ON THE INACTIVATION OF TRANSFORMING DNA BY TEMPERATURES BELOW THE MELTING POINT

Abstract

The sensitivity of the transforming activity of a DNA preparation to heating at temperatures below the critical melting temperature depends strongly on the method of preparing the DNA. DNA deproteinized by a few cycles of shaking with chloroform-isoamyl alcohol showed concave-downward,con-centration-dependent, survival curves. The same DNA, treated further with a single phenol extraction, exhibited exponential survival curves, which were concentration-independent and more stable and were very similar to the previously observed curves for a phenol preparation from a different strain of pneumococcus. A fraction of the first preparation recovered from a CsCl gradient showed intermediate stability.