synthetic polymers have main chains composed of carbon, i.e. C-C-C-C.... Examples include polyolefins such as polyethylene ((CH2CH2)n) and many substituted derivative ((CH2CH(R))n) such as polystyrene (R = C6H5), polypropylene (R = CH3), and acrylates (R = CO2R').

Other major classes of organic polymers are

nylon-6
((NH(CH2)5C(O))n).

Inorganic polymers

Polydimethylsiloxane is classified as an "inorganic polymer", because the backbone lacks carbon.

methyl as in the case of polydimethylsiloxane. Some uncommon but illustrative inorganic polymers include polythiazyl
((SN)x) with alternating S and N atoms, and polyphosphates ((PO3)n).

Biopolymers

Major families of biopolymers are polysaccharides (carbohydrates), peptides, and polynucleotides. Many variants of each are known.[3]

Proteins and peptides

Proteins are characterized by

hydrogen bonding between the carbonyl oxygens and amide hydrogens in the backbone, i.e. C=O---HN. Further interactions between residues of the individual amino acids form the protein's tertiary structure. For this reason, the primary structure of the amino acids in the polypeptide backbone is the map of the final structure of a protein, and it therefore indicates its biological function.[4][3] Spatial positions of backbone atoms can be reconstructed from the positions of alpha carbons using computational tools for the backbone reconstruction.[5]

A simplified example of condensation showing the alpha and beta classification. Glucose and fructose form sucrose. The synthesis of glycogen in the body is driven by the enzyme glycogen synthase which uses a uridine diphosphate (UDP) leaving group.

Carbohydrates

Carbohydrates arise by condensation of

oxidized) carbon. In a Fischer Projection, if the glycosidic linkage is on the same side or face as carbon 6 of a common biological saccharide, the carbohydrate is designated as beta and if the linkage is on the opposite side it is designated as alpha. In a traditional "chair structure" projection, if the linkage is on the same plane (equatorial or axial) as carbon 6 it is designated as beta and on the opposite plane it is designated as alpha. This is exemplified in sucrose (table sugar) which contains a linkage that is alpha to glucose and beta to fructose. Generally, carbohydrates which our bodies break down are alpha-linked (example: glycogen) and those which have structural function are beta-linked (example: cellulose).[3][7]

Nucleic acids

Condensation of adenine and guanine forming a phosphodiester bond, the triphosphorylated ribose of the incoming nucleotide is attacked by the 3' hydroxyl of the polymer, releasing pyrophosphate.

complementary partners (A with T and G with C). This creates a double helix with pentose phosphate backbones on either side, thus forming a secondary structure.[8][3][9]

References

  1. ^ "Polymers". Archived from the original on 2015-10-02. Retrieved 2015-09-17.
  2. .
  3. ^ .V
  4. . NBK22364.
  5. .
  6. .
  7. .
  8. . NBK26850.
  9. . NBK21514.

See also