Herbert S. Rosenkranz

Studies on deoxyribonucleic acid after exposure to tritium gas

Deoxyribonucleic acid (DNA) from human leukocytes was exposed to 0·39 atm of tritium (2·4 curies) for 14 days at room temperature, and approximately 0·1 % replacement of hydrogen by tritium was effected. The molar ratios of tritium in the bases was adenine 1·0, thymine 9·8, guanine 1·4 and cytosine 2·4. The treatment caused a drop in average molecular weight from 5·2 to 1·3 × 106 as estimated from sedimentation data and there was a concomitant alteration in the anion exchange chromatographic behavior. Evidence was also obtained for some aggregation in addition to the degradation. These macromolecular changes did not appear to be accompanied by significant denaturation (i.e., twin-strand separation).

A correlation between the sedimentation coefficient of deoxyribonucleic acid and its paper chromatographic migration

Abstract A method for the paper chromatographic examination of DNA is described. The rate of migration of DNA on paper has been found to be related to the sedimentation coefficient. Accordingly, a rough estimate of the sedimentation coefficient of DNA may be obtained without recourse to ultracentrifugation.

Studies on the fractionation of transforming deoxyribonucleic acid of pneumococcus I. Recovery and dose-desponse relationships

Abstract Evidence is presented that pneumococcal transforming DNA is not degraded by chromatography on columns of the cellulose derivative anion-exchanger ECTEOLA. Essentially all of the mannitol- and penicillin-transforming activities added to the column were recovered in the column eluates, although more streptomycin-transforming activity was recovered than was apparent in the original, unfractionated DNA. The results obtained by determining the transforming activity-dose response curves of selected fractions have been interpreted as indicating that DNA-induced transformation to streptomycin-resistance in pneumococci can be a property of DNA molecules which vary intrinsically in relative transforming ability. The transforming activities were not restricted to any one chromatographic peak or region, but were present in several DNA fractions which had been obtained with eluting solutions of widely varying ionic strength and pH.