Side Chain

In organic chemistry and biochemistry, a side chain is a chemical group that is attached to a core part of the molecule called "main chain" or backbone. The placeholder R is often used as a generic placeholder for alkyl (saturated hydrocarbon) group side chains in chemical structure diagrams. To indicate other non-carbon groups in structure diagrams, X, Y, or Z is often used. The R, historically, was introduced by 19th-century French chemist Charles Frédéric Gerhardt and may be derived from radical, or from residue and its German equivalent Rest.

In polymer science, the side chain or pendant chain is oligomeric or polymeric offshoot extends from the backbone chain of a polymer. Side chains have noteworthy influence on a polymer's properties, mainly its crystallinity and density. An oligomeric branch may be termed a short-chain branch and a polymeric branch may be termed a long-chain branch. Side groups are different from side chains; they are neither oligomeric nor polymeric.

In proteins (composed of amino acids) the side chains are attached to the alpha-carbon atoms of the amide backbone.

Famous quotes containing the words side and/or chain:

    We crossed a deep and wide bay which makes eastward north of Kineo, leaving an island on our left, and keeping to the eastern side of the lake. This way or that led to some Tomhegan or Socatarian stream, up which the Indian had hunted, and whither I longed to go. The last name, however, had a bogus sound, too much like sectarian for me, as if a missionary had tampered with it; but I knew that the Indians were very liberal. I think I should have inclined to the Tomhegan first.
    Henry David Thoreau (1817–1862)

    A chain is no stronger than its weakest link, and life is after all a chain.
    William James (1842–1910)