Halftime of spontaneous DNA hydrolysis at 25°C

Value 140000 years
Organism Generic
Reference Wolfenden R, Snider MJ. The depth of chemical time and the power of enzymes as catalysts. Acc Chem Res. 2001 Dec34(12):938-45. p.940 table 1 Table - link PubMed ID11747411
Primary Source Wolfenden, R. Ridgway, C. Young, G. Spontaneous Hydrolysis of Ionized Phosphate Monoesters and Diesters and the Proficiencies of Phosphatases and Phosphodiesterases as Catalysts. J. Am. Chem. Soc. 1998, 120, 6814-6815.
Method Reaction rates were measured at series of elevated temperatures, following them to completion. The resulting Arrhenius plot, if linear, can then be extrapolated to 25 °C. In much of this work, reaction mixtures were sealed in quartz, heated over various intervals, and then opened for analysis by proton NMR. The vapor pressure of water does not change enough to affect reaction rates significantly, but aqueous samples tend to burst at temperatures above 250 °C (40 atm). Explosions are avoided by placing reaction tubes in water inside a steel bomb, equalizing pressure across the wall of each tube. PTFE vessels must be used for alkaline solutions which attack quartz.
Comments Researchers examined the hydrolysis of dimethyl phosphate, as a model for the cleavage of phosphodiester linkages in DNA, and observed a half-time, pH-independent in the range near neutrality, of 140,000 years (primary source). Even at that level of stability, it can be inferred that a single DNA molecule from the human genome (with ~3×10^9 linkages of this kind) undergoes one backbone cleavage in 20 min. Accordingly, the genetic material would be highly unstable without enzymes to bring about DNA repair. See table link.
Entered by Uri M
ID 105355