Structural alterations in deoxyribonucleic acid on chemical ethylation.

Ethylation of DNA by diethyl sulfate gave 7-ethylguanine as the major product. Dimethyl sulfate was much more reactive than diethyl sulfate in forming 7-alkylguanine. The hydrodynamic properties of DNA did not change as a direct consequence of ethylation. On incubation at 37 °C, the viscosity of ethylated DNA decreased at a rate similar to that of methylated DNA. The rate of depurination of 7-ethylguanine from ethylated DNA was the same as that of 7-methylguanine from methylated DNA. These results demonstrate that ethyl groups have identical effects as methyl groups on the secondary structure and stability of DNA.