Chain breakage of deoxyribonucleic acid following treatment with low doses of sulphur mustard

Abstract

The effect of low doses of mono- and difunctional sulphur mustards on the physical properties of DNA has been examined by viscosity and sedimentation methods. Alkylation produces no immediate effect on the shape or size of the DNA molecule. On incubation at 37 °C and pH 7 the molecular weight of the alkylated molecules decreases slowly with no indication of a coiling up of the molecule. The rate of breakage is proportional to the extent of alkylation and constant with time over a period of 3 weeks, the rate for the difunctional mustard being significantly greater than for the monofunctional mustard. Various possible mechanisms are considered for the formation of breaks. It is possible that a break in one strand of the double helix leads to a break in the opposite strand during prolonged incubation. The effect of heat treatment and exposure to mild alkali was also investigated by viscosity measurements.