Physical properties of single- and double-stranded coliphage ribonucleic acid

Abstract

The physical characteristics of single- and double-stranded coliphage RNA with regard to their sedimentation behaviour in gradients of sucrose in high or low ionic conditions were examined. The effect of heat on their sedimentation characteristics was also determined. Single-stranded coliphage RNA was found to exist in three different forms having sedimentation coefficients 28 s, 20 a and 12 s. The latter two were interchangeable, depending on ionic strength. All three were almost equally infectious to spheroplasts. Double-stranded coliphage RNA was found to be non-infectious to spheroplasts and had sedimentation coefficients 15 s and 12 s. Thermal denaturation gave rise to infectious single-stranded 12 s RNA. Four possible hypotheses on the mechanism of replication of coliphage RNA are discussed.