ISSN:
1432-2099
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Summary The initial effect of N-methyl-N-nitrosourea (MNU) on double-stranded calf thymus DNA was studied by means of derivative pulse polarography, kinetic formaldehyde method and spectrophotometric denaturation curves. In the first 30 min of the reaction it was found that, at a molar ratio MNU : DNA P = 20 : 1, changes in the pulse-polarographic behaviour of DNA took place, while no changes in Tm were detected. A higher reactivity of DNA with formaldehyde was observed in the same time interval, when a higher ratio MNU : DNA P (50 : 1) was used. The increase of the pulse-polarographic peak that was observed at room temperature and slightly acid pH, or at neutral pH and elevated (premelting) temperature was explained by a local destabilization of the double helix. Further experiments showed that the initial effects of MNU are strongly dependent on the DNA conformation; the rate of reaction of single-stranded (denatured) DNA was substantially higher. As a consequence of the initial effects of MNU on the double-stranded DNA thermolabile bonds were formed, which resulted in the breakage of sugar-phosphate backbone in the course of DNA heating. The number of single-strand breaks appearing primarily due to the effects of MNU on the double-stranded DNA during the first 30 min of the reaction was under the limits of detection.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01323941
Permalink