Editing Quantum tunnelling (section)

==== Quantum biology ====
Quantum tunnelling is among the central non-trivial quantum effects in [[quantum biology]].<ref name="life">{{cite journal |title=Quantum Tunnelling to the Origin and Evolution of Life |year=2013 |pmc=3768233 |last1=Trixler |first1=F. |journal=Current Organic Chemistry |volume=17 |issue=16 |pages=1758–1770 |doi=10.2174/13852728113179990083 |pmid=24039543 }}</ref> Here it is important both as electron tunnelling and [[proton tunneling|proton tunnelling]]. Electron tunnelling is a key factor in many biochemical [[redox reactions]] ([[photosynthesis]], [[cellular respiration]]) as well as enzymatic catalysis. Proton tunnelling is a key factor in spontaneous [[DNA]] mutation.<ref name="Trixler2013" />

Spontaneous mutation occurs when normal DNA replication takes place after a particularly significant proton has tunnelled.<ref>{{cite book |last=Matta |first=Cherif F. |title=Quantum Biochemistry: Electronic Structure and Biological Activity |location=Weinheim |publisher=Wiley-VCH |year=2014 |url=https://books.google.com/books?id=a4JhVFaUOjgC |isbn=978-3-527-62922-0 }}</ref> A hydrogen bond joins DNA base pairs. A double well potential along a hydrogen bond separates a potential energy barrier. It is believed that the double well potential is asymmetric, with one well deeper than the other such that the proton normally rests in the deeper well. For a mutation to occur, the proton must have tunnelled into the shallower well. The proton's movement from its regular position is called a [[Tautomer|tautomeric transition]]. If DNA replication takes place in this state, the base pairing rule for DNA may be jeopardised, causing a mutation.<ref>{{cite book |last=Majumdar |first=Rabi |title=Quantum Mechanics: In Physics and Chemistry with Applications to Bioloty |location=Newi |publisher=PHI Learning |year=2011 |url=https://books.google.com/books?id=IJDvyNVeBiYC |isbn=9788120343047 }}</ref> [[Per-Olov Lowdin]] was the first to develop this theory of spontaneous mutation within the [[Nucleic acid double helix|double helix]]. Other instances of quantum tunnelling-induced mutations in biology are believed to be a cause of ageing and cancer.<ref>{{cite journal |last=Cooper |first=W. G. |date=June 1993 |title=Roles of Evolution, Quantum Mechanics and Point Mutations in Origins of Cancer |journal=Cancer Biochemistry Biophysics |volume=13 |issue=3 |pages=147–170 |pmid=8111728}}</ref>