Topoisomer
Encyclopedia
Topoisomers or topological isomers are molecule
s with the same chemical formula
and stereochemical bond connectivities but different topologies
. Examples of molecules for which there exist topoisomers include DNA
, which can form knot
s, and catenane
s. DNA topoisomers can be interchanged by enzyme
s called topoisomerase
s.
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s with the same chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
and stereochemical bond connectivities but different topologies
Topology
Topology is a major area of mathematics concerned with properties that are preserved under continuous deformations of objects, such as deformations that involve stretching, but no tearing or gluing...
. Examples of molecules for which there exist topoisomers include DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
, which can form knot
Knot theory
In topology, knot theory is the study of mathematical knots. While inspired by knots which appear in daily life in shoelaces and rope, a mathematician's knot differs in that the ends are joined together so that it cannot be undone. In precise mathematical language, a knot is an embedding of a...
s, and catenane
Catenane
A catenane is a mechanically-interlocked molecular architecture consisting of two or more interlocked macrocycles. The interlocked rings cannot be separated without breaking the covalent bonds of the macrocycles. Catenane is derived from the Latin catena meaning "chain"...
s. DNA topoisomers can be interchanged by enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s called topoisomerase
Topoisomerase
Topoisomerases are enzymes that regulate the overwinding or underwinding of DNA. The winding problem of DNA arises due to the intertwined nature of its double helical structure. For example, during DNA replication, DNA becomes overwound ahead of a replication fork...
s.
See also
- Mechanically-interlocked molecular architecturesMechanically-interlocked molecular architecturesMechanically interlocked molecular architectures are connections of molecules not through traditional bonds, but instead as a consequence of their topology. This connection of molecules is analogous to keys on a key chain loop. The keys are not directly connected to the key chain loop but they...
- CatenaneCatenaneA catenane is a mechanically-interlocked molecular architecture consisting of two or more interlocked macrocycles. The interlocked rings cannot be separated without breaking the covalent bonds of the macrocycles. Catenane is derived from the Latin catena meaning "chain"...
- Rotaxanes
- Molecular knotMolecular knotIn chemistry, a molecular knot, or knotane, is a mechanically-interlocked molecular architecture that is analogous to a macroscopic knot. A molecular knot in a trefoil knot configuration is chiral, having at least two enantiomers. Examples of naturally formed knotanes are DNA and certain proteins....
- Molecular Borromean ringsMolecular Borromean ringsMolecular Borromean rings are an example of a mechanically-interlocked molecular architecture in which three macrocycles are interlocked in such a way that breaking any macrocycle allows the others to disassociate. They are the smallest examples of Borromean rings. The synthesis of molecular...