Mechanisms of Inactivation of Deoxyribonucleic Acids by Heat

Abstract

BIOCHEMISTRY: GINOZA AND ZIMM 639 small effects here. We find no difference in the sensitivity of four markers at subcritical temperatures, whereas the Tm's are different, as first reported by Roger and Hotchkiss4 and by Marmur and Doty.3 No striking effect has yet been found for dependence of subcritical sensitivity on molecular weight, but there is a dependence of the Tm's on molecular weight, which varies for different markers. This will be the subject of a future report. Summary.-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, concentration-dependent, survival curves. The same DNA, treated further with a single phenol extraction, exhibited exponential survival curves, which were concentrationindependent 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.

Studies on the Genetic Multiplicity of a Gene in Yeast Cells, I Characteristics of the Induced Mutations by Subcritical Temperature and Ultraviolet Light

“…The former results in rapid denaturation; whereas the latter is a slow process, and the temperature that leads to this process may be called subcritical temperature (Ginoza and Zimm 1961). In this definition the experimental condition 60°C for 4 minutes in this study is apparently subcritical.…”

“…Concerning the mechanism of high temperature action on the DNA molecule, Ginoza and Zimm (1961) were able to show experimentally that inactivation of transforming DNA by subcritical temperature was of the exponential type indicating the process was the one-hit type. Surprisingly enough, in the present study we also encountered the same sort of phenomenon when it was found that whole-colony mutation represented the majority of the total mutation.…”

Features of the damage produced by proflavine on transforming deoxyribonucleic acid

“…The permanent inactivation produced by proflavine on renatured DNA was higher at 370C than at 45, 55, or 650C, but at these last three temperatures the DNA was highly inactivated in the absence of proflavine, suggesting that the mechanisms of inactivation by proflavine and heat may involve depurination of DNA (5).…”

Isolation of heavy satellite deoxyribonucleic acid from sea-urchin spermatozoa

“…former could be purified by one cycle of CsCl centriIfthe DNA recovered in the top phase is centrifuged fugation, but when high-molecular-weight spermatoto equilibrium in CsCl in a 60Ti rotor (Spinco model 1978 L preparative ultracentrifuge), the resolution of satellite rDNA is not satisfactory. This is because the resolution of satellite DNA by CsCl centrifugation depends on both the molecular weight and concentration of DNA (Brown & Weber, 1968 (Tamm et al, 1952) and thus create single-strand breaks (Walker, 1971;Ginoza & Guild, 1961;Ginoza & Zimm, 1961). Moreover, the poly(ethylene glycol)/dextran two-phase system depends on the separation ofsingle-and double-stranded DNA in the two phases, i.e., on their distribution coefficient, K. As K=exp- (T) where M is molecular weight, k the Boltzmann constant, A a constant, T temperature in K, it is obvious that the partition coefficient (K) also depends on the molecular weight of DNA.…”