Backbone chain

In chemistry, particularly in biochemistry and molecular biology, is meant by a backbone or main chain of a continuous series of covalently bonded atoms, the actual molecular chain, which form the "backbone" of a macromolecule. Not for the backbone include the parts of the molecule that does not make this actual chain but are only bound by them.

Proteins

Of proteins is the backbone of the peptide bonds of the amino acids are linked to the protein. The torsion angles of the backbone of proteins with φ, ψ and ω denotes, the former two are shown in the Ramachandran plot. The torsion angles in the side chains are referred from the backbone, starting with χ1, χ2, etc.. In representations of proteins only the course of the backbone with different colors is often depicted for different secondary structures, see Fig.

Nucleic acids

With deoxyribonucleic acid ( DNA) is the backbone of the acid - and deoxyribose subunits. In contrast to other biopolymers having "normal" double-stranded DNA molecule, two opposite backbone.

Wherein ribonucleic acid ( RNA), the backbone consists of the phosphoric acid and ribose subunits.

Polysaccharides

All polysaccharides having a backbone of sugar residues. For linear molecular chains makes this the entire molecular mass (for example, cellulose).

Examples of branched polysaccharides:

Amylopectin contains a chain of 1,4- α -glycosidically linked D - glucose monosaccharide units and assuming at approximately every 25 glucose residue an α -1 ,6 -glycosidic linked side chain.

At galactoglucomannan is the backbone of 1,4- glycosidically linked α - D- monosaccharide units of glucose and mannose, approximately in the ratio of about 2:1. This main chain takes analogous to amylose starch a helical coil structure. On this main chain α -1 ,6 -glycosidic monomers or short side chains of sugar residues are attached, which make up about 8 % of the molecular mass, so that there is a complex branched polymer, but which appears essentially as an unbranched ( figures refer on glucomannan konjac ). The " side chains " composed predominantly of single galactose residues.

In glycogen glucose units linked α -1 ,4 -glycosidic, every 8 to 12 glucose residues of these also will be a side chain at a 1.6 - glycosidic linkage. Because here are built alike " side chains " and " backbone ", the whole molecule can be considered more as a network than as a backbone.

In xanthan gum is the backbone of β - (1 → 4 )-linked D-glucose units. Of every second glucose unit is α - ( 1 → 3) - glycoside, a β-D-Mannopyranosyl-(1→4)-β-D-glucuronopyranosyl-(1→2)-6-O-acetyl-α-D-mannopyranosyl-Seitenkette established.