Control of extraction of deoxyribonucleic acid and apurinic acid by polyethylene glycol in Feulgen hydrolysis.

The polymer polyethylene glycol combined with hydrochloric acid was used during the hydrolysis stage of the Feulgen method in order to limit the movement of the soluble molecular fragments developed through hydrolytic breakdown of the deoxyribonucleic acid. The diffusion of the purines was not influenced by the addition of concentration of the polymer up to 30%. On the other hand, a substantial retardation of the extraction of deoxyribonucleic acid and apurinic acid was noted. This indicates that deoxyribonucleic acid and apurinic acid are extracted in chains of considerable length. The decrease in diffusion rate was greater at 1 M HCl than at 0.3 and 6 M HCl, which indicates that the deoxyribonucleic acid-apurinic acid fragments are larger at the medium concentration of acid than at the low and high concentrations. The results thus strengthen the view that deoxyribonucleic acid and apurinic acid are extracted in chains during hydrolysis, and that the critical length at which the chains becomes diffusible is one of the main factors determining the form of the Feulgen hydrolysis curve. The use of polyethylene glycol to extend the maximum of the hydrolysis curve, and thus to make the temperature and time of hydrolysis less critical, is recommended.