Topoisomers or topological isomers are

molecule A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

s with the same

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

and stereochemical bond connectivities but different topologies. Examples of molecules for which there exist topoisomers include

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

, which can form

knot A knot is an intentional complication in Rope, cordage which may be practical or decorative, or both. Practical knots are classified by function, including List of hitch knots, hitches, List of bend knots, bends, List of loop knots, loop knots, ...

s, and catenanes. Each topoisomer of a given DNA molecule possesses a different linking number associated with it. DNA topoisomers can be interchanged by

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

s called

topoisomerase DNA topoisomerases (or topoisomerases) are enzymes that catalyze changes in the topological state of DNA, interconverting relaxed and supercoiled forms, linked (catenated) and unlinked species, and knotted and unknotted DNA. Topological issues in ...

s. Using a topoisomerase along with an intercalator, topoisomers with different linking number may be separated on an

agarose Agarose is a heteropolysaccharide, generally extracted from certain red algae. It is a linear polymer made up of the repeating unit of agarobiose, which is a disaccharide made up of D-galactose and 3,6-anhydro-L-galactopyranose. Agarose is on ...

gel via

gel electrophoresis Gel electrophoresis is an electrophoresis method for separation and analysis of biomacromolecules (DNA, RNA, proteins, etc.) and their fragments, based on their size and charge through a gel. It is used in clinical chemistry to separate ...

References

* ''New Molecular Topologies Beyond Catenanes and Rotaxanes'' Essay 2000 Theresa Chang American Chemical Societ
Online Article
Stereochemistry Molecular topology {{Stereochemistry-stub

See also

References