Branch
Side-chain
Pendant chain
Anoligomeric orpolymeric offshoot from amacromolecular chain.Notes
- An oligomeric branch may be termed ashort-chain branch.
- A polymeric branch may be termed along-chain branch.[1]
Inorganic chemistry andbiochemistry, aside chain is achemical group that is attached to a core part of the molecule called the "main chain" orbackbone. The side chain is ahydrocarbon branching element of a molecule that is attached to a larger hydrocarbon backbone. It is one factor in determining a molecule's properties and reactivity.[2] A side chain is also known as apendant chain, but apendant group (side group) has a different definition.
The placeholderR is often used as a generic placeholder foralkyl (saturated hydrocarbon) group side chains instructural formulae. To indicate other non-carbon groups in structure diagrams,X,Y, orZ are often used.
TheR symbol was introduced by 19th-century French chemistCharles Frédéric Gerhardt, who advocated its adoption on the grounds that it would be widely recognizable and intelligible given its correspondence in multipleEuropean languages to the initial letter of "root" or "residue": Frenchracine ("root") andrésidu ("residue"), these terms' respective English translations along withradical (itself derived from Latinradix below), Latinradix ("root") andresiduum ("residue"), and GermanRest ("remnant" and, in the context of chemistry, both "residue" and "radical").[3]
Inpolymer science, the side chain of anoligomeric orpolymeric offshoot extends from thebackbone chain of a polymer. Side chains have noteworthy influence on a polymer's properties, mainly itscrystallinity anddensity. 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.[4]
Inproteins, which are composed ofamino acid residues, the side chains are attached to thealpha-carbon atoms of theamide backbone. The side chain connected to the alpha-carbon is specific for each amino acid and is responsible for determiningcharge andpolarity of the amino acid. The amino acid side chains are also responsible for many of the interactions that lead to properprotein folding and function.[5] Amino acids with similar polarity are usually attracted to each other, while nonpolar and polar side chains usually repel each other. Nonpolar/polar interactions can still play an important part in stabilizing the secondary structure due to the relatively large amount of them occurring throughout the protein.[6] Spatial positions of side-chain atoms can be predicted based on protein backbone geometry using computational tools for side-chain reconstruction.[7]
