title: Carbon-14 decay as a source of non-canonical bases in DNA.
abstract: BACKGROUND
  Significant experimental effort has been applied to study radioactive beta-decay in biological systems. Atomic-scale knowledge of this transmutation process is lacking due to the absence of computer simulations. Carbon-14 is an important beta-emitter, being ubiquitous in the environment and an intrinsic part of the genetic code. Over a lifetime, around 50 billion (14)C decays occur within human DNA.
  
  
  METHODS
  We apply ab initio molecular dynamics to quantify (14)C-induced bond rupture in a variety of organic molecules, including DNA base pairs.
  
  
  RESULTS
  We show that double bonds and ring structures confer radiation resistance. These features, present in the canonical bases of the DNA, enhance their resistance to (14)C-induced bond-breaking. In contrast, the sugar group of the DNA and RNA backbone is vulnerable to single-strand breaking. We also show that Carbon-14 decay provides a mechanism for creating mutagenic wobble-type mispairs.
  
  
  CONCLUSIONS
  The observation that DNA has a resistance to natural radioactivity has not previously been recognized. We show that (14)C decay can be a source for generating non-canonical bases.
  
  
  CONCLUSIONS
  Our findings raise questions such as how the genetic apparatus deals with the appearance of an extra nitrogen in the canonical bases. It is not obvious whether or not the DNA repair mechanism detects this modification nor how DNA replication is affected by a non-canonical nucleobase. Accordingly, (14)C may prove to be a source of genetic alteration that is impossible to avoid due to the universal presence of radiocarbon in the environment.
authors.affiliation: Nanochemistry Research Institute, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.
authors.forename: Michel
authors.initials: M
authors.lastname: Sassi
authors.forename: Damien J
authors.initials: DJ
authors.lastname: Carter
authors.forename: Blas P
authors.initials: BP
authors.lastname: Uberuaga
authors.forename: Chris R
authors.initials: CR
authors.lastname: Stanek
authors.forename: Nigel A
authors.initials: NA
authors.lastname: Marks
mesh_terms: D020029:Base Pairing; D002250:Carbon Radioisotopes / Q000378:metabolism*; D003198:Computer Simulation; D004247:DNA / Q000737:chemistry*; D004260:DNA Repair; D006801:Humans; D008958:Models, Molecular
chemical_list: D002250:Carbon Radioisotopes; D004247:DNA
keywords: Beta-decay; Bond-breaking; Carbon-14; DNA; Mutation; Non-canonical base